US3455270A - Protective dome for underwater mooring swivel - Google Patents

Description

July 15, 1969 .J. MAscr-:NIK ETAL y l 3,455,270

PROTECTIVE lDOME FOR UNDERWATER MOORING SWIVEL Filed May 8, 1968 WAM/'Po f. w )You nw ATTORNEY United States Patent 3,455,270 PROTECTIVE DOME FUR UNDERWATER MOORING SWIVEL John Mascenik, Mount Tabor, John F. Flory, Morristown,

and Leonard E. Van Houten, Montclair, NJ., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed May 8, 1968, Ser. No. 727,457 Int. Cl. B63b 21/38, 21/52 U.S. Cl. 114-230 11 Claims ABSTRACT OF THE DISCLOSURE A watertight dome is placed over an underwater mooring swivel and supplied with gas under pressure to exclude water from the area of the swivel and other sensitive components. The level of water in the dome is controlled by a float controlled valve on a pressurized fluid line from the shore.

Background of the invention The instant invention relates to protective equipment to be used in conjunction with remote operating systems which are adapted to be submerged in uids such as seawater, for example. More particularly, the invention relates to the protection of offshore tank ship mooring and loading systems which are used for the loading and unloading of liquid materials particularly petroleum products, crude oils and chemicals in areas where inadequate docking facilities are available. More particularly, the invention relates to the improvement which provides effective means for insulating an underwater mooring and loading system from the corrosive seawater environment.

Several systems are known in the art for the loading and unloading of seagoing vessels. Suitable systems must provide means for mooring and loading a vessel which insure operations which are essentially unaffected by a continuous shifting of the vessel due to variations in the tide, the degree of load carried and wind or wave action. In the loading of liquids such as petroleum products, chemicals and the like, provision must also be made for a conduit between the vessels storage chambers and onshore storage facilities.

Systems known in the art for the loading and unloading of tankers include permanent piers, submarine anchorages, floating terminals and rotating booms. Customarily, tankers are loaded at permanent piers in protected waters or harbors whereby the ship is moored to appear running parallel thereto and liquid connection is provided by flexible pipelines. The pier restrains lateral movement of the ship and the fiexible lines adjust to vertical movement due to tidal and loading variations without undue strain on the vessel connections. It is to be appreciated, however, that piers are not available or suitable in many remote areas and consequently in such areas the mooring and loading of tankers must be accomplished without the protection of permanent xed piers in harbors or other protective waters.

The customary alternative where permanent piers are unavailable is offshore mooring whereby a exible coupling is provided for the transfer of liquid between a fixed submarine line running from shore storage and a moored continuously shifting tanker. Common methods of this type of mooring and loading include submarine anchorages, floating terminals and rotating booms. Submarine anchorages normally comprise a xed submarine line running to an anchorage on sea bottom, coupled to flexible loading hoses running to a tanker manifold. Bow mooring of the tanker is usually provided for to allow the tanker to face the wind, waves and current.

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Because the mooring swivel must withstand high mooring forces and must provide a concentric passage for cargo, it is necessarily large and complex. In many applications it is desirable to place this mooring swivel on the ocean -bottom to eliminate the large surface buoy or support towers which require much maintenance and constitute navigation hazards. However, to date the problems of designing adequate underwater mooring swivels have been diflicult due to problems of sealing and lubrication of the mooring swivel in the salt water environment. These problems have necessitated in many instances the use of exotic materials and designs to prevent seawater corrosion.

Summary of the invention According to the invention herein to be further described, a water-excluding dome is placed over the under` Water mooring swivel and lled with a gas under pressure to exclude the seawater from the area of the swivel and its associated sensitive components. The level of water allowed into the dome is readily controlled by providing a float valve, which valve controls the pressurizing gas feed line. The use of the dome allows conventional materials to be used in the construction of the swivel and also allows the use of less exotic swivel designs, thus effecting great reductions in cost and complexity. In addition to preventing seawater penetration, the dome shuts out sunlight and, therefore, prevents marine growth` The dome also protects the components from silt and falling debris. Furthermore, if inert gases are used within the dome, the problems of corrosion are avoided. Of additional advantage is the fact that the gas atmosphere surrounding the swivel provides a dry environment which would allow divers to perform eicient maintenance work using conventional tools; and if the inert gas atmosphere is replaced with an oxygen mixture, divers could remove diving gear and work in complete comfort. While the invention will be described as preferably employing a gas within the dome, the use of a lighter than water lluid such as kerosene or oil may also be employed and is fully contemplated within the scope of the present invention. When a liquid is employed instead of a gas, a marine growth inhibitor may be added to the liquid if desired.

Thus, an object of the instant invention is to provide an eicient underwater swivel to be used in conjunction with a single point mooring system.

A further object is to provide an improved mooring system with a trouble-free underwater swivel joint, which joint may be fabricated from non-exotic materials which could not normally be used in a seawater environment.

Yet, another object is to provide protection means for underwater mooring swivels which assure trouble-free operation and allow for ready accessibility and easy access during maintenance.

These as well as further objects and a fuller understanding of the invention may be had by referring to the accompanying detailed description taken in conjunction with the associated drawing.

Brief description of the drawing FIGURE l is a diagrammatic illustration of the device of the instant invention in a single point mooring system; and

FIGURE 2 is a plan view of the gas dome protection means of the instant invention.

