GB1604339A - Quick disengaging valve actuator - Google Patents

Description

(54) QUICK DISENGAGING VALVE ACTUATOR (71) We, BAKER INTERNATIONAL CORPORATION, a corporation organised and existing under the laws of the State of California, of 500 City Parkway West, Orange, California 92688, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following state- ment: The present invention relates to a fluid operable valve actuator having means thereon for quickly disengaging the actuator from the valve body.

Actuators are utilised to manipulate a valve mechanism within a flow fine into open and/or closed position in response to control pressure variation. Normally, these actuators comprise a shaft and a fluid acti vated mechanism in association therewith which, upon activation thereof by increase in control line pressure, causes longitudinal movement of the shaft to shift the valve in relation to its seat. Venting of control line pressure will cause a subsequent and second longitudinal shifting of the shaft and the valve head to a second position. Such valve systems are frequently utilised in safety systems used in conjunction with the drilling, completion and production of offshore, as well as inland, oil and gas wells. Additionally, such components are utilised in natural gas transmission lines, and the like.

During the completion, testing and/or workover of a subterranean well, it may be necessary to run equipment such as a perforating gun, or the like, on a wire or other line into the well when the well is under pressure. This is achieved by inserting the equipment into a length of production tubing above the christmas tree, the length of tubing being commonly referred to as a "lubricator". The lubricator is isolated from the portion of the well therebelow by a valve or a series of readily accessible hand manipulated valves. In view of the fact that the lubricator assembly must contain the well pressure while the equipment is inserted therethrough for subsequent utilization in the well, it is necessary to control the well pressure below the lubricator assembly during this procedure.To contain the well, in the event of failure of the components of the lubricator, a safety valve mechanism is positioned below the lubricator. This valve should be "fail safe" and should be activatable remotely or automatically upon loss of control.

When a gate valve mechanism is utilized below the lubricator, the valve actuator should be of such design and construction that, upon longitudinal shifting of the stem therein, the gate is permitted to completely close with sufficient force such that a wire line carrying downhole tools may be sheared by the gate upon longitudinal shifting of the shaft within the actuator. Upon detection of pressure leaks within the lubricator, or when control of the well is lost and it begins to prematurely flow, the actuator should have sufficient force to cause the wire line to be sheared when the gate is closed in order to assure that the gate is sealingly interfaced onto its seat to prevent flow there through.

The force which shears the wire line penetrating through the gate opening should be independent of the well pressure within the valve body.

Normally, valve actuators depend upon pressure within the valve body operable associated with a compressed spring assembly to shift the bonnet stem longitudinally in order to permit the valve to close. The spring assembly within the actuator is present only for minor friction forces, and fail safe gate valve actuators heretofore made commercially available do not have sufficient force to shear a wire line during the valve closing sequence, in the absence of well pressure in the valve body.

Standard fail safe gate valve actuators are not afforded sufficient force to shear wire inserted through the valve due to physical and technological limitations and sizing requirements for the valves and their associated operating components. A double acting actuator with pressure operable upon either side of a piston element could be utilized in conjunction with spring force to cause man ipulation of a shaft within the actuator to, in turn, cause sufficient force to be exerted on the shaft such that longitudinal movement of the shaft shears the wire line inserted through the valve body. It should be noted that this double acting actuator design is not fail safe, because loss of control pressure will not assure closing of the valve head onto its seat. This piston arrangement would require an external charging force, such as a nitrogen accumulator.Consequently, a stock of nitrogen bottles would be required at the well or other commercial site. The nitrogen charged accumulator would force control fluid out of one of the piston chambers, whereby the valve head is shifted to the closed position. Thus, it is clear that longitudinal movement of the stem when control pressure is vented off to close the valve would require two control lines, the first line being in association with a supply port and one piston chamber, and a second control line in a second or boost port communicating with a second or boost piston chamber.

In view of the fact that the actuator design must be "fail safe", that is, it must assure closure of the valve when control line pressure is intentionally or unintentionally bled off, the incorporafion of two control lines into the design of the actuator renders the design doubly susceptible to failure by leaks and/or breaks in the lines.

