GB2461989A

GB2461989A - Gate valve testing

Info

Publication number: GB2461989A
Application number: GB0912423A
Authority: GB
Inventors: Angus George Bowie
Original assignee: STATS
Current assignee: STATS
Priority date: 2008-07-18
Filing date: 2009-07-17
Publication date: 2010-01-27
Anticipated expiration: 2029-07-17
Also published as: GB2461989B; GB0912423D0

Abstract

A valve 10 comprises a gate or slab 12 located within a valve housing 14 defining a flow passage 18. The slab 12 translates relative to the housing 14 to permit opening and closing of the fluid flow passage 18. Two seals 30, 32 are mounted in a recess on a first side of the slab 12. The seals 30, 32 are adapted for location between the slab 12 and the housing 14 and are energized by a reaction force 35 generated by a fluid pressure differential 28 acting across the slab 12 between fluid upstream of the valve 10 and fluid downstream of the valve 10. An annulus (37, Fig. 2) is defined between the seals 30, 32 and the annulus pressure can be tested via test port 38. A second pair of seals 40, 42 may be provided on the opposite side of the slab.

Description

VALVE

FIELD OF THE INVENTION

This invention relates to a valve for use in a pipeline and, in particular, but not exclusively, to a dual seal gate or slab valve.

BACKGROUND TO THE INVENTION

Pipelines are used in a wide variety of industries to transport fluid over distance, control over the fluid flow into, through and exiting from the pipes making up the pipeline typically achieved by means of valves. One common valve type is known as a gate valve, the valve having a generally planar valve member, or gate, which can be positioned across the pipe bore to block flow. In larger pipes and in applications involving transport of fluid at high pressure, the gate may consist of a slab having an aperture, wherein the slab is translated relative to the bore to selectively open and close the bore, and large gate valves are often also known as slab valves.

In the oil and gas industry, valves are used in a number of pipeline applications. For example, in some circumstances it may be necessary to access a "live" section of pipe, that is one containing fluid at pressure, to fit a branch or tee connection. In one such process, the branch or tee connection is welded or otherwise secured to the pipe. Following this, a valve, such as a gate valve or slab valve, is fitted to the connection and a drilling tool is then connected to the valve.

The drilling tool is operated to drill through the pipe wall to create the connection, the drilling tool configured to prevent leakage of fluid from the pipe during operation of the drilling tool. On completion of the drilling process, the drilling tool is withdrawn and the valve closed to complete the connection. The drilling tool can then be removed from the pipe and fluid may be selectively directed through the branch or tee by controlling the opening and closing of the valve.

In other applications, slab valves are used to shut off flow through the pipe or to permit isolation of a section of pipe, for example for repair or replacement.

For high pressure applications and large pipe diameters, to ensure that valve integrity is maintained in the event that a failure occurs, there is a requirement for double block and bleed isolation. Traditionally, this requires two separate valves with a fluid port located between the valves to permit testing of the valves to be carried out. In this arrangement, each of the valves must be capable of resisting the full differential pressure in the isolation direction and the bleed between the valves is maintained at ambient pressure to ensure that fluid bypass of the second valve does not occur.

More recently, single valves have been developed as an alternative for providing double block and bleed isolation. For example, one valve design uses a gate having a tapered split which causes the gate to widen on closing. The splaying of the gate compresses seals to provide double block isolation.

Slab and gate valves may now also be used where both inner and outer seals of the valve are pressure energised by the isolated pressure. In one arrangement, a floating slab is forced against an outer seal by the isolated pressure and an inner seal is mounted in a floating piston which is forced against the slab again by the isolated pressure. A fluid bleed port is positioned in the body cavity of the valve. In use, the downstream fluid is vented until the pressure equals ambient pressure such that the outer seal is energised. The outer seal can then be verified by a pressure test of the valve body pressure over the outer seal. The valve body pressure can then be vented, in order to energise the inner seal and a pressure test carried out between the pipeline pressure and the valve body.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a gate valve for use in controlling fluid flow through a fluid flow passage, the valve comprising: a valve member adapted to selectively open and close the fluid flow passage; and at least two fluid pressure activated seals arranged on a first side of the valve member, wherein each of the seals is energised by a pressure differential across the valve member.

