US20050074296A1 - Hydro-pneumatic tensioner with stiffness altering secondary accumulator - Google Patents
Hydro-pneumatic tensioner with stiffness altering secondary accumulator Download PDFInfo
- Publication number
- US20050074296A1 US20050074296A1 US10/685,681 US68568103A US2005074296A1 US 20050074296 A1 US20050074296 A1 US 20050074296A1 US 68568103 A US68568103 A US 68568103A US 2005074296 A1 US2005074296 A1 US 2005074296A1
- Authority
- US
- United States
- Prior art keywords
- bore
- fluid
- piston
- accumulator
- barrel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000012530 fluid Substances 0.000 claims abstract description 275
- 238000004891 communication Methods 0.000 claims abstract description 72
- 238000000926 separation method Methods 0.000 claims abstract description 4
- 238000007667 floating Methods 0.000 claims description 61
- 230000007423 decrease Effects 0.000 claims description 17
- 230000000670 limiting effect Effects 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 7
- 230000004888 barrier function Effects 0.000 claims 2
- 230000001419 dependent effect Effects 0.000 description 10
- 238000005553 drilling Methods 0.000 description 8
- 230000002829 reductive effect Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 5
- 239000003921 oil Substances 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 230000033001 locomotion Effects 0.000 description 4
- 230000037361 pathway Effects 0.000 description 4
- 230000036961 partial effect Effects 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 230000000712 assembly Effects 0.000 description 2
- 238000000429 assembly Methods 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000010720 hydraulic oil Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 238000012217 deletion Methods 0.000 description 1
- 230000037430 deletion Effects 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000000452 restraining effect Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- F16F9/00—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium
- F16F9/06—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium using both gas and liquid
- F16F9/064—Units characterised by the location or shape of the expansion chamber
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B19/00—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables
- E21B19/002—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables specially adapted for underwater drilling
- E21B19/004—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables specially adapted for underwater drilling supporting a riser from a drilling or production platform
- E21B19/006—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables specially adapted for underwater drilling supporting a riser from a drilling or production platform including heave compensators
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- F16F9/00—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium
- F16F9/06—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium using both gas and liquid
- F16F9/062—Bi-tubular units
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- F16F9/00—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium
- F16F9/10—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium using liquid only; using a fluid of which the nature is immaterial
- F16F9/14—Devices with one or more members, e.g. pistons, vanes, moving to and fro in chambers and using throttling effect
- F16F9/16—Devices with one or more members, e.g. pistons, vanes, moving to and fro in chambers and using throttling effect involving only straight-line movement of the effective parts
- F16F9/18—Devices with one or more members, e.g. pistons, vanes, moving to and fro in chambers and using throttling effect involving only straight-line movement of the effective parts with a closed cylinder and a piston separating two or more working spaces therein
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- F16F9/00—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium
- F16F9/32—Details
- F16F9/50—Special means providing automatic damping adjustment, i.e. self-adjustment of damping by particular sliding movements of a valve element, other than flexions or displacement of valve discs; Special means providing self-adjustment of spring characteristics
- F16F9/512—Means responsive to load action, i.e. static load on the damper or dynamic fluid pressure changes in the damper, e.g. due to changes in velocity
Definitions
- This invention relates to tensioning of seabed-to-vessel marine risers. More particularly, this invention relates to tensioning the marine risers with a plurality of pneumatic or hydraulic cylinders.
- a problem presented by offshore hydrocarbon drilling and producing operations conducted from a floating platform is the need to establish a sealed fluid pathway between each borehole or well at the ocean floor and the work deck of the platform at the ocean surface.
- a riser typically provides this sealed fluid pathway.
- the drill string extends through a drilling riser, the drilling riser serving to protect the drill string and to provide a return pathway outside the drill string for drilling fluids.
- a production riser is used to provide a pathway for the transmission of oil and gas to the work deck.
- the riser is projected up through an opening referred to as a moon pool in the vessel to working equipment and connections proximate an operational floor on the vessel.
- a riser pipe operating on the floating vessel in water depths greater than about 200 feet (34.72 meters) can buckle under the influence of its own weight and the weight of drilling fluid contained within the riser if it is not partially or completely supported.
- a special piece of equipment known as a “riser tensioner” is required to maintain each riser within a range of safe operating tensions as the work deck moves relative to the upper portion of the riser. If a portion of the riser is permitted to go into compression, it could be damaged by buckling or by bending and colliding with adjacent risers. It is also necessary to ensure that the riser is not over-tensioned when the vessel hull moves to an extreme lateral position under extreme wave conditions or when ocean currents exert a significant side loading on the riser.
- a tension leg platform is a type of marine structure having a buoyant hull secured to a foundation on the ocean floor by a set of tethers.
- the tethers are each attached to the buoyant hull so that the hull is maintained at a significantly greater draft than it would assume if free floating.
- the resultant buoyant force of the hull exerts an upward loading on the tethers, maintaining them in tension.
- the tensioned tethers limit vertical motion of the hull, thus substantially restraining it from pitch, roll and heave motions induced by waves, currents and wind.
- TLPs are not designed to resist horizontal forces induced by waves.
- the marine risers have been tensioned in various manners, including the use of counterweights and pneumatic spring systems.
- the counterweight was the first technique utilized to apply tension to the top of the marine riser.
- the weight was hung from a wire rope which was run up through wire rope sheaves and down to an upper portion of the riser pipe. The tension was equal to the counterweight and therefore was practicable only for shallow water that required low tension.
- the pneumatic spring systems replaced the counterweight systems as deeper water drilling evolved.
- the pneumatic tensioning devices stored energy in the form of compressed air to apply tension to the top of the riser through wire ropes.
- the pneumatic tensioning devices typically involved the use of cylinders from which a piston rod was extended, the piston rod having a sheave engaged by the wire rope to be tensioned. The fluid within the hydraulic cylinder was thereby compressed into an accumulator.
- the cylinder and the accumulator were normally supported by support structures on the floating vessel.
- tensioner systems in use today act as oil-damped pneumatic springs.
- a large gas supply keeps a nearly constant pressure above the oil in a gas-oil accumulator.
- the oil then provides pressure to the face of the piston.
- the piston moves up and down against a relatively constant force and the tension lines maintain a relatively constant pull.
- riser tensioners today utilize hydraulically actuated cylinders with pneumatic pressure accumulators to provide the force necessary to maintain the upper portion of the riser within a preselected range of operating tensions.
- One implementation is accomplished by the use of sheaves attached to the buoyant drilling structure whereby tensioning cables are run over the sheaves and attached to the riser so that the riser is supported by one end of the tensioning cables.
- the other end of each tensioning cable is connected to a piston of a hydraulic cylinder.
- the hydraulic cylinders are connected to a relatively large accumulator which maintains the load applied by the cylinders at a relatively constant level over the full range of travel of the pistons.
- the pistons stroke to maintain a relatively constant upward loading on the riser.
- riser tensioner typically used on TLPs also uses a pneumatically pressurized fluid accumulator but eliminates the cables and sheaves used in earlier riser tensioners.
- Gas and oil accumulators are connected to the cylinders to control the stroke of pistons.
- the piston rods are directly attached to a riser tensioning ring which supports the riser.
- an embodiment of the present invention advantageously provides a tensioner unit including a barrel having a bore with pressurized fluid contained within.
- the barrel forms at least part of a primary accumulator having a preset volume of gas Vg 1 at pressure P 1 .
- the barrel of the tensioner unit also includes an aperture to allow extension and retraction of a piston rod.
- the tensioner unit also includes a piston slidably carried in the bore of the barrel.
- the piston has a piston rod that extends from one side of the piston and through an aperture in the barrel.
- the piston has one of its sides in communication with the pressurized fluid, and is so positioned to increase the pressure P 1 of the primary accumulator when the piston strokes in the direction of the pressurized fluid.
- the tensioner unit also includes a secondary accumulator housing having a bore which forms at least part of a secondary accumulator having a preset volume of gas Vg 2 at pressure P 2 .
- the tensioner unit also includes a fluid separator positioned between the primary and secondary accumulators to maintain functional separation of fluid volumes of the primary and secondary accumulators when the primary accumulator pressure P 1 is less than the secondary accumulator pressure P 2 .
- the fluid separator also allows functional combining of the fluid volumes of the primary and secondary accumulators when the primary accumulator pressure P 1 is greater than or equal to the secondary accumulator pressure P 2 .
- the tensioner unit is configured so that when the primary accumulator pressure P 1 is less than the secondary accumulator pressure P 2 , the effective total gas volume VgT available to the tensioner to maintain tension on a supported system, such as a riser system, is substantially equivalent to the primary accumulator gas volume Vg 1 .
- the effective total gas volume VgT available to the tensioner to maintain tension on the supported system equals the sum of the primary accumulator gas volume Vg 1 plus the secondary accumulator gas volume Vg 2 . This provides for reduced stiffness and reduced maximum tension applied by the tensioner unit to a supported system when the system is directing a maximum load on the tensioner unit.
- FIG. 1 is a perspective view of a hydro-pneumatic tensioner system in accordance with the invention.
- FIG. 2 is an enlarged perspective view of one of the hydro-pneumatic tensioner units of the hydro-pneumatic tensioner system of FIG. 1 .
- FIG. 3 is a schematic view of the hydro-pneumatic tensioner unit having a first piston enclosing a second piston shown with the first piston in an extended position.
- FIG. 4 is a schematic view of the hydro-pneumatic tensioner unit of FIG. 3 , shown a mid-point position.
- FIG. 5 is a schematic view of the hydro-pneumatic tensioner unit of FIG. 3 , shown a retracted position.
- FIG. 6 is a schematic view of an embodiment of a hydro-pneumatic tensioner unit, including an internal cylinder barrel connected to an external cylinder having a second piston.
- FIG. 7 is a schematic view of a variation of FIG. 6 .
- FIG. 8 is a schematic view of a variation of FIG. 6 having no internal cylinder barrel.
- FIG. 9 is a schematic view of an external cylinder for use with the tensioner unit of Figure 6 , having a bladder which forms an enclosure containing a gas volume Vg 2 and a hydraulic volume Vh 1 .
- FIG. 10 is a schematic view of an external cylinder for use with the tensioner unit of FIG. 6 , having a pilot valve interface that forms an enclosure containing a gas volume Vg 2 and a hydraulic volume Vh 2 .
- FIG. 11 is a schematic view of another embodiment of a hydro-pneumatic tensioner unit, having a first piston connected to an external cylinder having a second piston, shown with the first piston in an extended position.
- FIG. 12 is a schematic view of the hydro-pneumatic tensioner unit of FIG. 11 , shown with the first piston in a mid-point position.
- FIG. 13 is a schematic view of the hydro-pneumatic tensioner unit of FIG. 11 , shown with the first piston in a retracted position.
- FIG. 14 is a schematic view of an external cylinder for use with the tensioner unit of FIG. 11 , having a bladder which forms an enclosure containing a gas volume Vg 2 .
- FIG. 15 is a schematic view of an external cylinder for use with the tensioner unit of FIG. 11 , having a pilot valve interface that forms an enclosure containing a gas volume Vg 2 .
- FIG. 16 is a schematic view of a variation of FIG. 7 .
- FIG. 17 is a schematic view of a pull-type hydro-pneumatic tensioner unit having a first external cylinder hydraulically connected to the hydraulic side of a first piston.
- a hydro-pneumatic riser tensioner system 20 for maintaining a riser system within a range of safe operating tensions as a work deck or platform moves relative to the upper portion of the riser system.
- the system 20 advantageously provides a methodology for incorporating high nominal stiffness while limiting peak loads at extreme up and down strokes. More specifically, the system 20 includes a riser system 22 , extending between a floating vessel having an operational platform 24 , 26 , and the sea bottom (not shown).
- the riser system 22 is supported in tension at its upper end to prevent the riser system 22 from buckling due to its own weight.
- the upward tension is maintained within acceptable limits over a typical platform deviation range by the hydro-pneumatic riser tensioner system 20 .
- the riser tensioner system 20 includes a plurality of hydro-pneumatic tensioner units 28 .
- the tensioner units 28 include a main body or housing 30 , typically tubular shaped, stationarily located between support frames 24 , 26 , of a support module 23 .
- Each tensioner unit 28 includes a hydro-pneumatic ram tensioner piston rod 32 attached at its upper end to a riser tensional mount or top plate 34 , which includes a riser tensional ring 36 .
- the riser tensional ring 36 engages a tension joint 38 of the riser system 22 .
- the hydro-pneumatic ram tensioner piston rod 32 telescopes relative to housing 30 in response to movement of the operational platform.
- each hydro-pneumatic tensioner unit upper section is attached to the top plate 34 and the lower section is connected to the support module lower support frame 24 , with each unit 28 protruding through an aperture 27 in the upper support frame 26 of the support module 23 .
- the riser system 22 includes a riser conductor 42 and roller assemblies 44 , on lower and upper support frames 24 , 26 , of the support module 23 to provide for axial movement of the support module 23 with respect to the riser system 22 .
- the riser system 22 slides up and down through the roller assemblies 44 and is engaged with tension from the hydro-pneumatic riser tensioner system 20 through the tensioner units 28 applying tension to the top plate 34 .
- the top plate 34 via the mounting ring 36 translates the tension from the tensioner units 28 to the tension joint 38 of the riser system 22 .
- the hydro-pneumatic riser tensioner system 20 includes a plurality of hydro-pneumatic tensioner units 28 .
- Each of the units 28 has an upper end and a lower end.
- the upper end can include a rod end cap 46 .
- the rod end cap 46 and thus the upper end of each unit 28 can be connected to the top plate 34 ( FIG. 1 ) to provide the requisite tension to the tension ring 36 ( FIG. 1 ) and thus to the riser system 22 .
- the rod end cap 46 is shown as threadingly attached to a shoulder or flange 48 formed of or attached to the main body of piston rod 32 , using a plurality of bolts 50 , each affixed in a bolt cavity (not shown), however, any appropriate attachment or sealing methodology as known by those skilled in the art is appropriate and within the scope of the invention.
- the lower end of the tension unit 28 is connected to the operational marine platform (not shown).
- the lower end of the units 28 is connected to a lower platform or frame 24 of a hydro-pneumatic tensioner support module 23 ( FIG. 1 ).
- the tensioner unit 28 includes a barrel such as inner cylinder barrel 60 or main body 30 each having a bore and an aperture on at least one end and having a pressurized fluid contained within.
- the barrel forms at least part of a primary accumulator having a preset volume of gas Vg 1 at pressure P 1 .
- a piston such as piston 72 is slidably carried in the bore of the barrel.
- the piston has a piston rod that extends from a side of the piston and through the aperture of the barrel.
- One side 82 of the piston 72 is in communication with the pressurized fluid.
- the piston 72 is positioned to increase pressure P 1 of the primary accumulator when the piston 72 strokes in the direction of the pressurized fluid.
- a secondary accumulator housing such as the piston rod 32 with inner bore 76 or the external housings shown in FIG. 9 or 12 - 15 (described later) form at least part of a secondary accumulator having a preset volume of gas Vg 2 at pressure P 2 .
- a fluid separator such as floating piston 92 ( FIG. 3 ), or the bladder or valve arrangement shown in FIGS. 9-12 (described later), is positioned between the primary and secondary accumulators to maintain functional separation of fluid volumes of the primary and secondary accumulators when the primary accumulator pressure P 1 is less than the secondary accumulator pressure P 2 , and to allow functional combining of the fluid volumes of the primary and secondary accumulators when the primary accumulator pressure P 1 is greater than or equal to the secondary accumulator pressure P 2 .
- This arrangement results in an effective total gas volume VgT available to the tensioner 28 to maintain tension on a supported system, such as a riser system, to substantially equal the primary accumulator gas volume Vg 1 when the primary accumulator pressure P 1 is less than the secondary accumulator pressure P 2 , and to substantially equal the sum of the primary accumulator gas volume Vg 1 plus the secondary accumulator gas volume Vg 2 when the pressure P 1 is greater than or equal to the secondary accumulator pressure P 2 .
- a supported system such as a riser system
- tensioner unit 28 includes a primary accumulator 52 .
- the primary accumulator 52 includes an upper end having a piston seal housing aperture 54 , a lower end preferably including an endcap 56 ( FIG. 2 ), and a main body 30 having an axial bore 58 , therebetween.
- the primary accumulator 52 contains a gas volume Vg 1 and a hydraulic volume Vh 1 .
- the lower end cap 56 ( FIG. 2 ) is threadingly connected within a lower end bore (not shown), although any appropriate attachment or seal means as known by those skilled in the art is acceptable and within the scope of the invention.
- the sealed enclosure of the primary accumulator 52 forms a gas and hydraulic fluid reservoir.
- a charging connection (not shown) can be interfaced with the main body 30 of the accumulator 52 to permit intermittent or continuous charging of both the gas and hydraulic volumes Vg 1 , Vh 1 , from an external pressure source (not shown).
- the hydro-pneumatic riser tensioner system 20 ( FIG. 1 ) also can include a stationery or internal cylinder barrel 60 located within the primary accumulator 52 .
- the cylinder barrel 60 is secured sealingly to aperture 54 of accumulator 52 .
- the cylinder barrel 60 includes an upper end having an upper piston rod aperture 62 , a lower end having a lower fluid inlet aperture 64 , and a main body having an axial inner bore 66 , therebetween.
- the cylinder barrel 60 includes a lower fluid aperture channel extension 68 which protrudes to a position adjacent the lower end of primary accumulator 52 , and provides for fluid communication between the cylindrical barrel inner bore 66 and primary accumulator hydraulic volume Vh 1 .
- the length of aperture channel extension 68 is generally formulated for the purpose of ensuring only hydraulic fluid entry into the cylinder barrel inner bore 66 , not gas.
- the length of the channel extension 68 may be established depending upon the operating conditions the unit 28 will be subjected to and the desired ratio of gas Vg 1 to fluid Vh 1 .
- the cylinder barrel 60 interfaces and is thus in fluid communication through its lower aperture 68 with the primary accumulator hydraulic volume Vh 1 .
- the volume of hydraulic fluid contained within the cylinder barrel 60 is directly dependent upon the gas pressure P 1 within the primary accumulator 52 and stroke position of the tensioner piston rod 32 .
