GB2133472A

GB2133472A - Gate valve actuator

Info

Publication number: GB2133472A
Application number: GB08400446A
Authority: GB
Inventors: John Nolan Mcintyre
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1983-01-10
Filing date: 1984-01-09
Publication date: 1984-07-25
Also published as: GB8400446D0; NO160873B; CA1228582A; SG61486G; GB2133472B; NO160873C; NO840062L; BR8400108A; MX158221A

Abstract

A hydraulically operated actuator for a sliding gate valve designed for use in a subsea environment. The actuator includes (a) a manual override system (41, 42) that functions independently of the actuator's hydraulic piston (54) and return spring (56); (b) an externally accessible valve gate drift adjustment (40) in the form of a sleeve with left and right hand threads (40a, 40b); and (c) a hydraulic control pressure porting system (96, 98, 100) integral with the hydraulic cylinder (46) to minimize space requirements. An externally adjustable upstop (60) is provided for the actuator stem (42, 44). The facility exists for accommodating an optional external electrical stem position indicator package on the cap (62). <IMAGE>

Description

SPECIFICATION Gate valve actuator This invention relates to gate valve actuators, and more particularly to hydraulically operated actuators forsubseawell gate valves.

Forsometimethe oil and gas industry has required hydraulic actuators for operating gate valves on subseawell christmastrees, pipe manifolds, and other underwater well apparatus, and such actuators of various designs are in widespread use for this purpose. Preferably, an actuatorforthis type of service would be capable of manual operation in the eventofhydraulicpowerfailure,would have provision for external adjustment to compensate for valve gate drift, could be manually operated and adjusted with readilyavailabletools and minimal effort, and would be compact in size and functionally reliable.

The present invention is embodied in a hydraulic operated gate valve actuator having one or more of the abovefeatures. Such an actuator can include an externally adjustable valve gate drift adjustment system, a manual override system that does not exercisethe hydraulic piston or its return spring at any time during the manual override operation,thereby requiring the application of only minimal actuation torque bythe diver, andthatdoes not introduce a potential leakpath to control pressure fluid during said override cycle, an externally adjustable upstop for the actuator stem that can be used instead ofthe backseat between the valve stem and bonnet, and a separate and readily replaceable thread assembly for the actuator stem that offers reduced manufacturing costs and Iesspotentialforthreadgallingduringthe actuator's service life.

The actuator has a high spring load-to-actuation piston area ratio with multiple control ports for more rapid responseto command control pressure. Should the control pressurefail the spring automatically and quicklyreturnsthe piston to its "valve closed" position, thereby providing effective fa I-safe closed protection tothefluid conduit in which the valve is installed In its preferred form the actuator also includes a hydraulic control pressure porting system that is integral to the cylinder to minimize external plumbing requirements and the overall length and diameter of theactuator.Amanifolding hydraulic distribution system forthe control pressure porting assures positive distribution offluid to the cylinder during actuation, and minimizes the number of fabricated parts in the system.

In its preferred form the actuator further includes an ambient pressure compensation porting system on the backside ofthe piston and piston cylinderto almost equalize the pressure in the static nonoperating mode control pressure porting system caused by hydrostatic hydraulic head from sea level to the instailed subsea valve. This compensation system assures that the actuator is only operated to the open position by a positive control pressure command from the surface control system, and not by hydrostatic head pressure in the control pressure porting system.

The preferred form of actuator additionally includes an accommodationforan externally mounted electrical position indication packagefor monitoring the position ofthe actuator stem and, ultimately, the valve gate to which the stem is connected. Provision for manually monitoring the stem and gate positions, from outsidethe actuator, also is present in the preferred embodiment in a form that is readily accessible to a diver.

Figure lisa diagrammatic side elevation of a subsea well completion system, showing valve actuators incorporating the present invention in functional position on gate valves of a subsea christmas tree.

Figure 2 is a central longitudinal section, on an enlarged scale, of a valve actuatorthat includes the features ofthe present invention.

