GB2278905A - Emergency shutdown valve - Google Patents

Abstract

An emergency shutdown check valve (10, Fig. 1) having a check plate (34) which pivots about an axis (40) to open and close a bore (18) through the valve housing (12) to limit fluid flow through the valve (10) to one direction only (from direction 14 to 16) during functioning as a check valve during which plate 34 occupies generally the figure 1 position. The check plate (34) can be lifted clear of the bore (18) by a plate-lifting mechanism (42 - 50) to the figure 2 position to allow bi-directional flow and/or the passage of a pig. In its raised position (Fig. 2), the check plate (34) can be latched up by a latch mechanism (52 - 66) whose operation requires constant pressurisation of a linear actuator (60). A built-in spring (68) biasses the latch mechanism (52 - 66) to a delatched state in which plate 34 falls through gravity, as a result of its displaced mass from pivot axis 40, to the figure 1 position to provide for automatic fail safe reversion to check valve functioning. The valve (10) is particularly applicable to the protection of submarine hydrocarbon pipelines and facilities connected thereto. <IMAGE>

Description

"Emerqencv Shutdown Valve" This invention relates to an emergency shutdown valve ("ESV"), and relates more particularly but not exclusively to an ESV in the form of a check valve which can be selectively latched open for bidirectional fluid flow therethrough, and delatched in a failsafe manner for reversion to normal check valve operation permitting only unidirectional fluid flow therethrough.

In the context of pipeline transport of hydrocarbons (oil and/or gas, etc) is desirable or mandatory that the pipeline be fitted with an emergency shutdown valve capable of isolating the pipeline on the downstream side of the valve and/or of preventing reverse flow through the pipeline, and that the valve should operate in a failsafe manner even if the operating conditions are abnormal. Known forms of ESV include ball valves and gate valves closed by a hydraulic or pneumatic actuator upon the receipt of a "close" signal and/or upon loss of an "open" signal.In order to make the operation of closing the valve independent of an external hydraulic or pneumatic power supply for the actuator, these known forms of ESV usually employ a fluid-pressure-energised rotary or linear actuator that holds the ball or gate of the valve in its open position against the force of a spring and/or against the force of internal valve pressure. Loss of the hydraulic or pneumatic power supply will then allow the spring force and/or internal pressure to operate the valve to its closed (fluid flow blocking) configuration.

However, in such known forms of ESV, considerable forces are required to move the ball or gate to its valve-closing position. As this closure force is usually stored only in a spring mechanism, a very large spring is required, particularly in the case of ball valves which generally do not utilise internal pressure to assist the valve-closing operation. Moreover, the valve-closing operation is usually slow because a substantial quantity of air or hydraulic fluid has to be driven from the valve actuator by means of the closure spring during the valve-closing operation, and such slowness is undesirable in an emergency (when valve closure should be as rapid as possible).An additional hazard of such known forms of ESV is that as the valve closes, differential pressure across the valve builds up, thus increasing the force required to continue closing the valve at the same time as the spring force available to close the valve is diminishing by reason of the expansion of the spring concomitant on the fraction of the valve-closing operation already performed. In other words, demanded spring energy rises just as available spring energy decreases. As a consequence, the valve may fail to close completely if deposits or corrosion have increased operation friction of the valve above the original design parameters.

If the normal (non-emergency) flow of fluid through a pipeline is in one direction only, and the pipeline and/or connected installations can be adequately protected merely by preventing reverse flow (ie by preventing fluid flow through the pipeline in the direction opposite to the normal direction), a conventional check valve may serve as the ESV in such particular circumstances. At its simplest, a conventional check valve comprises a fixed valve seat closable by a flap hinged to one side of the flap, the flap pivoting about its hinge alternately to come against the valve seat to close the valve to fluid flow therethrough, and to swing clear of the valve seat so as to open the valve to fluid flow therethrough.

Closing of the flap against the valve seat is generally by the weight of the flap (the flap pivot being horizontal and above the flap), assisted at least in the latter stages of closing by differential fluid pressure across the valve seat.