- the tensioner 28 has a first piston assembly 70 that moves axially within barrel 60 .
- the piston assembly 70 includes a combination first piston 72 and piston rod 32 .
- the piston assembly 70 also includes an upper end typically interfaced with a rod end cap 46 ( FIG. 2 ), a lower end having a piston 72 including an aperture 74 , and a main body therebetween including an inner bore 76 .
- the combination forms a channel which forms an enclosure of varying size depending on primary accumulator gas pressure P 1 and stroke position of the riser tensioner piston rod 32 .
- the aperture 74 of piston 72 is not the same diameter as bore 76 .
- the piston 72 has an outer diameter substantially equivalent to the inner diameter of the axial inner bore 66 of cylinder barrel 60 .
- the outer diameter of piston rod 32 is substantially equivalent to the diameter of piston rod aperture 62 .
- the first piston assembly 70 is slidably positioned to telescope from inside the cylinder barrel 60 to provide tension and stiffness to the riser system 22 .
- the outer diameter of piston rod 32 is smaller than the inner diameter of cylinder barrel inner bore 66 .
- This differential diameter between the first piston diameter/cylindrical barrel inner bore diameter and the piston rod main body diameter/piston rod aperture diameter forms a back annulus 78 .
- the back annulus 78 is preferably vented to the atmosphere or through vent lines (not shown) following an appropriate methodology as known by those skilled in the art.
- the telescopic range of the first piston 72 can be limited by stops, described below, which present an upper and lower limit for the travel of the first piston 72 .
- the differential diameter between the piston rod 32 and first piston 72 form a shoulder 79 on the upper surface of the first piston 72 adjacent its outer circumference.
- the upper limit is the position where the first piston upper shoulder 79 contacts the lower surface 80 of the upper end of the cylinder barrel 60 .
- the lower limit is a position where the lower surface 82 of the first piston 72 contacts the upper surface 84 of the bottom of the cylinder barrel 60 .
- the piston assembly inner bore 76 interfaces and is in fluid communication through its lower aperture 64 with hydraulic fluid in the cylinder barrel 60 , which as previously stated is in communication with primary accumulator hydraulic volume Vh 1 .
- the volume of hydraulic fluid entering the piston assembly inner bore 76 adjacent its lower side is directly dependent upon gas pressure P 1 within the primary accumulator 52 , which is directly dependent upon stroke position of the tensioner piston rod 32 .
- the first piston 72 includes seals 90 that slidably engage and seal the bore 66 of barrel 60 .
- the first piston 72 particularly, the inner bore 76 , encloses a second piston 92 which form a housing for a secondary accumulator.
- the second piston 92 a fluid separator, has an upper and lower surface 94 , 96 , and a diameter that is substantially equal to the diameter of the first piston rod inner bore 76 .
- the second piston 92 is slidably carried within the piston rod inner bore 76 .
- the second piston 92 includes pressure seals that slidingly engage inner bore 76 .
- the second piston upper surface 94 in combination with the piston rod inner bore 76 form an enclosure, which along with a gas volume Vg 2 and hydraulic volume Vh 2 , sealingly contained on the upper side 94 of the second piston 92 , define a secondary accumulator 98 having a gas pressure P 2 .
- a charging connection (not shown) is located on the piston assembly 70 to permit intermittent or continuous charging of both the gas Vg 2 and hydraulic volumes Vh 2 from an external pressure source (not shown), depending on the embodiment implemented.
- the secondary accumulator 98 may include an interface (not shown) with an external accumulator (not shown) to provide added gas volume Vg 2 .
- the first piston rod inner bore 76 can also include a set of stops, 86 , 88 .
- retraction stops 86 are fixedly attached or formed of a protrusion in a position to define the maximum upper travel limit of the second piston 92 and ensure secondary accumulator 98 integrity.
- Extension stops 88 can be formed within either the inner bore 76 of the piston rod 72 or within or as part of the first piston aperture 74 .
- FIGS. 3-5 depict the extension stop 88 as formed from part of a lower surface 82 of the first piston 72 which effectively forms the aperture 74 into a two-stage aperture within the first piston 72 .
- Peak loads or tension on the tensioner unit 28 occurring during a retraction and extension of the piston rod 32 are reduced due to the implementation of floating piston 92 within the piston rod 32 . While the floating piston 92 is free-floating (not pegged against a retraction or extension stop, 86 , 88 ), the primary accumulator pressure P 1 equals the same pressure P 2 as in the secondary accumulator 98 , and the total effective gas volume VgT of the unit is effectively increased by the gas volume Vg 2 of the secondary accumulator 98 . The increase in gas volume provides a slower rate of increase in gas pressure P 1 due to the added volume Vg 2 , and also reduces the peak load or tension of a given downstroke (retraction of piston rod 32 ).
- the hydro-pneumatic tensioner unit 28 maintains the riser system 22 within a range of safe operating tensions as a work deck or platform (not shown) moves relative to the upper portion of the riser system 22 .
- the hydro-pneumatic tensioner system 20 ideally should be in a similar configuration to that shown in FIG. 3 .
- the first piston 72 is established in the vicinity of the upper portion of the cylinder barrel 60
- the second piston 92 is normally established in a contact position with the lower stop 88 .
- pressure P 1 on the lower side 96 of the second piston 92 is normally less than the pressure P 2 on the upper side 94 of the second piston 92 .
- a tensioner unit 128 similar to the tensioner unit 28 described with respect to FIG. 3 can be modified to remove second piston 92 from bore 76 of piston rod 32 .
- the piston inner bore 176 also interfaces and is in communication through its lower aperture 164 with hydraulic fluid in the cylinder barrel 160 .
- the pressure and any gas volume within a bore 176 of piston rod 132 is that of the primary accumulator 152 .
- the gas volume contained within main body 130 and any gas volume contained in piston rod 132 combine to form the primary accumulator gas volume Vg 1 .
- the amount of hydraulic fluid entering the piston assembly inner bore 176 adjacent its lower side is directly dependent upon gas pressure P 1 within the primary accumulator 152 , which is directly dependent upon stroke position of the piston rod 132 .
- FIG. 6 depicts a gas volume in the bore 176 of piston rod 132
- piston rod 132 may be filled entirely with part of the hydraulic volume of the primary accumulator 152 .
- bore 176 at for example aperture 174 , may be capped so that gas volume Vg 1 is contained entirely within main body 130 .
- optional features, such as upper and lower stops, 86 , 88 , described with respect to FIG. 3 are unnecessary. If installed, however, they do not affect the functional operation of the embodiment as configured and shown in FIG. 6 .
- the tensioner unit 128 includes a secondary accumulator 121 having housing 101 , separate from the cylinder barrel 160 , piston rod 132 , and main body 130 , which interfaces and is in fluid communication through its aperture 103 with primary accumulator hydraulic fluid Vh 1 (or gas Vg 1 ) either in the cylinder barrel 160 , piston rod 132 , or main body 130 (as shown).
- primary accumulator hydraulic fluid Vh 1 or gas Vg 1
- either cylinder barrel 160 , piston rod 132 , or main body 130 can have an aperture 105 and a fluid connection assembly 107 , as known and understood by those skilled in the art, to be connected to the aperture 103 of the secondary accumulator housing 101 .
- the secondary accumulator housing 101 is in the form of an external cylinder having an inner bore 109 .
- the secondary accumulator housing 101 includes a fluid separator in the form of a floating piston 111 .
- the inner bore 109 encloses the floating piston 111 .
- the floating piston 111 has an upper and lower surface 113 , 115 , and a diameter that is substantially equal to the diameter of the secondary accumulator housing inner bore 109 .
- the floating piston 111 can include pressure seals that slidingly engage the inner bore 109 .
- the floating piston upper surface 113 in combination with the secondary accumulator housing inner bore 109 form an enclosure, which along with a gas volume Vg 2 and a hydraulic volume Vh 2 , sealingly contained on the upper side 113 of the floating piston 111 , define secondary accumulator 121 having a gas pressure P 2 .
- the lower side 115 of the floating piston 111 in combination with the secondary accumulator housing inner bore 109 form an additional portion of the primary accumulator 152 .
- the secondary accumulator housing inner bore 109 includes a set of stops 123 , 125 .
- Retraction stops 123 are fixedly attached and form a protrusion to define a maximum upper travel limit of the floating piston 111 and ensure secondary accumulator 121 integrity.
- Extension stops 125 are formed within the secondary accumulator housing inner bore 109 .
- the floating piston 111 rests against extension stops 125 .
- the loads occurring during a retraction of the piston rod 32 are reduced due to the implementation of the floating piston 111 within the secondary accumulator housing 101 .
- either the primary accumulator 152 or the secondary accumulator 121 may include charging connections (not shown) to permit intermittent or continuous charging of both the gas volumes Vg 1 , Vg 2 , and hydraulic volumes Vh 1 , Vh 2 , from an external pressure source (not shown).
- the secondary accumulator 121 may include an interface (not shown) with another external accumulator (not shown) to provide added gas volume.
- a tensioner unit 228 similar to the tensioner unit 128 described with respect to FIG. 6 can be modified to either cap lower end 164 of cylinder barrel 160 and/or remove lower fluid aperture channel extension 168 , or, as shown in FIG. 7 , cap channel extension 268 with cap 269 .
- the main body 230 in this embodiment, if implemented, generally functions to provide protection and to provide an attachment point to a supported structure.
- the piston inner bore 276 interfaces and is in communication through its lower aperture 274 with hydraulic fluid in bore 266 of the cylinder barrel 260 .
- the amount of hydraulic fluid entering the piston assembly inner bore 276 adjacent its lower side is directly dependent upon gas pressure P 1 within the primary accumulator 252 , which is directly dependent upon stroke position of piston 272 and piston rod 232 .
- the gas volume contained within the piston rod 232 solely forms the primary accumulator gas volume Vg 1 .
- the tensioner unit 228 also includes secondary accumulator 121 having housing 101 , separate from the cylinder barrel 260 , piston rod 232 , and main body 230 (if so configured), which interfaces and is in fluid communication through its aperture 103 with primary accumulator hydraulic fluid Vh 1 in the cylinder barrel 260 (as shown).
- cylinder barrel 260 has aperture 205 fluidly connected to fluid connection assembly 207 and to aperture 103 of the secondary accumulator housing 101 .
- the secondary accumulator housing 101 also includes a fluid separator in the form of a floating piston 111 .
- the inner bore 109 encloses the floating piston 111 .
- the floating piston 111 has an upper and lower surface 113 , 115 , and a diameter that is substantially equal to the diameter of the secondary accumulator housing inner bore 109 .
- the floating piston 111 can include pressure seals that slidingly engage the inner bore 109 .
- the floating piston upper surface 113 in combination with the secondary accumulator housing inner bore 109 form an enclosure, which along with a gas volume Vg 2 and a hydraulic volume Vh 2 , sealingly contained on the upper side 113 of the floating piston 111 , define a secondary accumulator 121 having a gas pressure P 2 .
- the lower side 115 of the floating piston 111 in combination with the secondary accumulator housing inner bore 109 form an additional portion of the primary accumulator 252 .
- a tensioner unit 328 similar to the tensioner unit 128 described with respect to FIG. 6 can be modified to either remove inner barrel 160 or to cap the lower end 164 of cylinder barrel 160 and remove the main body (tubular housing) 130 and channel extension 168 .
- the diameter of the first piston 172 can be modified so that the outer diameter of piston 372 is substantially equivalent to the inner diameter of the axial inner bore 358 of the main body or barrel 330 .
- back annulus 378 performs the same function described above and interfaces with the bore 358 of main body 330 instead of bore 166 ( FIG. 6 ) of cylinder barrel 160 .
- the piston inner bore 376 interfaces and is in communication through its lower aperture 374 with hydraulic fluid in the barrel housing the piston rod 332 .
- the amount of hydraulic fluid entering the piston assembly inner bore 376 adjacent its lower side is directly dependent upon gas pressure P 1 within the primary accumulator 352 , which is directly dependent upon stroke position of piston 372 and piston rod 332 .
- the gas volume contained within the piston rod 332 again solely forms the primary accumulator gas volume Vg 1 .
- the tensioner unit 328 can include secondary accumulator 121 having housing 101 , separate from either the main body (bore) 330 and piston rod 332 , which interfaces and is in fluid communication through its aperture 103 with primary accumulator hydraulic fluid Vh 1 in the main body 330 .
- the main body 330 has aperture 305 fluidly connected to a fluid connection assembly 307 and to aperture 103 of the secondary accumulator housing 101 .
- the secondary accumulator housing 101 also includes a fluid separator in the form of a floating piston 111 , which along with secondary accumulator housing 101 forms an enclosure containing a gas volume Vg 2 and hydraulic volume Vh 2 , which define a secondary accumulator 121 , as previously described, in detail, with respect to the embodiments shown in FIGS. 6 and FIG. 7 .
- FIGS. 7 and 8 not only depict a possible position for a hydraulic Vh 1 tap (aperture 305 ) but also a possible position of a gas Vg 1 tap in the piston rod 332 where the secondary accumulator housing and is configured in the form of an external gas accumulator (described later).
- FIGS. 3-8 depict the housing for a secondary accumulator in the form of either a piston rod 32 having inner bore 76 ( FIGS. 3-5 ) or secondary accumulator housing 101 having inner bore 109 and containing within a fluid separator in the form of a floating piston 92 , 111 , sealingly engaging the inner bore 76 , 109 , respectively ( FIGS. 6-8 ).
- the floating piston 111 sealingly and slidingly engages inner bore 109 of secondary accumulator housing 101 and functions in a similar manner as floating piston 92 , described with respect to FIGS. 3-5 (previously described in detail).
- Alternative embodiments of the fluid separator in the secondary accumulator are, however, within the scope of the present invention.
- the floating piston 111 ( FIGS. 6-8 ) can be replaced by a bladder 211 that sealingly engages inner bore 209 of secondary accumulator housing 201 in a fixed position.
- upper surface 213 of the bladder 211 in combination with the secondary accumulator housing inner bore 209 form an enclosure, which along with a gas volume Vg 2 sealingly contained on the upper side 213 of the bladder 211 , define a secondary accumulator 221 having a gas pressure P 2 .
- the lower side 215 of the bladder 211 in combination with the secondary accumulator housing inner bore 209 form an additional portion of the primary accumulator through aperture 203 .
- bladder 211 is selected to “balloon” when pressure P 1 of the primary accumulator equals or exceeds pressure P 2 of the secondary accumulator.
- Hydraulic volume Vh 1 having pressure P 1 serves to compress bladder 211 at a preselected pressure P 2 , which, in turn, serves to compress the secondary accumulator gas volume Vg 2 to substantially the same extent as that of the hydraulic volume Vh 1 having pressure P 1 compresses primary accumulator gas volume Vg 1 .
- This “ballooning effect” results in functionally combining the gas volume of the primary accumulator Vg 1 and with the gas volume Vg 2 of the secondary accumulator when the pressure P 1 of the primary accumulator equals or exceeds pressure P 2 of the secondary accumulator.
- valve arrangement 311 typically in the form of a pilot valve, has a first fluid connection assembly 343 in fluid communication with pressurized fluid in the primary accumulator through an aperture 105 ( FIG. 10 ).
- the valve arrangement 331 In operation, as primary accumulator pressure P 1 equals or exceeds secondary accumulator pressure P 2 , the valve arrangement 331 allows a portion of hydraulic volume Vh 1 to enter the secondary accumulator and compress the secondary accumulator gas volume Vg 2 to substantially the same extent the hydraulic volume Vh 1 having pressure P 1 compresses primary accumulator gas volume Vg 1 .
- This “effect” results to combine the gas volume of the primary accumulator Vg 1 and with the gas volume Vg 2 of the secondary accumulator when the pressure P 1 of the primary accumulator equals or exceeds pressure P 2 of the secondary accumulator. This produces an increased total gas volume VgT which serves to reduce maximum tension and stiffness during a downstroke of the piston rod.
- the valve arrangement 311 allows substantially the same amount of hydraulic fluid from the primary accumulator hydraulic volume Vh 1 equivalent to the amount that entered the secondary accumulator hydraulic volume Vh 2 to be returned through the valve arrangement 311 by the expanding secondary accumulator gas volume Vg 2 .
- the primary accumulator pressure P 1 decreases below the secondary accumulator preset pressure P 2
- the two hydraulic volumes Vh 1 , Vh 2 are isolated from each other by valve arrangement 311 and the total equivalent gas volume VgT of the tensioner unit is that of the primary accumulator gas volume Vg 1 .
- FIGS. 3-8 and described above in detail depict a housing for a secondary accumulator combined with a fluid separator either in the form of a piston, bladder, or valve arrangement, functionally engaged through use of a primary accumulator hydraulic volume Vh 1 .
- a fluid separator either in the form of a piston, bladder, or valve arrangement
- Vh 1 a primary accumulator hydraulic volume
- FIGS. 6-8 little modification to those embodiments need be necessary in order to provide a secondary accumulator which is functionally engaged entirely through use of a gas such as primary accumulator gas volume Vg 1 .
- FIGS. 11-15 shown is the implementation of a tensioner unit 428 , similar to that described with reference to FIG. 7 , having three variations of a secondary accumulator in the form of the gas accumulator.
- the tensioner unit 428 can have secondary accumulator housing 401 positioned in fluid (gas) communication with either of the previously described embodiments primary accumulator gas volume Vg 1 .
- aperture 405 can be located in piston rod 432 to provide primary accumulator pressure P 1 to either of the embodiments of a fluid separator, described above.
- the floating piston 411 performs the same function as floating piston 111 as described with respect to FIG.
- the seals used to seal floating piston 411 in inner bore 409 of the secondary accumulator housing 401 are gas seals, otherwise the configuration within secondary accumulator housing 401 can be substantially the same as that shown in FIGS. 6-8 .
- the first piston 472 is established in the vicinity of the upper portion of the cylinder barrel 460 , and the floating piston 411 is normally established in a contact position with the lower stop 425 .
- pressure P 1 on the lower side 415 of the floating piston 411 is normally less than the pressure P 2 on the upper side 413 of the floating piston 411 .
