Underwater Compressor Arrangement And Underwater Process Fluid Conveying Arrangement Equipped Therewith

Abstract

Underwater compressor arrangement and underwater process fluid conveying arrangement outfitted therewith. The underwater compressor arrangement has a housing, a turbocompressor with a compressor rotor, and a rotary drive unit with a drive rotor. The turbocompressor and rotary drive unit are arranged in the housing, and the compressor rotor is in rotationally driving connection with the drive rotor. The housing is hermetically sealed with the exception of operating connections for the turbocompressor and rotary drive unit, The compressor rotor is rotatably supported in the housing by a rolling element bearing arrangement.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This is a U.S. national stage of application No. PCT/DE2010/050052, filed on 28 Jul. 2010. Priority is claimed on German Application No. 10 2009 045 633.3 filed 13 Oct. 2009 the content of which is incorporated here by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention is directed to an underwater compressor arrangement and an underwater process fluid conveying arrangement outfitted with an underwater compressor arrangement.

[0004] 2. Description of Prior Art

[0005] An underwater compressor arrangement or subsea compressor arrangement in the form of a HOFIM Sealed (High Speed Oil Free Integrated Motor compressor) available from MAN Turbo AG is described on pages 24-25 of the magazine "MANforum", issue 01/2007, from the MAN Group.

[0006] FIG. 1 shows an underwater compressor arrangement 1' of this kind having a high-frequency electric motor 10' as a rotary drive unit and two turbocompressors 30' which are each in direct rational driving connection with the high-frequency motor 10' via a shared rotor shaft 20'. The high-frequency motor 10', rotor shaft 20', and two turbocompressors 30' are combined and arranged in a housing 40', which is hermetically closed with the exception of operating connections for the turbocompressors 30' (e.g., process fluid inlet 31' and process fluid outlet 32') and the high-frequency motor 10' (e.g., power supply 11'). The shared rotor shaft 20' is supported in the housing 40' by a plurality of electrically operated magnetic bearings 21'.

[0007] The underwater compressor arrangement 1' shown in FIG. 1 can be used for moving process fluids, e.g., natural gas, into and out of storage in a process fluid receiver such as an intermediate storage. So-called caverns for example, cavities in depleted natural gas fields or tanks arranged below or above sea level, can be used as intermediate storages. Therefore, the underwater compressor arrangement 1' can advantageously be used, e.g., for natural gas extraction, on the open sea, e.g., by platforms or ships.

[0008] Since the pressure in a borehole in developed natural-gas fields continuously decreases until normal conveying is impossible, it is scarcely possible to fully exploit the gas reserves in such natural-gas fields. With the underwater compressor arrangement 1', which can raise the pressure after the borehole to a desired value, natural-gas fields located up to 3000 meters below seal level can be fully exploited. Accordingly, the completely outwardly sealed housing 40' of the underwater compressor arrangement 1' makes this underwater compressor arrangement 1' ideally suited for conveying directly at the borehole on the sea floor, i.e., for subsea applications. To this end, the underwater compressor arrangement 1' is sunk and is connected to an undersea pipeline and conveying robots.

[0009] The rotor shaft 20' of the underwater compressor arrangement 1' is rotatably mounted in the housing 40' by electrically operated magnetic bearings 21', which must be controlled by one or more electronic control devices (not shown in FIG. 1) as is described, e.g., in WO 97/13986 A1, e.g., referring to FIGS. 1 and 6, or in EP 1 069 313 B1, e.g., referring to FIG. 4.

[0010] Further details on magnetic bearing technology and on the use of underwater compressor arrangements are also described in Lecture Notes 2009, "Theorie and Praxis der Magnetlagertechnik--eine kurze Einfuhrung" by R. Schob, Eidgenossischen Technischen Hochschule Zurich.