Referring to FIGURE l in more detail, referenceI numeral 2 denotes a tanker. Tanker 2 is secured to a mooring buoy 4 by the mooring line 6. The underwater mooring swivel indicated generally at 12 is provided with a frame member 10. An anchor chain 8 secures the buoy 4 to frame 10 at eyelet 14. The lower portion of frame 10 is rigidly secured to a turntable 16 adapted for rotation in turntable support means 18. Suitable bearings indicated schematically at 20 and 21 are provided to insure that the turntable 16 may freely rotate within support means 18. Support means 18 are firmly attached to a foundation block or base 22 which is firmly atiixed to ocean bed 24. A cargo swivel 26 is affixed in the central region of the turntable 16. Swivel 26 is designed to allow continuous 360 rotation about a pipeline 28, which is used to transfer cargo from the mooring swivel 12 to suitable land based storage vessels (not shown).

Frame 1li is provided also with a mounting lug 30. A gas dome 40 is provided over the turntable and swivel assembly and firmly affixed to lug 30 and eyelet portion 14 of frame 10. As may be more clearly seen in FIGURE 2, portion 14 and lug 30 of the frame 12 project through the surface of gas dome 40 and are affixed thereto by suitable joints such as welds 48 and 50. Lug 30 is provided with a pivot hole 52 adapted to receive a pivot 36. Pivot 36 secures the yoked end 34 of a loading arm 32 to the lug 30. Within the loading arm 32 is provided a cargo transfer line 46. A liexible piping connection 38 is provided to transfer the cargo around the rotatable connection formed by yoke 34 and lug 30.

Once again referring to FIGURE l, it may be seen that upon passing through the surface of dome 40, the liexible pipe 3S is connected to the cargo swivel 26. Thus, it may be seen that the instant system is able to accommodate any movement of the tanker 2; the swivel joint between the loading arm and the lug 30 accommodating the up and down motion of the moored ship and the turntable 16 with its associated pivot 26 accommodating motions of the tanker 2 about the mooring point.

To protect cargo swivel 26, turntable 16, bearings 20 and 21 and the connection between flexible' piping 38 and swivel 26 from the corrosive seawater environment, dome 40 is provided with means for eliminating seawater therefrom. These means comprise apparatus for introducing a gas under pressure into the dome 40, which gas displaces seawater from its interior and includes a gas line' 54 for piping a gas under pressure from the shore to the dome 40. Gas line 54 is provided with a control valve 58, which is actuated by a oat 57 which rides on the surface 60 of the water within the dome 40. If water level 60 should begin to rise, iioat 57 is elevated and this in turn opens the valve 58, thus allowing pressurized gas into the dome, which in turn displaces the water in dome 40 until it is back to its desired level.

It will be appreciated that ready access to the interior of dome 40 is achieved through the peripheral gap 61 between the lower portion of dome 40 and base 22. As hereinbefore indicated, if the pressurizing gas is oxygen containing, divers could readily work in comfort and without breathing apparatus within dome 40 to do any necessary periodic maintenance such as the lubrication of bearings 20 and 21, for example.

While the instant invention has been described in considerable detail for the purposes of illustration, it is to be appreciated that various changes in the elements depicted may be made without departing from the spirit of the invention.

What is claimed is:

1. An underwater mooring which comprises a base, a frame, bearing means for rotatably mounting said frame on said base, a swivel joint adapted to rotate with said frame, conduit means for transferring fluid to and from said swivel joint, a uid tight open bottomed dome secured to said frame and extending over said bearing means, and means for introducing into said dome a fluid at a pressure sufficient to exclude water from the region of said bearing means and said swivel.

2. The mooring of claim 1 further including a float controlled valve on said uid introducing means.

3. The mooring of claim 1 wherein said fluid is selected from the group comprising oxygen, nitrogen and mixtures thereof.

4. The mooring 0f claim 1 wherein said fluid is a liquid lighter than water.

5. The mooring of claim 4 wherein said liquid is a lubricant.

6. The mooring of claim 5 wherein said liquid contains a marine growth inhibitor.

7. An underwater mooring suitable for transferring uid between a shore facility and a moored vessel which comprises, a base, a turntable rotatably mounted on said base, a frame mounted on said turntable, a swivel joint adapted to rotate with said turntable, a first conduit means in communication with said swivel joint for transferring fluid between said joint and said shore facility, a second conduit means in communication with said swivel joint for transferring uid between said moored vessel and said joint, a fluid tight open bottomed dome rigidly secured to said frame and extending over said turntable and means for introducing into said dome a uid at a pressure suicient to exclude water, from the region of said turntable.

8. The mooring of claim 7 further characterized in that a float-controlled valve is provided on said fluid introducing means and said uid is an inert gas.

9. In an offshore mooring and ship loading and unloading system, an improved underwater mooring which comprises a base supported by the ocean bottom, a turntable rotatably mounted on said base, a swivel joint adapted to rotate with said turntable, said swivel suitable for transferring materials between a shore facility and a moored vessel, a mooring frame mounted on said turntable', a irst conduit means in communication with said swivel for transferring uid between said swivel and said shore facility, a second conduit means in communication with said swivel for transferring fluid between said moored vessel and said swivel, a gas tight open bottomed dome rigidly secured to said frame and extending over said turntable, and means for excluding water from said dome to protect said turntable, said last means including a gas conduit from said shore facility to the interior of said dome and control means to admit said gas from said gas conduit into said dome at a pressure suicient to prevent said water from rising above a predetermined level.

10. The underwater mooring of claim 9further characterized in that said frame is provided with a mooring portion and a portion to which said second conduit is pivotably attached, both of said portions extending outside of said dome and rigidly connected thereto.

11. The underwater mooring of claim 10 wherein a mooring buoy for mooring said Vessel is exibly connected to the mooring portion of said frame.

TRYGVE M. BLIX, Primary Examiner U.S. Cl. X.R.

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