- the first piston 472 is established in some mid-range position of the cylinder barrel 460 , and the floating piston 411 is still normally established in a contact position with the lower stop 425 .
- pressure P 1 on the lower side 415 of the floating piston 411 is still normally less than the pressure P 2 on the upper side 413 of the floating piston 411 but with a decreased pressure differential (P 2 -P 1 ) maintaining that position.
- the total effective gas volume VgT is maintained substantially at that volume of the primary accumulator Vg 1 .
- tension increases at a sufficient rate to provide sufficient support to the supported system.
- the floating piston 411 ( FIGS. 11-13 ) can be replaced by a bladder 511 that sealingly engages inner bore 509 of secondary accumulator housing 501 in a fixed position.
- the gas volume contained within the bore 476 of piston rod 432 , lower side 515 of the bladder 511 in combination with the secondary accumulator housing inner bore 509 , and fluid connection assembly 507 connected to aperture 503 combine to form a primary accumulator having the primary accumulator gas volume Vg 1 .
- upper surface 513 of the bladder 511 in combination with the secondary accumulator housing inner bore 509 form an enclosure, which along with a gas volume Vg 2 sealingly contained on the upper side 513 of the bladder 511 , define a secondary accumulator 521 having a gas pressure P 2 .
- the second piston 92 FIGS. 3-5
- bladder 511 is selected to “balloon” when pressure P 1 of the primary accumulator equals or exceeds pressure P 2 of the secondary accumulator.
- gas volume Vg 1 serves to compress bladder 511 at a preselected pressure P 2 , which, in turn, serves to compress the secondary accumulator gas volume Vg 2 to relatively the same extent as that hydraulic volume Vh 1 having pressure P 1 compresses the portion of the primary accumulator gas volume Vg 1 within bore 476 of piston rod 432 .
- the gas volumes Vg 1 , Vg 2 functionally combine to produce an increased total gas volume VgT which serves to reduce maximum tension and stiffness during a downstroke of the piston rod 432 .
- the primary accumulator pressure P 1 is again reduced below the preset secondary accumulator pressure P 2 , the total effective gas volume VgT returns to that of the primary accumulator gas volume Vg 1 , and stiffnesses to the supported unit is increased.
- valve arrangement 611 typically in the form of a pilot valve, has a first fluid connection assembly 643 in fluid communication with pressurized fluid in the primary accumulator through aperture 405 positioned to access primary accumulator gas volume Vg 2 , and a second fluid connection assembly 645 in fluid communication with the pressurized fluid contained within secondary accumulator housing 601 through aperture 603 to intermittently connect pressurized fluid in the primary accumulator with pressurized fluid in the secondary accumulator housing when pressure P 1 in the primary accumulator pressure P 1 equals or exceeds the preselected pressure P 2 of the secondary accumulator.
- the bore 609 of secondary accumulator housing 601 contains gas volume Vg 2 only which, in combination with the second fluid connection assembly 645 of the valve arrangement 611 , defines the secondary accumulator 621 .
- the valve arrangement 611 In operation, as primary accumulator pressure P 1 equals or exceeds secondary accumulator pressure P 2 , the valve arrangement 611 allows a portion of gas volume Vg 1 to enter the secondary accumulator and compress the secondary accumulator gas volume Vg 2 to substantially the same extent the gas volume Vg 1 is compressed. This “effect” results to combine the gas volume of the primary accumulator Vg 1 and with the gas volume Vg 2 of the secondary accumulator when the pressure P 1 of the primary accumulator equals or exceeds pressure P 2 of the secondary accumulator. This produces an increased total gas volume VgT which serves to reduce maximum tension and stiffness during a downstroke of the piston rod 432 .
- the valve arrangement 611 allows substantially the same amount of gas volume that entered the secondary accumulator to be returned through the valve arrangement 611 by the expanding secondary accumulator gas volume Vg 2 .
- the two gas volumes Vg 1 , Vg 2 are isolated from each other by valve arrangement 611 and the total equivalent gas volume VgT of the tensioner unit is that of the primary accumulator gas volume Vg 1 .
- a tensioner unit 528 similar to the tensioner unit 128 ( FIG. 6 ) is modified to prevent primary accumulator hydraulic volume Vh 1 or primary accumulator gas volume Vg 1 from entering either piston 572 , piston rod 532 , or both.
- This embodiment can interface with either of the secondary accumulators described with respect to FIGS. 6-15 .
- the primary accumulator includes the inner bore of the main body (barrel) 530 and the lower surface 582 of piston 572 along with the fluid connection assembly and the primary accumulator side of the fluid separator, according to the type of secondary accumulator selected.
- aperture 505 is positioned in the main body 530 , above the maximum hydraulic volume fluid line (not shown) corresponding to the level of the primary accumulator hydraulic volume Vh 1 within the main body 530 that is external to the cylinder barrel 560 and reached when piston 572 is in full downstroke.
- Primary accumulator hydraulic volume Vg 1 interfaces with the fluid separator of the selected secondary accumulator to effectively combine the primary accumulator gas volume Vg 1 with the selected secondary accumulator gas volume Vg 2 .
- aperture 505 is positioned below the minimum hydraulic volume fluid line (not shown) corresponding to the level of the hydraulic volume Vh 1 within the main body 530 when piston 572 is in full up-stroke.
- the primary accumulator hydraulic volume Vh 1 interfaces with the fluid separator of the selected secondary accumulator to effectively combine the primary accumulator gas volume Vg 1 with the selected secondary accumulator gas volume Vg 2 .
- an alternative embodiment of the present invention includes a pull-type hydro-pneumatic tensioner unit 628 having a primary accumulator housing 601 and a secondary accumulator housing including those described with respect to FIGS. 6 , 9 - 11 , 14 , or 15 .
- a piston 672 similar to the one described in FIG. 16 moves axially within main body (barrel) 630 having inner bore 666 .
- the piston 672 has a piston rod 632 extending from the lower side 682 of piston 672 , the piston rod extends through a piston rod aperture 662 and through high-pressure seals associated with the aperture 662 .
- the piston 672 also includes high-pressure seals 690 .
- the combination forms an enclosure of varying size depending upon primary accumulator pressure P 1 and stroke position of the piston rod 632 .
- the diameter of the piston 672 is substantially equivalent to the diameter of the inner bore 666 of main body 630
- the diameter of the piston rod 632 is preferably substantially equivalent to the inner diameter of the diameter of the piston rod aperture 662 .
- the volume formed between the upper side 684 of the piston 672 and the inner bore 666 of the main body 630 forms a low-pressure annulus that is preferably vented to the atmosphere.
- the volume formed between the lower side 682 of the piston 672 and the main body inner bore 666 forms a portion of the primary accumulator 652 having a portion of the primary accumulator hydraulic volume Vh 1 .
- the main body 630 also includes an aperture 605 located adjacent the lower end of the main body to provide fluid communication between the main body portion of the primary accumulator and primary accumulator housing 601 .
- the primary accumulator housing 601 preferably takes the form of an external cylinder or barrel.
- the primary accumulator housing includes aperture 603 in fluid communication with main body 630 through a fluid connection assembly 607 connected between aperture 603 of the primary accumulator housing 601 and aperture 605 of the main body 630 .
- the bore 609 of the primary accumulator housing 601 includes a portion of the primary accumulator hydraulic volume Vh 1 .
- the bore 609 of the primary accumulator housing 601 also includes at least a portion of the primary accumulator gas volume Vg 1 , depending on the configuration of the selected secondary accumulator.
- the amount of primary accumulator hydraulic volume Vh 1 is dependent upon primary accumulator pressure P 1 and stroke position of piston 672 .
- the tensioner unit 628 can at least interface with either of the secondary accumulators described with respect to FIGS. 6-15 .
- the primary accumulator housing 601 and secondary accumulator housing 101 are in fluid communication through a fluid connection assembly 608 connected to aperture 602 of the primary accumulator housing 601 and aperture 103 of the secondary accumulator housing 101 .
- the primary accumulator 652 includes the inner bore of the main body (barrel) 630 and the lower surface 682 of piston 672 , fluid connection assembly 607 , the bore 609 of the primary accumulator housing 601 , the fluid connection assembly 608 , and the bore 109 of secondary accumulator housing 101 in combination with the primary accumulator side of the fluid separator according to the type of secondary accumulator configuration selected.
- the secondary accumulator 121 includes the inner bore 109 of the secondary accumulator housing 101 and the secondary accumulator side of the fluid separator according to the type of secondary accumulator configuration selected.
- the configuration depicted in FIG. 17 includes a hydraulic-type secondary accumulator similar to that described with respect to FIG. 6 , whereby primary accumulator hydraulic volume Vh 1 provides the impetus to functionally combine the primary accumulator gas volume Vg 1 with the secondary accumulator gas volume Vg 2 to provide the tensioner unit 628 an effective total gas volume VgT substantially equivalent to that of the sum of the primary accumulator gas volume Vg 1 and secondary accumulator gas volume. If a gas-type accumulator is used, such as that described with respect to FIG. 14 , the fluid connection assembly 608 would instead be connected to the upper aperture 602 of primary accumulator housing 601 in communication with the primary accumulator gas volume Vg 1 .
- the maximum amount of primary accumulator hydraulic volume Vh 1 can be configured under expected extreme operating conditions not to exceed a level within the bore 609 of the primary accumulator housing 601 to that of communicating with the upper aperture 602 .
- the primary accumulator gas volume Vg 1 provides the impetus to functionally combine the primary accumulator gas volume Vg 1 with the secondary accumulator gas volume Vg 2 to provide the tensioner unit 628 an effective total gas volume VgT substantially equivalent to that of the sum of the primary accumulator gas volume Vg 1 and secondary accumulator gas volume Vg 2 .
- the hydro-pneumatic riser tensioner units provide high nominal stiffness while limiting peak loads at extreme extended and retracted positions.
- the telescopic piston rod of the riser tensioner unit incorporates the bore or annulus of the piston rod as a secondary accumulator and incorporates a floating piston within the annulus of the piston rod.
- a separate housing having the bore or annulus is used to form the secondary accumulator.
- the total effective gas volume of the unit is increased by that of the secondary accumulator.
- the increased effective gas volume results in the load on the riser system increasing at a much lower rate and a reduced peak load.
- the increased total effective gas volume results in a slower decrease in pressure and results in limiting the minimum tension applied to the riser system.
- a smaller primary accumulator may be utilized.
- the tensioner unit can be attached to the top plate at an intermediate point along the barrel rather than at the upper end as shown in figures.
- the tensioner unit can be connected to the support module lower support frame at an intermediate point along the barrel rather than at the lower end as shown in the figures.
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Mining & Mineral Resources (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Fluid Mechanics (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Supply Devices, Intensifiers, Converters, And Telemotors (AREA)
- Devices For Conveying Motion By Means Of Endless Flexible Members (AREA)
Abstract
A hydro-pneumatic tensioner includes a barrel having an inner bore and a pressurized fluid contained within to form at least part of a primary accumulator having a preset volume of gas at a preselected pressure. A piston having a piston rod extending from an aperture in the barrel is slidably carried in the bore of the barrel and is in communication with the pressurized fluid and positioned to increase the fluid pressure when the piston strokes in the direction of the pressurized fluid. A secondary accumulator also has a preset volume of gas at a preselected pressure. A fluid separator maintains functional separation of the fluid volumes of the primary and secondary accumulators when the primary accumulator pressure is less than a preselected secondary accumulator pressure. The fluid separator allows functional combining of the fluid volumes of the primary and secondary accumulators when the primary accumulator pressure equals or is greater than the preselected secondary accumulator pressure.
Description
- 1. Field of the Invention
- This invention relates to tensioning of seabed-to-vessel marine risers. More particularly, this invention relates to tensioning the marine risers with a plurality of pneumatic or hydraulic cylinders.
- 2. Brief Description of the Related Art
- A problem presented by offshore hydrocarbon drilling and producing operations conducted from a floating platform is the need to establish a sealed fluid pathway between each borehole or well at the ocean floor and the work deck of the platform at the ocean surface. A riser typically provides this sealed fluid pathway. In drilling operations, the drill string extends through a drilling riser, the drilling riser serving to protect the drill string and to provide a return pathway outside the drill string for drilling fluids. In producing operations, a production riser is used to provide a pathway for the transmission of oil and gas to the work deck.
- The riser is projected up through an opening referred to as a moon pool in the vessel to working equipment and connections proximate an operational floor on the vessel. A riser pipe operating on the floating vessel in water depths greater than about 200 feet (34.72 meters) can buckle under the influence of its own weight and the weight of drilling fluid contained within the riser if it is not partially or completely supported. For floating platforms, a special piece of equipment known as a “riser tensioner” is required to maintain each riser within a range of safe operating tensions as the work deck moves relative to the upper portion of the riser. If a portion of the riser is permitted to go into compression, it could be damaged by buckling or by bending and colliding with adjacent risers. It is also necessary to ensure that the riser is not over-tensioned when the vessel hull moves to an extreme lateral position under extreme wave conditions or when ocean currents exert a significant side loading on the riser.
- A tension leg platform (“TLP”) is a type of marine structure having a buoyant hull secured to a foundation on the ocean floor by a set of tethers. The tethers are each attached to the buoyant hull so that the hull is maintained at a significantly greater draft than it would assume if free floating. The resultant buoyant force of the hull exerts an upward loading on the tethers, maintaining them in tension. The tensioned tethers limit vertical motion of the hull, thus substantially restraining it from pitch, roll and heave motions induced by waves, currents and wind. However, unlike conventional platforms which are rigidly attached to the subsea floor, TLPs are not designed to resist horizontal forces induced by waves.
- The marine risers have been tensioned in various manners, including the use of counterweights and pneumatic spring systems. The counterweight was the first technique utilized to apply tension to the top of the marine riser. The weight was hung from a wire rope which was run up through wire rope sheaves and down to an upper portion of the riser pipe. The tension was equal to the counterweight and therefore was practicable only for shallow water that required low tension.
- The pneumatic spring systems replaced the counterweight systems as deeper water drilling evolved. The pneumatic tensioning devices stored energy in the form of compressed air to apply tension to the top of the riser through wire ropes. The pneumatic tensioning devices typically involved the use of cylinders from which a piston rod was extended, the piston rod having a sheave engaged by the wire rope to be tensioned. The fluid within the hydraulic cylinder was thereby compressed into an accumulator. The cylinder and the accumulator were normally supported by support structures on the floating vessel.
- Many tensioner systems in use today act as oil-damped pneumatic springs. A large gas supply keeps a nearly constant pressure above the oil in a gas-oil accumulator. The oil then provides pressure to the face of the piston. As the vessel heaves, the piston moves up and down against a relatively constant force and the tension lines maintain a relatively constant pull.
- Many riser tensioners today utilize hydraulically actuated cylinders with pneumatic pressure accumulators to provide the force necessary to maintain the upper portion of the riser within a preselected range of operating tensions. One implementation is accomplished by the use of sheaves attached to the buoyant drilling structure whereby tensioning cables are run over the sheaves and attached to the riser so that the riser is supported by one end of the tensioning cables. The other end of each tensioning cable is connected to a piston of a hydraulic cylinder. The hydraulic cylinders are connected to a relatively large accumulator which maintains the load applied by the cylinders at a relatively constant level over the full range of travel of the pistons. Thus, as the platform moves vertically, the pistons stroke to maintain a relatively constant upward loading on the riser.
- Another type of riser tensioner typically used on TLPs also uses a pneumatically pressurized fluid accumulator but eliminates the cables and sheaves used in earlier riser tensioners. Gas and oil accumulators are connected to the cylinders to control the stroke of pistons. The piston rods are directly attached to a riser tensioning ring which supports the riser.
- Both classes of riser tensioning systems described generally require separate and relatively large accumulators to maintain the load applied by the cylinders with an acceptable range. Accordingly, it can be appreciated that there still exists a need for an improved riser tensioner system which provides high-capacity tension and provides for limiting peak loads while incorporating high nominal stiffness, and that does not require an excessively large accumulator.
- In view of the foregoing, an embodiment of the present invention advantageously provides a tensioner unit including a barrel having a bore with pressurized fluid contained within. The barrel forms at least part of a primary accumulator having a preset volume of gas Vg1 at pressure P1. The barrel of the tensioner unit also includes an aperture to allow extension and retraction of a piston rod. The tensioner unit also includes a piston slidably carried in the bore of the barrel. The piston has a piston rod that extends from one side of the piston and through an aperture in the barrel. The piston has one of its sides in communication with the pressurized fluid, and is so positioned to increase the pressure P1 of the primary accumulator when the piston strokes in the direction of the pressurized fluid. The tensioner unit also includes a secondary accumulator housing having a bore which forms at least part of a secondary accumulator having a preset volume of gas Vg2 at pressure P2. The tensioner unit also includes a fluid separator positioned between the primary and secondary accumulators to maintain functional separation of fluid volumes of the primary and secondary accumulators when the primary accumulator pressure P1 is less than the secondary accumulator pressure P2. The fluid separator also allows functional combining of the fluid volumes of the primary and secondary accumulators when the primary accumulator pressure P1 is greater than or equal to the secondary accumulator pressure P2. The tensioner unit is configured so that when the primary accumulator pressure P1 is less than the secondary accumulator pressure P2, the effective total gas volume VgT available to the tensioner to maintain tension on a supported system, such as a riser system, is substantially equivalent to the primary accumulator gas volume Vg1. Correspondingly, when the pressure P1 is greater than or equal to the secondary accumulator pressure P2, the effective total gas volume VgT available to the tensioner to maintain tension on the supported system equals the sum of the primary accumulator gas volume Vg1 plus the secondary accumulator gas volume Vg2. This provides for reduced stiffness and reduced maximum tension applied by the tensioner unit to a supported system when the system is directing a maximum load on the tensioner unit.
- So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.
