GB2222230A

GB2222230A - A pipeline check valve

Info

Publication number: GB2222230A
Application number: GB8912236A
Authority: GB
Inventors: Charles Buchan Ritchie
Original assignee: SCORE
Current assignee: SCORE
Priority date: 1988-08-23
Filing date: 1989-05-26
Publication date: 1990-02-28
Also published as: GB8912236D0

Abstract

A pipeline check valve comprises a substantially straight conduit (10) for in-line connection in the pipe, and a branch (16) extending from the conduit (10). A plug member (22) is located in the branch (16) in normal flow conditions. However, in the event of reverse flow occurring the plug member (22) is urged into the conduit (10) to seal the pipe and thus prevent reverse flow of fluid in the pipeline. Member (22) is guided by curved ramps (24) or by grooves which receive spigots extending from the member (22) (Fig 8A). A vane or baffle may be provided downstream of the branch (16), in the direction of normal flow, so as to promote turbulence on the occurrence of reverse flow, which condition assists in closing the valve. As shown in Fig 9B, the branch (16) may be connected to the conduit (10) by a further pipe 105, so that the member (22) is normally held in the branch by a pressure differential. A dogleg rail 32 may be pivoted by movement of the closure member (22) and serves to provide a guide across the mouth of the branch (16) for pipeline pigs. The closure member (22) may be a ball or a cylindrical pig (Fig 7A). <IMAGE>

Description

'~ Pipeline Check Valve" This invention relates to one-way check valves for preventing reverse flow in pipelines, for example sub-sea pipelines for oil, gas or other fluids.

An object of the invention is to provide a check valve which operates in a simple, preferably automatic, manner to permit substantially unobstructed flow in one direction while preventing flow in the opposite direction.

The invention accordingly provides a one-way check valve for insertion in a pipeline to permit flow in a normal direction and prevent flow in a reverse direction, comprising a substantially straight conduit for in-line connection in the pipeline, a branch extending from the conduit and having a closed end, a plug member movable between a first position within the branch and a second position within the conduit, and means in the conduit co-operating with the plug member such that when in said second position the plug member blocks the conduit against flow in the reverse direction.

In one form of the invention, the branch is arranged in a curved path diverging upwardly from the conduit, and the plug member has a specific gravity such that it assumes said first position under the influence of pressure produced by normal flow and drops to said second position in the absence of such pressure.

The plug member may suitably be spherical, and guide rails be provided in the form of protrusions from the sides of the conduit or grooves in the branch and conduit which slideably receive abutments on the plug member. Sealing means may be provided which comprise an annular seat within the conduit. Preferably, a groove is formed in the floor of the conduit immediately adjacent the seat in the downstream normal flow direction to impart upward momentum to the plug member when unseating.

Preferably, there is a vane provided, immediately downstream of the branch, which is formed so that on the occurrence of reverse fluid flow the vane produces turbulence or other variation in fluid flow which tends to suck the plug member into the conduit.

Alternatively, the pipeline check valve is provided with an L-shaped or dog-leg rail which is attached at its corner to a hinge located at the junction between the conduit and the branch so that the L-shaped member guides the plug member into the branch under normal fluid flow conditions and into the conduit in the event of reverse flow occurring. One arm of the L-shaped member being formed so as to provide a continuous guide line in the roof of the conduit, in normal flow conditions, thus facilitating the ease of passage of inspection pigs through the conduit.

Alternatively, the branch may comprise an imbalance flow pipe connected between the outer end of the branch and the conduit at a location downstream, in normal flow, of the valve, the cross-sectional area of the imbalance flow pipe being greater than that of the annular area between the plug member and the branch bore, resulting in an upward pressure on the plug member urging it into, and retaining it in, the branch line as long as the normal flow of fluid continues, and releasing it in the event of reverse flow occurring.

In another form, the branch lies at an acute angle to the reverse flow direction and the plug member is expelled impulsively from the branch by pneumatic, hydraulic or mechanical means. The plug member may be spherical, and the conduit may comprise an annular seat or bottleneck.

Alternatively, the plug member may comprise a cylindrical pig having anchor legs engageable with locking means in the conduit, which may suitably comprise an annular groove in the wall of the conduit.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a cross-sectional side view of one embodiment of valve according to the invention; Fig. 2 is a similar view showing the valve of Fig. 1 in closed condition; Fig. 3 is a view down the bore of the valve of Figs. 1 and 2; Fig. 4 is an enlarged view of part of the structure of Figs. 1 and 2; Figs. 5A, B and C illustrate the operation of a modified form of the foregoing embodiment; Figs. 6A, B and C are cross-sectional side views illustrating a second embodiment; Figs. 7A, B and C are similar views illustrating another embodiment; Figs. 8A, B and C illustrate a pig friendly design using trunnions and rolling grooves; Figs. 9A and B illustrate an embodiment incorporating imbalance lines; and Fig. 10 illustrates a modified rolling groove design.

Referring to Figs. 1 to 3, a check valve comprises a tubular conduit 10 having end flanges 12, 14 for in-line connection in a pipeline. A curved branch 16 extends vertically from the conduit 10 and is closed at its outer end 18.