As an alternative design, a concentric accumulator exteriorly surrounding the actuator could be utilized as an integral part of the actuator. This design would require the utiliziation of nitrogen bottles in a bank for continuous charging of the accumulator.

Additionally, the two control lines would, of necessity, still be required to maintain nitrogen charges. Use of plural lines would, in turn, continue to double expose the apparatus to the likelihood of nitrogen leaks which are exteremely difficult to detect and seal.

In the past, when it has been found necessary to repair the valve mechanism or the actuator itself on location, considerable down time has been required during the dismanteling of the actuator from the valve bonnet stem in order to have access to the valve or actuator components. The down time has necessitated shut in of a flowing well or isolation of the valve mechanism from the flow stream of a transmission line, which, in turn, has an adverse economic impact because of the cost of lost rig time, lost production, and the like. Moreover, many prior art actuators are designed such that in the event of onsite failure of the attached valve mechanism or the actuator, the actuator must be almost completely disassembled in order to remove or replace the actuator or repair the valve.For example, the prior art has taught use of an actuator valve assembly wherein the actuator is affixed onto the valve body by means of bolts inserted through the lower housing and into companion bores in the upper face of the valve housing. Also, the prior art typically provides for connection of the actuator shaft to the valve head by means of a shoulder on the actuator shaft insertible within a companion slot in the valve head, all within the valve body, the actuator shaft and bonnet stem being one continuous piece. Variations of prior art actuators include those generally as above described and including an actuator expander which functions to adaptably mount an actuator onto the valve body.The present invention overcomes this deficiency by providing means for quickly engaging and disengaging the actuator with respect to the valve body and within the approximate total length of the actuator.

An apparatus according to the invention comprises operative means for moving a control valve and an actuator responsive to control fluid pressure for moving the operative means between open and closed positions, the actuator comprising a housing having a cylindrical bore, a shaft carried in the housing, piston means carried by one of the shaft and the housing in a slidable sealing fit with the other, fluid chamber means companionly associated with the piston means within the bore, and the actuator is such that upon increase in fluid control pressure the shaft moves longitudinally relative to the housing in a first direction and the operative means is thereby moved to one of the open and closed positions, and upon decrease in fluid control pressure the shaft moves longitudinally relative to the housing in a second direction and the operative means is thereby moved to the other of the open and closed positions, and in which apparatus one of the (1) the operative means and (2) the shaft or housing carries a slot positioned for transverse receipt of companion engagement means carried by the other, whereby the shaft or housing and the operative means may be positioned for longitudinal engagement. As a result of the invention engagement and disengagement can thus be achieved merely by small transverse motion of the operative means or of the shaft or housing.

It is generally preferred that the shaft should be engageable with the operative means and should carry the slot or the companion engagement means. Advantageously there may be means for removably securing the housing to the control valve. Thus the actuator can easily be affixed to or removed from a valve mechanism in close proximity to, for instance, a well head and the operative means of the valve and the actuator will be within the approximate total length of the actuator.

An important preferred feature of the invention is that the slot is open for receipt of the companion engagement means at one end only. Thus engagement of the actuator and the operative means is achieved merely by small transverse movement of one with the other and disengagement is achieved by the opposite transverse movement.

The engagement means preferably comprise a recessed ring head in which event the slot is preferably T-shaped in longitudinal section such that the ring head can slide transversely but not longitudinally in the slot.

The actuator should be constructed such that the fluid chamber means and the piston means yield a differential force across the piston means upon variation in fluid control pressure within the actuator.

The piston means may comprise first and second piston elements defining respectively first and second effective piston areas and the fluid chamber means may comprise first and second fluid chambers companionly associated with the first and second piston elements within the bore. The first and second fluid chambers may yield a differential force across the first and second piston elements defining the first and second effective piston areas upon increase of fluid control pressure within the actuator.

The invention is applicable to any actuator device of the type defined above and conveniently may be applied to an actuator as described and claimed in British Patent Application 9991/78 (Serial No.