[0011] In the case of a natural gas-compressing underwater compressor arrangement on the sea floor, a MTBF (Mean Time Between Failure) of five years is required. However, magnetic bearings with electronic control devices have a digital failure behavior; that is to say, a stoppage or outage of the entire underwater compressor arrangement due to failure of the magnetic bearings that takes place without prior warning. In the case of an underwater compressor arrangement, this means that the underwater compressor arrangement must be hoisted from the sea floor at a moment's notice by a ship's crane, which can be very time-consuming due to preparation of the ship's crane. Further, additional costs and damages can occur due to the sudden outage of the underwater compressor arrangement.

SUMMARY OF THE INVENTION

[0012] It is an object of one embodiment of the invention to provide an underwater compressor arrangement in which a sudden outage of the bearing support can be prevented for the most part. The invention further provides an underwater process fluid conveying arrangement outfitted with an underwater compressor.

[0013] According to first aspect of the invention, an underwater compressor arrangement for compressing a process fluid has a housing, a turbocompressor with a compressor rotor, and a rotary drive unit with a drive rotor, and the turbocompressor and rotary drive unit are arranged in the housing, and the compressor rotor is in rotationally driving connection with the drive rotor, the housing is hermetically sealed with the exception of operating connections for the turbocompressor and rotary drive unit, and the compressor rotor is rotatably mounted in the housing by a rolling element bearing arrangement.

[0014] The rotary drive unit is preferably formed by an electric motor but can also be formed, e.g., by a fluid motor or the like.

[0015] The rolling element bearing arrangement, according to one embodiment of the invention, of the compressor rotor--and preferably also of the drive rotor--prevents a digital failure behavior in a simple and robust manner because a failure of rolling element bearings is generally preceded by gradually increasing vibrations in the respective bearing location. This makes it possible for an operator of the underwater compressor arrangement to schedule a maintenance window based on vibration trends and to replace the underwater compressor arrangement according to schedule in due time before a failure.

[0016] The rolling element bearing arrangement is preferably formed by at least one, particularly a plurality of, ball bearings, roller bearings and/or needle bearings. Bearings of this kind are available as standard parts for a broad range of loads and can accordingly be supplied quickly and inexpensively.

[0017] According to one embodiment of the invention, the rotary drive unit is arranged such that a maximum rotational speed which is determined for the fatigue strength of the rolling element bearing arrangement is not exceeded during rotational driving of the compressor rotor.

[0018] Turbocompressors are generally operated at rotational speeds that are too high for standard rolling element bearings and therefore lead to premature failure. For this reason, among others, noncontacting magnetic bearings or hydrodynamic bearings, for example, are used for turbocompressors in the prior art. However, by limiting the rotational speed of the rotary drive unit to a maximum rotational speed suited to the fatigue strength, the fatigue strength can also be ensured for rolling element bearings. The rotational speed can be limited, for example, by mechanically and/or electrically as known to the person skilled in the art.

[0019] According to another embodiment of the invention, the compressor rotor and the rotary drive unit have a shared rotor shaft by which the compressor rotor and the rotary drive unit are in direct rotationally driving connection with one another.

[0020] In this way, clutches and transmissions which can present other sources of failure can advantageously be eliminated and costs can also be lowered.

[0021] Further, according to yet another embodiment of the invention, the underwater compressor arrangement has a maintenance device arranged to ensure a lubrication and/or a cooling of the rolling element bearing arrangement, and a liquid and/or a gas are/is provided as operating media/medium (lubricant and/or coolant) for lubricating and/or cooling the rolling element bearing arrangement.

[0022] The operating medium for lubricating and/or cooling the rolling element bearing arrangement is preferably a methanol-ethanol-glycol mixture which, e.g., in order to prevent hydrate formation at a borehole, is injected into an underwater ground such as a sea bottom and is therefore present in large quantities at the underwater ground.

[0023] The maintenance device is preferably arranged to supply the operating medium for lubrication and/or cooling of the rolling element bearing arrangement to the rolling element bearing arrangement via the process fluid to be compressed.