A check valve may be provided with positive opening means by which the flap can be positively lifted away from the valve seat, and held up to keep the valve open. Such opening means enables the valve to permit reverse flow of fluid on selected occasions, and to permit the free passage in either direction of a pig (a pipeline cleaning and/or inspection device which travels along the bore of the pipeline). When a check valve is held open in this manner, its normal reverse flow prevention function is inhibited, and the check valve is unable to perform its ESV function of preventing reverse flow. Thus a check valve which is intended as an ESV and which can be selectively held open should be capable of being returned from its held open state to its normal check valve mode in a rapid and failsafe manner.

According to a first aspect of the present invention there is provided an emergency shutdown valve ("ESV") capable of selectively either permitting fluid flow therethrough in an open configuration of said valve or substantially preventing fluid flow in at least one direction therethrough in a closed configuration of said valve, biassing means biassing said valve from said open configuration thereof to said closed configuration thereof, latch means selectively operable to inhibit said biasing means and to hold said valve in said open configuration thereof, and latch disabling means biassed to disable said latch means to allow said biassing means to reconfigure said valve from said open configuration thereof to said closed configuration except when said latch disabling means is positively held from disabling said latch means.

Said ESV may further comprise valve opening means selectively operable positively to reconfigure said valve from said closed configuration thereof to said open configuration whereof against the biassing influence of said biassing means, said latch means being subsequently operable selectively to hold said valve in said open configuration thereof against the biassing influence of said biassing means.

Said ESV may comprise a through bore for transport of fluid through said valve when in said open configuration thereof, an obturator seating means circumscribing said through bore, and an obturator means movable under the biassing influence of said biassing means from a first position in which said obturator means is displaced from said obturator seating means and said valve is in said open configuration thereof for the flow of fluid through said through bore, to a second position in which said obturator means is substantially seated on said obturator seating means and said valve is in said closed configuration thereof in which the flow of fluid through said through bore is substantially prevented in at least one direction therethrough, said obturator means being displaceable by said valve opening means from said second position of said obturator means to said first position of said obturator means to reconfigure said valve from said closed configuration thereof to said open configuration thereof.

Said biassing means preferably comprises an arrangement by which the centre of gravity of said obturator means descends during displacement of said obturator means from said first position thereof to said second position thereof, said valve opening means functioning to raise said obturator means from said second position thereof to said first position thereof.

Said latch means preferably functions temporarily to anchor said obturator means in said first position thereof by energisation of an actuator means to bring a latch member into an obturator-baulking position, said latch disabling means comprising spring means disposed to move said latch member away from said obturatorbaulking position upon de-energisation of said actuator means.

According to a second aspect of the present invention there is provided an emergency shutdown check valve comprising a valve housing defining a through bore for the transport of fluid through said valve, a valve seat circumscribing said through bore, a check plate mounted for pivoting movement about a substantially nonvertical pivot axis, said check plate being pivotable about said pivot axis between a first position in which said check plate is above and displaced from said valve seat such that said check valve is open for the flow of fluid through said bore, and a second position in which said check plate is lowered onto said valve seat such that said check valve is substantially closed to the flow of fluid through said bore, said check plate being biassed by the weight thereof from said first position towards said second position, said check plate being movable from said second position towards said first position by differential pressure across said valve in a forward direction of normal fluid flow through said bore such that said valve performs a check valve function permitting fluid flow through said bore substantially only in said forward direction while substantially preventing fluid flow through said bore in a reverse direction opposite to said forward direction, said check valve further comprising plate lifting means for lifting said check plate from said second position to said first position to disable said check valve function and to open said bore to fluid flow therethrough in both directions, said check valve additionaLly comprising latch means selectively operable to latch said check plate in said first position against the weight of said check plate biassing said check plate from said first position towards said second position, and latch disabling means conditionally biassing said latch means to a non-latching disposition freeing said check plate for movement from said first position to said second position, except when said latch disabling means is positively held from so biassing said latch means.