1 602 644), which claims priority from US Application 777,373 of 14th March 1977.

The invention is therefore described below by reference to such apparatus. In the accompanying drawings Figure 1 to 3 illustrate in detail the construction of the actuator mechanism as in Application 9991/78 whilst Figures 4 to 6 illustrate the present invention. In particular: Figure 1 is a longitudinal schematic and sectional view of the actuator with the shaft of the actuator engaged with the operative means, or bonnet assembly, of a gate valve which, in turn, forms a part of a lubricator assembly, with a wire line being inserted through the gate valve, the gate of the valve being shown in open position.

Fig. 2 is a view similar to that shown in Fig. 1, with the gate of the valve being shown in closed position and the wire line completely sheared.

Fig. 3 is a longitudinal sectional drawing of the actuator shown in Figs. 1 and 2, the position of the respective components of the actuator being as is illustrated in Fig. 1.

Fig. 4 is a partial longitudinal sectional drawing of the actuator in position during removal from the valve body, with its bolts securing the actuator housing to the valve body being removed to permit the housing to be pumped up to permit relative transverse shifting of the shaft and the bonnet to completely disengage the actuator from the valve body.

Fig. 5 is a detailed view of the shaft and bonnet in completely disengaged position.

Fig. 6 is a view of an alternative design illustrating the slotted means on the valve bonnet and the companion engagement ring on the shaft of the actuator.

The actuator A basically is comprised of a shaft 1, an inner housing 2 longitudinally extending exteriorly of the shaft 1, and an accumulator housing 3 defined exteriorly from the inner housing 2. In Figs. 1 and 2, the actuator A is shown in engagement onto a valve body C by means of a bonnet assem blyB.

The shaft 1 is a longitudinally extending elongated member having exteriorly and circumferentially mounted thereon upper and lower piston head members 4 and 5.

The upper piston head 4 has defined thereon an elastomeric exteriorly protruding T-seal element 6 which slides longitudinally along a smooth wall 8A of the inner cylinder3 when the shaft 1 is manipulated.

The seal element 6 provides a dynamic seal between the piston head 4 and the inner cylinder 30 and defines the lower end of an upper piston chamber 8. Arl interiorly protruding beveled shoulder 10 on the inner cylinder 30 defines the down stop for downward travel of the upper piston head 4.

The lower piston head 5 carries exteriorly thereon a T-seal element 7 of substantially the same construction as T-seal 6, the T-seal 7 being permitted to travel longitudinally along the smooth wall 1IA of the inner cylinder 30 and forming a dynamic seal therebetween and thereby defining the lower end of the lower piston chamber 11.

The upper piston head 4 is the lower end of an upper piston chamber 8 interiorly defined within the inner cylinder 30 by means of the smooth wall 8A. The upper piston chamber 8 is terminated by means of dynamic T-seal 9 carried within and protruding outwardly from a shaft guide 15, the T-seal 9 preventing fluid communication between the shaft 1 and the shaft guide 15 while the shaft 1 is longitudinally stabilized as well as when the shaft 1 is shifted to open or close the gate valve described below.

The lower piston head 5 defines the lower end of a second or lower piston chamber 11 defined thereabove and extending interiorly of the inner cylinder 30 along the smooth wall 11A thereof. T-seals 6 and 7 define the upper and lowermost ends, respectively, of the lower chamber 11, while T-seals 9 and 6 define the upper and lower ends, respectively, of the upper piston chamber 8.

At the top end 13 of the shaft 1 is a plastic wiper seal 12 which wipes contaminants off the shaft 1 as the shaft 1 is longitudonally manipulated within the inner housing 2 and T-seal 9. A "T" shaped slot 14 is defined at the lowermost end of the shaft 1 for receipt of a companion bonnet stem B-l in the bonnet assembly B.