[0024] Accordingly, a lubrication and/or cooling of the rolling element bearing arrangement is substantially guaranteed in a simple and economical manner and the life of the rolling element bearing arrangement is additionally prolonged in this way.

[0025] According to one embodiment of the invention, the turbocompressor is arranged to process natural gas as process fluid to be compressed.

[0026] According to one embodiment of the invention, the underwater compressor arrangement has a vibration monitoring unit arranged to monitor vibrations in the rolling element bearing arrangement with respect to amplitude and/or frequency thereof.

[0027] For example, the vibration monitoring unit can have one or more vibration sensors at one or all bearings. Further, the vibration monitoring unit is preferably arranged to transmit monitoring data reproducing the amplitude and/or the frequency of the vibrations to an above-water position remote from the underwater compressor arrangement. This can be realized, for example, by a cable connection or via ultrasonic waves.

[0028] An above-water position of this kind remote from the underwater compressor arrangement can be, for example, a corresponding receiver on a ship, on a production platform or even on a bank of the body of water in question.

[0029] Finally, an underwater compressor arrangement or subsea compressor unit with rolling element bearing arrangement is provided according to one embodiment of the invention. According to an embodiment of the invention, the turbocompressor of the underwater compressor arrangement operates with the rolling element bearing arrangement. According to one embodiment of the invention, the rotor of the turbocompressor is held by rolling element bearing arrangements. According to embodiments of the invention, the rolling element bearings are constructed either with balls, rollers (cylindrical or spherical), needles or the like rolling elements of suitable materials. According to an embodiment of the invention, the lubrication and/or cooling of the rolling elements is carried out with liquids and/or gases. According to an embodiment of the invention, the monitoring of the bearings is carried out.

[0030] According to a second aspect of the invention, an underwater process fluid conveying arrangement is provided which has an underwater compressor arrangement according to one or more or all of the embodiment forms of the invention described above in any conceivable combination, a process fluid source which is fluidically connected via a feed line to a process fluid inlet of the turbocompressor of the underwater compressor arrangement so that process fluid can be supplied to the turbocompressor from the process fluid source, and a process fluid receiver which is fluidically connected via a discharge line to a process fluid outlet of the turbocompressor of the underwater compressor arrangement so that compressed process fluid can be supplied to the process fluid receiver from the turbocompressor, and at least the process fluid source and the underwater compressor arrangement are arranged below a water surface of a body of water.

[0031] A body of water within the meaning of the invention can be a sea or ocean, a lake, a river or a canal. If the body of water is a sea or ocean, the water surface forms the seal level.

[0032] The underwater compressor arrangement is preferably arranged on an underwater ground such as a sea bottom.

[0033] According to one embodiment of the invention, the process fluid receiver has a storage space for receiving compressed process fluid.

[0034] According to one embodiment of the invention, the process fluid receiver is arranged below the surface of the body of water.

[0035] According to yet another embodiment of the invention, the process fluid receiver is formed by a cavern.

[0036] According to one embodiment of the invention, the process fluid receiver is arranged above the surface of the body of water.

[0037] According to yet another embodiment of the invention, the process fluid receiver is formed by a ship or a production platform.

[0038] According to another embodiment of the invention, the process fluid source is formed by a borehole in the underwater ground, e.g., a sea bottom. Naturally, the process fluid source could also be formed, e.g., by any other suitable storage such as, e.g., a tank arranged on the underwater ground.

[0039] According to one embodiment of the invention, the process fluid is formed by natural gas.

