Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K5/00—Casings; Enclosures; Supports
  • H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
  • H02K5/12—Casings or enclosures characterised by the shape, form or construction thereof specially adapted for operating in liquid or gas
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D25/00—Pumping installations or systems
  • F04D25/02—Units comprising pumps and their driving means
  • F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D25/00—Pumping installations or systems
  • F04D25/02—Units comprising pumps and their driving means
  • F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
  • F04D25/0686—Units comprising pumps and their driving means the pump being electrically driven specially adapted for submerged use
• • 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
  • F04D29/102—Shaft sealings especially adapted for elastic fluid pumps

Definitions

• the present invention relates to the provision of a secure environment for an electric motor of the type in which a single housing accommodates both the motor and rotating machinery driven by the motor.
• FIG. 1 shows a schematic representation of a typical prior art arrangement including a motor 2 linked to a compressor unit 4 by means of a shaft 6 mounted in bearings 8 and 1 0. All of these components are mounted in a single housing 1 2. Inlet pipe 1 4 and outlet pipe 1 6 lead gas respectively into and out of the compressor 1 2.
• the arrangement is only suitable for pumping dry gas because the motor will be damaged if exposed to moisture.
• Such a restriction makes the arrangement unsuitable for use in the pumping of gas from a hydrocarbon reservoir which will generally have a high water vapour content and contain droplets of water.
• an assembly comprising a housing, an electric motor accommodated within a first portion of the housing, rotating machinery accommodated within a second portion of the housing and driven by the electric motor, separation means in the housing between the first and second portions thereof for separating fluid acted upon by the rotating machinery from the electric motor, gas introduction means for introducing at least substantially dry motor protection gas into the first housing portion and restricted gas flow means for permitting a leakage of the motor protection gas from the first housing portion into the second housing portion.
• the gas introduction means includes means for supplying the at least substantially dry gas.
• This may comprise a gas drying and supply unit on a remote host facility linked to the first housing portion by an umbilical.
• the invention is particularly applicable to the driving of machinery for raising the pressure of fluid such as compressors or centrifugal pumps.
• the second housing portion includes a compressor inlet for receiving gas at a first pressure and a compressor outlet for delivering gas at a second pressure higher than the first pressure and the gas flow means allows leakage of the motor protection gas into the second housing portion adjacent to the compressor inlet.
• the assembly preferably also includes means for automatically maintaining the motor protection gas at a pressure above that of fluid in a part of the second housing portion adjacent to the gas flow means.
• the apparatus When the fluid being acted upon by the rotating machinery is a gas, the apparatus preferably includes circulating apparatus for diverting a portion of the acted upon gas to the first housing portion, the circulating apparatus including drying means for reducing the moisture content of the acted upon gas diverted back to the first housing portion.
• the apparatus will still further reduce the amount of motor protection gas which needs to be supplied and will still further reduce the cost of running the assembly.
• the motor can tolerate wet gas for a short start up period without damage to its components, then the requirement for an external supply of motor protection gas can be obviated if such circulating apparatus is provided.
• the drying means separates the extracted portion of the acted upon gas into an at least substantially moisture-free first outlet flow and the circulating apparatus includes first routing means for routing the first outlet flow from a first outlet of the drying means to the housing first portion.
• the drying means incorporates moisture extracted from the first outlet flow into a second outlet flow.
• the second outlet flow from the drying means can conveniently be transported away from the assembly by means of the gas being acted upon by the compressor.
• the circulating apparatus preferably also includes second routing means for routing the second outlet flow containing the extracted moisture from a second outlet of the drying means and for incorporating it into the flow of gas acted upon by the compressor.
• the second routing means incorporates the second outlet flow containing the extracted moisture into the acted upon gas at least substantially prior to it being acted upon by the compressor.
• the second routing means incorporates the second outlet flow containing the extracted moisture into the acted upon gas at least substantially after it has been acted upon by the compressor.
• the second routing means includes a pressure equalising device such as an ejector for incorporating the second outlet flow containing the extracted moisture into acted upon gas downstream of the compressor.
• a pressure equalising device such as an ejector for incorporating the second outlet flow containing the extracted moisture into acted upon gas downstream of the compressor.
• one or more gas outlet flows from the drying means pass through non-return valves configured to prevent such flow or flows returning directly to outlets of the drying means.
• the invention also provides a method of operating an electric motor accommodated in a first portion of a housing and arranged to drive a rotating machine accommodated in a second portion of the housing in which fluid in the second housing portion which is acted upon by the rotating machine is separated from the first housing portion by separation means, the method including the steps of: (i) providing gas introduction means for introducing at least substantially dry motor protection gas into the first housing portion; (ii) providing restricted gas flow means between the first and second housing portions; and