The inner housing 2 of the actuator A is comprised of the longitudinally extending shaft guide 15, the inner cylinder 30 immediately therebelow, an upper cap 20 adjacent and affixed to shaft guide 15, and a bonnet attachment 36 defined exteriorly around the lowermost portion of the inner cylinder 30. The shaft guide 15 is elongatedly defined around the exterior of the shaft 1 and has thread members 16 for affixation onto the actuator A of accessory components, such as heat-sensitive lock open elements, and the like.Additionally, the threads 16 serve to receive a protector element (not shown) which is threadedly secured thereon to position the shaft 1 within the actuator A during shipment and on-site assembly to the bonnet and valve, the protector and its companion washer being rotatably removable by hand from the threads 16 and the actuator A prior to initial operation of the actuator A. The shaft guide 15 also houses the wiper ring 12 and the T-seal 9, and is secured by threads 19 to the cap member 20 exteriorly thereof, an O-ring 17 circumferentially extending around the shaft guide 15 within its companion bore 18 preventing fluid communication between the shaft guide 15 and the cap 20.

In order to assure elimination of relative rotational movement between the members 15 and 20, a pin 29 is longitudinally extended therebetween. The cap member 20 has at its upper end a supply port 22 for receipt of a control line 23 sealingly engagable therewithin and in communication with a control panel (not shown) containing sup ply of fluid under pressure. The supply port 22 is directly communicable at all times with a longitudinally extending passageway 21A defined within the cap 20, the passageway 21A terminating at its lower end at a check valve 24, the passageway 21A being intersected at a point defined as the beginning of a latitudinal passageway 21B extending laterally of the passageway 21A within the cap 20 for fluid communication between the upper piston chamber 8 and the passageway 21A.

The check valve 24 comprises a lower plug element 24A threadedly securable within the cap 20 and having therein a longitudinally extending passageway 24B, the plug element 24A provided on its upper end a seat for the receipt of the lower end of a compressible spring element 25. The spring element 25 normally urges a companion spherical ball element 26 at the top thereof onto its seat 27 at the lower end of the passageway 21A. However, fluid under pressure within the passageway21A is permitted to travel exteriorly around the ball 26 within the check valve 24 and thence through the passageway 24B when the ball 26 is urged off its seat 27 at such time as the compressive force contained within the spring 25 is overcome by the higher control fluid pressure transmitted within the passageway 21A.

Extending below the shaft guide 15 and secured to the lower portion of the cap member 20 by means of threads 31 is the inner cylinder 30 which has a circumferentially extending elastomeric seal element 32 defined within its bore 33 for prevention of fluid communication between the cylinder 30 and the cap 20. The upper portion of the inner cylinder 30 has a smooth interior wall 8A which defines a travelway for the T-seal 6 carried on the piston head 4 upon longitudinal shifting of the shaft 1, as described below. Additionally, the in inner cylinder 30 comprises the bevelled shoulder I ed foroulderifordefin- ition of the down stop for the piston head 4 and the shaft 1.The inner cylinder 30 has, immediately below the shoulder 10, a latitudinally defined boost port 34 to permit continuous fluid transmission and communication between the lower or boost chamber 11 below the lower or piston head 4 and the accumulator chamber 48. The inner cylinder 30 also has a smooth wall IIA which is a companion wall to smooth wall 8A for travel thereon of the T-seal 7 carried on the lower boost piston head 5 when the shaft 1 is longitudinally manipulated. The inner cylinder 30 also contains at its lowermost end a longitudinally extending outwardly protruding shoulder member 30A which, when the inner cylinder 30 is affixed to the bonnet attachment 36 therebelow by means of threads 35, serves to carry load thereon and through the inner housing 2. A set screw 39 serves to further secure the bonnet attachment 36 to the inner cylinder 30 during on-site assembly of the actuator A with the bonnet and valve members.

The bonnet attachment 36 is a cylindrical member having defined therethrough a series of circular bores 36A for receipt of threaded bolt members B7 of the bonnet assembly B when the actuator A is affixed to the bonnet B.

The accumulator housing 3 is comprised of an elongated cylindrical body 3A which is affixed at its upper and lower ends by upper and lower plates 40 and 49, respectively.