Said substantially non-vertical pivot axis is preferably a substantially horizontal axis when said valve housing is substantially upright. Said check plate may be a disc member mounted on the free end of a plate-mounting arm pivoted about said axis. Said plate lifting means may comprise a cam means movable against a cam follower means secured to or integral with said plate-mounting arm, said cam means preferably being in the form of a rotary cam or eccentric rotatable about a cam axis which is non-coincident with said pivot axis, and said cam follower means preferably being in the form of a projection on said plate-mounting arm.Said latch means may comprise a linearly movable detent means movable by a linear actuator means against said plate-mounting arm or against an extension of said plate-mounting arm, said latch disabling means preferably comprising spring means acting on said detent means or on said linear actuator means in a direction to move said detent means out of contact with said plate-mounting arm or said extension thereof.

Said linear actuator means may comprise a fluid motor energised by pressurised fluid and conveniently in the form of a hydraulic or pneumatic piston and cylinder assembly.

Embodiments of the invention will now be described by way of example, with reference to the accompanying drawing wherein: Fig. 1 is a longitudinal section of a preferred embodiment of emergency shutdown check valve in accordance with the present invention; Fig. 2 is a part view of the Fig. 1 arrangement wherein certain parts of the preferred embodiment are in an altered configuration; and Fig. 3 details an optional modification of the preferred embodiment.

Referring first to Fig. 1, an emergency shutdown check valve 10 comprises a housing 12 having a fluid inlet 14 and a fluid outlet 16 by which the valve 10 is connected in use into a hydrocarbon pipeline (not shown). The inlet 14 and the outlet 16 are mutually joined by a cylindrical through bore 18 extending horizontally through the housing 12. The upper part of the housing 12 is formed with a cavity 20 which intersects the bore 18 and which contains parts of the valve mechanism about to be described. The top of the cavity 20 is normally closed by a valve bonnet 22 which is sealed to the housing 12 by a circumferential seal 24.The bonnet 22 can be secured to the housing 12 by any suitable means, shown by way of example at the top left of Fig. 1 as a manacle clamp 26 and shown by way of an alternative example at the top right of Fig. 1 as a stud 28 and nut 30 (an array of which will be suitably distributed around the periphery of the bonnet 22). (A further alternative bonnet clamping arrangement will subsequently be described with reference to Fig. 3).

A conical valve seat 32 circumscribes the through bore 18 in a plane which is inclined to the longitudinal axis of the bore 18 such that the conical valve seat 32 is tangential to the bottom of the cylindrical bore 18 and extends slightly upwards into the cavity 20 above the top of the bore 18. The smooth blending of the valve seat 32 onto the bottom of the bore 18 eliminates any sump or cavity in the bore 18 which would otherwise tend to collect undesirable accumulations of debris, sand, or fluids.

The movable obturator of the valve 10 is a disc-form check plate 34 having a periphery which is tapered to match the conicity of the valve seat 32 and which is fitted with a circumferential seal ring 36. The check plate 34 is secured on its downstream face (on the right as viewed in Fig. 1) to the free end of a platemounting arm 38 pivotable in a vertical plane (the plane of Fig. 1) about a horizontal pivot axis 40. The pivotal mounting of the check plate 34 allows the check plate 34 to pivot about the axis 40 between a downward position as shown in Fig. 1 and an upward position as shown in Fig. 2. In its downward position (Fig. 1), the check plate 34 is seated on the valve seat 32 and sealed thereto by the seal 36 such that the through bore 18 is blocked against the flow of fluid (oil, gas, etc) from the valve outlet 16 to the valve inlet 14.

In its upward position (Fig. 2), the check plate 34 is lifted clear of the valve seat 32 such that the bore 18 is clear for the flow of fluid therethrough.

In the absence of fluid pressure differentials (see below), the normal tendency of the check plate 34 is to move under gravity from the upper position (Fig. 2) towards the lower position (Fig. 1). This gravity biassing of the check plate position arises from the pivot axis 40 being horizontal and above the bore 18, and from the centre of gravity of the arm 38, and not least, of the check plate 34 itself being substantially offset from the pivot axis 40 such that the whole arrangement lacks weight balance and therefore tends to pivot clockwise as viewed in Figs. 1 and 2.While elevation of the check plate 34 against gravity biassing to the extreme upward position shown in Fig. 2 requires operation of a check plate lifting mechanism (detailed subsequently), partial lifting of the check plate 34 off the valve seat 32 can be brought about by a suitable pressure differential, as will now be described.