The pressure differential may be generated between fluid upstream of the valve member and fluid downstream of the valve member.

Accordingly, the valve is adapted to control fluid flow through the flow passage and provides dual seal isolation of fluid upstream of the valve member utilising a single valve member. Each of the seals is energised by the pressure differential such that sealing is maintained even where the pressure differential across the valve member is relatively low. Furthermore, the provision of at least two seals permits each of the seals to be independently tested to ensure the integrity of the valve is maintained in the event of a seal failure.

The valve may comprise a valve body and the valve member may be housed in the body. The valve body may define the fluid flow passage and the valve member may be adapted to translate relative to the body to open and close the fluid flow passage.

Alternatively, or in addition, the valve may be coupled to a tubular component, for example a tube, pipe, pipeline or other suitable tubular, having a fluid flow passage and the valve member may be adapted to control fluid flow through the tubular component. In particular embodiments, the valve body may comprise a separate component adapted to be coupled to the tubular component or between tubular components. Alternatively, the valve body may be integrally formed with the tubular component.

The seals may be adapted for location between the valve member and the valve body. For example, the seals may be coupled to the valve member and, in particular embodiments, the seals may be arranged in a recess provided in the valve member. Alternatively, the seals may be coupled to the valve body and the seals may be arranged in a recess provided in the valve body.

The seals may be of any suitable form. The seals may comprise elastomeric seals, for example. The seals may comprise compression seals, the seals adapted to be compressed by the pressure differential. The seals may comprise D-section seals.

In particular embodiments, two seals may be provided, a primary seal and a secondary seal, though it will be understood that any number of seals may be provided. The primary seal may be provided between fluid upstream of the valve member and the secondary seal. The secondary seal may be provided between the primary seal and fluid downstream of the valve member.

The at least two seals may be provided by a single seal member. For example, the seals may be coupled together to define a single seal member. The provision of a single seal member defining at least two seals, may assist in overcoming tear-out stresses as may be experienced by conventional slab or gate valves. Alternatively, each of the at least two seals may be provided by a separate seal member.

The seals may be substantially annular, the seals arranged concentrically.

However, it will be recognised that the seals may be of any suitable shape to provide sealing around the fluid flow passage.

The valve may further comprise an annulus defined between the seals.

The valve may further comprise a retaining member and the retaining member may be adapted to secure the seals in the annulus.

Where the seals comprise a single seal member, the seal member may be ported to provide fluid communication through and around the seal member.

The valve may further comprise a void defined beneath the annulus, the void assisting in maintaining the independence of the seals.

The valve may further comprise an annulus test port arranged to provide fluid communication with the annulus between the seals.

This arrangement facilitates testing the secondary seal to a pressure above 1 0 the differential pressure. For example, fluid may be inserted into the annulus via the test port to provide a test pressure to the secondary seal up to and greater than the pressure differential across the valve member. This obviates or mitigates the possibility that fluid leaking into and out from the annulus at substantially the same rate will not be detected.

Alternatively, or in addition, the primary seal may be tested by venting the annulus via the annulus test port.

In each case, the relatively small volume of the annulus may facilitate accurate testing of seal integrity.

In particular embodiments, the valve member may comprise a disc shaped valve member or gate, valves according to embodiments of the present invention permitting the use of a smaller valve body. However, it will be understood that the valve member may be of any suitable form or shape and may, for example, comprise a slab having an enclosed through-port as may be found on piston housed

seals, for example.

The valve may further comprise a seal on a second side of the valve member. For example, the seal may be provided on an opposite side of the valve member from the first seals. In particular embodiments, at least two second seals may be provided on the second side of the valve member. This facilitates bi-directional operation of the valve, the first seals energised when the pressure differential acts in a first direction and the second seals energised when the pressure differential acts in a second direction.