The upper plate 40 is affixed to the body 3A by means of threads 43, with a circumferentially extending O-ring 41 within its bore 42 on the cap 20 preventing fluid communica tion between the cap 20 and the upper plate 40, while O-ring 44 defined within a circumferentially extending bore 45 prevents fluid communication between the upper plate 40 and the body3A . The upper plate 40 has defined there-in a port 46 at the upper end of a longitudinally extending passageway 46A . The port 46 receives a valve 47 which is in normally closed position. The valve 47 is manipulated to open position subsequent to operation of the actuator A in the event and at such time that it is desired to permanently or temporarily remove the actuator A from the bonnet B in order to relieve residual pressure within the chamber 48 and remove residual fluid therefrom.

The lower plate 49 is a companion plate to the upper plate 40 and is secured to the body 3A by means of threads 50. An O-ring element 53 circumferentially carried within a bore 54 defined on the bonnet attachment 36 prevents fluid communication between the bonnet attachment 36 and the lower plate 49, while a companion elastomeric O-ring element 51 within its bore 52 prevents fluid communication between the lower plate 49 and the body 3A.

A passageway 56A longitudinally extending through the lower plate 49 terminates within an area defining a port 56 within the lower plate 49 and receives a check valve 58 on a fluid line 57 which may be in fluid communication with a pressurized fluid source utilized as a second or back-up means for continuously or incrementally charging the accumulator housing 3, with the valve 58 in closed position assuring "fail safe" operation of the apparatus A. Additionally, the line 57 and valve 58 may be disconnected from the back-up accumulator charging means and the port sealingly plugged. A thermal relief valve 60 is sealingly engaged within a relief port 61 defined through the lower plate 49.

This valve 60 permits automatic pressure relief down to normal control level in the event that the actuator A is exposed to increased temperature environments to prevent overpressurization. Thus, as above described, the accumulator housing 3 and its associated parts define a chamber 48 within the actuator A, this chamber being referred to as the "accumulator" for the actuator A.

The actuator A is affixed to a bonnet assembly B and, in turn, to a gate or other valve mechanism C by means of the threaded bolts B7 being inserted through the bores 36A of the bonnet attachment 36 and the T-slot 14 being engagably secured to the bonnet head B2 on the upper end of a longitudoinally extending bonnet stem B1 carried within the housing base B4 of the bonnet assembly B. The threaded bolts B7 secure the bonnet attachment 36 to the outer housing B6 of the bonnet assembly B, with the housing B6 being secured by threads B5 to the housing base B4. The bonnet assembly B and, in turn, the actuator A, are secured to the uppermost end of the gate valve C by means of nut and bolt assembly B3 extending through the housing base B4 and through the uppermost end of the valve seat S of the gate valve C.A plurality of O-rings B9 in a seal assembly housing B10 are defined in grooveways Bi 1 to prevent fluid communication between the base B4 and the housing B10. Similarly designed O-ringsB12 are carried within grooveways B13 to prevent fluid communication between the housing BlO and the bonnet stem B1. The housing B6 is threadedly secured to the housing base B4.

As seen in Fig. 5, the bonnet stem B1 has provided at the uppermost end thereof a recessed ringhead B2, the outer diameter of which is somewhat less than the inner diameter of the T-slot 14 on the actuator stem 1.

The T-slot 14 is defined at one end by a U-shaped outwardly protruding shoulder B2t which is designed for slidable engagement of the end 141 of the ring B2, when the ring B2 is transversely shifted through the T-slot 14, either during engagement or disengagement of the actuator shaft 1 to the bonnet stem Bl. The usage of the T-slot permits the bonnet stem BI to be transversely inserted within, but not completely through, the actuator shaft awl such that disengagement and engagement thereof may be conducted transversely without requirement of longitudinal movement of the bonnet stem B1 and/or the actuator shaft 1.Fig. 6 is an alternative embodiment depicting the ring B21 on the actuator shaft 1 and the T-slot 141 defined on the bonnet stem B1.

The gate valve C basically is comprised of a valve seat S which has defined longitudinally therethrough the gate G carried by the bonnet stem B1. As shown in Fig. 1, the gate G is in its upper and opened position with wire line W extending therethrough and through the gate valve C.