-
FIG. 1 is a perspective view of a hydro-pneumatic tensioner system in accordance with the invention. -
FIG. 2 is an enlarged perspective view of one of the hydro-pneumatic tensioner units of the hydro-pneumatic tensioner system ofFIG. 1 . -
FIG. 3 is a schematic view of the hydro-pneumatic tensioner unit having a first piston enclosing a second piston shown with the first piston in an extended position. -
FIG. 4 is a schematic view of the hydro-pneumatic tensioner unit ofFIG. 3 , shown a mid-point position. -
FIG. 5 is a schematic view of the hydro-pneumatic tensioner unit ofFIG. 3 , shown a retracted position. -
FIG. 6 is a schematic view of an embodiment of a hydro-pneumatic tensioner unit, including an internal cylinder barrel connected to an external cylinder having a second piston. -
FIG. 7 is a schematic view of a variation ofFIG. 6 . -
FIG. 8 is a schematic view of a variation ofFIG. 6 having no internal cylinder barrel. -
FIG. 9 is a schematic view of an external cylinder for use with the tensioner unit ofFigure 6 , having a bladder which forms an enclosure containing a gas volume Vg2 and a hydraulic volume Vh1. -
FIG. 10 is a schematic view of an external cylinder for use with the tensioner unit ofFIG. 6 , having a pilot valve interface that forms an enclosure containing a gas volume Vg2 and a hydraulic volume Vh2. -
FIG. 11 is a schematic view of another embodiment of a hydro-pneumatic tensioner unit, having a first piston connected to an external cylinder having a second piston, shown with the first piston in an extended position. -
FIG. 12 is a schematic view of the hydro-pneumatic tensioner unit ofFIG. 11 , shown with the first piston in a mid-point position. -
FIG. 13 is a schematic view of the hydro-pneumatic tensioner unit ofFIG. 11 , shown with the first piston in a retracted position. -
FIG. 14 is a schematic view of an external cylinder for use with the tensioner unit ofFIG. 11 , having a bladder which forms an enclosure containing a gas volume Vg2. -
FIG. 15 is a schematic view of an external cylinder for use with the tensioner unit ofFIG. 11 , having a pilot valve interface that forms an enclosure containing a gas volume Vg2. -
FIG. 16 is a schematic view of a variation ofFIG. 7 . -
FIG. 17 is a schematic view of a pull-type hydro-pneumatic tensioner unit having a first external cylinder hydraulically connected to the hydraulic side of a first piston. - The present invention will now be described more fully hereinafter with reference to the accompanying drawings which illustrate embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and the prime notation, if used, indicates similar elements in alternative embodiments.
- Referring to
FIG. 1 , shown is a hydro-pneumaticriser tensioner system 20 for maintaining a riser system within a range of safe operating tensions as a work deck or platform moves relative to the upper portion of the riser system. Thesystem 20 advantageously provides a methodology for incorporating high nominal stiffness while limiting peak loads at extreme up and down strokes. More specifically, thesystem 20 includes ariser system 22, extending between a floating vessel having anoperational platform - The
riser system 22 is supported in tension at its upper end to prevent theriser system 22 from buckling due to its own weight. The upward tension is maintained within acceptable limits over a typical platform deviation range by the hydro-pneumaticriser tensioner system 20. Theriser tensioner system 20, discussed in detail below, includes a plurality of hydro-pneumatic tensioner units 28. Thetensioner units 28 include a main body orhousing 30, typically tubular shaped, stationarily located between support frames 24, 26, of asupport module 23. Eachtensioner unit 28 includes a hydro-pneumatic ramtensioner piston rod 32 attached at its upper end to a riser tensional mount ortop plate 34, which includes ariser tensional ring 36. Theriser tensional ring 36 engages a tension joint 38 of theriser system 22. The hydro-pneumatic ramtensioner piston rod 32 telescopes relative tohousing 30 in response to movement of the operational platform. - Referring now to
FIGS. 1 and 2 , in a typical implementation of the hydro-pneumatic tensioner system 20, typically each hydro-pneumatic tensioner unit upper section is attached to thetop plate 34 and the lower section is connected to the support modulelower support frame 24, with eachunit 28 protruding through anaperture 27 in theupper support frame 26 of thesupport module 23. In this implementation, theriser system 22 includes ariser conductor 42 androller assemblies 44, on lower and upper support frames 24, 26, of thesupport module 23 to provide for axial movement of thesupport module 23 with respect to theriser system 22. - In this embodiment, as the
support module 23 shifts position with respect to theriser system 22, theriser system 22 slides up and down through theroller assemblies 44 and is engaged with tension from the hydro-pneumaticriser tensioner system 20 through thetensioner units 28 applying tension to thetop plate 34. Thetop plate 34 via the mountingring 36 translates the tension from thetensioner units 28 to the tension joint 38 of theriser system 22. - Referring now to
FIGS. 2 and 3 , as stated, the hydro-pneumaticriser tensioner system 20 includes a plurality of hydro-pneumatic tensioner units 28. Each of theunits 28 has an upper end and a lower end. The upper end can include arod end cap 46. Therod end cap 46, and thus the upper end of eachunit 28 can be connected to the top plate 34 (FIG. 1 ) to provide the requisite tension to the tension ring 36 (FIG. 1 ) and thus to theriser system 22. Therod end cap 46 is shown as threadingly attached to a shoulder orflange 48 formed of or attached to the main body ofpiston rod 32, using a plurality ofbolts 50, each affixed in a bolt cavity (not shown), however, any appropriate attachment or sealing methodology as known by those skilled in the art is appropriate and within the scope of the invention. In an embodiment, the lower end of thetension unit 28 is connected to the operational marine platform (not shown). In another embodiment, the lower end of theunits 28 is connected to a lower platform orframe 24 of a hydro-pneumatic tensioner support module 23 (FIG. 1 ). - Referring to
FIG. 3 for illustrative purposes only, generic to embodiments, described below, thetensioner unit 28 includes a barrel such asinner cylinder barrel 60 ormain body 30 each having a bore and an aperture on at least one end and having a pressurized fluid contained within. The barrel forms at least part of a primary accumulator having a preset volume of gas Vg1 at pressure P1. A piston such aspiston 72 is slidably carried in the bore of the barrel. The piston has a piston rod that extends from a side of the piston and through the aperture of the barrel. Oneside 82 of thepiston 72 is in communication with the pressurized fluid. Thepiston 72 is positioned to increase pressure P1 of the primary accumulator when thepiston 72 strokes in the direction of the pressurized fluid. A secondary accumulator housing, such as thepiston rod 32 withinner bore 76 or the external housings shown inFIG. 9 or 12-15 (described later) form at least part of a secondary accumulator having a preset volume of gas Vg2 at pressure P2. A fluid separator, such as floating piston 92 (FIG. 3 ), or the bladder or valve arrangement shown inFIGS. 9-12 (described later), is positioned between the primary and secondary accumulators to maintain functional separation of fluid volumes of the primary and secondary accumulators when the primary accumulator pressure P1 is less than the secondary accumulator pressure P2, and to allow functional combining of the fluid volumes of the primary and secondary accumulators when the primary accumulator pressure P1 is greater than or equal to the secondary accumulator pressure P2. This arrangement results in an effective total gas volume VgT available to thetensioner 28 to maintain tension on a supported system, such as a riser system, to substantially equal the primary accumulator gas volume Vg1 when the primary accumulator pressure P1 is less than the secondary accumulator pressure P2, and to substantially equal the sum of the primary accumulator gas volume Vg1 plus the secondary accumulator gas volume Vg2 when the pressure P1 is greater than or equal to the secondary accumulator pressure P2. The specific details of the various embodiments implementing the above described are further introduced below. - Referring to the embodiment shown in
FIG. 3 ,tensioner unit 28 includes aprimary accumulator 52. Theprimary accumulator 52 includes an upper end having a pistonseal housing aperture 54, a lower end preferably including an endcap 56 (FIG. 2 ), and amain body 30 having anaxial bore 58, therebetween. The combination, as described, along with internal components, described below, form an enclosure. Theprimary accumulator 52 contains a gas volume Vg1 and a hydraulic volume Vh1. Also in an embodiment, the lower end cap 56 (FIG. 2 ) is threadingly connected within a lower end bore (not shown), although any appropriate attachment or seal means as known by those skilled in the art is acceptable and within the scope of the invention. The sealed enclosure of theprimary accumulator 52 forms a gas and hydraulic fluid reservoir. A charging connection (not shown) can be interfaced with themain body 30 of theaccumulator 52 to permit intermittent or continuous charging of both the gas and hydraulic volumes Vg1, Vh1, from an external pressure source (not shown). - Referring to
FIGS. 3-5 , the hydro-pneumatic riser tensioner system 20 (FIG. 1 ) also can include a stationery orinternal cylinder barrel 60 located within theprimary accumulator 52. Thecylinder barrel 60 is secured sealingly toaperture 54 ofaccumulator 52. Thecylinder barrel 60 includes an upper end having an upperpiston rod aperture 62, a lower end having a lowerfluid inlet aperture 64, and a main body having an axial inner bore 66, therebetween. In the preferred embodiment, thecylinder barrel 60 includes a lower fluidaperture channel extension 68 which protrudes to a position adjacent the lower end ofprimary accumulator 52, and provides for fluid communication between the cylindrical barrel inner bore 66 and primary accumulator hydraulic volume Vh1. The length ofaperture channel extension 68 is generally formulated for the purpose of ensuring only hydraulic fluid entry into the cylinder barrelinner bore 66, not gas. The length of thechannel extension 68 may be established depending upon the operating conditions theunit 28 will be subjected to and the desired ratio of gas Vg1 to fluid Vh1. The combination, as described, along with internal components, described below, form a partial enclosure. Thecylinder barrel 60 interfaces and is thus in fluid communication through itslower aperture 68 with the primary accumulator hydraulic volume Vh1. The volume of hydraulic fluid contained within thecylinder barrel 60 is directly dependent upon the gas pressure P1 within theprimary accumulator 52 and stroke position of thetensioner piston rod 32. - The
tensioner 28 has afirst piston assembly 70 that moves axially withinbarrel 60. Thepiston assembly 70 includes a combinationfirst piston 72 andpiston rod 32. Thepiston assembly 70 also includes an upper end typically interfaced with a rod end cap 46 (FIG. 2 ), a lower end having apiston 72 including anaperture 74, and a main body therebetween including aninner bore 76. The combination, as described above and as to be described below, forms a channel which forms an enclosure of varying size depending on primary accumulator gas pressure P1 and stroke position of the risertensioner piston rod 32. In this embodiment, preferably theaperture 74 ofpiston 72 is not the same diameter asbore 76. Thepiston 72 has an outer diameter substantially equivalent to the inner diameter of the axial inner bore 66 ofcylinder barrel 60. Also, preferably, the outer diameter ofpiston rod 32 is substantially equivalent to the diameter ofpiston rod aperture 62. - The
first piston assembly 70 is slidably positioned to telescope from inside thecylinder barrel 60 to provide tension and stiffness to theriser system 22. Preferably the outer diameter ofpiston rod 32 is smaller than the inner diameter of cylinder barrelinner bore 66. This differential diameter between the first piston diameter/cylindrical barrel inner bore diameter and the piston rod main body diameter/piston rod aperture diameter forms aback annulus 78. Theback annulus 78 is preferably vented to the atmosphere or through vent lines (not shown) following an appropriate methodology as known by those skilled in the art. - The telescopic range of the
first piston 72 can be limited by stops, described below, which present an upper and lower limit for the travel of thefirst piston 72. In the configuration shown inFIGS. 3-5 , the differential diameter between thepiston rod 32 andfirst piston 72 form ashoulder 79 on the upper surface of thefirst piston 72 adjacent its outer circumference. The upper limit is the position where the first pistonupper shoulder 79 contacts thelower surface 80 of the upper end of thecylinder barrel 60. The lower limit is a position where thelower surface 82 of thefirst piston 72 contacts theupper surface 84 of the bottom of thecylinder barrel 60. - The piston assembly inner bore 76 interfaces and is in fluid communication through its
lower aperture 64 with hydraulic fluid in thecylinder barrel 60, which as previously stated is in communication with primary accumulator hydraulic volume Vh1. The volume of hydraulic fluid entering the piston assembly inner bore 76 adjacent its lower side is directly dependent upon gas pressure P1 within theprimary accumulator 52, which is directly dependent upon stroke position of thetensioner piston rod 32. Thefirst piston 72 includesseals 90 that slidably engage and seal thebore 66 ofbarrel 60. - The
first piston 72, particularly, theinner bore 76, encloses asecond piston 92 which form a housing for a secondary accumulator. Thesecond piston 92, a fluid separator, has an upper andlower surface second piston 92 is slidably carried within the piston rod inner bore 76. In the embodiment shown, thesecond piston 92 includes pressure seals that slidingly engageinner bore 76. The second pistonupper surface 94 in combination with the piston rod inner bore 76 form an enclosure, which along with a gas volume Vg2 and hydraulic volume Vh2, sealingly contained on theupper side 94 of thesecond piston 92, define asecondary accumulator 98 having a gas pressure P2. In a preferred variation, a charging connection (not shown) is located on thepiston assembly 70 to permit intermittent or continuous charging of both the gas Vg2 and hydraulic volumes Vh2 from an external pressure source (not shown), depending on the embodiment implemented. In an alternative variation, thesecondary accumulator 98 may include an interface (not shown) with an external accumulator (not shown) to provide added gas volume Vg2. AlthoughFIGS. 3-5 show use of hydraulic volumes Vh1 and Vh2, theprimary accumulator 52 andsecondary accumulator 98 can be made purely of a gas having volume Vg1 and Vg2, respectively. The use of hydraulic oil or fluid is, however, preferred in this embodiment as it reduces the requirements on the first and second piston high-pressure seals. - The first piston rod inner bore 76 can also include a set of stops, 86, 88. Preferably retraction stops 86 are fixedly attached or formed of a protrusion in a position to define the maximum upper travel limit of the
second piston 92 and ensuresecondary accumulator 98 integrity. Extension stops 88 can be formed within either theinner bore 76 of thepiston rod 72 or within or as part of thefirst piston aperture 74.FIGS. 3-5 depict the extension stop 88 as formed from part of alower surface 82 of thefirst piston 72 which effectively forms theaperture 74 into a two-stage aperture within thefirst piston 72. - Peak loads or tension on the
tensioner unit 28 occurring during a retraction and extension of thepiston rod 32 are reduced due to the implementation of floatingpiston 92 within thepiston rod 32. While the floatingpiston 92 is free-floating (not pegged against a retraction or extension stop, 86, 88), the primary accumulator pressure P1 equals the same pressure P2 as in thesecondary accumulator 98, and the total effective gas volume VgT of the unit is effectively increased by the gas volume Vg2 of thesecondary accumulator 98. The increase in gas volume provides a slower rate of increase in gas pressure P1 due to the added volume Vg2, and also reduces the peak load or tension of a given downstroke (retraction of piston rod 32). This advantageously allows for the use of asmaller tensioner unit 28. The net effect of the inclusion of the gas volume Vg2 into the total effective gas volume VgT and its deletion when pressure P1 decreases below the preselected pressure P2 is to limit the minimum tension applied to the supported system (FIG. 1 ) at full extension and to also limit the maximum tension applied at near full retraction. - The following, for illustrative purposes only, is a description of the operation of
tensioner unit 28 on riser system of 20 according to an embodiment of the present invention as depicted inFIGS. 3-5 . In operation, the hydro-pneumatic tensioner unit 28 maintains theriser system 22 within a range of safe operating tensions as a work deck or platform (not shown) moves relative to the upper portion of theriser system 22. The hydro-pneumatic tensioner system 20 ideally should be in a similar configuration to that shown inFIG. 3 . With the hydro-pneumatic tensioner system 20 properly installed, normally, thefirst piston 72 is established in the vicinity of the upper portion of thecylinder barrel 60, and thesecond piston 92 is normally established in a contact position with thelower stop 88. In this situation, pressure P1 on thelower side 96 of thesecond piston 92 is normally less than the pressure P2 on theupper side 94 of thesecond piston 92. - In a partial retraction situation, as best shown in
FIG. 4 , normally, thefirst piston 72 is established in some mid-range position of thecylinder barrel 60, and thesecond piston 92 is still normally established in a contact position with thelower stop 88. In this situation, pressure P1 on thelower side 96 of thesecond piston 92 is still normally less than the pressure P2 on theupper side 94 of thesecond piston 92 but with a decreased pressure differential (P2-P1) maintaining that position. The total effective gas volume VgT is maintained substantially at that volume of the primary accumulator Vg1. As thepiston 72 continues to stroke down (retract) tension increases at a sufficient rate to provide sufficient support to theriser system 22. - In a near full retraction situation, as best shown in
FIG. 5 , normally, in a situation where thefirst piston 72 was operating without the benefit of the addedsecond piston accumulator 98, tension would increase rapidly. Thesecond piston 92, however, having its own “charge” moves upward to maintain the two pressures P1 and P2 in substantial equilibrium unless theupper stop 86 is contacted. Thus, the implementation of thesecond piston 92, within thepiston assembly 70, results in the effective amount of gas VgT being effectively increased over that of Vg1. The increase in gas volume provides a slower rate of increase in gas pressure P1 due to the added volume and also reduces the peak load of a given downstroke (retraction of piston rod 32). - Beginning now with the
piston assembly 70 in a fully retracted position (not shown), whereby the pressure in the primary accumulator P1 may exceed that of the secondary accumulator 98 (piston 92 in contact with upper stop 86), as thepiston 72 strokes up (extends), the pressure in the primary accumulator P1 decreases until it substantially reaches the pressure of the secondary accumulator P2. At that point, the floatingpiston 92 becomes evenly loaded on either side (e.g.FIG. 5 ). As mentioned above, while the floatingpiston 92 is free-floating, the primary accumulator pressure P1 substantially equals that of the secondary accumulator P2, which results in a total effective gas volume VgT increase by the gas volume of the secondary accumulator Vg2. - Beginning at a near full retraction position, as best shown in
FIG. 5 , in an extension situation, without thesecond piston accumulator 98, tensions would decrease rapidly. Thesecond piston 92, however, having its own “charge” moves downward, maintaining the two pressures P1 and P2 in substantial equilibrium until thelower stop 88 is contacted. Thus, as stated previously, due to the implementation of asecond piston 92, within thepiston assembly 70, the effective amount of gas VgT is effectively increased. The increase in gas volume provides a slower rate of decrease in gas pressure due to the added volume. Once the primary accumulator pressure P1 decreases sufficiently, thesecond piston 92 is again established in a contact position with the lower stop 88 (e.g.FIG. 4 ). The increase in stiffness is reduced at near full retraction unless pressure P1 increases above the charging pressure of thesecondary accumulator 98. The net effect of increasing the gas volume VgT at the near full retraction positioned to decrease maximum stiffness and to limit the minimum tension applied to the riser system 22 (FIG. 1 ) at full upstroke (extension of piston rod 32). - In another embodiment of the present invention, as perhaps best shown in