The valve is adapted to permit normal flow in direction 1 and to block reverse flow in direction 2. The upstream end of conduit 10 is provided with an annular reduced diameter seat 20. A spherical plug 22 has a diameter conforming with the bore of the valve and may move between an open position at the outer end 18 of the branch 16 (Fig. 1) and a closed position abutting the seat 20 (Fig. 2).

The plug 22 assumes the appropriate position automatically.

When normal flow in direction 1 is present, the pressure produced by the fluid flow maintains the plug 22 in the position shown in Fig. 1. If the flow reverses to direction 2 (for example, because of a rupture in the pipeline) the plug 22 falls under gravity to the closed position of Fig.

2. For this purpose, the specific gravity of plug 22 should preferably be slightly greater than that of the fluid in the pipeline.

To ensure correct movement of the plug 22 between these two positions, the conduit 10 is provided with guide surfaces, suitably in the form of curved ramps 24 with a horizontal spacing D3 (Fig. 3) smaller than the diameter D2 of the plug 22; D1 designates the internal diameter of the conduit 10.

Referring to Fig. 4, a groove 28 is formed in the floor of the conduit 10. The purpose of this is that, when reverting to normal flow in direction 1, the initial flow unseats the plug 22 from the seat 20 allowing fluid to enter the groove 28; fluid flow in the groove 28 imparts upward momentum to the plug 22 which assists in causing motion of the plug into the branch 16.

As shown in Fig. 2 only, a vane 30 may be provided immediately downstream of the branch 16 in the direction of normal flow. The vane 30 is shaped such that, if reverse flow occurs, it produces turbulence or other variation in the fluid flow which tends to suck the plug 22 into the main flow stream in the conduit 10.

Fig. 5 illustrates a modification to the foregoing to facilitate use with pipeline pigs. It is obviously desirable to ensure that the pig does not deviate from the main conduit into the branch. In the modification of Fig.

5, a dogleg rail 32 is hinged at 34 and in normal conditions is held in the position shown in Fig. 5A by the plug bearing on the upper leg 32A, thus aligning the lower leg 32B with the wall of the conduit 10. This allows pipeline pigs to pass freely along the conduit 10 and prevents deviation into the branch 16.

In the event of reverse flow, as in Fig. 5B, the plug 22 moves into engagement with the seat 20 as before, and during this movement the rail 32 is rotated by the plug 22 to the position shown. The length of the rail 32 is selected in relaton to the diameter of the plug 22 such that the rail 32 cannot rotate back from this position while the plug 22 is seated in the seat 20.

Fig. 5C shows the plug 22 returning to its original position on resumption of normal flow The dog-leg rail 32 may be a single, centrally-positioned rail, or may comprise a plurality of longitudinal rails in a gate-like structure. In either case, the dog-leg rail may provide sufficient guidance for movement of the plug 22 to allow the ramps 24 to be dispensed with.

The rail 32 may be freely pivoted on the hinge 34.

Alternatively, it may be spring-biased or hydraulically actuated depending on requirements.

In the foregoing embodiments of Figs. 1 to 5, the plug 22 may be arranged to move, as described, simply under the combined influences of fluid flow and gravity; or movement may be assisted by a pressure blast of working fluid or additional fluid, as indicated at P in Fig. 2.

Also, where pigs are used, the seat 20 is suitably of an axial length chosen in relation to its bore to impart to the pig as it passes through an increased velocity which tends to prevent the pig deviating towards the branch.

In Fig. 6, a conduit 50 has normal flow in direction 1.

Reverse flow in direction 2, caused for example by a leak 52, is blocked by a spherical plug 54 seating against a reduced diameter bottleneck section 56 (Fig. 6C). The plug 54 is normally (Fig. 6A) located in an angled closed branch 58 from which it is ejected when required into the conduit 50 by a remotely-actuated impulse which may for example be provided by a pneumatic, hydraulic or spring-loaded device.

This embodiment may be used in any orientation, since operation of the plug is not gravity dependent.

The embodiment of Fig. 7 is similar to that of Fig. 6, but the spherical plug 54 is replaced by a cylindrical pig 60 provided with annular resilient seals 62 and anchor arms 64 which lock into an annular recess 66. Such a pig is described in our co-pending application number 8804705, which also describes means by which the anchor arms 64 may be disengaged.

The embodiment of Fig. 7 has the same advantages as that of Fig. 6 but does not require a bottleneck section or reduced diameter seat.

Referring now to figs. 8A, B and C, there is described an embodiment which embodies a pig friendly design. This embodiment does away with the need of the guides of Fig. 2 or the rails of Figs. 5A-5C. In this embodiment the ball 82 is provided with a pair of diametrically opposed trunnions 83 which run in rolling grooves 84 formed in the pipe.

The position of the ball 82 is determined by its movement along the path of the rolling grooves 84 in which the trunnions 83 are constrained.

A buffer seat 90 is provided which limits the upward movement of the ball 82 such that the lower part of the ball acts as a guide to a pig passing through. The mating face of the buffer 90 is provided with a circular seal 91 against which the seal 82 seats. The circular seal 91 serves to prevent turbulent flow behind the ball, thus mitigating wear.