OPERATION To install the actuator A onto a valve body C, such as shown in Figs., the actuator shaft 1 should be stroked to the down position, as shown in Fig. 1, either manually or by control line pressure being applied through passageways 21A and 21B and within the chamber 8. Thereafter, the actuator A is lowered over the bonnet stem B1. When the ring B2 is in substantial alignment with the T-slot 14 and the shoulder B21 the actuator shaft 1 and the bonnet stem B1 are transversely moved such that the ring B2 slides through the T-slot 14 with the end 14t of the ring B2 sliding along the shoulder B21 of the T-slot 14 until further transverse movement is prevented and the bonnet stem B1 and the actuator shaft 1 are in substantial longitudinal alignment, as shown in Fig. 4.Thereafter, pressure acting within chamber 8 and on pis ton 4 is bled off to permit the housing 3 to move longitudinally downwardly with respect to the bonnet assembly B. Thereafter, the bolts B7 may be affixed through the bores 36A to secure the actuator A to the bonnet assembly B. Thereafter, the bonnet assembly may be affixed to the gate valve C by means of bolt B3. Alternatively, the bonnet assembly B may first be affixed to the valve C, and, thereafter, the bonnet stem B1 and actuator shaft I affixed as above described.

To remove the actuator A from the gate valve C and the bonnet assembly B, pressure within the control line 23 is permitted to be bled off to permit closure of the gate with respect to the valve seat S. The uppermost end of the actuator shaft I will rise to the position as shown in Fig. 2. Thereafter, the bolts B7 within their respective bores 36A may be easily removed. Thereafter, pressure is applied through the control line 23 and passageways 21A and 21B to exert pressure within chamber 8 on piston 4.Because the actuator A has been disengaged from the bonnet assembly B at the bonnet attachment 36 which, in turn, is secured to the housing 3 of the actuator A, the housing 3 will be caused to shift longitudinall upwardly with respect to the actuator shaft I which still is affixed to the bonnet stem Bl of the bonnet assembly B. Thereafter, the bonnet stem BI may be disengaged from the actuator shaft I by moving one of the shaft I and the stem Bl transversely to permit the stem Bl to become disengaged from the shaft I and out of the T-slot 14. The actuator A then is completely free of the bonnet assembly B and the valve C and can be removed for repair of the actuator A or the valve C.

When the actuator is affixed to the bonnet assembly B, in order to place the gate in the down or open position, the control line 23 is affixed within the supply port 22 of the cap 20 on the actuatorA and is, in turn, placed in fluid communication with the control panel for transmission of hydraulic or other pressurized fluid therethrough to the actuator A.

The fluid passes within control line 23 through the cap 20 by way of the passageway 21A and concurrently is transmitted through passageway 21B into the upper piston chamber 8 and, when pressure is increased with the line 23, resistance afforded by the compression in spring 25 is overcome by a slight but negligible pressure increase such that the ball 26 will be removed and sealingly disengaged from its seat 27, thus permitting fluid transmission through the check valve 24, and the passage 24B to the accumulator chamber 48.Concurrently with the filling of the accumulator chamber 48, the pressure within the chamber 8 defined by dynamic T-seals 6 and 9 exerts a force upon the piston head 4 greater than the opposing force contained within the chamber 11 between the seals 6 and 7 such that the shaft 1 is urged downwardly because of chamber area differential until the gate G of the gate valve is completely opened.

As fluid is permitted to build up within the upper piston chamber 8, fluid also is transmitted through the check valve 24 and is contained within the accumulator chamber 48. Additionally, since the accumulator chamber 48 always is in fluid communication with the lower chamber 11 by means of the boost port 34, pressure and fluid are always permitted to enter the lower chamber 11.

Since the check valve 24 is one-way acting, that is, it permits fluid within passageway 21A to travel therethrough and into the accumulator chamber 48, but prevents fluid within the chamber 48 from passing out of the chamber 48 and into the passageway 21A, the accumulator chamber 48 is fluid tight, and lower longitudinal travel of the piston head 4 will permit contraction of the lower chamber 11 area, with fluid being transmitted out of the lower chamber 11 through the boost port 34 and within the accumulator chamber 48 whereby the fluid is compressed.

