GB2534226A - Rotary shaft sealing system - Google Patents

Rotary shaft sealing system Download PDF

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Publication number
GB2534226A
GB2534226A GB1500858.4A GB201500858A GB2534226A GB 2534226 A GB2534226 A GB 2534226A GB 201500858 A GB201500858 A GB 201500858A GB 2534226 A GB2534226 A GB 2534226A
Authority
GB
United Kingdom
Prior art keywords
pressure
fluid
water
gas
seal
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.)
Withdrawn
Application number
GB1500858.4A
Other versions
GB201500858D0 (en
Inventor
Coppock Peter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Marine Current Turbines Ltd
Original Assignee
Marine Current Turbines Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Marine Current Turbines Ltd filed Critical Marine Current Turbines Ltd
Priority to GB1500858.4A priority Critical patent/GB2534226A/en
Publication of GB201500858D0 publication Critical patent/GB201500858D0/en
Publication of GB2534226A publication Critical patent/GB2534226A/en
Withdrawn legal-status Critical Current

Links

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
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J15/00—Sealings
    • F16J15/16—Sealings between relatively-moving surfaces
    • F16J15/40—Sealings between relatively-moving surfaces by means of fluid
    • F16J15/406—Sealings between relatively-moving surfaces by means of fluid by at least one pump
    • 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
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J15/00—Sealings
    • F16J15/16—Sealings between relatively-moving surfaces
    • F16J15/164—Sealings between relatively-moving surfaces the sealing action depending on movements; pressure difference, temperature or presence of leaking fluid
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B11/00—Parts or details not provided for in, or of interest apart from, the preceding groups, e.g. wear-protection couplings, between turbine and generator
    • F03B11/006—Sealing arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/26—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using tide energy
    • F03B13/264—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using tide energy using the horizontal flow of water resulting from tide movement
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B17/00—Other machines or engines
    • F03B17/06—Other machines or engines using liquid flow with predominantly kinetic energy conversion, e.g. of swinging-flap type, "run-of-river", "ultra-low head"
    • F03B17/061—Other machines or engines using liquid flow with predominantly kinetic energy conversion, e.g. of swinging-flap type, "run-of-river", "ultra-low head" with rotation axis substantially in flow direction
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/08—Sealings
    • F04D29/086—Sealings especially adapted for liquid pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/08—Sealings
    • F04D29/10—Shaft sealings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/08—Sealings
    • F04D29/10—Shaft sealings
    • F04D29/106—Shaft sealings especially adapted for liquid pumps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
    • B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
    • B63B2035/4433—Floating structures carrying electric power plants
    • B63B2035/4466—Floating structures carrying electric power plants for converting water energy into electric energy, e.g. from tidal flows, waves or currents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/30—Energy from the sea, e.g. using wave energy or salinity gradient

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Power Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Oceanography (AREA)
  • Mechanical Sealing (AREA)

Abstract

A sealing system for a rotary shaft 1 is provided. The rotary shaft sealing system is adapted to be connected between a rotating body in water and equipment mounted out of the water. The rotary shaft sealing system comprises: a gas tight housing 3 for the equipment; a fluid tight enclosure 5; a first shaft seal 4 between the gas tight housing 3 and the fluid tight enclosure 5; and a second seal 12 between the fluid tight enclosure 5 and the water. The system further comprises a source of fluid 9 for the fluid tight enclosure 5; and a pressure compensator 10 to maintain the pressure of the fluid in the fluid tight housing 5 at or above the pressure of the water.