Referring now to Figs. 9A and 9B, a valve imbalance line 100 connects the closest end of the branch 101 to the main pipeline upstream of the branch at 102. The ball 103 is held within the branch by virtue of pressure differential caused by the imbalance flow line. To this end, the imbalance line is a larger cross-sectional area than the annular area between the ball and the bore. In Fig. 9B the imbalance line 105 extends through the buffer seat 106. In both embodiments the imbalance line may be non-flowing.

Referring now to Fig. 10 the branch pipe is in the form of a modified T-piece 110. The rolling groove 112 is in the form of an elongate L-section. The advantage of the embodiment of Fig. 10 is that a more continuous guide for a passing pig is provided.

Modifications and improvements may be made to the invention without departing from the scope of the invention.

Claims

1. A pipeline check valve comprising a substantially straight conduit for in-line connection in a pipeline, a branch extending from the conduit and having a closed end, a plug member moveable between a first position within the branch and a second position within the conduit, and means in the conduit co-operating with the plug member such that when in said second position the plug member blocks the conduit against flow in the reverse direction.

2. A pipline check valve according to claim 1, wherein the branch is arranged in a curved path diverging upwardly from the conduit and the plug member has a specific gravity slightly greater than that of the fluid in the conduit such that it assumes said first position under the influence of pressure produced by normal flow and drops to said second position in the absence of such pressure.

3. A pipeline check valve according to claim 1 or claim 2, wherein the plug member is substantially spherical.

4. A pipeline check valve according to any preceding claim, in which said means comprises an annular seat located at said second position in the conduit, which receives the plug member in order to close the pipeline check valve.

5. A pipeline check valve according to any preceding claim, in which a vane is provided, immediately downstream of the branch, in normal flow direction, the vane being formed that, on the occurrence of reverse fluid flow, the vane produces turbulence or other variation in fluid flow which tends to suck the plug member into the conduit.

6. A pipeline check valve according to any preceding claim, wherein a groove is formed in the floor of the conduit.

7. A pipeline check valve according to claim 4 and claim 6, wherein the groove in the floor of the conduit is formed immediately adjacent said annular seat on the downstream (in normal flow) side of the seat, to impart upward momentum to the plug member when it is unseated by the reinstatement of normal fluid flow.

8. A pipeline check valve according to any preceding claim, in which the conduit and branch comprise a pair of guide rails in the form of protrusions from the sides of the branch and conduit, spaced apart by a distance less than the transverse dimension of the plug member.

9. A pipeline check valve according to any of claims 1 to 7, wherein the valve includes a substantially L-shaped dogleg member which is attached at its corner to a hinge located at the junction between the conduit and the branch so that the L-shaped member guides the plug member into the branch under normal flow conditions and into the conduit in the event of reverse flow occurring, one arm of the L-shaped member forming a continuous guide line in the roof of the conduit, in normal flow conditions, providing a guidance means for inspection pigs which pass through the conduit.

10. A pipeline check valve according to any of claims 1 to 7, in which the plug member is substantially spherical with trunnions spaced symmetrically on either side of the plug member which are slideably received by a pair of grooves, one on each side of the branch and conduit, providing a guidance means for the plug member.

11. A pipeline check valve according to any of claims 1 to 7, in which an imbalance flow pipe is connected between the outer end of the branch and the conduit at a location downstream, in normal flow of the valve, the cross-sectional area of the imbalance flow pipe being greater than that of the annular area between the plug member and the branch bore, resulting in an upward pressure on the plug member urging it into and retaining it in the branch line as long as the normal flow of fluid continues, and releasing it in the event of reverse flow occurring.

12. A pipeline check valve according to claim 1, wherein the plug member, in normal flow conditions, is positioned in a straight branch attached, at an acute angle, to the conduit, the plug member being ejected from the branch, under reverse flow conditions, by a remotely-actuated impulse provided by a pneumatic hydraulic or spring-loaded device whereupon it is received by a bottleneck section of reduced diameter bore pipe in the conduit and thus closes the valve, the branch being positioned at any point radially on the pipe as the plug member is not gravity dependent.

13. A pipeline check valve according to claim 1, wherein the plug member is in the form of a cylindrical pig comprising annular resilient seals and anchor arms, the plug member, in normal flow conditions being positioned in a straight branch attached at an acute angle to the conduit, the plug member being ejected from the branch, under reverse flow conditions, by a remotely-actuated impulse, provided by a pneumatic hydraulic or spring-loaded device whereupon the resilient annular seals of the plug member seal against the walls of the conduit preventing backward flow of fluid, and the anchor arms at this point open automatically to be disengagably received by an annular recess in the conduit, the branch being positioned at any point radially on the pipe as the plug member is not gravity dependent.

14. A pipeline check valve substantially as hereinbefore described with reference to and as illustrated in Figs 1 to 4, Fig. S, Fig. 6, Fig. 7, Fig. 8, Fig. 9 or Fig. 10 of the drawings.