As diagrammatically represented in Figure 1, valve actuators 8 embodying the present invention are especially suitable for use on subsea well completion apparatus 10 to open and close gate valves 12 located in the christmas tree 14that is mounted on the subsea wellhead assembly 16. The illustrated wellhead assembly 16typically includes a welihead housing 18, a tree connector 20 securing the tree 14 to the housing 18, and a permanent guide base 22 surrounding and secured to the housing 18 and associated wellhead components 24 by support struts 26. The actuators 8 are operated by hydraulic pressure conducted from a suitable source (not shown) through hydraulic lines (not shown), and the pressure is applied to the actuator pistons through internal passages in the actuator as described below.

Referring to Figure 2,the preferred embodiment of the present invention is illustrated in one ofthe valve actuators 8that is shown attached to the bonnet 30 of one ofthe gate valves 12 by a plurality of screws 31.

The actuator 8 broadly comprises a housing 32 secured to a main body 34 by th reads 36, a flange body 38 connectedto the main body 34 by a flange body coIIar4O,astem assembly41 comprising an outer or manual override stem 42 and an inner or actuation cylinder stem 44, a sleeve-type hydraulic cylinder 46 secured by threads 48 to the main body 34, a cylinder cap 50 secured by threads 52 and a set screw 53to the cylinder46, a piston 54 mounted on the inner stem 44 within the cylinder 46, and a piston-return coil spring 56 surrounding the cyliner46 and extending between the main body 34 and a spring compression hub 58 thatsurroundsthe outer stem 42.

The outer end of the housing 32, i.e., the right-hand end as viewed in Fig. 2, has a central opening into which is threaded a packing gland 60, and threaded onto the outer end of the packing gland is an end cap 62 with a central opening 62a. The outer stem 42 extends through the packing gland 60 and into the end cap 62, preferably terminating within the central opening 62a when the stem is in its "vale closed" position shown in Fig. 2. Between a radial flange 60a of the packing gland 60 and the adjacent end face ofthe actuator housing 30 is a spacer ring 63 that is removed to facilitate furtherth reading ofthe gland into the housing to provide a stop forthe actuator stem, as will be more fully explained later.An annularstatic seal 64 provides fluid-tight integrity between the gland 60 and the housing 32, and annular dynamic seals 66 provide a fluid barrier between the gland and the actuator's outer stem 42.

The outer stem 42 has a radially enlarged area or flange 42a located within a central bore 58a ofthe hub 58, and a pair of bearing assemblies 68,70, located on oppositesidesoftheflange42a,provide relative rotation support between the stem 42 and the hub 58.

A retainer ring 72 holds the bearing assembly 70 in position againstthe stem flange 42a.

The outerstem 42 is connected to the inner stem 44 by means of a stem adjustment screw 74 that is secured to the end ofthe inner stem by a cap screw 76.

The inner end of the stem adjustment screw 74 has a central transverse tongue 74a that cooperates with a mating groove 44a in the adjacent end of the inner stem 44to prevent relative rotation between the screw 74 and the stem 44when properly assembled as shown. The adjustment screw74 and the adjacent portion of the inner stem 44 reside in a central threaded bore 42b in the outer stem 42, and external threads on the screw 74 cooperate with the threads in the bore 42b to axiallychangethe location of the screw in the bore, and thusthe axial position ofthe inner stem 44 with respect to the outer stem 42, when the outer stem is rotated with respecttothe inner stem.

Theouterstem 42 extendsthrough a central borein the cylinder cap 50 and is sealed in afluid-tight mannerthereto by annular dynamic seals 78. Between the inner end ofthe outer stem 42 and the piston 54 is an annular bushing 80 to prevent galling of the adjacent piston face by the stem 42 when the stem is rotated with respect to the inner stem 44 into the position shown in Fig. 2. When in that position the outer stem 42 holds the piston 54 against an annular shoulder44b on the inner stem 44, and when the actuator is operated by hydraulic pressure the piston 54, inner stem 44 and outer stem 42 translate in unison. Annular seals 82 assure a fluid-tight barrier between the piston and the inner stem.