Description

ROTARY SHAFT SEALING SYSTEM
This invention relates to a rotary shaft sealing system, in particular for low speed shaft seal pressure control, such as in a subsea turbine, or a submersible vessel, 5 such as an ROV.
Underwater turbine or propeller shafts rotate, so a dynamic seal is required to keep water out of the body in which the shaft is installed, for example a powertrain of a subsea turbine, or the hull of a vessel. Typically, shafts are also lubricated with oil to prevent overheating and reduce wear, so the shaft seal also needs to prevent loss of the lubricating oil into the water. In a two part shaft seal, there may be a void between the two parts of the seal which is filled with lubricating oil at a pressure slightly above the pressure of the surrounding seawater. The specific gravity of the oil is less than that of seawater, so the oil is supplied by a hose to the void from a tank at a sufficient height above the seal to generate a static head. However, as the depth of the installation increases, so the height above the seal from which the oil is supplied must be increased, which may increase the overall size of the installation.
A further problem is that for stationary objects maintained at a constant height above the seabed, keeping the pressure differential at the required level is complicated by changes in the external pressure due to rise and fall of the tide and to some extent, due to wave action. For an ROV, which may be on station for a relatively short time, measured in hours or days, the seals can be checked and maintained between operations. However, for tidal turbines, operating in deep water, access is difficult and with a desired servicing interval of one or two years, it is important to maintain the correct pressure differential. The static pressure generated by the tank mounted above the seal cannot compensate for the tidal range, nor for pressure fluctuations due to waves.
In accordance with the present invention, a rotary shaft sealing system for a shaft adapted to be connected between a rotating body in water and equipment mounted out of the water comprises a gas tight housing for the equipment; a fluid tight enclosure; a first shaft seal between the gas tight housing and the fluid tight enclosure; and a second seal between the fluid tight enclosure and the water; the system further comprising a source of fluid for the fluid tight enclosure; and a pressure compensator to maintain the pressure of the fluid in the fluid tight housing at or above the pressure of the water.
Preferably, the system further comprises a source of gas for the gas tight housing; and wherein the pressure compensator maintains a relative pressure of the gas in the gas tight housing and the fluid in the fluid tight enclosure, in response to changes in the pressure of the water.
Preferably, the pressure compensator comprises a fluid filled chamber connected to the fluid tight enclosure; one wall of the fluid filled chamber comprising a spring, bladder, or bellows, wherein the spring, bladder, or bellows further comprises an surface in contact with the water adapted to move the spring, bladder or bellows in response to a change in the pressure of the water on the external wall.
Preferably, the pressure compensator comprises a pressure sensing valve and a controller to maintain the pressure of the fluid in the fluid tight housing at or above the pressure of the water.
Preferably, the pressure compensator comprises a pressure sensing valve and a controller to maintain a relative pressure of the gas in the gas tight housing and the fluid in the fluid tight enclosure, in response to changes in the pressure of the water.
Preferably, the system further comprises additional sealing elements.
Preferably, the seals comprise flexible, or rigid seals, shaft sealing, or face sealing seals.
Preferably, the fluid comprises oil.
Preferably, the gas comprises air.
Preferably, the rotating body in water comprises a subsea turbine, or submersible vessel propeller; and the equipment mounted out of the water comprises a drivetrain, or gearbox.
The present invention overcomes the problem by setting the seal pressure at the external pressure plus a differential and changing the absolute value of that automatically in response to changes in the external pressure, so that it is always at the external pressure plus the differential. This increases reliability of the seals and avoids the need for mounting the fluid supply to the seal at a significant height above the seal.
An example of a rotary shaft sealing system according to the present invention and method of operation will now be described with reference to the accompanying drawings in which: Figure 1 is a block diagram of a rotary shaft sealing system according to the present invention; and, Figure 2 is a flow diagram of a method of operation of the system of Fig.1 Rotary shaft seals are in use in a variety of applications, including propeller shaft seals in submersible vessels and rotary shaft seals in gearboxes for tidal turbines. The speed of rotation of this shaft tends to be quite low, for example of the order of 15 revolutions per minute and the gearbox converts up to a higher rotational speed required to generate electricity. As discussed above, tidal turbines have a need for high reliability due to the difficulties of access for repair and maintenance, so it is desirable to keep the relative pressure between the rotary shaft seal and the external sea water as constant as possible.