• the method involves providing circulating apparatus and diverting a portion of the acted upon gas to the first housing portion via the circulating apparatus, incorporating drying means in the circulating apparatus and reducing the moisture content of the acted upon gas diverted back to the first housing portion by means of the drying means.
• Figure 1 shows in schematic form a prior art arrangement
• Figure 2 shows in schematic form a further prior art arrangement
• Figure 3 shows in schematic form a first embodiment of the invention
• FIG 4 shows in schematic form a second embodiment of the invention.
• the prior art arrangements shown in Figs. 1 and 2 have been described above.
• an electric motor 30 is linked to a compressor 32 by a shaft 34 which is supported by a first bearing 36 and a second bearing 38.
• a housing 40 having first and second portions 42 and 44 respectively accommodating the motor 30 and the compressor 32.
• Separation means in the form of a wall 46, separates the housing portions 42 and 44 from each other.
• Gas introduction means in the form of an umbilical 48 leads to an inlet 50 of the first housing portion 42 for supplying at least substantially dry, and more preferably completely dry, motor protection gas 52 thereinto.
• Gas flow means 54 comprising one or more passages between the first and second housing portions 42 and 44, are provided to allow a leakage of the motor protection gas 52 from the first housing portion 42 into the second housing portion 44. This leakage is indicated by arrows A.
• the compressor 32 includes an inlet 56 connected to an inlet pipe 58 (at pressure p1 ) and an outlet 60 connected to an outlet pipe 62 (at a higher pressure p2).
• the first housing portion 42 containing the motor is maintained at a pressure p3 by the supply of motor protection gas 52.
• p3 is maintained higher than p1 in order that motor protection gas 52 steadily leaks through the gas flow means 54 in the direction of arrows A into the second housing portion.
• This pressure differential prevents any of the gas supplied to the compressor via inlet pipe 58, which may contain moisture, from entering the first housing portion 42.
• Control means are preferably provided to maintain p3 only slightly above p1 in order that only a low volumetric flow of motor protection gas through the gas flow means 54 occurs. This will reduce the amount of motor protection gas required and thereby minimise running costs.
• Man Turbo Maschinen AG would be the type of motor compressor assembly to which the invention could be applied.
• the embodiment shown in Figure 4 includes circulating apparatus shown generally as 1 70.
• An extraction pipe 1 72 is arranged to extract a portion, for example 10%, of the gas leaving the compressor via the outlet pipe 1 62 and route it to a gas drying unit 1 74.
• the gas drying unit 1 74 may suitably be of the type manufactured under the name TWISTER by Shell and its partner Stork Product Engineering. This drying unit uses a Laval nozzle to expand gas to supersonic velocities leading to low temperature and pressure resulting in nucleation and condensation of water. Droplets of water formed come into contact with a wing member and are centrifuged onto walls of the device.
• a first flow 1 76 of at least substantially dry gas (at pressure P3) leaves the gas drying unit via a first gas outlet 1 78 and is routed by dry gas conduit 1 82 via a non-return valve 1 80 to the umbilical 148 immediately upstream of the housing first portion 142 and downstream of a further non- return valve 1 84 in the umbilical 148.
• the pressure P3 is arranged to be greater than the pressure P5 of gas entering the compressor.
• the umbilical 1 48 for supplying dry gas may not be necessary in which case the dry gas conduit 1 82 would lead directly into the housing first portion 142.
• a second flow 1 86 of wet gas (at pressure P4) containing all, or substantially all, of the water contained in the gas extracted from the compressor outlet pipe leaves the gas drying unit 1 74 via a second outlet 188 and is routed by a wet gas conduit 1 90 to the inlet pipe 1 58 through a further non-return valve 1 92.
• the pressure P4 is arranged to be greater than P1 , the pressure of gas approaching the compressor through the inlet pipe 1 58. This flow of wet gas 186 will assist the flow of new gas entering the compressor from the inlet pipe 1 58.
• the second outlet 188 of the gas drying unit 1 74 may be connected by a high pressure wet gas conduit 1 93 which routes the wet gas 1 86 through a non-return valve 1 94 to an ejector 1 96 which acts to entrain the wet gas 1 86 into the flow of pressurised gas leaving the compressor via the outlet 160.
• the ejector 1 96 is necessary because the pressure P4 of the wet gas will be lower than the pressure P2 of the gas at the compressor outlet 1 60. Downstream of the ejector 1 96 the pressure P6 of the combined gas streams will be less than P2 but high enough to ensure satisfactory conveyance of the gas to the host facility.
• the alternative route for the wet gas 186 avoids reintroducing the moisture extracted by the gas drying unit 174 back into the compressor.
• the pressure of gas in the housing first portion 142 will be arranged to be slightly higher than the pressure P5 of gas entering the compressor so as to ensure that a steady leakage (A) of at least substantially dry gas from the first housing portion to the second is maintained and flow in the reverse direction is prevented.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Compressor (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9931528

Family Applications (1)

Country Status (7)

Cited By (6)

Families Citing this family (5)

Citations (7)

• 2002
  • 2002-02-21 GB GBGB0204139.0A patent/GB0204139D0/en not_active Ceased
• 2003
  • 2003-02-21 US US10/505,297 patent/US20050142004A1/en not_active Abandoned
  • 2003-02-21 WO PCT/GB2003/000779 patent/WO2003071139A1/en not_active Application Discontinuation
  • 2003-02-21 AU AU2003214370A patent/AU2003214370A1/en not_active Abandoned
  • 2003-02-21 BR BR0307982-1A patent/BR0307982A/pt not_active IP Right Cessation
  • 2003-02-21 EP EP03709940A patent/EP1478856A1/en not_active Withdrawn
• 2004
  • 2004-09-20 NO NO20043934A patent/NO20043934L/no not_active Application Discontinuation

Patent Citations (8)

Non-Patent Citations (1)

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