When the actuator 8 is functionally connected to a gate valve the actuator's inner stem 44 is connected to the valve's bonnet stem 84 by suitable means such as theT-slot arrangement shown in Fig. so that when the actuator is operated the stems 44,84 translate in unison.The other end portion of the valve bonnet stem 84 includes an annular beveled shoulder 84a that cooperates with an annular beveled backseat surface 30a on the valve bonnet 30 to establish a metal-tometal seal betweenthestem 84andthe bonnetwhen thevalveisclosedasshown in Fig. 2.An annular packing 86, held in place in the bonnet 30 by a packing retainer nut 88, provides a dynamic seal between the bonnet and the bonnet stem 84, and annular dynamic seals 90 provide a fl u id-tig ht barrier between the stem 84 and the packing nut 88. The packing nut 88 is sealed to the bonnet 33 by an annular seal element 92, and an annular seal 94 providesfluid-tight integrity between the bonnet and the actuator main body 34.

Hydraulic Operation The valve actuator 8 is designed for hydraulic operation but is provided with manual override capability when required. When operated hydraulical ly, control pressure is introduced through one or more ports 96 (only one shown) and conducted byan annularmanifold98toandthrougha pluralityof circumferentially spaced longitudinal passageways 100 in thewall ofthe cylinder 46 into an annular chamber 102 between the piston 54 and the cylinder cap 50.Annular seals 104 between the piston and the cylinder and 106 between the cylindercap and the cylinder cooperate with the seals 78,82 to confine actuation control pressure to the chamber 102, whereby in responsetothis pressure the piston, the actuator stem assembly41 and the valve bonnet stem 84translate in unisontothe left as viewed in Fig. 2, unseating the bonnet stem shoulder84a from the bonnet backseat 30a andtranslating the valve gate (not shown) into its open position.

Pressure compensation forthe actuator 8 to ease its operation at deep sea depths is provided by an external compensator (not shown) that is functionally connected to one or more ports 108 (only one shown) in the actuator main body 34. Compensated oil pressure entering port 108 is conducted by a passageway 110 into an annular chamber 112 in the cylinder46 and in front ofthe piston 54, and also by a passageway 114 into the spring housing 32. This pressure compensation precludes external hydrostatic pressure from crushing the housing 32 and rendering the actuator inoperable.

The actuator spring 56 functions to automatically close the valve whenever control pressure is lost or removed from the backside of the piston 54. The spring 56 provides a force sufficientto rapidly overcome the hydrostatic head of the control pressure column situated above the water surface; i.e., platform control room height above the water. Since the above-described pressure compensation system eli minatesthe effect ofthe ambientwater pressure on the actuator, which pressure can be very great depending upon the depth atwhich the actuator is located, the size ofthe spring 56 required to close the valve is substantially lessthan if such pressure compensation were absent.

When the actuator is hydraulically operated by control pressurecommandtheouterstem 42 is moved from its "valve closed" position towards the valve bonnet 30, carrying with itthe spring compression hub 58 and the bearing assemblies 68,70. This movement of the hub 58compresses the actuator spring 56 which remains compressed as long as the valve remains open. This movement of the outer stem 42 also results in relocation of the stem's outer end face 42c, sothatthe position ofthe stem, and thus the position ofthe valve gate, can be manually ascertained fromthe outside ofthe actuatorthrnugkthe end cap opening 62a.

Manual Override Operation The present invention provides manual override operation ofthe valve operator 8, even under valve operating pressure or hydraulic system control pressure, by removing the end cap 62, installing a wheel crank 116 (Fig. 1) on the outer stem 42, and then rotating the stem. As the stem 42 rotates the stem adjustment screw 74 is forced to the left (Fig. 2); i.e., towards the valve bonnet 30, thereby translating the inner stem 44, the bonnet stem 84, and the valve gate (notshown) to the leftto open the valve.During this valve opening rotation the operation resultant forces from the stems44 and 84 and the valve gate are reacted through the bearing assembly 70 by the stem 42,andthe bearing assembly 70 is reacted bythe packing gland 60.

It should be notedthatthe manual override feature ofthe present invention enables the stems 44 and 84, and of course, also the valve gate, to translate without exercising the piston 54, the spring 56 orthespring compression hub 58. Because ofthis, significantly less torque is required to manually open the valve, and thus an important advantage is achieved as compared with operation requiring spring compression.