It should be noted that the O-rings in association with the accumulator chamber 48 prevent fluid leakage. Additionally, it also should be noted that valves 58 and 47A are closed.

When it is desired to close the gate of the gate valve C, fluid within the control line 23 will be bled off. As a result, pressure within the upper piston chamber 8 and the passageway 21A will be reduced below the amount necessary to position the shaft 1 downwardly and maintain the gate G in open position.

However, it should be emphasized that pressure within the accumlator chamber 48 is not reduced, bled off or lost inasmuch as the ball 26 is sealingly engaged on its seat 27 by the compressive force afforded by the spring 25 in the check valve 24. Thus, the pressure within the accumulator chamber 48 will be at least equal to the initial high pressure carried to the actuator A within the control line 23, the passageway 21A and the upper piston chamber 8. Upon reduction of pressure within the upper piston chamber 8, the pressure within the chambers 11 and 48 acting on the piston head 4 will permit the shaft 1 to be urged longitudinally upwardly with a force determined by accumulator pressure and the area defined within chamber 11. Thus, pres sure is permitted to be built up within the accumulator chamber 48 such that the vent ing of control pressure within the control line 23 will enable the compressive fluid force contained within the accumulator chamber 48 to act as a compressed "spring", thus urg ing the shaft 1 longitudinally upwardly with sufficient force that the wire line W carried through and within the valve seat S within a lubricator assembly (not shown) will be completely sheared.

In order to reactivate the actuator A after shearing of the wire line W, pressure within the control line 23 is increased and the procedure as above described is repeated.

The desired compressive force to be charged within the accumlator chamber 48 is preselectable, with parameters being dependent upon the volume of the accumulator, the area of the upper and lower piston chambers 8 and 11, the pressure within the control line 23, the compressive force exerted by the spring 25, and the compressibility of the selected hydraulic or pneumatic control fluid.

Even though the accumulator chamber 48 and the lower chamber 11 are initially filled, the can be continuously and incrementally recharged in the event that O-rings and/or valves leak. Thus, it can be clearly seen that the accumulator chamber 48 is a continuously charged one, assuring a fixed pressurized force for selectively acting upon the lower end of the piston head 4 and, in turn, urging the shaft 1 to an upward position to shear the wire W and close the gate.

As an alternative source of shifting the shaft 1 longitudinally upwardly, a nitrogen or other fluid source may be affixed to the line 57, with the valve 58 being manipulated to "open" position. Thus, the nitrogen may be charged into the chamber 48 and the lower chamber 11 for activation upon the lower end of the piston head 4 to urge the shaft I in an upward direction to shift the gate to completely closed position while still assuring fail safe operation of the valve C.

WHAT WE CLAIM IS: 1. An apparatus comprising operative means for moving a control valve and an actuator responsive to control fluid pressure for moving the operative means between open and closed positions, the actuator comprising a housing having a cylindrical bore, a shaft carried in the housing, piston means carried by one of the shaft and the housing and in a slidable sealing fit with the other, fluid chamber means companionly associated with the piston means within the bore and the actuator being such that upon increase in fluid control pressure the shaft moves longitudinally relative to the housing in a first direction and the operative means is thereby moved to one of the open and closed positions and upon decrease in fluid control pressure the shaft moves longitudinally relative to the housing in a second direction and the operative means is thereby moved to the other of the open and closed positions, and in which apparatus one of (1) the operative means and (2) the shaft or housing carries a slot positioned for transverse receipt of companion engagement means carried by the other, whereby the shaft or housing and the operative means may be positioned for longitudinal engagement.

2. Apparatus according to claim 1 in which the shaft may be positioned for longitudinal engagement with the operative means and carries the slot or the companion engagement means.

3. Apparatus according to claim 1 or claim 2 in which the fluid chamber means and the piston means yield differential force across the piston means upon variation of fluid control pressure within the actuator.