[0040] According to one embodiment of the invention, the operating medium for lubricating and/or cooling the rolling element bearing arrangement of the turbocompressor of the underwater compressor arrangement is formed by methanol-ethanol-glycol mixture injected into the process fluid at the process fluid source.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The invention will be described in more detail in the following with reference to preferred embodiment forms and the accompanying drawings. The drawings show:

[0042] FIG. 1 is a perspective view in partial section of an underwater compressor arrangement according to the prior art;

[0043] FIG. 2 is a schematic longitudinal section through an underwater compressor arrangement according to one embodiment of the invention;

[0044] FIG. 3 is a schematic longitudinal section through an underwater compressor arrangement according to one embodiment of the invention; and

[0045] FIG. 4 is a schematic view of an underwater process fluid conveying arrangement according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] FIG. 2 shows a schematic longitudinal section through an underwater compressor arrangement 10 for compressing a process fluid, e.g., in this case, natural gas, according to an embodiment form of the invention.

[0047] As can be seen from FIG. 3, the underwater compressor arrangement 10 has a housing 100, two radial-type turbocompressors 200 each having a compressor rotor 210, and a rotary drive unit 300 constructed as an electric motor with a drive rotor 310 and a drive stator 320.

[0048] The two turbocompressors 200, 200 and the rotary drive unit 300 are arranged in the housing 100; the two compressor rotors 210, 210 and the drive rotor 310 are in a direct rotationally driving connection with one another via a shared rotor shaft 400.

[0049] Depending on the desired compression or the intended compression task, a user can connect the two turbocompressors 200, 200 of the underwater compressor arrangement 10 in tandem or in series according to process or can also operate them in parallel or individually according to process.

[0050] The housing 100 is hermetically sealed with the exception of operating connections (not shown in FIG. 2 but similar to process fluid inlet 31', process fluid outlet 32' and power supply 11; see FIG. 1) for the turbocompressors 200, 200 and the rotary drive unit 300.

[0051] The shared rotor shaft 400 which is preferably formed in one piece is rotatably supported in the housing 100 by a rolling element bearing arrangement so that the compressor rotors 200, 200 arranged on the rotor shaft 400 and the drive rotor 310 which is also arranged on the rotor shaft 400 are rotatably supported in the housing 100 by the rolling element bearing arrangement.

[0052] According to one embodiment of the invention, the rolling element bearing arrangement has four cylindrical roller bearings 410 that provide the rotor shaft 400 with the needed radial support as well as the needed axial support in the housing 100. Naturally, one or more radial rolling element bearings (such as radial ball bearings) and, additionally, one or more axial rolling element bearings (such as axial ball bearings) could also be provided according to embodiment forms of the invention which are not shown in the drawings.

[0053] Further, the underwater compressor arrangement 10 has a rotational speed control device 330 for the rotary drive unit 300. The rotational speed control device 330 is configured in such a way that a maximum rotational speed determined for the fatigue strength of the rolling element bearing arrangement is not exceeded during rotational driving of the compressor rotors 210, 210.

[0054] The rotational speed control device 330 is only shown schematically in FIG. 2 because it can be constructed in a wide variety of forms, e.g., as a frequency converter, a corresponding winding configuration (e.g., pole number) of drive rotor 310 and drive stator 320, or a mechanical speed limiter.

[0055] The underwater compressor arrangement 10 further has a maintenance device arranged to ensure a lubrication and cooling of the rolling element bearing arrangement; a methanol-ethanol-glycol mixture is provided as operating medium for lubricating and cooling the rolling element bearing arrangement and is supplied to the rolling element bearing arrangement via the process fluid to be compressed, e.g., in this case, natural gas. In other words, according to one embodiment of the invention, the maintenance unit is realized in that sealing systems have been omitted in the underwater compressor arrangement 10 so that the process fluid containing the operating medium can circulate around the rolling element bearing arrangement and can therefore lubricate it and cool it.

[0056] The underwater compressor arrangement 10 further has a vibration monitoring unit 500 which is arranged to monitor the amplitude and frequency of vibrations in the rolling element bearing arrangement. More precisely stated: the vibration monitoring unit 500 has a vibration sensor 510 for each cylindrical roller bearing 410, and the vibration sensors 510 are signal-coupled, respectively, with an evaluating and transmitting unit 520.