The second seals may be substantially the same as the first seals and an annulus and annulus test port may be provided between the primary and secondary second seals.

The valve may further comprise a fluid vent port provided in the valve body.

The body vent port may facilitate monitoring or bleeding of fluid between the seals on the first side of the valve member and the seals on the second side of the valve member.

According to a second aspect of the present invention there is provided a gate valve comprising: a valve body defining a fluid flow passage; a valve member adapted to selectively open and close the fluid flow passage; and at least two fluid pressure activated seals arranged on a first side of the valve member, wherein each of the seals is energised by a pressure differential between fluid upstream of the valve member and fluid downstream of the valve member.

According to another aspect of the present invention there is provided a method of controlling fluid flow through a fluid passage, the method comprising: providing a valve member comprising at least two fluid pressure activated seals arranged on a first side of the valve member; locating the valve member in a fluid passage, the valve member adapted to block flow through the fluid passage whereby each of the seals is energised by a pressure differential between fluid upstream of the valve member and fluid downstream of the valve member.

According to another aspect of the present invention there is provided a method of testing the integrity of a valve, the method comprising: providing a valve member comprising at least two fluid pressure activated seals arranged on a first side of the valve member, an annulus defined between the seals; locating the valve member in a fluid flow passage such that the valve member blocks the fluid flow passage; and monitoring the annulus pressure.

The method may further comprise applying a test pressure to the annulus to permit testing of at least one of the seals.

It should be understood that the features defined above in accordance with any aspect of the present invention may be utilised, either alone or in combination with any other defined feature, in any other aspect of the invention.

Furthermore, it will be understood that features described herein provide a number of advantages, some of which are outlined below:-Particular embodiments may provide double block and bleed isolation on a single slab gate valve with two independent verifiable seals.

Particular embodiments may facilitate the pressure testing of the secondary seal to a higher pressure than the incumbent pipeline pressure.

Particular embodiments may permit highly accurate seal verification in that the trapped pressure occurs in a small volume.

Particular embodiments may provide absolute verification of seal integrity by raising the annulus pressure above the isolated pressure; Particular embodiments may be used with a disc gate so allowing for a smaller housing; In particular embodiments, both seals may be compressed by the isolated pressure acting over the gate area, this assisting in ensuring that seal compression may be maintained by a low differential pressure; and In particular embodiments, the annulus ports on both sides of the valve may be suitable for valve sealant injection.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawing, in which: Figure 1 is a diagrammatic cross-sectional view of a portion of a valve in accordance with an embodiment of the present invention; Figure 2 is an enlarged view of part of the valve portion shown in Figure 1; and Figure 3 is a table comparing features of the present invention to a floating gate valve such as described hereinabove.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring initially to Figure 1, there is shown a portion of a valve 10 in accordance with an embodiment of the present invention. The valve, generally indicated by reference numeral 10, comprises a valve member in the form of gate or slab 12 located within a valve housing 14. A bore 16 extends through the housing 14, the bore 16 defining a fluid flow passage 18 through the valve 10.

In use, the slab 12 is adapted to translate relative to the housing 14 to permit opening and closing of the flow passage 18. The housing 14 is adapted to be coupled to a tubular component, such as an oil or gas pipeline 20, having a fluid flow passage 22 and the valve and pipeline 20 are coupled so that the valve fluid passage 18 and pipeline flow passage 22 are substantially contiguous.

Figure 1 shows the slab 12 in a valve-closed configuration in which the fluid flow passage 18 is fully closed. In this configuration, an end portion 24 of the slab 12 engages a recess 26 provided in the housing 14. Thus, where fluid, such as oil or gas, is directed through the fluid flow passages 18, 22, a fluid pressure differential (shown by arrows 28) is created across the slab 12 between fluid upstream of the slab 12 and fluid downstream of the slab 12.