Elevation of the check plate 34 even partly above the lowermost position shown in Fig. 1 will lift the check plate 34 off the valve seat 32 and at least partly open the bore 18 to the flow of fluid therethrough. Such lifting of the check plate 34 off the valve seat 32 is brought about in normal operation of the valve 10 by differential fluid pressure in the normal flow direction, ie a situation in which fluid pressure at the valve inlet 14 exceeds fluid pressure at the valve outlet 16.Conversely a reverse pressure differential will force the check plate 34 against the valve seat 32 (assuming the check plate 34 is not held fully elevated as in Fig. 2), ie in normal check valve operation of the valve 10, an excess of fluid pressure at the outlet 16 over the fluid pressure at the inlet 14 will close the valve 10 to fluid flow therethrough and thus effectively prevent fluid flow in the reverse direction.

From time to time, it may become desirable or necessary to allow reverse flow through the valve 10, and/or to open the bore 18 to its fullest extent, eg to permit the passage of a pig in either direction. To this end, it is necessary to be able selectively to inhibit the normal check valve function with its inherent unidirectionality of flow, and to lift the check plate 34 into the cavity 20 to be completely clear of the bore 18. The means for achieving this reconfiguration of the valve 10 will now be described.

The check plate lifting arrangement comprises an eccentric 42 or other suitable rotary cam secured to the lower end of an operating shaft 44 depending through the valve bonnet 22. The shaft 44 is rotatably mounted in bearing bushes 46 and is sealed to the bonnet 22 by means of seals 48. Other than for a small clearance at its inactive position as shown in Fig. 1 (to avoid interference with full seating of the check plate 34 on the valve seat 32), the periphery of the eccentric 42 bears against a projection 50 on the plate-mounting arm 38. Progressive rotation of the shaft 44 in either direction away from the alignment shown in Fig. 1 causes corresponding rotation of the eccentric 42 and progressive displacement of the projection 50 about the pivot axis 40.

Correspondingly, the arm 38 (of which the projection 50 is a rigid and integral part) tilts about the axis 40 to lift the check plate 34 from its lowermost position (Fig. 1), ultimately raising the check plate 34 into the cavity 20 and clear of the through bore 18 (Fig. 2).

In order to latch the check plate 34 in its highest position (Fig. 2), a detent pin 52 is lowered through the bonnet 22 into contact with an extension 54 of the plate-mounting arm 38. The detent pin 52 is slidably mounted in bearing bushes 56 and is sealed to the bonnet 22 by means of seals 58. The detent pin 52 is lowered from its inactive position (Fig. 1) to its active position (Fig. 2) by a linear actuator 60 comprising a piston 62 secured to the upper end of the pin 52 and sliding within a closed-end cylinder 64 secured to the upper face of the bonnet 22. A conduit 66 leading into the upper end of the cylinder 64 selectively admits pressurised fluid (oil or gas) from a controlled source (not shown) to drive down the piston 62 and hence force the lower end of the detent pin 52 down onto the arm extension 54.In this configuration, the eccentric 42 can be rotated 1800 backwards (or onwards) to return the eccentric 42 to its starting position, leaving the check plate 34 held up solely by the action of the detent pin 52 on the arm 50, as specifically illustrated in Fig. 2.

The detent pin 52 is biased to its upward position (Fig. 1) by means of a coil compression spring 68 located in the lower end of the cylinder 64 to act between the upper face of the bonnet 22 and the underside of the piston 62. The upward force of the spring 68 on the piston 62 and hence on the detent pin 52 can readily be overcome by normal fluid pressure in the upper end of the cylinder 64, but as soon as the linear actuator 60 is de-energised by depressurisation, the spring 68 forces the piston 62 upwards to retract the detent pin 52 back up into the thickness of the bonnet 22.