[0057] The evaluating and transmitting unit 520 is arranged to transmit the monitoring data reproducing the amplitude and the frequency of the vibrations via an ultrasonic transmitter 521 to an above-water position (see, e.g., FIG. 4) remote from the underwater compressor arrangement 10.

[0058] FIG. 3 shows a schematic longitudinal section through an underwater compressor arrangement 10A for compressing a process fluid, e.g., in this case, natural gas, according to one embodiment of the invention.

[0059] The embodiment of the underwater compressor arrangement 10A shown in FIG. 3 is identical to the embodiment of the underwater compressor arrangement 10 shown in FIG. 2 except for a few differences which will be described in the following. Therefore, only the differences will be described in the following, and the same reference numerals are used to designate identical or similar components.

[0060] In contrast to FIG. 2, the underwater compressor arrangement 10A according to FIG. 3 has only one individual turbocompressor 200. Further, the rolling element bearing arrangement has only three cylindrical roller bearings 410. As a result, the underwater compressor arrangement 10A according to FIG. 3 is somewhat shorter in length than the underwater compressor arrangement 10 according to FIG. 2.

[0061] FIG. 4 shows a schematic view of an underwater process fluid conveying arrangement 1 according to an embodiment form of the invention.

[0062] The underwater process fluid conveying arrangement 1 has an underwater compressor arrangement 10, 10A according to FIG. 2 or FIG. 3 and a process fluid source 20 fluidically connected via a feed line 30 to a process fluid inlet 220 of the underwater compressor arrangement 10, 10A or of the first turbocompressor 200 in the process so that process fluid can be supplied to the turbocompressor 200 from the process fluid source 20.

[0063] The underwater process fluid conveying arrangement 1 further has a process fluid receiver 50 fluidically connected via a discharge line 40 to a process fluid outlet 230 of the underwater compressor arrangement 10, 10A or of the last turbocompressor 200 in the process, so that compressed process fluid can be supplied to the process fluid receiver 50 from the turbocompressor 200.

[0064] As is shown in FIG. 4, at least the process fluid source 20 and the underwater compressor arrangement 10, 10A are arranged below the water surface 71 of a body of water 70.

[0065] The process fluid receiver 50 has a storage space 52, 54, 56 for receiving compressed process fluid.

[0066] According to a first variant shown in FIG. 4, the process fluid receiver 50 is arranged below the water surface 71 of the body of water 70, and the process fluid receiver 50 is formed by a cavern 51 formed in the underwater ground 72 or by a storage tank 53 located on the underwater ground.

[0067] According to a second variant shown in FIG. 4, the process fluid receiver 50 is arranged above the water surface 71 of the body of water 70, and the process fluid receiver 50 is formed by a ship 55 (or a production platform, not shown).

[0068] When the process fluid receiver 50 is formed by a ship 55, it can have an ultrasonic receiver 57, as is shown in FIG. 4, which can receive monitoring data sent by the ultrasonic transmitter 521 of the underwater compressor arrangement 10, 10A and transmit this monitoring data to an on-board evaluating device (not shown). Naturally, even if the process fluid receiver 50 is not formed by a ship 55, a corresponding ultrasonic receiver 57 can be provided, e.g., at a separate monitoring ship.

[0069] The process fluid source 20 is formed by a borehole in the underwater ground 72, and natural gas is conveyed from the borehole as process fluid.

[0070] The methanol-ethanol-glycol mixture which serves as operating medium for lubricating and cooling the rolling element bearing arrangement of the underwater compressor arrangement 10, 10A arranged on the underwater ground 72 is injected into the process fluid during the conveying operation at the process fluid source 20.

[0071] Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

1-19. (canceled)

20. An underwater compressor arrangement for compressing a process fluid, comprising: a hermetically sealed housing; a rotary drive unit with a drive rotor arranged in the housing; a turbocompressor with a compressor rotor arranged in the housing in rotational driving connection with the drive rotor; and a rolling element bearing arrangement arranged in the housing configured to rotatably support the compressor rotor.