In reference now also to Figure 2, which shows an enlarged view of part of the valve portion shown in Figure 1, the valve 10 comprises two seals, a primary seal 30 and a secondary seal 32, both seals 30, 32 mounted in a recess or groove 34 on a first side 36 of the slab 12. The seals 30,32 are substantially annular and are arranged concentrically on the slab 12. The seals 30,32 are adapted for location between the slab 12 and the housing 14: the primary seal 30 provided between fluid upstream of the slab 12 and the secondary seal 32; and the secondary seal 32 provided between the primary seal 30 and fluid downstream of the slab 12.

In the embodiment shown in the figures, the seals 30,32 are constructed as a single seal member having two d-section seal portions. The provision of a single seal member defining the two seals 30,32 assists in overcoming tear-out stresses that may otherwise by experienced by conventional slab or gate valves utilising o-ring seals. The seals 30,32 comprise elastomeric compression seals and are adapted to be energised by a reaction force (shown by arrow 35 in Figure 1) generated by the fluid pressure differential 28.

Accordingly, the valve 10 is adapted to control fluid flow through the flow passages 18,22 and provides dual seal isolation of the upstream fluid utilising a single slab 12. The seals 30,32 are energised by the pressure differential 28 such that sealing is maintained even where the pressure differential 28 is relatively low.

An annulus 37 is defined between the seals 30,32, the valve 10 further comprising an annulus test port 38 for providing fluid communication with the annulus 37.

Thus, each of the seals 30,32 are independently verifiable when testing.

In use, the slab 12 is configured to block the fluid flow passage 18, the slab end portion 24 engaging the recess 26 in the housing 14. When the fluid flow passage 18 is closed, fluid downstream of the slab 12 is de-pressurised to generate the fluid pressure differential across the slab 12 in the direction shown by arrow 28.

The slab 12 is urged in this direction and the seals 30,32 are energised by compression of the seals 30,32 against the opposing wall of the recess 26.

The primary seal 30 is thus subject to the pressure differential 28 and can be tested by venting the annulus 37 via the annulus test port 38.

In order to test the secondary seal 32, test fluid is inserted into the annulus 37 via the test port 38 to provide a test pressure to the secondary seal 32.

Furthermore, the secondary seal 32 can be tested to a higher pressure than the pressure differential 28 by selecting the pressure of fluid inserted into the annulus 37 to be higher than the pressure differential. The relatively small volume of the annulus 37 facilitates accurate testing of seal integrity.

In the embodiment shown in the figures, the valve further comprises two seals 40,42 on the opposite side 44 of the slab 12 from the first seals 30, 32, these comprising primary seal 40 and secondary seal 42. Accordingly, the valve 10 is suitable for bi-directional operation, the first seals 30, 32 energised when the pressure differential 28 acts in the first direction shown by arrow 28 and the second seals 40,42 energised when the pressure differential acts in a second direction (as shown by dotted arrow 46 in Figure 1).

The second seals 40,42 are substantially the same as the first seals 30, 32 and an annulus 48 and annulus test port 50 are provided between the primary and secondary seals 40, 42.

The valve 10 further comprises a fluid vent port 52 provided in the housing 14, the vent port 52 facilitating monitoring and/or bleeding of fluid between the seals 30,32 on the first side of the slab 12 and the seals 40,42 on the second side 44 of the slab 12.

It should be understood that the embodiment described herein is merely exemplary and that various modifications may be made thereto without departing from the scope of the invention.

For example, the valve housing may be integrally formed with the tubular component.

Furthermore, it will be recognised that in particular embodiments, the seal design may be suitable for valve sealant injection into the annulus between the seals on both sides of the slab. In this arrangement, the valve cavity would be used as a bleed port to provide a dual seal valve with monitor capability. The primary seal may not be compressed by the isolated pressure so further risk assessment may be required prior to breach of containment.

Referring to Figure 3, there is shown a table comparing features of the present invention to a floating gate valve such as described hereinabove.