Therefore when the linear actuator 60 is de-energised for whatever reason (either deliberately or because of equipment malfunction, signal loss, or any other cause), and provided the eccentric 42 is returned to its projection-freeing position (as in Fig. 1), the check plate 34 will be automatically and immediately detached to return under gravity from its flow-freeing configuration (Fig. 2) to its flow-controlling configuration (Fig. 1). Thus the above-described arrangement provides an emergency shutdown function for the basic check valve with its additional positive opening arrangement.

The above-described emergency shutdown check valve is particularly applicable to submarine pipelines for the protection of offshore facilities.

Means for controllably rotating the operating shaft 44 of the check plate lifting mechanism are not shown in the drawings and could take any suitable form, for example, a remote operated tool (not shown) temporarily landed on top of the valve 10.

Modifications and variations of the preferred embodiment described above can be adopted without departing from the scope of the invention. For example, the fluid pressure actuator 60 could be replaced by a suitable electric linear actuator.

The de-latching function of the spring 68 can be augmented by providing a fluid passage between the interior of the valve housing 12 and the underside of the piston 62 (eg a fluid passage through the bonnet 22 between its top and bottom faces immediately alongside the detent pin 52) such that the internal pressure of the valve 10 adds to the upward force on the piston 62 tending to lift the detent pin 52 to its delatching position.

The plate-mounting arm 38 and the latch mechanism (5266) could be modified to provide the plate-lifting function in place of the plate-lifting mechanism 42-50 described above with reference to Fig. 1, thereby enabling these components 42-50 to be eliminated.

The various alternative bonnet-clamping arrangements previously described with reference to Fig. 1 could be substituted by the clamping arrangement shown in Fig. 3 wherein the bonnet 22 is provided with a peripheral array of circumferentially distributed segments 70 conjointly movable radially outwards-and inwards of the bonnet 22. When the bonnet 22 is plug-fitted within a suitable opening in the valve housing 12, the segments 70 are moved outwards by means of a vertically displaceable segment actuating ring 72, until the segments 70 fit tightly within a circumferential groove 74 inside the opening in the housing 12 to lock the bonnet 22 to the housing 12. Full details of the bonnet clamping arrangement outlined with reference to Fig. 3 are given in our co-pending British Patent Application No. 9408348.2, to which reference should be made for further information.

The above-described emergency shutdown facility enables or causes the valve to close with the normal flow direction through the valve, in contrast to the conventional check valve wherein it is necessary to have flow reversal for closure to take place. This distinction may result in considerable check plate velocities being reached during closure, and severe resultant impacts when the check plate lands on the valve seat (this being termed as the "slam close effect"). It may therefore be considered desirable to incorporate a damping device that reduces the impact velocity of the check plate, eg in the form of a decelerating linkage (like a shock absorber) acting on the plate-mounting arm or swivel mechanism, and/or in the form of a ring of impact-damping and energyabsorbing material disposed to be hit by the check plate just prior to impacting upon the actual valve seat.

Other modifications and variations can be adopted without departing from the scope of the invention as defined in the appended claims.

Claims (16)

1. An emergency shutdown valve ("ESV") capable of selectively either permitting fluid flow therethrough in an open configuration of said valve or substantially preventing fluid flow in at least one direction therethrough in a closed configuration of said valve, biassing means biassing said valve from said open configuration thereof to said closed configuration thereof, latch means selectively operable to inhibit said biassing means and to hold said valve in said open configuration thereof, and latch disabling means biassed to disable said latch means to allow said biassing means to reconfigure said valve from said open configuration thereof to said closed configuration thereof except when said latch disabling means is positively held from disabling said latch means.

2. An ESV as claimed in Claim 1 wherein said valve further comprises valve opening means selectively operable positively to reconfigure said valve from said closed configuration thereof to said open configuration thereof against the biassing influence of said biassing means, said latch means being subsequently operable selectively to hold said valve in said open configuration thereof against the biassing influence of said biassing means.