FIG. 6 , atensioner unit 128 similar to thetensioner unit 28 described with respect toFIG. 3 can be modified to removesecond piston 92 frombore 76 ofpiston rod 32. In this embodiment, the pistoninner bore 176 also interfaces and is in communication through itslower aperture 164 with hydraulic fluid in thecylinder barrel 160. However, withsecond piston 92 removed, the pressure and any gas volume within abore 176 ofpiston rod 132 is that of theprimary accumulator 152. In this embodiment, the gas volume contained withinmain body 130 and any gas volume contained inpiston rod 132 combine to form the primary accumulator gas volume Vg1. The amount of hydraulic fluid entering the piston assembly inner bore 176 adjacent its lower side is directly dependent upon gas pressure P1 within theprimary accumulator 152, which is directly dependent upon stroke position of thepiston rod 132. Note, althoughFIG. 6 depicts a gas volume in thebore 176 ofpiston rod 132,piston rod 132 may be filled entirely with part of the hydraulic volume of theprimary accumulator 152. Additionally, bore 176, at forexample aperture 174, may be capped so that gas volume Vg1 is contained entirely withinmain body 130. Also note, if the structure described inFIG. 3 were used to form this embodiment, optional features, such as upper and lower stops, 86, 88, described with respect toFIG. 3 are unnecessary. If installed, however, they do not affect the functional operation of the embodiment as configured and shown inFIG. 6 . - In this embodiment, the
tensioner unit 128 includes asecondary accumulator 121 havinghousing 101, separate from thecylinder barrel 160,piston rod 132, andmain body 130, which interfaces and is in fluid communication through itsaperture 103 with primary accumulator hydraulic fluid Vh1 (or gas Vg1) either in thecylinder barrel 160,piston rod 132, or main body 130 (as shown). Correspondingly, depending on the configuration, eithercylinder barrel 160,piston rod 132, ormain body 130, can have anaperture 105 and afluid connection assembly 107, as known and understood by those skilled in the art, to be connected to theaperture 103 of thesecondary accumulator housing 101. Preferably, thesecondary accumulator housing 101 is in the form of an external cylinder having aninner bore 109. In the configuration shown inFIG. 6 , thesecondary accumulator housing 101 includes a fluid separator in the form of a floatingpiston 111. Theinner bore 109 encloses the floatingpiston 111. The floatingpiston 111 has an upper andlower surface inner bore 109. The floatingpiston 111 can include pressure seals that slidingly engage theinner bore 109. The floating pistonupper surface 113 in combination with the secondary accumulator housinginner bore 109 form an enclosure, which along with a gas volume Vg2 and a hydraulic volume Vh2, sealingly contained on theupper side 113 of the floatingpiston 111, definesecondary accumulator 121 having a gas pressure P2. Thelower side 115 of the floatingpiston 111 in combination with the secondary accumulator housinginner bore 109 form an additional portion of theprimary accumulator 152. - In the preferred configuration, the secondary accumulator housing
inner bore 109 includes a set ofstops piston 111 and ensuresecondary accumulator 121 integrity. Extension stops 125 are formed within the secondary accumulator housinginner bore 109. Under normal conditions, where pressure P2 of thesecondary accumulator 121 is greater than the pressure P1 of theprimary accumulator 152, the floatingpiston 111 rests against extension stops 125. As with the embodiment depicted inFIGS. 3-5 , the loads occurring during a retraction of thepiston rod 32 are reduced due to the implementation of the floatingpiston 111 within thesecondary accumulator housing 101. As with the embodiment described inFIG. 3 , either theprimary accumulator 152 or thesecondary accumulator 121 may include charging connections (not shown) to permit intermittent or continuous charging of both the gas volumes Vg1, Vg2, and hydraulic volumes Vh1, Vh2, from an external pressure source (not shown). In another variation, thesecondary accumulator 121 may include an interface (not shown) with another external accumulator (not shown) to provide added gas volume. - In another embodiment of the present invention, as perhaps best shown in
FIG. 7 , atensioner unit 228 similar to thetensioner unit 128 described with respect toFIG. 6 can be modified to either caplower end 164 ofcylinder barrel 160 and/or remove lower fluidaperture channel extension 168, or, as shown inFIG. 7 ,cap channel extension 268 withcap 269. Themain body 230, in this embodiment, if implemented, generally functions to provide protection and to provide an attachment point to a supported structure. As in the previous embodiment, described with respect toFIG. 6 , the pistoninner bore 276 interfaces and is in communication through itslower aperture 274 with hydraulic fluid inbore 266 of thecylinder barrel 260. The amount of hydraulic fluid entering the piston assembly inner bore 276 adjacent its lower side is directly dependent upon gas pressure P1 within theprimary accumulator 252, which is directly dependent upon stroke position ofpiston 272 andpiston rod 232. The gas volume contained within thepiston rod 232, however, in the depicted configuration, solely forms the primary accumulator gas volume Vg1. - In this embodiment, the
tensioner unit 228 also includessecondary accumulator 121 havinghousing 101, separate from thecylinder barrel 260,piston rod 232, and main body 230 (if so configured), which interfaces and is in fluid communication through itsaperture 103 with primary accumulator hydraulic fluid Vh1 in the cylinder barrel 260 (as shown). Correspondingly,cylinder barrel 260 hasaperture 205 fluidly connected tofluid connection assembly 207 and toaperture 103 of thesecondary accumulator housing 101. As described with respect to the embodiment shown inFIG. 6 , thesecondary accumulator housing 101 also includes a fluid separator in the form of a floatingpiston 111. Theinner bore 109 encloses the floatingpiston 111. The floatingpiston 111 has an upper andlower surface inner bore 109. The floatingpiston 111 can include pressure seals that slidingly engage theinner bore 109. The floating pistonupper surface 113 in combination with the secondary accumulator housinginner bore 109 form an enclosure, which along with a gas volume Vg2 and a hydraulic volume Vh2, sealingly contained on theupper side 113 of the floatingpiston 111, define asecondary accumulator 121 having a gas pressure P2. Thelower side 115 of the floatingpiston 111 in combination with the secondary accumulator housinginner bore 109 form an additional portion of theprimary accumulator 252. - In still another embodiment of the present invention, as perhaps best shown in
FIG. 8 , atensioner unit 328 similar to thetensioner unit 128 described with respect toFIG. 6 can be modified to either removeinner barrel 160 or to cap thelower end 164 ofcylinder barrel 160 and remove the main body (tubular housing) 130 andchannel extension 168. If theinner barrel 160 is removed, the diameter of the first piston 172 can be modified so that the outer diameter ofpiston 372 is substantially equivalent to the inner diameter of the axialinner bore 358 of the main body orbarrel 330. Correspondingly,back annulus 378 performs the same function described above and interfaces with thebore 358 ofmain body 330 instead of bore 166 (FIG. 6 ) ofcylinder barrel 160. - Regardless of the configuration selected, as with the previous embodiment described with respect to
FIG. 7 , the pistoninner bore 376 interfaces and is in communication through itslower aperture 374 with hydraulic fluid in the barrel housing thepiston rod 332. The amount of hydraulic fluid entering the piston assembly inner bore 376 adjacent its lower side is directly dependent upon gas pressure P1 within theprimary accumulator 352, which is directly dependent upon stroke position ofpiston 372 andpiston rod 332. The gas volume contained within thepiston rod 332, however, in the depicted configuration, again solely forms the primary accumulator gas volume Vg1. - Still referring to
FIG. 8 , thetensioner unit 328 can includesecondary accumulator 121 havinghousing 101, separate from either the main body (bore) 330 andpiston rod 332, which interfaces and is in fluid communication through itsaperture 103 with primary accumulator hydraulic fluid Vh1 in themain body 330. Correspondingly, themain body 330 hasaperture 305 fluidly connected to afluid connection assembly 307 and toaperture 103 of thesecondary accumulator housing 101. Thesecondary accumulator housing 101 also includes a fluid separator in the form of a floatingpiston 111, which along withsecondary accumulator housing 101 forms an enclosure containing a gas volume Vg2 and hydraulic volume Vh2, which define asecondary accumulator 121, as previously described, in detail, with respect to the embodiments shown in FIGS. 6 andFIG. 7 . Note,FIGS. 7 and 8 not only depict a possible position for a hydraulic Vh1 tap (aperture 305) but also a possible position of a gas Vg1 tap in thepiston rod 332 where the secondary accumulator housing and is configured in the form of an external gas accumulator (described later). - The previous embodiments, as shown in
FIGS. 3-8 and described above, depict the housing for a secondary accumulator in the form of either apiston rod 32 having inner bore 76 (FIGS. 3-5 ) orsecondary accumulator housing 101 havinginner bore 109 and containing within a fluid separator in the form of a floatingpiston inner bore FIGS. 6-8 ). Regarding the embodiments described with respect toFIGS. 6-8 , the floatingpiston 111 sealingly and slidingly engagesinner bore 109 ofsecondary accumulator housing 101 and functions in a similar manner as floatingpiston 92, described with respect toFIGS. 3-5 (previously described in detail). Alternative embodiments of the fluid separator in the secondary accumulator are, however, within the scope of the present invention. - For example, as best shown in
FIG. 9 , the floating piston 111 (FIGS. 6-8 ) can be replaced by abladder 211 that sealingly engagesinner bore 209 ofsecondary accumulator housing 201 in a fixed position. Similar to the floatingpiston 111 implementation,upper surface 213 of thebladder 211 in combination with the secondary accumulator housinginner bore 209 form an enclosure, which along with a gas volume Vg2 sealingly contained on theupper side 213 of thebladder 211, define asecondary accumulator 221 having a gas pressure P2. Thelower side 215 of thebladder 211 in combination with the secondary accumulator housinginner bore 209 form an additional portion of the primary accumulator throughaperture 203. - In operation,
bladder 211 is selected to “balloon” when pressure P1 of the primary accumulator equals or exceeds pressure P2 of the secondary accumulator. Hydraulic volume Vh1 having pressure P1 serves to compressbladder 211 at a preselected pressure P2, which, in turn, serves to compress the secondary accumulator gas volume Vg2 to substantially the same extent as that of the hydraulic volume Vh1 having pressure P1 compresses primary accumulator gas volume Vg1. This “ballooning effect” results in functionally combining the gas volume of the primary accumulator Vg1 and with the gas volume Vg2 of the secondary accumulator when the pressure P1 of the primary accumulator equals or exceeds pressure P2 of the secondary accumulator. This results in an increased total gas volume VgT which serves to reduce maximum tension and stiffness during a downstroke of the piston rod. However, as with the configuration described with respect toFIG. 9 , secondary hydraulic volume Vh2 would be unnecessary. As stated above, the secondary hydraulic volume Vh2 in the above described embodiments and their corresponding configurations is generally used for the purpose of maintaining hydraulic seals of the floating piston. As thebladder 211 is fixedly mounted, the second hydraulic fluid volume is unnecessary. Note also, the second piston 92 (FIGS. 3-5 ) can be replaced by a bladder similar tobladder 211 fixedly mounted withinbore 76 ofpiston rod 32. - As best shown in
FIG. 10 , the floating piston 111 (FIGS. 6-8 ) can also be replaced by a fluid separator in the form of a valve orvalve arrangement 311. In this embodiment of the present invention,valve arrangement 311, typically in the form of a pilot valve, has a firstfluid connection assembly 343 in fluid communication with pressurized fluid in the primary accumulator through an aperture 105 (FIG. 6 ) and a secondfluid connection assembly 345 in fluid communication with the pressurized fluid contained withinsecondary accumulator housing 301 throughaperture 303 to intermittently connect pressurized fluid in the primary accumulator with pressurized fluid in the secondary accumulator housing when pressure P1 in the primary accumulator pressure P1 equals or exceeds the preselected pressure P2 of the secondary accumulator. Referring to the configurations shown inFIGS. 6-8 , when combined with the fluid separator shown inFIG. 10 , the interface between the fluid separator and the primary accumulator is with hydraulic volume Vh1. Thebore 309 ofsecondary accumulator housing 101 contains gas volume Vg2 and hydraulic volume Vh2 which, in combination with the secondfluid connection assembly 345 of thevalve arrangement 311, define asecondary accumulator 321. - In operation, as primary accumulator pressure P1 equals or exceeds secondary accumulator pressure P2, the valve arrangement 331 allows a portion of hydraulic volume Vh1 to enter the secondary accumulator and compress the secondary accumulator gas volume Vg2 to substantially the same extent the hydraulic volume Vh1 having pressure P1 compresses primary accumulator gas volume Vg1. This “effect” results to combine the gas volume of the primary accumulator Vg1 and with the gas volume Vg2 of the secondary accumulator when the pressure P1 of the primary accumulator equals or exceeds pressure P2 of the secondary accumulator. This produces an increased total gas volume VgT which serves to reduce maximum tension and stiffness during a downstroke of the piston rod. As the pressure P1 of the primary accumulator decreases to that of the preselected secondary accumulator pressure P2, the
valve arrangement 311 allows substantially the same amount of hydraulic fluid from the primary accumulator hydraulic volume Vh1 equivalent to the amount that entered the secondary accumulator hydraulic volume Vh2 to be returned through thevalve arrangement 311 by the expanding secondary accumulator gas volume Vg2. When the primary accumulator pressure P1 decreases below the secondary accumulator preset pressure P2, the two hydraulic volumes Vh1, Vh2, are isolated from each other byvalve arrangement 311 and the total equivalent gas volume VgT of the tensioner unit is that of the primary accumulator gas volume Vg1. - As stated above, the previous embodiments shown in
FIGS. 3-8 and described above in detail, depict a housing for a secondary accumulator combined with a fluid separator either in the form of a piston, bladder, or valve arrangement, functionally engaged through use of a primary accumulator hydraulic volume Vh1. With respect to the embodiments described that utilize a separate external secondary accumulator housing, and with reference toFIGS. 6-8 , little modification to those embodiments need be necessary in order to provide a secondary accumulator which is functionally engaged entirely through use of a gas such as primary accumulator gas volume Vg1. - Referring to
FIGS. 11-15 , shown is the implementation of atensioner unit 428, similar to that described with reference toFIG. 7 , having three variations of a secondary accumulator in the form of the gas accumulator. Thetensioner unit 428 can havesecondary accumulator housing 401 positioned in fluid (gas) communication with either of the previously described embodiments primary accumulator gas volume Vg1. For example,aperture 405 can be located inpiston rod 432 to provide primary accumulator pressure P1 to either of the embodiments of a fluid separator, described above. Referring to the implementation of a fluid separator taking the form of a floating piston 411 (FIGS. 11-13 ), the floatingpiston 411 performs the same function as floatingpiston 111 as described with respect toFIG. 6-8 or floatingpiston 92 described with respect toFIGS. 3-5 . In this configuration, however, the gas volume contained within the bore 476 ofpiston rod 432,lower side 415 of the floatingpiston 411 in combination with the secondary accumulator housinginner bore 409, and fluid connection assembly 407 positioned betweenapertures bore 409 of thesecondary accumulator housing 401 in combination with theupper side 413 of floatingpiston 411 and containing secondary accumulator gas volume Vg2 form thesecondary accumulator 421. Note, no hydraulic volume Vh2 is used within thesecondary accumulator 421 in this configuration. Note also, due to the absence of hydraulic oil, the seals used to seal floatingpiston 411 ininner bore 409 of thesecondary accumulator housing 401 are gas seals, otherwise the configuration withinsecondary accumulator housing 401 can be substantially the same as that shown inFIGS. 6-8 . - In operation, with a supported system such as the hydro-
pneumatic tensioner system 20 properly installed, normally, thefirst piston 472 is established in the vicinity of the upper portion of the cylinder barrel 460, and the floatingpiston 411 is normally established in a contact position with thelower stop 425. In this situation, pressure P1 on thelower side 415 of the floatingpiston 411 is normally less than the pressure P2 on theupper side 413 of the floatingpiston 411. - In a partial retraction situation, as best shown in
FIG. 12 , normally, thefirst piston 472 is established in some mid-range position of the cylinder barrel 460, and the floatingpiston 411 is still normally established in a contact position with thelower stop 425. In this situation, pressure P1 on thelower side 415 of the floatingpiston 411 is still normally less than the pressure P2 on theupper side 413 of the floatingpiston 411 but with a decreased pressure differential (P2-P1) maintaining that position. The total effective gas volume VgT is maintained substantially at that volume of the primary accumulator Vg1. As thepiston 472 continues to stroke down (retract) tension increases at a sufficient rate to provide sufficient support to the supported system. - In a near full retraction situation, as best shown in
FIG. 13 , normally, in a situation where thefirst piston 472 was operating without the benefit of the addedsecond piston accumulator 421, tension would increase rapidly. The floatingpiston 411, however, having its own “charge” moves upward to maintain the two pressures P1 and P2 in substantial equilibrium unless theupper stop 423 is contacted. Thus, the implementation of the floatingpiston 411 in the externalsecondary accumulator housing 401 provides the same function as the second piston 92 (FIGS. 3-5 ) within thepiston rod 32. The implementation of the floating piston results in the effective amount of gas VgT being increased over that of Vg1. The increase in gas volume provides a slower rate of increase in gas pressure P1 due to the added volume and also reduces the peak load of a given downstroke (retraction of the piston rod). - Referring now to
FIG. 14 , the floating piston 411 (FIGS. 11-13 ) can be replaced by abladder 511 that sealingly engagesinner bore 509 ofsecondary accumulator housing 501 in a fixed position. In this configuration, the gas volume contained within the bore 476 ofpiston rod 432,lower side 515 of thebladder 511 in combination with the secondary accumulator housinginner bore 509, andfluid connection assembly 507 connected toaperture 503 combine to form a primary accumulator having the primary accumulator gas volume Vg1. As with the floatingpiston 411,upper surface 513 of thebladder 511 in combination with the secondary accumulator housinginner bore 509 form an enclosure, which along with a gas volume Vg2 sealingly contained on theupper side 513 of thebladder 511, define asecondary accumulator 521 having a gas pressure P2. Note, the second piston 92 (FIGS. 3-5 ) can also be replaced by a bladder similar tobladder 511 and fixedly mounted withinbore 76 ofpiston rod 32. - In operation,