Claims

CLAIMS1. A gate valve for use in controlling fluid flow through a fluid flow passage, the valve comprising: a valve member adapted to selectively open and close the fluid flow passage; and at least two fluid pressure activated seals arranged on a first side of the valve member, wherein each of the seals is energised by a pressure differential across the valve member.
2. The valve of claim 1, wherein the pressure differential is generated between fluid upstream of the valve member and fluid downstream of the valve member.
3. The valve of claim 1 or 2, wherein the valve is configurable to provide dual seal isolation of the upstream fluid utilising a single valve member.
4. The valve of claim 1, 2 or 3, wherein the valve comprises a valve body and the valve member is housed in the body.
5. The valve of claim 4, wherein the valve body defines the fluid flow passage and the valve member is adapted to translate relative to the body to open and close the fluid flow passage.
6. The valve of any preceding claim, wherein the valve is coupled to a tubular component having a fluid flow passage and the valve member is adapted to control fluid flow through the tubular component.
7. The valve of any one of claims 4, 5 or 6, wherein the valve body comprises a separate component adapted to be coupled to the tubular component or between tubular components.
8. The valve of any one of claims 4, 5 or 6, wherein the valve body is integrally formed with the tubular component.
9. The valve of any one of claims 4 to 8, wherein the seals are adapted for location between the valve member and the valve body.
10. The valve of any preceding claim, wherein the seals are coupled to the valve member.
11. The valve of any one of claims 4 to 9, wherein the seals are coupled to the valve body and the seals are arranged in a recess provided in the valve body.
12. The valve of any preceding claim, wherein the seals comprise a primary seal and a secondary seal, the primary seal provided between fluid upstream of the valve member and the secondary seal and the secondary seal provided between the primary seal and fluid downstream of the valve member.
13. The valve of any preceding claim, wherein the seals are provided by a single seal member.
14. The valve of any one of claims 1 to 12, wherein each of the seals are provided by a separate seal member.
15. The valve of any preceding claim, wherein the seals are substantially annular.
16. The valve of claim 15, when dependent on claim 12, wherein the annulus defined between the seals is adapted to be vented to permit testing of the primary seal.
17. The valve of claim 15 or 16, further comprising a test port arranged to provide fluid communication with the annulus.
18. The valve of claim 17, when dependent on claim 12, wherein the test port is adapted to receive a test pressure to permit testing of the secondary seal.
19. The valve of claim 18, wherein the test pressure is up to or greater than the differential pressure.
20. The valve of any preceding claim, further comprising at least one seal on a second side of the valve member.
21. The valve of claim 20, wherein at least one seal on the first side of the valve member is energised when the pressure differential acts in a first direction and at least one seal on the second side of the valve member is energised when the pressure differential acts in a second direction.
22. The valve of claim 20 or 21, further comprising a fluid vent port provided in the valve body, the vent port arranged to permit monitoring or bleeding of fluid between the seals on the first side of the valve member and the seal on the second side of the valve member.
23. A method of controlling fluid flow through a fluid passage, the method comprising: providing a valve member comprising at least two fluid pressure activated seals arranged on a first side of the valve member; locating the valve member in a fluid passage, the valve member adapted to block flow through the fluid passage whereby each of the seals is energised by a pressure differential between fluid upstream of the valve member and fluid downstream of the valve member.
24. A method of testing the integrity of a valve, the method comprising: providing a valve member comprising at least two fluid pressure activated seals arranged on a first side of the valve member, an annulus defined between the seals; locating the valve member in a fluid flow passage such that the valve member blocks the fluid flow passage; and monitoring the annulus pressure.
25. The method of claim 23 or 24, further comprising applying a test pressure to the annulus to permit testing of at least one of the seals.
26. The method of claim 25, wherein the test pressure is up to or greater than the differential pressure.
27. A gate valve substantially as described herein and as shown in the accompanying drawings.
28. A method of controlling fluid flow through a fluid passage substantially as described herein.
29. A method of testing the integrity of a valve substantially as described herein.