When using the manual overrideto closethe valve from its open position, the stem 42 is rotated by the wheel crank 116 in the opposite direction. This rotation causes the stem adjustment screw 74to move to the right; i.e., towards the packing gland 60, thereby pulling the stems 44 and 84 and the valve gate in the same direction, and resulting in closing the valve.

During this valve-closing rotation the operation resultantforces from the valve gate and the stems 84 and 44 are reacted through bearing assembly 68 by the stem 42. Also during this valve-closing the bearing assembly 68 is reacted by the spring compression hub 58, and the hub is reacted by the spring 56.

It should be noted thatthe retainer ring 72, which retains the bearing assembly70 on the outer stem 42, is required for normal hydraulic operation of the actuator8when the stem 42, hub 58 and spring 56 cycle forward and aft many times during normal actuation of a subsea valve by control pressure command.

ExternalAdjustments The present invention further provides for externally adjusting the position of the valve gate to which the actuator8 is connected.

External adjustment of valve gate drift is accomplished by rotating the flange collar40 eitherclockwise or counterclockwise. The collar 40 has two sets of internal threads 40a, 40b, one right-hand and the other left-hand, that engage external threads on the flange body 38 and the main body 34. Relative rotation of the bodies 38, 34 is prevented byan anti-rotation key 118 that resides in opposed keyway slots in the adjacent body surfaces.Accordingly, rotation ofthe collar40 either draws the main body 34 and the housing 32 towards the flange body 38 orforces them away from the body 38, thereby changing the position of the bonnet stem 84 and the actuator's inner stem 44 with respect to the actuator cylinder 46, and thus changing the drift; i.e., the valve gate position with respect to the valve body/bonneV actuator assembly.

External stop adjustmentforthe stems 42,44,84 and the valve gate is accomplished by rotation ofthe packing gland 60. Thus, if it is desired to stop closing movement ofthese stems and the gate before the stem shoulder 84a backseats on the bonnet surface 30a, the frangible spacer ring 63 is knocked out and the gland 60 is threaded further into the housing 32 until its axial position stops the movement at the desired point.

The ability to achieve these two adjustments from outside the actuator offers signigicant cost savings in assembly adjustment, both in the shop and in the field, as well as adjustment when in a subsea location.

Valve Gate Position Indication As discussed above, the present invention facilitates determination ofthe position of the valve gate by viewing orfeeling/measuring the relative position of the outer stem 42 to the end cap 62. Afully extended stem indicates the valve gate is closed, and of course a fully retracted stem indicates the valve gate is in its open position.

The invention also envisions determination of the valve gate position by electrical means, such as by an external electrical sensor (not shown) mounted on the end cap 62. Using a permanently magnetized stem 42, the proper sensor can determine the presence (valve closed position) of the stem orthe non-presence (valve open position) thereof, and send an appropriate signal to the control room on the surface platform (not shown).

It should further be noted that although the abovedescribed valve actuator is intended for use on gate valves on subsea well completion christmas trees and/or manifolds, the actuator also has utility on shore where remote operation of gate valves is required.

Thus the adjustment features described above offer an economic advantage where valve adjustments are required in the field, either on landorsubsea.

Although the best mode contemplated for carrying outthe present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention as setforth in the Claims.

Claims

1. A hydraulic powered actuatorfor a sliding gate valve, said actuator comprising: a) a housing: b) means for attaching the housing to the bonnetof a sliding gatevalve; c) a hydraulic cylinder within and attached to the housing; d) an actuator stem extending through the housing; e) a piston within the cylinderfor moving the actuator stem axially in response to hydraulic pressure; f) means to connect the actuator stem to the stem of said sliding gate valve; g) hydraulic pressure passageway means to conduct hydraulic pressure to the piston for advancing said piston and the actuator stem in one axial direction; h) means for returning the piston and the actuator stem in the opposite axial direction; and i) externally accessible valve gate drift adjustment means for adjusting the drift of the valve gate.

2. An actuator according to claim 1 wherein the means for attaching the housing to a valve bonnet comprises a main body connected to the housing and a flange body for attachment to said valve bonnet, said main body and said flange body interconnected by the valve gate drift adjustment means.

3. An actuator according to claim 2 wherein the position of the main body relative to the flange body can be adjusted axially by the valve gate drift adjustment means.