bladder 511 is selected to “balloon” when pressure P1 of the primary accumulator equals or exceeds pressure P2 of the secondary accumulator. However, in this configuration, gas volume Vg1, as opposed to hydraulic volume Vh1 having pressure P1 (FIG. 9 ), serves to compressbladder 511 at a preselected pressure P2, which, in turn, serves to compress the secondary accumulator gas volume Vg2 to relatively the same extent as that hydraulic volume Vh1 having pressure P1 compresses the portion of the primary accumulator gas volume Vg1 within bore 476 ofpiston rod 432. Where primary accumulator pressure P1 equals or exceeds the secondary accumulator pressure P2, the gas volumes Vg1, Vg2, functionally combine to produce an increased total gas volume VgT which serves to reduce maximum tension and stiffness during a downstroke of thepiston rod 432. When the primary accumulator pressure P1 is again reduced below the preset secondary accumulator pressure P2, the total effective gas volume VgT returns to that of the primary accumulator gas volume Vg1, and stiffnesses to the supported unit is increased. - As best shown in
FIG. 15 , the floating piston 411 (FIGS. 11-13 ) can also be replaced by a fluid separator in the form of an entirely gas fluid operated valve orvalve arrangement 611. In this configuration,valve arrangement 611, typically in the form of a pilot valve, has a firstfluid connection assembly 643 in fluid communication with pressurized fluid in the primary accumulator throughaperture 405 positioned to access primary accumulator gas volume Vg2, and a secondfluid connection assembly 645 in fluid communication with the pressurized fluid contained withinsecondary accumulator housing 601 throughaperture 603 to intermittently connect pressurized fluid in the primary accumulator with pressurized fluid in the secondary accumulator housing when pressure P1 in the primary accumulator pressure P1 equals or exceeds the preselected pressure P2 of the secondary accumulator. Referring still to thetensioner unit 428 ofFIG. 11 combined with thesecondary accumulator 621 shown inFIG. 15 , when the interface between the fluid separator and the primary accumulator is with gas volume Vg1, thebore 609 ofsecondary accumulator housing 601 contains gas volume Vg2 only which, in combination with the secondfluid connection assembly 645 of thevalve arrangement 611, defines thesecondary accumulator 621. - In operation, as primary accumulator pressure P1 equals or exceeds secondary accumulator pressure P2, the
valve arrangement 611 allows a portion of gas volume Vg1 to enter the secondary accumulator and compress the secondary accumulator gas volume Vg2 to substantially the same extent the gas volume Vg1 is compressed. This “effect” results to combine the gas volume of the primary accumulator Vg1 and with the gas volume Vg2 of the secondary accumulator when the pressure P1 of the primary accumulator equals or exceeds pressure P2 of the secondary accumulator. This produces an increased total gas volume VgT which serves to reduce maximum tension and stiffness during a downstroke of thepiston rod 432. As the pressure P1 of the primary accumulator decreases to that of the preselected secondary accumulator pressure P2, thevalve arrangement 611 allows substantially the same amount of gas volume that entered the secondary accumulator to be returned through thevalve arrangement 611 by the expanding secondary accumulator gas volume Vg2. When the primary accumulator pressure P1 decreases below the secondary accumulator preset pressure P2, the two gas volumes Vg1, Vg2, are isolated from each other byvalve arrangement 611 and the total equivalent gas volume VgT of the tensioner unit is that of the primary accumulator gas volume Vg1. - Referring now to
FIG. 16 , an alternative embodiment, atensioner unit 528 similar to the tensioner unit 128 (FIG. 6 ) is modified to prevent primary accumulator hydraulic volume Vh1 or primary accumulator gas volume Vg1 from entering eitherpiston 572,piston rod 532, or both. This embodiment can interface with either of the secondary accumulators described with respect toFIGS. 6-15 . In the configuration shown inFIG. 16 , the primary accumulator includes the inner bore of the main body (barrel) 530 and thelower surface 582 ofpiston 572 along with the fluid connection assembly and the primary accumulator side of the fluid separator, according to the type of secondary accumulator selected. - In a configuration where the
tensioner unit 528 is implemented with a gas-type secondary accumulator, such as those described with respect toFIGS. 11, 14 , or 15,aperture 505 is positioned in themain body 530, above the maximum hydraulic volume fluid line (not shown) corresponding to the level of the primary accumulator hydraulic volume Vh1 within themain body 530 that is external to thecylinder barrel 560 and reached whenpiston 572 is in full downstroke. Primary accumulator hydraulic volume Vg1 interfaces with the fluid separator of the selected secondary accumulator to effectively combine the primary accumulator gas volume Vg1 with the selected secondary accumulator gas volume Vg2. In a configuration where thetensioner unit 528 is implemented with a hydraulic-type secondary accumulator, such as those described with respect toFIGS. 6, 9 , and 10,aperture 505 is positioned below the minimum hydraulic volume fluid line (not shown) corresponding to the level of the hydraulic volume Vh1 within themain body 530 whenpiston 572 is in full up-stroke. The primary accumulator hydraulic volume Vh1 interfaces with the fluid separator of the selected secondary accumulator to effectively combine the primary accumulator gas volume Vg1 with the selected secondary accumulator gas volume Vg2. - Referring now to
FIG. 17 , an alternative embodiment of the present invention includes a pull-type hydro-pneumatic tensioner unit 628 having aprimary accumulator housing 601 and a secondary accumulator housing including those described with respect to FIGS. 6, 9-11, 14, or 15. Apiston 672 similar to the one described inFIG. 16 moves axially within main body (barrel) 630 havinginner bore 666. Thepiston 672 has apiston rod 632 extending from thelower side 682 ofpiston 672, the piston rod extends through a piston rod aperture 662 and through high-pressure seals associated with the aperture 662. Thepiston 672 also includes high-pressure seals 690. The combination, as described above and as to be described below, forms an enclosure of varying size depending upon primary accumulator pressure P1 and stroke position of thepiston rod 632. - In the preferred configuration, the diameter of the
piston 672 is substantially equivalent to the diameter of theinner bore 666 ofmain body 630, and the diameter of thepiston rod 632 is preferably substantially equivalent to the inner diameter of the diameter of the piston rod aperture 662. The volume formed between theupper side 684 of thepiston 672 and theinner bore 666 of themain body 630 forms a low-pressure annulus that is preferably vented to the atmosphere. The volume formed between thelower side 682 of thepiston 672 and the main body inner bore 666 forms a portion of theprimary accumulator 652 having a portion of the primary accumulator hydraulic volume Vh1. Themain body 630 also includes an aperture 605 located adjacent the lower end of the main body to provide fluid communication between the main body portion of the primary accumulator andprimary accumulator housing 601. Theprimary accumulator housing 601 preferably takes the form of an external cylinder or barrel. The primary accumulator housing includesaperture 603 in fluid communication withmain body 630 through afluid connection assembly 607 connected betweenaperture 603 of theprimary accumulator housing 601 and aperture 605 of themain body 630. Thebore 609 of theprimary accumulator housing 601 includes a portion of the primary accumulator hydraulic volume Vh1. Thebore 609 of theprimary accumulator housing 601 also includes at least a portion of the primary accumulator gas volume Vg1, depending on the configuration of the selected secondary accumulator. The amount of primary accumulator hydraulic volume Vh1 is dependent upon primary accumulator pressure P1 and stroke position ofpiston 672. - The
tensioner unit 628 according to this embodiment can at least interface with either of the secondary accumulators described with respect toFIGS. 6-15 . For illustrative purposes, the following discussion will be with respect to thesecondary accumulator 121 described with respect toFIGS. 6-8 . Theprimary accumulator housing 601 andsecondary accumulator housing 101 are in fluid communication through afluid connection assembly 608 connected toaperture 602 of theprimary accumulator housing 601 andaperture 103 of thesecondary accumulator housing 101. In this configuration, theprimary accumulator 652 includes the inner bore of the main body (barrel) 630 and thelower surface 682 ofpiston 672,fluid connection assembly 607, thebore 609 of theprimary accumulator housing 601, thefluid connection assembly 608, and thebore 109 ofsecondary accumulator housing 101 in combination with the primary accumulator side of the fluid separator according to the type of secondary accumulator configuration selected. Thesecondary accumulator 121 includes theinner bore 109 of thesecondary accumulator housing 101 and the secondary accumulator side of the fluid separator according to the type of secondary accumulator configuration selected. - The configuration depicted in
FIG. 17 includes a hydraulic-type secondary accumulator similar to that described with respect toFIG. 6 , whereby primary accumulator hydraulic volume Vh1 provides the impetus to functionally combine the primary accumulator gas volume Vg1 with the secondary accumulator gas volume Vg2 to provide thetensioner unit 628 an effective total gas volume VgT substantially equivalent to that of the sum of the primary accumulator gas volume Vg1 and secondary accumulator gas volume. If a gas-type accumulator is used, such as that described with respect toFIG. 14 , thefluid connection assembly 608 would instead be connected to theupper aperture 602 ofprimary accumulator housing 601 in communication with the primary accumulator gas volume Vg1. Additionally, the maximum amount of primary accumulator hydraulic volume Vh1 can be configured under expected extreme operating conditions not to exceed a level within thebore 609 of theprimary accumulator housing 601 to that of communicating with theupper aperture 602. In this configuration, the primary accumulator gas volume Vg1 provides the impetus to functionally combine the primary accumulator gas volume Vg1 with the secondary accumulator gas volume Vg2 to provide thetensioner unit 628 an effective total gas volume VgT substantially equivalent to that of the sum of the primary accumulator gas volume Vg1 and secondary accumulator gas volume Vg2. - The invention has several advantages. The hydro-pneumatic riser tensioner units provide high nominal stiffness while limiting peak loads at extreme extended and retracted positions. In one configuration, the telescopic piston rod of the riser tensioner unit incorporates the bore or annulus of the piston rod as a secondary accumulator and incorporates a floating piston within the annulus of the piston rod. In other configurations, a separate housing having the bore or annulus is used to form the secondary accumulator. The total effective gas volume of the unit is increased by that of the secondary accumulator. During piston compression, the increased effective gas volume results in the load on the riser system increasing at a much lower rate and a reduced peak load. During piston decompression, the increased total effective gas volume results in a slower decrease in pressure and results in limiting the minimum tension applied to the riser system. Correspondingly, a smaller primary accumulator may be utilized.
- In the drawings and specification, there have been disclosed a typical preferred embodiment of the invention, and although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. The invention has been described in considerable detail with specific reference to these illustrated embodiments. It will be apparent, however, that various modifications and changes can be made within the spirit and scope of the invention as described in the foregoing specification. For example, optionally, the system could be entirely pressurized by gas only, using a separate lubricant for the seals, as known by those skilled in the art. Also, if full retraction is not required, the retraction stops used in the floating piston configurations could be eliminated. Further, the accumulator could be connected to the riser and the piston rod to the vessel in reverse to what was described. Still further, the tensioner unit can be attached to the top plate at an intermediate point along the barrel rather than at the upper end as shown in figures. Correspondingly the tensioner unit can be connected to the support module lower support frame at an intermediate point along the barrel rather than at the lower end as shown in the figures.
Claims (35)
1. A tensioner unit, comprising:
a barrel having a bore and an aperture on one end and having a pressurized fluid contained within and forming at least part of a primary accumulator, the primary accumulator having a preset volume of gas Vg1 at pressure P1;
a first piston having a first and second side and slidably carried in the bore of the barrel, the piston having a piston rod that extends from the second side of the piston and through the aperture of the barrel, having one of the sides of the piston in communication with the pressurized fluid, and positioned to increase the pressure P1 of the primary accumulator when the piston strokes in the direction of the pressurized fluid;
a secondary accumulator housing having a bore and forming at least part of a secondary accumulator, the secondary accumulator having a preset volume of gas Vg2 at preselected pressure P2;
a fluid separator having first and second sides and positioned between the primary and secondary accumulators to maintain functional separation of fluid volumes of the primary and secondary accumulators when the primary accumulator pressure P1 is less than the secondary accumulator pressure P2, and to allow functional combining of the fluid volumes of the primary and secondary accumulators when the primary accumulator pressure P1 is greater than or equal to the secondary accumulator pressure P2;
wherein an effective total gas volume VgT available to the tensioner to maintain tension on a supported riser system substantially equals the primary accumulator gas volume Vg1 when the primary accumulator pressure P1 is less than the secondary accumulator pressure P2; and
wherein the effective total gas volume VgT available to the tensioner to maintain tension on the supported system substantially equals the sum of the primary accumulator gas volume Vg1 plus the secondary accumulator gas volume Vg2 when the pressure P1 is greater than or equal to the secondary accumulator pressure P2.
2. The tensioner unit of claim 1 , further comprising a tubular housing surrounding the barrel and having pressurized fluid contained within and forming a part of the primary accumulator, and wherein:
the piston rod includes a bore which forms the secondary accumulator housing;
the barrel has a port on one end in fluid communication with the tubular housing;
the first piston has an opening in fluid communication with the port;
the bore of the piston rod is in fluid communication with the opening in the piston;
the fluid separator comprises a second piston having first and second sides and sealingly and slidably carried in the bore of the piston rod;
the bore of the barrel, the bore of the tubular housing, and the first sides of the first and second piston define the primary accumulator; and
the bore of the piston rod and the second side of the second piston define the secondary accumulator.
3. The tensioner unit of claim 1 , wherein:
the first piston has an opening in fluid communication with the barrel;
the piston rod includes a bore in fluid communication with the opening in the piston;
the secondary accumulator housing is separate from the barrel and is in fluid communication with the second side of the fluid separator; and
the first side of the fluid separator is in fluid communication with an opening in one of the bore of the piston rod and the bore of the barrel.
4. The tensioner unit of claim 3 , wherein:
the bore of the barrel, the bore of the piston rod, the bore of the secondary accumulator housing, the first side of the first piston, and first side of the fluid separator define the primary accumulator;
the bore of the secondary accumulator housing and a second side of the fluid separator define the secondary accumulator;
the fluid separator comprises a second piston sealingly and slidably carried in the bore of the secondary accumulator housing; and
the bore of the secondary accumulator housing further includes an extension stop spaced from an end of the secondary accumulator housing which limits maximum travel of the second piston during piston rod extension corresponding to a decrease in primary accumulator pressure P1 below that of the secondary accumulator pressure P2.
5. The tensioner unit of claim 3 , wherein:
the bore of the barrel, the bore of the piston rod, the bore of the secondary accumulator housing, the first side of the first piston, and first side of the fluid separator define the primary accumulator;
the bore of the secondary accumulator housing and a second side of the fluid separator define the secondary accumulator; and
the fluid separator comprises a bladder sealingly engaged in a fixed position within the bore of the secondary accumulator housing.
6. The tensioner unit of claim 3 , wherein:
the fluid separator comprises a valve having a first fluid connection assembly in fluid communication with the pressurized fluid in one of the bore of the piston rod and the bore of the barrel, and a second fluid connection assembly in fluid communication with the pressurized fluid in the bore of the secondary accumulator housing;
the bore of the barrel, the bore of the piston rod, the first side of the first piston, and the first fluid connection assembly of the valve define the primary accumulator;
the bore of the tubular housing and the second fluid connection assembly of the valve define a secondary accumulator; and wherein
the valve connects the pressurized fluid in the bore of the barrel with the pressurized fluid in the bore of the secondary accumulator housing when the pressure P1 in the primary accumulator exceeds the preselected pressure P2 of the secondary accumulator.
7. The tensioner unit of claim 1 , further comprising a tubular housing surrounding the barrel, the tubular housing having a bore, a fluid communication opening, and pressurized fluid contained within, and forming a part of the primary accumulator, and wherein:
the secondary accumulator housing is separate from both the barrel and the tubular housing and is in fluid communication with the second side of the fluid separator;
the first side of the fluid separator is in fluid communication with the tubular housing through the fluid communication opening; and
the first side of the first piston forms a fluid barrier.
8. The tensioner unit of claim 7 , wherein:
the bore of the barrel, the bore of the tubular housing, the bore of the secondary accumulator housing, the first side of the first piston, and first side of the fluid separator define the primary accumulator;
the bore of the secondary accumulator housing and a second side of the fluid separator define the secondary accumulator;
the fluid separator comprises a second piston sealingly and slidably carried in the bore of the secondary accumulator housing; and
the bore of the secondary accumulator housing further includes an extension stop spaced from an end of the secondary accumulator housing which limits maximum travel of the second piston during piston rod extension corresponding to a decrease in primary accumulator pressure P1 below that of the secondary accumulator pressure P2.
9. The tensioner unit of claim 7 , wherein:
the bore of the barrel, the bore of the piston rod, the first side of the first piston, the bore of the secondary accumulator housing, and first side of the fluid separator define the primary accumulator;
the bore of the secondary accumulator housing and a second side of the fluid separator define the secondary accumulator; and
the fluid separator comprises a bladder sealingly engaged in a fixed position within the bore of the secondary accumulator housing.
10. The tensioner unit of claim 7 , wherein:
the fluid separator comprises a valve having a first fluid connection assembly in fluid communication with the pressurized fluid in the bore of the tubular housing, and a second fluid connection assembly in fluid communication with the pressurized fluid in the bore of the secondary accumulator housing;
the bore of the barrel, the first side of the first piston, the bore of the tubular housing, and the first fluid connection assembly of the valve define the primary accumulator;
the bore of the secondary accumulator housing and the second fluid connection assembly of the valve define the secondary accumulator; and wherein
the valve connects the pressurized fluid in the bore of the tubular housing with pressurized fluid in the bore of the secondary accumulator housing when the pressure P1 in the primary accumulator exceeds the preselected pressure P2 of the secondary accumulator.