Fig.]. illustrates an example of a rotary shaft sealing system according to the present invention. A low speed shaft 1 is connected to a drive train gearbox 2, mounted in a housing 3 filled with a gas, typically air, or nitrogen, at a pressure Pg. The gearbox is also provided with gearbox oil. A housing 3 of the gearbox 2 has a seal 4 between the housing 3 and an internal volume of a rotary shaft seal comprising an enclosure 5 surrounding a section 6 of the low speed shaft, the enclosure containing a fluid 7. The seal prevents the gearbox oil from escaping into the enclosure 5 and keeps the fluid in the enclosure 5 out of the sensitive workings of the gearbox. The fluid filled enclosure is directly connected via a pipeline 8 to a fluid chamber 9 of a pressure compensator 10. The pressure compensator may be of a piston type, with a bellows or spring, or a bladder type, but in either case, a surface 11 of the piston, or bladder, remote from the fluid chamber 9 is open to the water, at the water pressure, Pw. A second seal 12 is provided between the enclosure 5 and a further section 13 of the shaft 1 to keep the seawater out and the fluid in the enclosure. The pressure of the second seal is at least equal to the external water pressure Pw and preferably the pressure of the second seal is Pw plus a differential, SP, to ensure that the seal pressure is higher than the water pressure.
The rotary shaft seal preferably comprises two sealing elements 4, 12 as shown in Fig.1, although additional sealing elements may be provided in the area of seal 4. The seals may be flexible, such as elastomeric seals, or rigid seals. The seals may be shaft sealing, or face sealing type seals. The volume of the enclosure 5 between the seals 4, 12 may be filled with any suitable fluid in its liquid state, such as fresh water, but more preferably oil and the fluid is typically supplied at pressure in order to provide a positive pressure differential to the external water pressure to ensure the effectiveness of the seal 12, although the pressure of the fluid in enclosure 5 may be the same as the water pressure, Pw.
During the operation of a tidal turbine, the pressure of the water in which the turbine is operating changes due to changes in the level of the water above the turbine, for example between low tide level 23a and high tide level 23b and due to changes in the pressure on the turbine caused by waves. In order to maintain the life of the shaft seal, the seal pressure needs to be precisely controlled. Water pressure on the open side 11 of the pressure compensator 10 may act directly on the fluid to maintain the pressure in the enclosure 5 at the same pressure as the external water pressure the other side of seal 12. When the pressure compensator 10 is configured to directly reflect the sea water pressure by omitting the spring, bellows, or bladder (not shown), there is only a short response time to enhance the life of the seal.
However, in the example shown, the external water pressure on the pressure compensator acts on a spring 14, bellows, or bladder, so that the pressure in the fluid chamber 9 is equal to the seawater pressure, plus the small amount 6P from the spring, bellows or bladder and the pressure of the seal 12 relative to the seawater pressure remains constant, independent of the depth of water above the seal at any state of tide, or short term effects of pressure due to wave action.
The pressure Pw, or Pw plus OP, from the compensator 10 may be applied to the seal 12 and also to an air regulating valve 15 controlling the air pressure Pg within the drive train gearbox housing 3. In this way, the air pressure in the gearbox may be controlled automatically and accurately by the pressure compensator to maintain a pressure that is directly proportional to the water pressure Pw and also to the pressure in the enclosure 5. Thus, the pressure across the seal 4 is controlled.
For shallower water installations, or turbines 17 which are mounted on a surface piercing structure 16, such as illustrated in Fig.2, where the source of the fluid in enclosure 5 may be either a surface installed tank 18, or an accumulator and the gas supply may be from a surface installed compressor 19, or a compressed gas bottle, with the fluid and gas supplied via an umbilical 20 to each turbine 17, then the pressure of both the fluid in the enclosure 5 and the gas in the gearbox housing 3 may be controlled using a differential pressure transducer 21 sensing water pressure at a position within the turbine that is open to the water, rather than by direct application of water pressure to a fluid chamber 9 as in the example of Fig.1. A change in measured water pressure is transmitted to a controller 22 via a cable in the umbilical and the controller then modifies the pressure at which the fluid and gas are supplied to the enclosure 5 and housing 3 respectively.
The specific example has been described with respect to a subsea tidal turbine rotary shaft seal, but the pressure control provided by the system of the present invention is applicable to any type of submersible rotary seal.