21. The underwater compressor arrangement according to claim 20, wherein the rolling element bearing comprises at least one of ball bearings, roller bearings, and needle bearings.

22. The underwater compressor arrangement according to claim 20, wherein the rotary drive unit is arranged such that a maximum rotational speed determined for a fatigue strength of the rolling element bearing arrangement is not exceeded during rotational driving of the compressor rotor.

23. The underwater compressor arrangement according to claim 20, further comprising a shared rotor shaft by which the compressor rotor and the drive rotor are in direct rotationally driving connection with one another.

24. The underwater compressor arrangement according to claim 20, further comprising: a maintenance device configured to ensure at least one of a lubrication and a cooling of the rolling element bearing arrangement, wherein at least one of a liquid and a gas is provided as an operating medium for the one of the lubricating and the cooling of the rolling element bearing arrangement.

25. The underwater compressor arrangement according to claim 24, wherein the medium for the at least one of the lubricating and the cooling of the rolling element bearing arrangement is a methanol-ethanol-glycol mixture.

26. The underwater compressor arrangement according to claim 25, wherein the maintenance device is arranged to supply the operating medium for the at least one of the lubricating and the cooling of the rolling element bearing arrangement to the rolling element bearing arrangement via the process fluid to be compressed.

27. The underwater compressor arrangement according to claim 26, wherein the turbocompressor is configured to process natural gas as process fluid to be compressed.

28. The underwater compressor arrangement according to claim 20, further comprising a vibration monitoring unit configured to monitor vibrations in the rolling element bearing arrangement with respect to at least one of amplitude and frequency of the vibrations.

29. The underwater compressor arrangement according to claim 28, wherein the vibration monitoring unit is configured to transmit monitoring data reproducing the one of the amplitude and the frequency of the vibrations to an above-water position remote from the underwater compressor arrangement.

30. An underwater process fluid conveying arrangement comprising: an underwater compressor arrangement having: a hermetically sealed housing; a rotary drive unit with a drive rotor arranged in the housing; a turbocompressor with a compressor rotor arranged in the housing in rotational driving connection with the drive rotor; and a rolling element bearing arrangement arranged in the housing configured to rotatably support the compressor rotor; a feed line by which a process fluid source is fluidically connected to a process fluid inlet of the turbocompressor of the underwater compressor arrangement to supply the process fluid to the turbocompressor from the process fluid source; and a discharge line by which a process fluid receiver is fluidically connected to a process fluid outlet of the turbocompressor of the underwater compressor arrangement so that compressed process fluid is supplied to the process fluid receiver from the turbocompressor, wherein at least the process fluid source and the underwater compressor arrangement are arranged below a water surface of a body of water.

31. The underwater process fluid conveying arrangement according to claim 30, wherein the process fluid receiver has a storage space configured to receive compressed process fluid.

32. The underwater process fluid conveying arrangement according to claim 31, wherein the process fluid receiver is arranged below the water surface of the body of water.

33. The underwater process fluid conveying arrangement according to claim 32, wherein the process fluid receiver is a cavern.

34. The underwater process fluid conveying arrangement according to claim 31, wherein the process fluid receiver is arranged above the water surface of the body of water.

35. The underwater process fluid conveying arrangement according to claim 34, wherein the process fluid receiver is one of a ship and a production platform.

36. The underwater process fluid conveying arrangement according to claim 35, wherein the process fluid source is a borehole in the underwater ground.

37. The underwater process fluid conveying arrangement according to claim 30, wherein the process fluid is natural gas.

38. The underwater process fluid conveying arrangement according to claim 30, wherein the operating medium for at least one of lubricating and cooling of the rolling element bearing arrangement of the turbocompressor of the underwater compressor arrangement is a methanol-ethanol-glycol mixture injected into the process fluid at the process fluid source.