4. Apparatus according to any preceding claim including the control valve and means for removably securing the housing to the control valve.

5. Apparatus according to any preceding claim in which the engagement means comprise a recessed ring head and the slot is T-shaped in longitudinal section such that the ring head can slide transversely but not longitudinally.

6. Apparatus according to any preceding claim in which the slot is open for transverse receipt of the companion engagement means at one end only of the slot.

7. Apparatus according to any preceding claim in which the piston means comprise first and second piston elements defining respectively first and second respective piston areas and the fluid chamber means comprise first and second fluid chambers companionly associated with the first and second piston elements within the bore.

8. Apparatus according to claim 7 in which the first and second fluid chambers yield a differential force across the first and second piston elements defining the first and second effective piston areas upon increase of fluid control pressure within the actuator.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. through and within the valve seat S within a lubricator assembly (not shown) will be completely sheared. In order to reactivate the actuator A after shearing of the wire line W, pressure within the control line 23 is increased and the procedure as above described is repeated. The desired compressive force to be charged within the accumlator chamber 48 is preselectable, with parameters being dependent upon the volume of the accumulator, the area of the upper and lower piston chambers 8 and 11, the pressure within the control line 23, the compressive force exerted by the spring 25, and the compressibility of the selected hydraulic or pneumatic control fluid. Even though the accumulator chamber 48 and the lower chamber 11 are initially filled, the can be continuously and incrementally recharged in the event that O-rings and/or valves leak. Thus, it can be clearly seen that the accumulator chamber 48 is a continuously charged one, assuring a fixed pressurized force for selectively acting upon the lower end of the piston head 4 and, in turn, urging the shaft 1 to an upward position to shear the wire W and close the gate. As an alternative source of shifting the shaft 1 longitudinally upwardly, a nitrogen or other fluid source may be affixed to the line 57, with the valve 58 being manipulated to "open" position. Thus, the nitrogen may be charged into the chamber 48 and the lower chamber 11 for activation upon the lower end of the piston head 4 to urge the shaft I in an upward direction to shift the gate to completely closed position while still assuring fail safe operation of the valve C. WHAT WE CLAIM IS:

1. An apparatus comprising operative means for moving a control valve and an actuator responsive to control fluid pressure for moving the operative means between open and closed positions, the actuator comprising a housing having a cylindrical bore, a shaft carried in the housing, piston means carried by one of the shaft and the housing and in a slidable sealing fit with the other, fluid chamber means companionly associated with the piston means within the bore and the actuator being such that upon increase in fluid control pressure the shaft moves longitudinally relative to the housing in a first direction and the operative means is thereby moved to one of the open and closed positions and upon decrease in fluid control pressure the shaft moves longitudinally relative to the housing in a second direction and the operative means is thereby moved to the other of the open and closed positions, and in which apparatus one of (1) the operative means and (2) the shaft or housing carries a slot positioned for transverse receipt of companion engagement means carried by the other, whereby the shaft or housing and the operative means may be positioned for longitudinal engagement.

2. Apparatus according to claim 1 in which the shaft may be positioned for longitudinal engagement with the operative means and carries the slot or the companion engagement means.

3. Apparatus according to claim 1 or claim 2 in which the fluid chamber means and the piston means yield differential force across the piston means upon variation of fluid control pressure within the actuator.

4. Apparatus according to any preceding claim including the control valve and means for removably securing the housing to the control valve.

5. Apparatus according to any preceding claim in which the engagement means comprise a recessed ring head and the slot is T-shaped in longitudinal section such that the ring head can slide transversely but not longitudinally.

6. Apparatus according to any preceding claim in which the slot is open for transverse receipt of the companion engagement means at one end only of the slot.

7. Apparatus according to any preceding claim in which the piston means comprise first and second piston elements defining respectively first and second respective piston areas and the fluid chamber means comprise first and second fluid chambers companionly associated with the first and second piston elements within the bore.

8. Apparatus according to claim 7 in which the first and second fluid chambers yield a differential force across the first and second piston elements defining the first and second effective piston areas upon increase of fluid control pressure within the actuator.