11. The tensioner unit of claim 1 , further comprising a primary accumulator housing having a bore, a plurality of fluid communication apertures, and having pressurized fluid contained within and forming a part of the primary accumulator, and wherein:
the first side of the first piston forms a fluid barrier;
the primary accumulator housing is separate from the barrel and is in fluid communication with the barrel and the first side of the fluid separator through the fluid communication apertures;
the secondary accumulator housing is separate from the barrel and the primary accumulator housing and is in fluid communication with the second side of the fluid separator; and
the first side of the fluid separator is in fluid communication with the bore of the primary accumulator housing and bore of the barrel through the fluid communication apertures.
12. The tensioner unit of claim 11 , wherein:
the bore of the barrel, the first side of the first piston, the bore of the primary accumulator housing, the bore of the secondary accumulator housing, and the first side of the fluid separator define the primary accumulator;
the bore of the secondary accumulator housing and the second side of the fluid separator define the secondary accumulator;
the fluid separator comprises a second piston sealingly and slidably carried in the bore of the secondary accumulator housing; and
the bore of the secondary accumulator housing further includes an extension stop spaced from an end of the secondary accumulator housing which limits maximum travel of the second piston during piston rod extension corresponding to a decrease in primary accumulator pressure P1 below that of the secondary accumulator pressure P2.
13. The tensioner unit of claim 11 , wherein:
the bore of the barrel, the first side of the first piston, the bore of the primary accumulator housing, the bore of the secondary accumulator housing, and the first side of the fluid separator define the primary accumulator;
the bore of the secondary accumulator housing and the second side of the fluid separator define the secondary accumulator; and
the fluid separator comprises a bladder sealingly engaged in a fixed position within the bore of the secondary accumulator housing.
14. The tensioner unit of claim 11 , wherein:
the fluid separator comprises a valve having a first fluid connection assembly in fluid communication with the pressurized fluid in the bore of the primary accumulator housing which is in communication with the bore of the barrel, and a second fluid connection assembly in fluid communication with the pressurized fluid in the bore of the secondary accumulator housing;
the bore of the barrel, the first side of the first piston, the bore of the primary accumulator housing, and the first fluid connection assembly of the valve arrangement define the primary accumulator;
the bore of the secondary accumulator housing and the second side of the fluid separator define the secondary accumulator; and
the valve connects the pressurized fluid in the bore of the primary accumulator housing and the bore of the barrel with the pressurized fluid in the bore of the secondary accumulator housing when the pressure P1 in the primary accumulator exceeds the preselected pressure P2 of the secondary accumulator.
15. A riser tensioning system having a riser extending between subsea well equipment and a floating vessel having an operational platform engaged with the riser, a tensioner unit comprising:
a barrel having a port on one end;
a first piston slidingly carried in the barrel and having an opening in fluid communication with the port;
a piston rod extending from the barrel and having a bore in fluid communication with the opening in the piston;
a second piston sealingly and slidably carried in the bore of the piston rod;
a primary accumulator in fluid communication with the port and having pressurized fluid therein that communicates with first sides of the first and second piston;
and wherein:
the bore of the piston rod and a second side of the second piston define a secondary accumulator containing a pressurized fluid;
the tensioner unit is positioned between the riser and the platform;
a first section of the tensioner unit is connected to the riser; and
a second section of the tensioner unit is connected to the platform.
16. The tensioning system of claim 15 , wherein the bore of the piston rod of the tensioner unit includes an extension stop which limits maximum travel of the second piston during piston rod extension.
17. The tensioning system of claim 15 , wherein the bore of the piston rod of the tensioner unit includes a retraction stop spaced from an end of the piston rod which limits maximum travel of the second piston during piston rod retraction.
18. The tensioning system of claim 15 , wherein the primary accumulator of the tensioner unit comprises a tubular housing surrounding the barrel.
19. The tensioning system of claim 15 , wherein the tensioner unit further comprises a barrel extension extending from the barrel which provides for fluid communication between the barrel port and the primary accumulator.
20. A tensioner unit, comprising:
a barrel including a bore;
a first piston slidingly carried in the bore of the barrel and having an opening in fluid communication with a pressurized fluid;
a piston rod extending from the barrel and having a bore in fluid communication with the opening in the piston;
a secondary accumulator housing having a bore;
a fluid separator sealingly engaging the bore of the secondary accumulator housing and having a first and a second side to separate a plurality of volumes of fluid;
a primary accumulator in fluid communication with the bore of the secondary accumulator housing through an opening in at least one of the piston rod and barrel and having pressurized fluid therein that communicates with the first side of the first piston and first side of the fluid separator; and
the bore of the secondary accumulator housing and a second side of the fluid separator defining a secondary accumulator containing a pressurized fluid within.
21. The tensioner unit of claim 20 , wherein the fluid separator comprises a second piston sealingly and slidably carried in the bore of the secondary accumulator housing.
22. The tensioner unit of claim 21 , wherein the bore of the secondary accumulator housing further includes an extension stop spaced from an end of the secondary accumulator housing which limits maximum travel of the second piston during piston rod extension corresponding to a decrease in primary accumulator pressure below that of the secondary accumulator pressure.
23. The tensioner unit of claim 20 , wherein the fluid separator comprises a bladder sealingly engaged in a fixed position within the bore of the secondary accumulator housing.
24. A tensioner unit, comprising:
a barrel having a port on one end and in communication with a pressurized fluid;
a tubular housing surrounding the barrel and having a bore, an opening, and an aperture on one end;
a piston having a first and second side, slidingly carried in the bore of the barrel, and having a piston rod extending from the barrel on the second side of the piston through the aperture;
a secondary accumulator housing including a bore, an opening in the bore in fluid communication with the opening in the bore of the tubular housing, and a fluid separator sealingly engaging the bore of the secondary accumulator housing and having a first and a second side to separate a plurality of volumes of fluid;
a primary accumulator in fluid communication with the port of the barrel and the opening in the bore of the tubular housing, and having pressurized fluid therein that communicates with the first side of the piston and the first side of the fluid separator; and
the bore of the secondary accumulator housing and the second side of the fluid separator defining a secondary accumulator containing a pressurized fluid.
25. The tensioner unit of claim 24 , wherein the fluid separator comprises a second piston sealingly and slidably carried in the bore of the secondary accumulator housing.
26. The tensioner unit of claim 25 , wherein the bore of the secondary accumulator housing further includes an extension stop spaced from an end of the secondary accumulator housing which limits maximum travel of the second piston during piston rod extension corresponding to a decrease in primary accumulator pressure below that of the secondary accumulator pressure.
27. The tensioner unit of claim 24 , wherein the fluid separator comprises a bladder sealingly engaged in a fixed position within the bore of the secondary accumulator housing.
28. A tensioner unit, comprising:
a barrel having a bore, a fluid communication opening, an aperture on one end, and having a volume of pressurized fluid therein;
a first piston having a first and a second side, slidingly carried in the bore of the barrel and having a piston rod that extends from the piston through the fluid communication opening of the barrel;
a primary accumulator housing having a bore, a plurality of fluid communication openings, and in fluid communication with the fluid communication opening of the barrel;
a secondary accumulator housing having a bore, a fluid communication opening, and having a fluid separator sealingly engaging the bore of the secondary accumulator housing, the fluid separator having a first and a second side to separate fluid in the secondary accumulator housing, the secondary accumulator housing further being in fluid communication with the primary accumulator housing through the fluid communication opening of the secondary accumulator housing and one of the fluid communication openings of the primary accumulator housing;
a primary accumulator in fluid communication with the fluid communication opening of the barrel and the fluid communication opening of the secondary accumulator housing and having pressurized fluid that communicates with the first side of the first piston and first side of the fluid separator; and
the bore of the secondary accumulator housing and the second side of the fluid separator defining a secondary accumulator containing a pressurized fluid.
29. The tensioner unit of claim 28 , wherein the fluid separator comprises a second piston sealingly and slidably carried in the bore of the secondary accumulator housing.
30. The tensioner unit of claim 29 , wherein the bore of the secondary accumulator housing further includes a lower stop spaced from an end of the secondary accumulator housing which limits maximum travel of the second piston during piston rod extension corresponding to a decrease in pressure of the primary accumulator below the pressure of the secondary accumulator.
31. The tensioner unit of claim 29 , wherein the fluid separator comprises a bladder sealingly engaged in a fixed position within the bore of the secondary accumulator housing.
32. A tensioner unit, comprising:
a barrel including a bore and an aperture on one end and having a pressurized fluid contained within and forming at least part of a primary accumulator;
a piston in communication with a pressurized fluid and slidingly carried in the bore of the barrel and having a piston rod that extends from the piston through the aperture;
a secondary accumulator housing having a bore and a pressurized fluid having a preselected pressure contained within;
a valve arrangement having a first fluid connection assembly in fluid communication with the pressurized fluid in one of the bore of the piston rod and the bore of the barrel, and a second fluid connection assembly in fluid communication with the pressurized fluid in the bore of the secondary accumulator housing to connect the pressurized fluid in the bore of the barrel with the pressurized fluid in the bore of the secondary accumulator housing when the pressure of the pressurized fluid in the bore of the barrel exceeds the preselected pressure of the pressurized fluid in the bore of the secondary accumulator housing;
the bore of the barrel, and the first fluid connection assembly of the valve arrangement defining a primary accumulator; and
the bore of the secondary accumulator housing and the second fluid connection assembly of the valve arrangement defining a secondary accumulator.
33. A method of maintaining a selected range of tension on a riser extending between subsea well equipment and a floating vessel, comprising the steps of:
providing a barrel having a bore and an aperture on one end, the barrel forming at least part of a primary accumulator;
mounting a piston slidably in the barrel, the piston having a piston rod extending from the barrel through the aperture;
providing a secondary accumulator housing having a bore and forming at least part of a secondary accumulator;
mounting a fluid separator between the primary and secondary accumulators;
connecting either the piston rod or the barrel to the vessel and the other to the riser;
applying fluid pressure from the primary accumulator to a first side of the first piston and a first side of the fluid separator;
applying fluid pressure into the secondary accumulator housing on a second side of the fluid separator until pressure on both sides of the fluid separator equal;
applying tension to the riser by the force due to pressure of fluid in the primary accumulator, urging the piston rod to extend;
if vessel moves closer to the subsea equipment, allowing the piston rod to extend farther and allowing the fluid separator to functionally isolate the fluid volume in the secondary accumulator from the fluid volume in the primary accumulator to maintain tension range; and
if vessel moves farther from the subsea equipment, allowing the piston rod to retract and allowing the fluid separator to functionally combine the fluid volume in the secondary accumulator with the fluid volume in the primary accumulator to maintain tension range.
34. The method of claim 33 , further comprising limiting maximum travel of the second piston during piston rod extension by contacting the second piston with an extension stop.
35. The method of claim 33 , further comprising limiting maximum travel of the second piston during piston rod retraction by contacting the second piston with a retraction stop.
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/685,681 US20050074296A1 (en) | 2003-10-15 | 2003-10-15 | Hydro-pneumatic tensioner with stiffness altering secondary accumulator |
NO20044384A NO20044384L (en) | 2003-10-15 | 2004-10-15 | Hydro-pneumatic tensioning machine with stiffness regulating secondary accumulator |
GB0422861A GB2407594B (en) | 2003-10-15 | 2004-10-15 | Hydro-pneumatic tensioner with stiffness altering secondary accumulator |
US11/003,051 US7112011B2 (en) | 2003-10-15 | 2004-12-03 | Hydro-pneumatic tensioner with stiffness altering secondary accumulator |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/685,681 US20050074296A1 (en) | 2003-10-15 | 2003-10-15 | Hydro-pneumatic tensioner with stiffness altering secondary accumulator |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/003,051 Continuation-In-Part US7112011B2 (en) | 2003-10-15 | 2004-12-03 | Hydro-pneumatic tensioner with stiffness altering secondary accumulator |
Publications (1)
Publication Number | Publication Date |
---|---|
US20050074296A1 true US20050074296A1 (en) | 2005-04-07 |
Family
ID=33477236
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/685,681 Abandoned US20050074296A1 (en) | 2003-10-15 | 2003-10-15 | Hydro-pneumatic tensioner with stiffness altering secondary accumulator |
US11/003,051 Expired - Fee Related US7112011B2 (en) | 2003-10-15 | 2004-12-03 | Hydro-pneumatic tensioner with stiffness altering secondary accumulator |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/003,051 Expired - Fee Related US7112011B2 (en) | 2003-10-15 | 2004-12-03 | Hydro-pneumatic tensioner with stiffness altering secondary accumulator |
Country Status (3)
Country | Link |
---|---|
US (2) | US20050074296A1 (en) |
GB (1) | GB2407594B (en) |
NO (1) | NO20044384L (en) |
Cited By (26)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060180314A1 (en) * | 2005-02-17 | 2006-08-17 | Control Flow Inc. | Co-linear tensioner and methods of installing and removing same |
US20070240882A1 (en) * | 2006-04-18 | 2007-10-18 | Tauna Leonardi | Accumulator for Subsea Equipment |
US20080166186A1 (en) * | 2007-01-08 | 2008-07-10 | Vetco Gray Inc. | Ram Style Tensioner With Fixed Conductor and Floating Frame |
US20080205992A1 (en) * | 2007-02-28 | 2008-08-28 | Vetco Gray Inc. | Soft Stop for Maximum Riser Tensioner Stroke |
US20080304916A1 (en) * | 2007-06-11 | 2008-12-11 | Gerald Crotwell | Pull-style tensioner system for a top-tensioned riser |
US7600998B1 (en) * | 2006-08-15 | 2009-10-13 | Eric Pitchford | Portable heater with roll cage |
US20110147002A1 (en) * | 2008-08-04 | 2011-06-23 | Cameron International Corporation | Subsea Differential-Area Accumulator |
US20110155388A1 (en) * | 2008-06-20 | 2011-06-30 | Norocean As | Slip Connection with Adjustable Pre-Tensioning |
US20120099930A1 (en) * | 2010-10-21 | 2012-04-26 | Vetco Gray Inc. | System for supplemental tensioning for enhanced platform design and related methods |
WO2012158821A1 (en) * | 2011-05-17 | 2012-11-22 | Drilling Technological Innovations | Ram tensioner system |
US8496409B2 (en) | 2011-02-11 | 2013-07-30 | Vetco Gray Inc. | Marine riser tensioner |
GB2503063A (en) * | 2013-02-07 | 2013-12-18 | Technip France | Passive heave compensator having variable compensation |
WO2014122526A2 (en) * | 2013-02-07 | 2014-08-14 | Technip France | Passive heave compensator |
GB2512441A (en) * | 2013-01-22 | 2014-10-01 | Dril Quip Inc | Hydro-pneumatic tensioner with fluid retention device |
WO2015038004A1 (en) * | 2013-09-12 | 2015-03-19 | Depro As | Computerized device for compensation of wave-caused distance variations on a drill string |
AU2014221195A1 (en) * | 2014-09-02 | 2016-03-17 | Icon Engineering Pty Ltd | Riser tension protector and method of use thereof |