Claims (10)

  1. CLAIMS1. A rotary shaft sealing system for a shaft adapted to be connected between a rotating body in water and equipment mounted out of the water; the system comprising a gas tight housing for the equipment; a fluid tight enclosure; a first shaft seal between the gas tight housing and the fluid tight enclosure; and a second seal between the fluid tight enclosure and the water; the system further comprising a source of fluid for the fluid tight enclosure; and a pressure compensator to maintain the pressure of the fluid in the fluid tight housing at or above the pressure of the water.
  2. 2. A system according to claim 1, wherein the system further comprises a source of gas for the gas tight housing; and wherein the pressure compensator maintains a relative pressure of the gas in the gas tight housing and the fluid in the fluid tight enclosure, in response to changes in the pressure of the water.
  3. 3. A system according to claim 1 or claim 2, wherein the pressure compensator comprises a fluid filled chamber connected to the fluid tight enclosure; one wall of the fluid filled chamber comprising a spring, bladder, or bellows, wherein the spring, bladder, or bellows further comprises an surface in contact with the water adapted to move the spring, bladder or bellows in response to a change in the pressure of the water on the external wall.
  4. 4. A system according to claim 1 or claim 2, wherein the pressure compensator comprises a pressure sensing valve and a controller to maintain the pressure of the fluid in the fluid tight housing at or above the pressure of the water.
  5. 5. A system according to claim 2, wherein the pressure compensator comprises a pressure sensing valve and a controller to maintain a relative pressure of the gas in the gas tight housing and the fluid in the fluid tight enclosure, in response to changes in the pressure of the water.
  6. 6. A system according to any preceding claim, wherein the system further comprises additional sealing elements.
  7. 7. A system according to any preceding claim, wherein the seals comprise flexible, or rigid seals, shaft sealing, or face sealing seals.
  8. 8. A system according to any preceding claim, wherein the fluid comprises oil.
  9. 9. A system according to at least claim 2, wherein the gas comprises air.
  10. 10. A system according to any preceding claim, wherein the rotating body in water comprises a subsea turbine, or submersible vessel propeller; and the equipment mounted out of the water comprises a drivetrain, or gearbox.
GB1500858.4A 2015-01-19 2015-01-19 Rotary shaft sealing system Withdrawn GB2534226A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1500858.4A GB2534226A (en) 2015-01-19 2015-01-19 Rotary shaft sealing system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1500858.4A GB2534226A (en) 2015-01-19 2015-01-19 Rotary shaft sealing system

Publications (2)

Publication Number Publication Date
GB201500858D0 GB201500858D0 (en) 2015-03-04
GB2534226A true GB2534226A (en) 2016-07-20

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GB1500858.4A Withdrawn GB2534226A (en) 2015-01-19 2015-01-19 Rotary shaft sealing system

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107489769A (en) * 2016-06-09 2017-12-19 耐驰精细研磨技术有限公司 Shaft sealer
WO2020156089A1 (en) * 2019-01-31 2020-08-06 长沙矿冶研究院有限责任公司 Deep water pump having pressure compensation function

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102966740A (en) * 2012-11-20 2013-03-13 中国舰船研究设计中心 Water lubrication deep-water passive dual-end-face stern shaft tube sealing device
CN203516072U (en) * 2013-11-02 2014-04-02 于信太 Pressure balance sealing device of high-pressure water injection pump
CN104179678A (en) * 2014-07-29 2014-12-03 苏州通力电气有限公司 Screw submersible pump

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102966740A (en) * 2012-11-20 2013-03-13 中国舰船研究设计中心 Water lubrication deep-water passive dual-end-face stern shaft tube sealing device
CN203516072U (en) * 2013-11-02 2014-04-02 于信太 Pressure balance sealing device of high-pressure water injection pump
CN104179678A (en) * 2014-07-29 2014-12-03 苏州通力电气有限公司 Screw submersible pump

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107489769A (en) * 2016-06-09 2017-12-19 耐驰精细研磨技术有限公司 Shaft sealer
WO2020156089A1 (en) * 2019-01-31 2020-08-06 长沙矿冶研究院有限责任公司 Deep water pump having pressure compensation function

Also Published As

Publication number Publication date
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