4. An actuator according to claim 2 wherein the valve gate drift adjustment means comprises a collar threaded to the main body and the flange body, and wherein rotation of said collar with respectto said main and flange bodies causes relative axial movement of said bodies.

5. An actuator according to claim 4 including a differential thread system between the collar and the main and flange bodies.

6. An actuator according to claim 2 including means for preventing relative rotation between the main body and the flange body.

7. An actuator according to claim 1 wherein the actuator stem comprises an assembly including an outer stem element, an inner stem element, and stem adjustment meansfor adjustably connecting said outer and inner stem elements.

8. An actuator according to claim 7 wherein the stem adjustment means facilitates axial adjustment of the relative positions of the outer and inner stem elements

9. An actuator according to claim 7 wherein the stem adjustment means comprises an adjustment screw secured to one ofthe stem elements and threadedly engaging the other stem element, whereby rotation of one element with respect to the other element changes the relative axial position ofthe two elements.

10. An actuator according to claim 1 wherein the actuatorstem includes meansfor manually operating the actuatorwithout advancing the piston or exercising the means for returning the piston and the actuator stem.

11. An actuator according to claim 1 including an externally adjustable stop means for the actuator stem.

12. An actuator according to claim 11 whereinthe stop means comprises a stop element surrounding the stem and extending through and threaded to the housing.

13. An actuatoraccording to claim 1 wherein the hydraulic pressure passageway means comprises a plurality of circumferentially spaced longitudinal passageways in the wall ofthecylinder,and an annular manifold interconnecting said longitudinal passageways with hydraulic pressure inlet means.

14. An actuator according to claim 13 including means to pressure compensate the housing and the cylinder with respectto the external ambient pressure.

15. A hydraulic powered actuator for a sliding gate valve, said actuator comprising: a) a housing; b) meansforattaching the housing to the bonnet of a sliding gate valve; c) a hydraulic cylinder within and attached to the housing; d) an actuator stem assembly extending through the housing, said stem assembly comprising an outer stem element, an inner stem element, and stem adjustmentmeansforadjustably interconnecting said outer and inner elements; e) a piston within the cylinderfor axially moving the actuator stem assembly in response to hydraulic pressure; f) means to connect the actuator stem assembly to the stem of said sliding gate valve; g) hydraulic pressure passageway means to conduct hydraulic pressure to the piston for advancing said piston and the actuator stem assembly in one axial direction; and h) means for returningthe piston and the actuator site assembly in the opposite axial direction.

16. An actuator according to claim 15 wherein the stem adjustment meanscomprises an adjustment screw secured to one of the stem elements and threadedly engaging the otherstem element, where- by rotating one element with respecttothe other element axially changes the relative positions of the two elements.

17. An actuator according to claim 15 wherein the actuator stem assembly includes manual override means for operating the actuator independently of the piston and the means for returning the piston and the actuator stem assembly.

18. An actuator according to claim 15 including an externally adjustable stop means forthe actuator stem assembly.

19. An actuator according to claim 18 wherein the stop means includes a stop element surrounding the stem assembly and threaded to the housing;

20. A hydraulic powered actuator for a sliding gate valve, said actuator comprising: a) a housing; b) meansfor attaching the housing to the bonnet of a sliding gatevalve; c) a hydraulic cylinder within and attached to the housing; d) a piston within the cyliner for axial movement with respectthereto in response to hydraulic pressure; e) an actuator stem connected to the piston; f) means to connectthe actuator stem to the stem of said sliding gate valve; ; g) hydraulic pressure passageway meansto conduct hydraulic pressure to the piston foradvancing said piston and the actuator stem in oneaxial direction, said passageway means comprising a plurality of circumferentially spaced longitudinal passageways inthe wall ofthe cylinder, and an annular manifold interconnecting said longitudinal passageways with hydraulic pressure inlet means; and h) means for returning the piston and the actuator stem in the opposite axial direction.

21. An actuator according to claim 20 including means to pressure compensate the housing and the cylinder with respectto the external ambient pressure.

22. Ahydraulicpoweredactuatorforasliding gate valve substantiallyas described and as shown by the accompanying drawings.