US20160145952A1 (en) * | 2014-11-21 | 2016-05-26 | Dril-Quip, Inc. | Enhanced ram-style riser tensioner |
WO2017018886A1 (en) * | 2015-07-24 | 2017-02-02 | Mcgregor Norway As | Hydraulic actuator |
NO340742B1 (en) * | 2015-05-08 | 2017-06-12 | Fmc Kongsberg Subsea As | Remote controlled well completion equipment |
NO341078B1 (en) * | 2015-02-04 | 2017-08-21 | Petrolution As | Device for compensation |
EP3269677A1 (en) | 2016-07-12 | 2018-01-17 | Ernst-B. Johansen AS | Heave compensator and method for reducing the risk of snap-loads during the splash-zone phase |
WO2018209407A1 (en) * | 2017-05-19 | 2018-11-22 | AME Pty Ltd | Compensated elevator link |
WO2022119449A1 (en) * | 2020-12-03 | 2022-06-09 | Momentum Technologies AS | Viscoelastic damper assembly |
US11603716B2 (en) * | 2018-10-10 | 2023-03-14 | Dril-Quip, Inc. | Hydro-pneumatic cylinder with annulus fluid bypass |
US11685208B2 (en) | 2021-04-26 | 2023-06-27 | Ree Automotive Ltd | Dual-axle vehicle corner assembly |
US11701935B2 (en) | 2021-08-16 | 2023-07-18 | Ree Automotive Ltd | Dual-wheels corner system with transverse suspension |
Families Citing this family (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN1329622C (en) * | 2002-08-21 | 2007-08-01 | O·霍兰德 | A method and device by a displacement tool |
DE102005041024A1 (en) * | 2005-08-23 | 2007-03-01 | Bielomatik Leuze Gmbh + Co.Kg | Apparatus and method for continuously producing a defect-free carrier web |
US8141644B2 (en) * | 2005-09-14 | 2012-03-27 | Vetco Gray Inc. | System, method, and apparatus for a corrosion-resistant sleeve for riser tensioner cylinder rod |
US7329070B1 (en) | 2007-03-30 | 2008-02-12 | Atp Oil & Gas Corporation | Ram-type tensioner assembly with accumulators |
US7270071B1 (en) | 2007-03-30 | 2007-09-18 | Atp Oil & Gas Corporation | Deep draft semisubmersible movable offshore structure |
US7934561B2 (en) * | 2007-04-10 | 2011-05-03 | Intermoor, Inc. | Depth compensated subsea passive heave compensator |
US8167312B2 (en) | 2008-07-10 | 2012-05-01 | Vetco Gray Inc. | Metal seal adjustable casing sub |
KR101065028B1 (en) * | 2010-04-13 | 2011-09-19 | 윤태삼 | Riser tensioner having an emergency seal |
KR101102809B1 (en) | 2010-04-13 | 2012-01-05 | 윤태삼 | Riser tensioner having oil collecting means |
US8157013B1 (en) * | 2010-12-08 | 2012-04-17 | Drilling Technological Innovations, LLC | Tensioner system with recoil controls |
US8746351B2 (en) | 2011-06-23 | 2014-06-10 | Wright's Well Control Services, Llc | Method for stabilizing oilfield equipment |
US9010436B2 (en) | 2012-12-13 | 2015-04-21 | Vetco Gray Inc. | Tensioner latch with sliding segmented base |
US8944723B2 (en) | 2012-12-13 | 2015-02-03 | Vetco Gray Inc. | Tensioner latch with pivoting segmented base |
BR112015026254B1 (en) * | 2013-04-15 | 2019-04-09 | Single Buoy Moorings, Inc. | HIGH TENSIONED RISER SYSTEM FOR A TREE-TREE SEMI-SUBMERSIBLE VESSEL |
NO339752B1 (en) * | 2014-02-27 | 2017-01-30 | Mhwirth As | Compact Compensation Unit |
US10174566B2 (en) | 2016-03-02 | 2019-01-08 | Vetco Gray, LLC | Inverted pull-up riser tensioner |
DE102016008882A1 (en) * | 2016-07-20 | 2018-01-25 | Hydac Technology Gmbh | Clamping cylinder device |
US9816538B1 (en) | 2016-08-31 | 2017-11-14 | Vetco Gray Inc. | Tensioner cylinder with internal gas bladder in high pressure chamber |
Citations (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3912227A (en) * | 1973-10-17 | 1975-10-14 | Drilling Syst Int | Motion compensation and/or weight control system |
US4222341A (en) * | 1978-01-11 | 1980-09-16 | Western Gear Corporation | Riser tensioning wave and tide compensating system for a floating platform |
US4272059A (en) * | 1978-06-16 | 1981-06-09 | Exxon Production Research Company | Riser tensioner system |
US4367981A (en) * | 1981-06-29 | 1983-01-11 | Combustion Engineering, Inc. | Fluid pressure-tensioned slip joint for drilling riser |
US4379657A (en) * | 1980-06-19 | 1983-04-12 | Conoco Inc. | Riser tensioner |
US4432420A (en) * | 1981-08-06 | 1984-02-21 | Exxon Production Research Co. | Riser tensioner safety system |
US4537533A (en) * | 1981-01-28 | 1985-08-27 | Sedco, Inc. | Installation and levelling of subsea templates |
US4799827A (en) * | 1986-11-17 | 1989-01-24 | Vetco Gray Inc. | Modular riser tensioner incorporating integral hydraulic cylinder accumulator units |
US4808036A (en) * | 1986-01-16 | 1989-02-28 | Santa Fe International Corporation | Mobile marine operations structure |
US4883387A (en) * | 1987-04-24 | 1989-11-28 | Conoco, Inc. | Apparatus for tensioning a riser |
US5252004A (en) * | 1992-07-13 | 1993-10-12 | Paul-Munroe Engineering | Rod accumulator riser tensioning cylinder assembly |
US5366324A (en) * | 1990-12-13 | 1994-11-22 | Ltv Energy Products Co. | Riser tensioner system for use on offshore platforms using elastomeric pads or helical metal compression springs |
US5846028A (en) * | 1997-08-01 | 1998-12-08 | Hydralift, Inc. | Controlled pressure multi-cylinder riser tensioner and method |
US6691784B1 (en) * | 1999-08-31 | 2004-02-17 | Kvaerner Oil & Gas A.S. | Riser tensioning system |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2264223B1 (en) * | 1974-03-14 | 1977-06-17 | Peugeot & Renault | |
US4638978A (en) * | 1983-07-22 | 1987-01-27 | Jordan Larry B | Hydropneumatic cable tensioner |
US4808035A (en) | 1987-05-13 | 1989-02-28 | Exxon Production Research Company | Pneumatic riser tensioner |
DE10251212B4 (en) * | 2002-10-31 | 2005-05-12 | Denk Engineering Gmbh | shock absorber |
US7008340B2 (en) * | 2002-12-09 | 2006-03-07 | Control Flow Inc. | Ram-type tensioner assembly having integral hydraulic fluid accumulator |
US6968900B2 (en) * | 2002-12-09 | 2005-11-29 | Control Flow Inc. | Portable drill string compensator |
-
2003
- 2003-10-15 US US10/685,681 patent/US20050074296A1/en not_active Abandoned
-
2004
- 2004-10-15 NO NO20044384A patent/NO20044384L/en not_active Application Discontinuation
- 2004-10-15 GB GB0422861A patent/GB2407594B/en not_active Expired - Fee Related
- 2004-12-03 US US11/003,051 patent/US7112011B2/en not_active Expired - Fee Related
Patent Citations (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3912227A (en) * | 1973-10-17 | 1975-10-14 | Drilling Syst Int | Motion compensation and/or weight control system |
US4222341A (en) * | 1978-01-11 | 1980-09-16 | Western Gear Corporation | Riser tensioning wave and tide compensating system for a floating platform |
US4272059A (en) * | 1978-06-16 | 1981-06-09 | Exxon Production Research Company | Riser tensioner system |
US4379657A (en) * | 1980-06-19 | 1983-04-12 | Conoco Inc. | Riser tensioner |
US4537533A (en) * | 1981-01-28 | 1985-08-27 | Sedco, Inc. | Installation and levelling of subsea templates |
US4367981A (en) * | 1981-06-29 | 1983-01-11 | Combustion Engineering, Inc. | Fluid pressure-tensioned slip joint for drilling riser |
US4432420A (en) * | 1981-08-06 | 1984-02-21 | Exxon Production Research Co. | Riser tensioner safety system |
US4808036A (en) * | 1986-01-16 | 1989-02-28 | Santa Fe International Corporation | Mobile marine operations structure |
US4799827A (en) * | 1986-11-17 | 1989-01-24 | Vetco Gray Inc. | Modular riser tensioner incorporating integral hydraulic cylinder accumulator units |
US4883387A (en) * | 1987-04-24 | 1989-11-28 | Conoco, Inc. | Apparatus for tensioning a riser |
US5366324A (en) * | 1990-12-13 | 1994-11-22 | Ltv Energy Products Co. | Riser tensioner system for use on offshore platforms using elastomeric pads or helical metal compression springs |
US5658095A (en) * | 1990-12-13 | 1997-08-19 | Continental Emsco Company | Riser tensioner system for use on offshore platforms using elastomeric pads or helical metal compression springs |
US5252004A (en) * | 1992-07-13 | 1993-10-12 | Paul-Munroe Engineering | Rod accumulator riser tensioning cylinder assembly |
US5846028A (en) * | 1997-08-01 | 1998-12-08 | Hydralift, Inc. | Controlled pressure multi-cylinder riser tensioner and method |
US6691784B1 (en) * | 1999-08-31 | 2004-02-17 | Kvaerner Oil & Gas A.S. | Riser tensioning system |
Cited By (70)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060254776A1 (en) * | 2005-02-17 | 2006-11-16 | Williams Richard D | Co-linear tensioner and methods of installing and removing same |
US7337849B2 (en) * | 2005-02-17 | 2008-03-04 | Control Flow Inc. | Co-linear tensioner and methods of installing and removing same |
US20060180314A1 (en) * | 2005-02-17 | 2006-08-17 | Control Flow Inc. | Co-linear tensioner and methods of installing and removing same |
US20100012327A1 (en) * | 2006-04-18 | 2010-01-21 | Schlumberger Technology Corporation | Accumulator for subsea equipment |
US20070240882A1 (en) * | 2006-04-18 | 2007-10-18 | Tauna Leonardi | Accumulator for Subsea Equipment |
US8002041B2 (en) | 2006-04-18 | 2011-08-23 | Schlumberger Technology Corporation | Accumulator for subsea equipment |
US7984764B2 (en) | 2006-04-18 | 2011-07-26 | Schlumberger Technology Corporation | Accumulator for subsea equipment |
US20100071907A1 (en) * | 2006-04-18 | 2010-03-25 | Schlumberger Technology Corporation | Accumulator for subsea equipment |
US7628207B2 (en) * | 2006-04-18 | 2009-12-08 | Schlumberger Technology Corporation | Accumulator for subsea equipment |
US7600998B1 (en) * | 2006-08-15 | 2009-10-13 | Eric Pitchford | Portable heater with roll cage |
US7632044B2 (en) * | 2007-01-08 | 2009-12-15 | Vetco Gray Inc. | Ram style tensioner with fixed conductor and floating frame |
US20100260556A1 (en) * | 2007-01-08 | 2010-10-14 | Vetco Gray Inc. | Ram Style Tensioner with Fixed Conductor and Floating Frame |
US20080166186A1 (en) * | 2007-01-08 | 2008-07-10 | Vetco Gray Inc. | Ram Style Tensioner With Fixed Conductor and Floating Frame |
US20110200397A1 (en) * | 2007-01-08 | 2011-08-18 | Vetco Gray Inc. | Ram Style Tensioner with Fixed Conductor and Floating Frame |
US20100143047A1 (en) * | 2007-01-08 | 2010-06-10 | Vetco Gray Inc. | Ram Style Tensioner With Fixed Conductor and Floating Frame |
US8215872B2 (en) | 2007-01-08 | 2012-07-10 | Vetco Gray Inc. | Ram style tensioner with fixed conductor and floating frame |
US20100254767A1 (en) * | 2007-01-08 | 2010-10-07 | Vetco Gray Inc. | Ram Style Tensioner |
US8011858B2 (en) * | 2007-01-08 | 2011-09-06 | Vetco Gray Inc. | Ram style tensioner with fixed conductor and floating frame |
US8123438B2 (en) | 2007-01-08 | 2012-02-28 | Vetco Gray Inc. | Ram style tensioner |
US7988385B2 (en) | 2007-01-08 | 2011-08-02 | Vetro Gray Inc. | Ram style tensioner with fixed conductor and floating frame |
GB2447140A (en) * | 2007-02-28 | 2008-09-03 | Vetco Gray Inc | Riser tensioner having a shock absorber |
GB2447140B (en) * | 2007-02-28 | 2011-09-07 | Vetco Gray Inc | Soft stop for maximum riser tensioner stroke |
US7708498B2 (en) | 2007-02-28 | 2010-05-04 | Vetco Gray Inc. | Soft stop for maximum riser tensioner stroke |
US20080205992A1 (en) * | 2007-02-28 | 2008-08-28 | Vetco Gray Inc. | Soft Stop for Maximum Riser Tensioner Stroke |
WO2008154545A3 (en) * | 2007-06-11 | 2010-07-15 | Technip France | Pull-style tensioner system for a top-tensioned riser |
US8021081B2 (en) | 2007-06-11 | 2011-09-20 | Technip France | Pull-style tensioner system for a top-tensioned riser |
US20080304916A1 (en) * | 2007-06-11 | 2008-12-11 | Gerald Crotwell | Pull-style tensioner system for a top-tensioned riser |
US20110155388A1 (en) * | 2008-06-20 | 2011-06-30 | Norocean As | Slip Connection with Adjustable Pre-Tensioning |
US8684090B2 (en) * | 2008-06-20 | 2014-04-01 | Norocean As | Slip connection with adjustable pre-tensioning |
US20110147002A1 (en) * | 2008-08-04 | 2011-06-23 | Cameron International Corporation | Subsea Differential-Area Accumulator |
US9303479B2 (en) * | 2008-08-04 | 2016-04-05 | Cameron International Corporation | Subsea differential-area accumulator |
US8833465B2 (en) * | 2008-08-04 | 2014-09-16 | Cameron International Corporation | Subsea differential-area accumulator |
US20150101822A1 (en) * | 2008-08-04 | 2015-04-16 | Cameron International Corporation | Subsea Differential-Area Accumulator |
US8540460B2 (en) * | 2010-10-21 | 2013-09-24 | Vetco Gray Inc. | System for supplemental tensioning for enhanced platform design and related methods |
US20120099930A1 (en) * | 2010-10-21 | 2012-04-26 | Vetco Gray Inc. | System for supplemental tensioning for enhanced platform design and related methods |
US8496409B2 (en) | 2011-02-11 | 2013-07-30 | Vetco Gray Inc. | Marine riser tensioner |
WO2012158821A1 (en) * | 2011-05-17 | 2012-11-22 | Drilling Technological Innovations | Ram tensioner system |
NO346400B1 (en) * | 2013-01-22 | 2022-07-11 | Dril Quip Inc | Hydropneumatic stretching machine with device to retain fluid |
GB2512441A (en) * | 2013-01-22 | 2014-10-01 | Dril Quip Inc | Hydro-pneumatic tensioner with fluid retention device |
NO345253B1 (en) * | 2013-01-22 | 2020-11-16 | Dril Quip Inc | Hydropneumatic HIV compensator with fluid retention device |
GB2512441B (en) * | 2013-01-22 | 2019-12-04 | Dril Quip Inc | Hydro-pneumatic tensioner with fluid retention device |
GB2503063A (en) * | 2013-02-07 | 2013-12-18 | Technip France | Passive heave compensator having variable compensation |
WO2014122527A3 (en) * | 2013-02-07 | 2015-07-02 | Technip France | Passive Heave Compensator |
WO2014122526A3 (en) * | 2013-02-07 | 2015-06-25 | Technip France | Passive heave compensator |
WO2014122526A2 (en) * | 2013-02-07 | 2014-08-14 | Technip France | Passive heave compensator |
AU2014213685B2 (en) * | 2013-02-07 | 2017-03-30 | Technip France | Passive heave compensator |
GB2503063B (en) * | 2013-02-07 | 2015-06-10 | Technip France | Passive heave compensator |
US9702428B2 (en) | 2013-02-07 | 2017-07-11 | Technip France | Passive heave compensator |
US9718652B2 (en) | 2013-02-07 | 2017-08-01 | Technip France | Passive heave compensator |
WO2015038004A1 (en) * | 2013-09-12 | 2015-03-19 | Depro As | Computerized device for compensation of wave-caused distance variations on a drill string |
AU2014221195A1 (en) * | 2014-09-02 | 2016-03-17 | Icon Engineering Pty Ltd | Riser tension protector and method of use thereof |
AU2014221195B2 (en) * | 2014-09-02 | 2016-07-21 | Icon Engineering Pty Ltd | Riser tension protector and method of use thereof |
US9410381B2 (en) | 2014-09-02 | 2016-08-09 | Icon Engineering Pty Ltd | Riser tension protector and method of use thereof |
US9926751B2 (en) * | 2014-11-21 | 2018-03-27 | Dril-Quip, Inc. | Enhanced ram-style riser tensioner |
US20160145952A1 (en) * | 2014-11-21 | 2016-05-26 | Dril-Quip, Inc. | Enhanced ram-style riser tensioner |
NO345715B1 (en) * | 2014-11-21 | 2021-06-28 | Dril Quip Inc | Ram-style riser tensioner system |
NO341078B1 (en) * | 2015-02-04 | 2017-08-21 | Petrolution As | Device for compensation |
NO340742B1 (en) * | 2015-05-08 | 2017-06-12 | Fmc Kongsberg Subsea As | Remote controlled well completion equipment |
WO2017018886A1 (en) * | 2015-07-24 | 2017-02-02 | Mcgregor Norway As | Hydraulic actuator |
US10287136B2 (en) | 2016-07-12 | 2019-05-14 | Ernst-B. Johansen AS | Heave compensator and method for reducing the risk of snap-loads during the splash-zone phase |
EP3269677A1 (en) | 2016-07-12 | 2018-01-17 | Ernst-B. Johansen AS | Heave compensator and method for reducing the risk of snap-loads during the splash-zone phase |
CN107601335A (en) * | 2016-07-12 | 2018-01-19 | 恩斯特-B.约翰森公司 | Heave compensator and the method that buckling load risk is reduced during the splash zone stage |
GB2576847A (en) * | 2017-05-19 | 2020-03-04 | AME Pty Ltd | Compensated elevator link |
WO2018209407A1 (en) * | 2017-05-19 | 2018-11-22 | AME Pty Ltd | Compensated elevator link |
GB2576847B (en) * | 2017-05-19 | 2021-12-29 | AME Pty Ltd | Compensated elevator link |
US11448017B2 (en) * | 2017-05-19 | 2022-09-20 | AME Pty Ltd | Compensated elevator link |
US11603716B2 (en) * | 2018-10-10 | 2023-03-14 | Dril-Quip, Inc. | Hydro-pneumatic cylinder with annulus fluid bypass |
WO2022119449A1 (en) * | 2020-12-03 | 2022-06-09 | Momentum Technologies AS | Viscoelastic damper assembly |
US11685208B2 (en) | 2021-04-26 | 2023-06-27 | Ree Automotive Ltd | Dual-axle vehicle corner assembly |
US11701935B2 (en) | 2021-08-16 | 2023-07-18 | Ree Automotive Ltd | Dual-wheels corner system with transverse suspension |
Also Published As
Publication number | Publication date |
---|---|
GB2407594A (en) | 2005-05-04 |
GB2407594B (en) | 2007-04-04 |
US20050123359A1 (en) | 2005-06-09 |
US7112011B2 (en) | 2006-09-26 |
NO20044384L (en) | 2005-04-18 |
GB0422861D0 (en) | 2004-11-17 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US7112011B2 (en) | Hydro-pneumatic tensioner with stiffness altering secondary accumulator | |
US4808035A (en) | Pneumatic riser tensioner | |
EP1428973B1 (en) | Portable heave compensator | |
CA2541168C (en) | Inline compensator for a floating drilling rig | |
US7131922B2 (en) | Ram-type tensioner assembly having integral hydraulic fluid accumulator | |
US8540460B2 (en) | System for supplemental tensioning for enhanced platform design and related methods | |
US9359837B2 (en) | Multi capacity riser tensioners | |
CN202338231U (en) | Steel wire rope type riser tensioner device | |
US9816538B1 (en) | Tensioner cylinder with internal gas bladder in high pressure chamber | |
US11448017B2 (en) | Compensated elevator link | |
EP3423668B1 (en) | Inverted pull-up riser tensioner | |
CN109703696A (en) | Passive type wave compensating device for ROV folding and unfolding | |
CN210396663U (en) | Compression type steel wire rope type marine riser tensioning device | |
NZ747890A (en) | Compensated Elevator Link | |
MXPA06003944A (en) | Inline compensator for a floating drilling rig |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: ABB VETCO GRAY INC., TEXAS Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MCCARTY, JEFFERY KIRK;KELLEY, ANDREW CAMPBELL;PALLINI, JOSEPH WILLIAM;REEL/FRAME:014617/0466 Effective date: 20030716 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |