WO2011071475A1

WO2011071475A1 - Self pressure-compensating housing assembly

Info

Publication number: WO2011071475A1
Application number: PCT/US2009/006522
Authority: WO
Inventors: Gabriel Silva
Original assignee: Fmc Technologies, Inc.
Priority date: 2009-12-10
Filing date: 2009-12-10
Publication date: 2011-06-16

Abstract

A housing assembly for a subsea electrical device comprises a main housing which includes a cavity within which the electrical device is positioned, a pressure compensating fluid in an amount sufficient to completely fill the cavity after the electrical device is positioned therein, and an electrical connector for transmitting electrical signals from the electrical device to a location outside the main housing. The main housing is constructed of an elastomer material and the cavity comprises a shape which generally conforms to the shape of the electrical device. Thus, external pressure acting on the housing assembly is transmitted to the pressure compensating fluid through substantially the entire surface of the main housing.

Description

SELF PRESSURE-COMPENSATING HOUSING ASSEMBLY

The present invention relates generally to housings for electrical devices used in subsea applications. More particularly, the invention relates to housings which automatically compensate for the external subsea pressure in order to protect the electrical devices housed within them.

BACKGROUND OF THE INVENTION

Electrical devices are commonly used in subsea hydrocarbon production applications to control production equipment components, such as flow valves and actuators, and to provide information regarding the conditions of the hydrocarbon fluid being produced, such as its pressure and temperature.

However, due to the sensitive nature of the electrical devices, they are usually placed in housings to protect them from the high pressures of the subsea environment.

Some prior art housings are rigid structures which are engineered to withstand the substantial subsea pressures within which the electrical devices are intended to operate. However, such housings tend to be relatively large and heavy.

Other prior art housings are filled with a non-compressible pressure compensating fluid to equalize the pressure inside the housing with the subsea pressure. However, in order for this arrangement to be effective, the housings must include means for transferring the subsea pressure to the pressure compensating fluid. Such means may include, for example, a pressure

compensating mechanism which moves in response to the external pressure to transmit this pressure to the pressure compensating fluid. However, these mechanisms tend to be bulky and complex and require the housings to be specially designed to accommodate them.

SUMMARY OF THE INVENTION

In accordance with the present invention, these and other limitations in the prior art are addressed by providing a housing assembly for a subsea electrical device which comprises a main housing which includes a cavity within which the electrical device is positioned, the main housing being constructed of an elastomer material and the cavity comprising a shape which generally conforms to the shape of the electrical device; a pressure compensating fluid in an amount sufficient to completely fill the cavity after the electrical device is positioned therein; and means for transmitting electrical signals from the electrical device to a location outside the main housing. In this manner, external pressure acting on the housing assembly is transmitted to the pressure compensating fluid through substantially the entire surface of the main housing.

In accordance with one embodiment of the invention, the housing assembly also comprises a cover which is attached to the main housing to seal the cavity. The cover may include at least one fill port through which the pressure compensating fluid is introduced into the cavity after the cover is attached to the main housing. In addition, the transmitting means may comprise at least one electrical connector which is mounted to the cover and electrically coupled to the electrical device.

In accordance with another embodiment of the invention, the electrical device comprises a circuit board, a number of electrical components which are mounted on the circuit board, and means for coupling the circuit board to the transmitting means. In this embodiment, the transmitting means may comprise an electrical connector which is accessible from outside the main housing and the coupling means may comprise a connector tab which extends from the circuit board and is electrically coupled to the electrical connector.

In accordance with yet another embodiment of the invention, the housing assembly also includes means for supporting the circuit board within the cavity such that the electrical components do not contact the main housing. For example, where the circuit board comprises a pair of generally parallel top and bottom plates which are connected together in spaced apart relation, the support means may comprise a pair of rails which extend along opposite sides of the cavity and are slidably received between the top and bottom plates. In an alternative construction, the rails may be connected to or formed integrally with the main housing.

In accordance with a further embodiment of the invention, the electrical device comprises a battery. In this embodiment, the housing assembly may also include a cover which is attached to the main housing to seal the cavity. The cover may comprise at least one fill port through which the pressure

compensating fluid is introduced into the cavity after the cover is attached to the main housing. In addition, the transmitting means may comprise at least one electrical connector which is mounted to the cover and electrically coupled to the battery.

In accordance with still another embodiment of the invention, the electrical device comprises a motor. In this embodiment, the motor may be supported in a frame member which is positioned in the cavity. In addition, the main housing may be constructed in a number of pieces which are attached together over the frame member after the motor is installed in the frame member. Also, the motor may comprise a shaft which extends through a bore in the main housing and is sealed to the main housing with a seal.

In accordance with yet another embodiment of the invention, the electrical device comprises a sensor. In this embodiment, the transmitting means may comprise an antenna which communicates wirelessly with a transceiver located outside the main housing.

The present invention is also directed to a wireless subsea sensor which comprises a sensor assembly which includes a flexible substrate, at least one sensor element which is mounted on the substrate and at least one antenna which is mounted on the substrate; a housing assembly which includes a main housing comprising a cavity within which the sensor assembly is positioned, the main housing being constructed of an elastomer material; and a pressure compensating fluid in an amount sufficient to completely fill the cavity after the sensor assembly is positioned therein. Also, the antenna is in wireless

communication with a transceiver which is located outside the housing assembly. As in the previous embodiments of the invention, external pressure acting on the housing assembly is transmitted to the pressure compensating fluid through substantially the entire surface of the main housing.

Thus, the present invention provides a flexible housing which effectively protects electrical devices from damage caused by high subsea pressures.

Since substantially the entire housing is made of an elastomer material, virtually the entire surface of the housing acts as a pressure compensating mechanism to transfer the external subsea pressure to the pressure compensating fluid inside. In addition, since the housing is configured to conform to the shape of the electrical device, the housing can be made relatively small. Additionally, the housing may be custom molded to fit into small and irregularly shaped spaces where prior art housings typically cannot be used. These and other objects and advantages of the present invention will be made apparent from the following detailed description, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an exploded perspective view of a general electrical device comprising a housing assembly in accordance with one embodiment of the present invention;

Figure 2 is an exploded perspective view of an exemplary battery comprising a housing assembly in accordance with another embodiment of the present invention;

Figure 3 is cut-away perspective view of an exemplary motor comprising a housing assembly in accordance with yet another embodiment of the present invention; .

Figure 4 is a cut-away perspective view of a sensor in accordance with one embodiment of the present invention;

Figure 5 is a longitudinal cross sectional view of the sensor shown in Figure 4;

Figure 6 is a cross sectional representation of the sensor of Figure 4 shown mounted in an exemplary riser;

Figure 7 is a cross sectional representation of two of the sensors of Figure

4 shown mounted in an exemplary wellhead assembly;

Figure 8 is a cross sectional representation of the sensor of Figure 4 shown mounted in an exemplary manifold assembly; and

Figure 9 is a cross sectional representation of the sensor of Figure 4 shown mounted in an exemplary plug valve.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a self pressure-compensating housing assembly for an electrical device which is intended to be used in subsea hydrocarbon production applications. The housing assembly comprises a main housing which is made of an elastomer material and includes a cavity within which the electrical device is positioned. The main housing is sealed and then filled with a pressure compensating fluid, such as a dielectric oil. In use, the flexible nature of the housing assembly causes the subsea ambient pressure to be transmitted to the pressure compensating fluid across substantially the entire surface area of the main housing. The housing assembly thus effectively equalizes the cavity pressure with the ambient pressure to protect both the housing assembly and the electrical device from the affects of the ambient pressure.

Referring to Figure 1 , one embodiment of the housing assembly of the present invention, which is indicated generally by reference number 10, is shown as an enclosure for an electrical device 12. The electrical device 12 comprises a number of electrical components 14 which are mounted on a circuit board 16. In this embodiment the circuit board 16 comprises a pair of parallel, generally rectangular top and bottom plates 18, 20 which are connected in a spaced-apart relation by a U-shaped bracket 22. The circuit board 16 ideally also includes a protruding connector tab 24 which comprises a number of suitable conductors via which power and/or data signals may be communicated to or from the

components 14.

The housing assembly 10 is ideally configured to generally conform to the shape of the electrical device 12. Thus, in the embodiment of the invention shown in Figure 1 , the housing assembly 10 comprises a main housing 26 which includes a generally rectangular blind cavity 28 that is sized to accept the electrical device 12. Once the electrical device 12 is positioned in the cavity 28, a cover 30 is secured and sealed to the main housing 26 to thereby form a pressure-tight enclosure for the electrical device.

The housing assembly 10 ideally also includes means for supporting the electrical device 12 within the cavity 28. As shown in Figure 1 , for example, the housing assembly 10 comprises a pair of rails 32 which extend longitudinally along opposite sides of the cavity 28. The rails may be connected to a support frame which is positioned in the cavity 28 or, as shown in Figure 1 , connected to or formed integrally with the inner side surfaces of the main housing 26.

The rails 32 are configured to form a sliding fit between the side edges of the top and bottom plates 18, 20 of the circuit board 16. This arrangement allows the circuit board 16 to be slid onto the rails 32 during assembly of the electrical device 12 with the main housing 26. In addition, the cavity 28 is optimally dimensioned so that, when the circuit board 16 is supported on the rails 32, the electrical components 14 will not contact the inner surfaces of the main housing 26. The cover 30 may be attached to the main housing 26 with any suitable adhesive or mechanical fastener. The cover comprises a fill port 34 via which a pressure compensating fluid, such as a dielectric oil, may be introduced into the cavity 28 after the cover has been attached to the main housing 26. In addition, an electrical connector 36 may be mounted to the cover 30 and electrically joined by suitable means (not shown) to the connector tab 24 to provide a means for transmitting power and/or data signals between the electrical device 12 and an external component, such as a power and/or communications cable (not shown).

The container 26 and the cover 30 may be molded or otherwise

constructed from an elastomer material which is impermeable to both the pressure compensating fluid and the ambient sea water. In addition, the material ideally comprises sufficient elasticity to allow it to expand and contract as the pressure compensating fluid expands and contracts due to variations in temperature.

During assembly, the electrical device 12 is inserted into the cavity 28, the connector tab 24 is connected to the electrical connector 36 and the cover 30 is attached to the main housing 26. The cavity 28 is then filled with the pressure compensating fluid using a vacuum fill procedure. In this regard, the cavity 28 may be filled to a pressure slightly above atmospheric pressure to cause the main housing 26 to expand and thereby provide added resistance to external pressure during use subsea. After the cavity 28 is filled, the fill port 34 is sealed and the housing assembly 10 is then ready to be deployed.

Due to the fact that the main housing 26 and preferably also the cover 30 are made from a flexible elastomer, external pressure acting on the housing assembly 10 is transmitted to the pressure compensating fluid across virtually the entire surface area of the housing assembly to thereby equalize the pressure within the cavity 28 with the external pressure. The pressure compensating fluid in turn transmits the pressure substantially uniformly throughout the cavity 28, which protects against damage to not only the housing assembly 10 but also the electrical device 12.

It should readily be appreciated that the housing assembly 10 can be configured in any number of custom shapes to house a variety of electrical components having different configurations. Referring to Figure 2, for example, another embodiment of the housing assembly of the present invention, generally 100, is shown as an enclosure for an exemplary battery 102. The battery 102 comprises a curved rectangular cross section, and the housing assembly 100 includes a main housing 104 which comprises a cavity 106 that is configured to generally conform to the battery. The cavity 106 is sized to be slightly larger than the battery 102, and the remaining volume is filled with a pressure compensating fluid.

The housing assembly 100 includes a cover 108 which is attached to the main housing 104 in a manner described above to form a pressure-tight enclosure for the battery 102. The cover 108 includes a number of fill ports 1 10 through which the pressure compensating fluid may be introduced into the cavity 106, and one or more electrical contacts or connectors 1 12 via which the battery 102 may be connected to a separate component (not shown).

During assembly, the battery 102 is inserted into the cavity 106, the electrical connectors 1 12 are connected to the battery by suitable means (not shown), the cover 108 is attached to the main housing 104, and a vacuum fill procedure is used to fill the cavity with a pressure compensating fluid. In use, ambient pressure exerted on the housing assembly 100 will be transmitted to the pressure compensating fluid across virtually the entire surface area of the housing assembly to thereby equalize the pressure within the cavity 106 with the ambient pressure. The pressure compensating fluid will in turn distribute the cavity pressure uniformly throughout the cavity 106 to protect both the housing assembly 100 and the battery 102 against damage.

Another embodiment of the housing assembly of the present invention is shown in Figure 3. The housing assembly of this embodiment, generally 200, is shown as an enclosure for an exemplary motor 202. The motor 202 comprises a stator 204 which surrounds a rotor 206. The rotor 206 is connected to a shaft 208 which is rotationally supported in a pair of bearing assemblies 210. The stator 204 and the bearing assemblies 210 are supported in a generally cylindrical frame member 212.

The housing assembly 200 includes a main housing 214 which comprises a cylindrical cavity 216 within which the frame member 212 is positioned. The cavity 216 conforms to the shape of a frame member 2 2, but the frame member extends axially beyond the bearing assemblies 210 to thereby define two spaces 218 which are filled with a pressure compensating fluid. In addition, the diameter of the cavity 216 may be made slightly larger than the diameter of the frame member 212 to provide additional space for the pressure compensating fluid within the main housing 214. The pressure compensating fluid is introduced into the cavity through a fill port 220 in the main housing 214.

In this embodiment of the invention, the housing assembly 200 need not be provided with a separate cover. Instead, the main housing 214 may be molded over the frame member 212 or formed in two or more pieces and then glued or otherwise attached over the frame member after the motor is installed. Each end of the shaft 210 extends axially through a corresponding bore in the main housing and is sealed thereto by an appropriate seal 222 to prevent egress of the pressure compensating fluid.

Referring now to Figures 4 and 5, an embodiment of the present invention is shown in the form of a pressure-tolerant wireless sensor which is suitable for use in subsea environments. The sensor of this embodiment, which is indicated generally by reference number 300, includes a sensor assembly comprising a number of sensor elements and associated electronics which are mounted on a flexible substrate or circuit board 302 that is positioned in a flexible housing assembly 304 similar to the embodiments described above.

In the illustrative embodiment of the invention shown in Figure 5, the sensor assembly includes a pressure sensor 306 and a temperature sensor 308. Each sensor 306, 308 is controlled by an associated processor 310 which is powered by an corresponding battery 312. In addition, each processor 310 comprises or is connected to a corresponding antenna 314 which communicates wirelessly, such as via electromagnetic induction signals, with an external transceiver 316 that in turn is connected to a central control module (not shown). In one embodiment of the invention, the processors 310 wirelessly transmit the signals from their respective sensors 306, 308 upon receiving an interrogation signal from the transceiver 316.

The housing assembly 304 includes a main housing 318 which is molded or otherwise constructed of an elastomer material of the type discussed above. The main housing 318 comprises a cavity 320 which is configured to receive the sensor assembly. The cavity 320 is filled with a pressure compensating fluid either during the manufacturing process or through a suitable fill port (not shown). The flexible main housing 318 ensures that ambient pressure will be transmitted to the pressure compensating fluid through nearly the entire surface of the main housing 318, and the pressure compensating fluid will uniformly distribute this pressure through the entire cavity 320.

The sensor 300 is particularly suitable for use in tight or irregularly shaped spaces to which electrical cables cannot be easily or practically routed. Due to the fact that both the substrate 302 and the housing assembly 304 are flexible, the sensor 300 can be bent, coiled or otherwise configured to fit within many spaces that are unsuitable for conventional sensors. In addition, since the antennas 314 communicate wirelessly with the transceiver 316, the sensor 300 does not require external electrical cables. Furthermore, the electromagnetic induction signals can penetrate many materials, including steel and cement, thereby allowing the sensor 300 to be positioned within spaces that normally are not accessible.

The sensor 300 is suitable for use in a variety of subsea applications.

Referring to Figure 7, for example, the sensor 300 is shown mounted within the annulus 322 between a marine riser 324 and a production string 326. In this embodiment, the sensor 300 is able to monitor the pressure and temperature of the fluid within the annulus 322 and transmit this information to the transceiver 316 without the need for an electrical cable penetrating the marine riser 324. Of course, another sensor 300 could be mounted in the production string 326.

As shown in Figure 8, one or more sensors 300 may be used to monitor conditions in an exemplary wellhead assembly 328 which comprises a wellhead housing 330 and a number of concentric casing strings that are suspended from the wellhead housing. As shown in Figure 8, a first sensor 300 is embedded in the cement which fills the annulus between the wellhead housing 330 and a first casing string 332, and a second sensor 300 is embedded in the cement which fills the annulus between the first casing string and a second casing string 334. In this embodiment, the sensors 300 monitor the conditions in their respective annuli and transmit this information to the transceiver 316.

Referring to Figure 8, the sensor 300 is shown being used to monitor the conditions of a fluid flowing through an illustrative subsea manifold 336. In this exemplary embodiment, the sensor 300 is mounted to or embedded in a plug 338 which seals a port 340 in the body of the manifold. As in the previous embodiments, the sensor 300 communicates wirelessly with a transceiver 316 located outside the manifold 336.

Referring finally to Figure 9, the sensor 300 is shown being used to monitor the conditions of a fluid flowing through an exemplary subsea valve, such as a plug valve 342. In this embodiment, the sensor 300 is embedded in a plug member 344 which when closed seals off the flow passage extending between the valve inlet 346 and the valve outlet 348. As in the previous embodiments, the sensor 300 communicates wirelessly with a transceiver 316 located outside the valve 342.

The combination of the flexible substrate or circuit board 302 and the flexible housing 304 provide the sensor 300 with several advantages and unique uses. Since both the housing 304 and the circuit board 302 are compliant, the sensor 300 may be attached to curved surfaces without imparting undue strain on the internal electronics. In addition, the flexible nature of the housing 304 and the circuit board 302 allow the sensor 300 to flex and vibrate with the structure to which the sensor is attached, thereby minimizing the effects of vibration and strain.

Also, the sensor 300 may be used as a free moving sensor to measure the characteristics of a fluid flowing through a pipe. Since the housing 304 and the circuit board 302 are flexible, the sensor 300 will readily bend and conform to the internal geometry of the pipe as it is conveyed along with the fluid. In addition, since the sensor 300 has a wireless data connection to an external transceiver 316, the sensor can move through the pipe without interference from attached communication cables.

In addition, the pressure compensating fluid and/or the material for the main housing 318 may be selected to provide the sensor 300 with a desired buoyancy for subsea applications. For example, the buoyancy could be selected to enable the sensor 300 to float at a specific ocean depth or in a particular well fluid. In addition, since the sensor 300 comprises a wireless data connection to the external transceiver 316, the sensor may be dropped into a structure which is filled with, e.g., a polymer or cement, and become part of the structure.

Several variations of the present invention may be readily developed from the teachings contained herein. For example, the electrical device 12 described in connection with the housing assembly 10 could be provided with a flexible circuit board 16. As with the sensor 300, this arrangement would allow the housing assembly 10 to be attached to curved surfaces without imparting undue strain on the electrical components 14. In addition, the flexible circuit board 16 would allow the electrical device 12 to move with the structure to which the housing assembly 10 is connected, thereby minimizing the effects of vibration and strain on the electrical components 14 as the structure flexes. Other benefits of combining a flexible circuit board 16 with the flexible housing assembly 10 will be apparent from the description of the sensor 300 above.

It should be recognized that, while the present invention has been described in relation to the preferred embodiments thereof, those skilled in the art may develop a wide variation of structural and operational details without departing from the principles of the invention. Therefore, the appended claims are to be construed to cover all equivalents falling within the true scope and spirit of the invention.

Claims

What is claimed is:

1. A housing assembly for a subsea electrical device which comprises: a main housing which includes a cavity within which the electrical device is positioned, the main housing being constructed of an elastomer material and the cavity comprising a shape which generally conforms to the shape of the electrical device;

a pressure compensating fluid in an amount sufficient to completely fill the cavity after the electrical device is positioned therein; and

means for transmitting electrical signals from the electrical device to a location outside the main housing;

wherein external pressure acting on the housing assembly is transmitted to the pressure compensating fluid through substantially the entire surface of the main housing.

2. The housing assembly of claim 1 , further comprising a cover which is attached to the main housing to seal the cavity.

3. The housing assembly of claim 2, wherein the cover comprises at least one fill port through which the pressure compensating fluid is introduced into the cavity after the cover is attached to the main housing.

4. The housing assembly of claim 3, wherein the transmitting means comprises at least one electrical connector which is mounted to the cover and electrically coupled to the electrical device.

5. The housing assembly of claim 1 , wherein the electrical device comprises a flexible circuit board and a number of electrical components which are mounted on the circuit board.

6. ^' The housing assembly of claim 1 , wherein the electrical device comprises a circuit board, a number of electrical components which are mounted on the circuit board, and means for coupling the circuit board to the transmitting means.

7. The housing assembly of claim 6, wherein the transmitting means comprises an electrical connector which is accessible from outside the main housing and the coupling means comprises a connector tab which extends from the circuit board and is electrically coupled to the electrical connector.

8. The housing assembly of claim 6, further comprising means for supporting the circuit board within the cavity such that the electrical components do not contact the main housing.

9. The housing assembly of claim 8, wherein the circuit board comprises a pair of generally parallel top and bottom plates which are connected together in spaced apart relation, and wherein the support means comprises a pair of rails which extend along opposite sides of the cavity and are slidably received between the top and bottom plates.

10. The housing assembly of claim 9, wherein the rails are connected to or formed integrally with the main housing.

1 1 . The housing assembly of claim 1 , wherein the electrical device comprises a battery.

12. The housing assembly of claim 1 1 , further comprising a cover which is attached to the main housing to seal the cavity.

13. The housing assembly of claim 12, wherein the cover comprises at least one fill port through which the pressure compensating fluid is introduced into the cavity after the cover is attached to the main housing.

14. The housing assembly of claim 12, wherein the transmitting means comprises at least one electrical connector which is mounted to the cover and electrically coupled to the battery.

15. The housing assembly of claim 1 , wherein the electrical device comprises a motor.

16. The housing assembly of claim 5, wherein the motor is supported in a frame member which is positioned in the cavity.

17. The housing assembly of claim 16, wherein the main housing is constructed in a number of pieces which are attached together over the frame member after the motor is installed in the frame member.

8. The housing assembly of claim 15, wherein the motor comprises a shaft which extends through a bore in the main housing and is sealed to the main housing with a seal.

19. The housing assembly of claim 1 , wherein the electrical device comprises a sensor.

20. The housing assembly of claim 19, wherein the transmitting means comprises an antenna which communicates wirelessly with a transceiver located outside the main housing.

21. A wireless subsea sensor which comprises:

a sensor assembly which includes a flexible substrate, at least one sensor element which is mounted on the substrate and at least one antenna which is mounted on the substrate;

a housing assembly which includes a main housing comprising a cavity within which the sensor assembly is positioned, the main housing being constructed of an elastomer material; and

a pressure compensating fluid in an amount sufficient to completely fill the cavity after the sensor assembly is positioned therein;

wherein the antenna is in wireless communication with a transceiver which is located outside the housing assembly; and