3. An ESV as claimed in Claim 1 or Claim 2 wherein said valve comprises a through bore for transport of fluid through said valve when in said open configuration thereof, an obturator seating means circumscribing said through bore, and an obturator means movable under the biassing influence of said biassing means from a first position in which said obturator means is displaced from said obturator seating means and said valve is in said open configuration thereof for the flow of fluid through said through bore, to a second position in which said obturator means is substantially seated on said obturator seating means and said valve is in said closed configuration thereof in which the flow of fluid through said through bore is substantially prevented in at least one direction therethrough, said obturator means being displaceable by said valve opening means from said second position of said obturator means to said first position of said obturator means to reconfigure said valve from said closed configuration thereof to said open configuration thereof.

4. An ESV as claimed in Claim 3 wherein said biassing means comprises an arrangement by which the centre of gravity of said obturator means descends during displacement of said obturator means from said first position thereof to said second position thereof, said valve opening means functioning to raise said obturator means from said second position thereof to said first position thereof.

5. An ESV as claimed in Claim 3 or Claim 4 wherein said latch means functions temporarily to anchor said obturator means in said first position thereof by energisation of an actuator means to bring a latch member into an obturator-baulking position, said latch disabling means comprising spring means disposed to move said latch member away from said obturatorbaulking position upon de-energisation of said actuator means.

6. An emergency shutdown check valve comprising a valve housing defining a through bore for the transport of fluid through said valve, a valve seat circumscribing said through bore, a check plate mounted for pivoting movement about a substantially nonvertical pivot axis, said check plate being pivotable about said pivot axis between a first position in which said check plate is above and displaced from said valve seat such that said check valve is open for the flow of fluid through said bore, and a second position in which said check plate is lowered onto said valve seat such that said check valve is substantially closed to the flow of fluid through said bore, said check plate being biassed by the weight thereof from said first position towards said second position, said check plate being movable from said second position towards said first position by differential pressure across said valve in a forward direction of normal fluid flow through said bore such that said valve performs a check valve function permitting fluid flow through said bore substantially only in said forward direction while substantially preventing fluid flow through said bore in a reverse direction opposite to said forward direction, said check valve further comprising plate lifting means for lifting said check plate from said second position to said first position to disable said 1 check valve function and to open said bore to fluid flow therethrough in both directions, said check valve additionally comprising latch means selectively operable to latch said check plate in said first position against the weight of said check plate biassing said check plate from said first position towards said second position, and latch disabling means conditionally biassing said latch means to a non-latching disposition freeing said check plate for movement from said first position to said second position, except when said latch disabling means is positively held from so biassing said latch means.

7. A valve as claimed in Claim 6 wherein said substantially non-vertical pivot axis is a substantially horizontal axis when said valve housing is substantially upright.

8. A valve as claimed in Claim 6 or Claim 7 wherein said check plate is a disc member mounted on the free end of a plate-mounting arm pivoted about said axis.

9. A valve as claimed in Claim 6 or Claim 7 or Claim 8 wherein said plate lifting means comprises a cam means movable against a cam follower means secured to or integral with said plate-mounting arm.

10. A valve as claimed in Claim 9 wherein said cam is in the form of a rotary cam or eccentric rotatable about a cam axis which is non-coincident with said pivot axis.

11. A valve as claimed in Claim 9 or Claim 10 wherein said cam follower means is in the form of a projection on said plate-mounting arm.

12. A valve as claimed in any of Claims 6 to 11 wherein said latch means comprises a linearly movable detent means movable by a linear actuator means against said plate-mounting arm or against an extension of said plate-mounting arm.

13. A valve as claimed in Claim 12 wherein said latch disabling means comprises spring means acting on said detent means or on said linear actuator means in a direction to move said detent means out of contact with said plate-mounting arm or said extension thereof.

14. A valve as claimed in Claim 12 or Claim 13 wherein said linear actuator means comprises a fluid motor energised by pressurised fluid.

15. An emergency shutdown check valve substantially as hereinbefore described with reference to and as shown in Figs. 1 and 2 of the accompanying drawings.

16. An emergency shutdown check valve as claimed in Claim 15, modified substantially as hereinbefore described with reference to and as shown in Fig. 3 of the accompanying drawings.