CA1284288C - Safety valve actuator - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An emergency shut-down system to close a gate valve in a pipeline and therefore terminate flow. The closing action is initiated when a pilot valve senses pressure in the pipeline outside predetermined limits.
This reduces the signal pressure in the system which, in turn, causes a fluid dump from the gate valve actuator which closes the gate valve and terminates fluid flow in the pipeline. The system is reactivated by manually pumping the system which re-opens the gate valve and allows fluid flow in the pipeline to again continue.

Description

~Z842~38 INTRODUCTION
This application relates to an emergency shut-down system and, more particularly, to an emergency shut-down system for a gate valve through which oil and gas can pass as in a pipeline.

BACKGROUND OF THE INVENTION

Gate valves are located intermittently along the length of gas and oil pipelines. Such valves are adapted to generally remain open but under dislocations in the fluid flow within the pipeline caused by, for example, a leak in the pipeline, the valves are each adapted to close thus shutting off the flow of oil or gas until the dislocation is located and repaired.

Gate valves and associated actuakor systems to perform such functions are known. Such an actuator system and gate valve is disclosed in our U.S. Patent 4,423,758 to Ellett entitled EMERGENCY SHUT DOWN DEVICE. Certain new and inventive improvements have been made, however, in the gate valve actuator system there disclosed.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is disclosed a pressure monitoring system for a pipeline, iZ8~Z~8 said system comprising a signal circuit having hydraulic fluid at a first pressure, an actuator circuit having hydraulic fluid at a second pressure and an accumulator, said hydraulic fluid flowing between said signal and actuator circuits, said accumulator being operable to receive fluid from and discharge fluid to said signal circuit, said first pressure being lower than said second pressure.

According to a further aspect of the invention, there is disclosed a shut down system for a pipeline comprising valve means in said pipeline, hydraulic fluid to actuate said valve means, circuit means to monitor the pres~ure in said pipeline, said circuit means including a signal circuit having hydraulic fluid at a first pressure and a high pressure circuit having hydraulic fluid at a second pre~sure, said second pressure being higher than said first pressure, said hydraulic fluid being circulated between both said signal and high pressure circuits, actuator means including reservoir means, said reservoir means being operable to hold said hydraulic fluid and spring means in said reservoir means to actuate said valve means.

According to a further aspect of the invention, there is disclosed an actuator for a valve means, said actuator comprising pumping means operable to pump hydraulic fluid from a reservoir to actuate said valve means in a first p~ ~'i"

.

~28~8 direction and spring means to actuate said valve means in a second direction, said spring means being contained in said reservoir.

According to yet a further aspect of the invention, there is disclosed a trip valve for a hydraulic ~iA`~

` ~28~38 circuit monitoring a pressure source, said valve comprising a rotatable con~rol knob having a first, second and third operating position, said first position being an ARMED position indicating said source is operating within predetermined limits, said second position being a TRIPPED
position indicating said source is operating outside said predetermined limits and said third position being a LATCHED position indicating said hydraulic circuit is ready to be returned to said ARMED position.

According ~o yet a further aspect of ~he invention, there is disclosed a pressure reducing valve for a hydraulic circuit comprising a nozzle, a seat operable to contact said nozzle and a poppet reciprocal on said nozzle and operable to hold said seat.

According to yet a further aspect of the invention, there is disclosed a reservoir for hydraulic fluid comprising a cylinder, a first closure member at one end of said cylinder operably connected thereto, a removable second closure member at the opposite end of said cylinder, a rod extending from said cylinder and a retaining ring to retain said second closure rnember within said cylinder, said cylinder further including a compression spring acting between said one and opposite ` ~2~42~8 end members and said retaining ring being unremovable unless said compression ring is compressed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE_DRAWINGS

Specific embodiments of the invention will now be described, by way of example only, with the use of drawings in which:

Figure 1 is a view of the shut-down system, shown partially in section, with the attached pump, pre~sure reduciny valve and latching trip valve~

Figure 2a is a sectional view of the pump, pressure reducing valve and latching trip mechanisms illustrated in the LATCHED and ARMED position;

Figure 2b is a sectional view of the pump, pressure reducing valve and latching trip mechanism illustrated in the TRIPPED position;

Figure 2c is an enlarged sectional view of the area shown as IIc in Figure 2b;

Figure 3 is a schematic diagram of the hydraulic circuit of the shut-down system;

--- 128'~88 Figure 4a is an enlarged sectional view of the latching mechanism used in the embodiment illustrated in Figures 2a and 2b;

Figure 4b is an enlarged sectional view of a latching mechanism according to a second embodiment of the invention; and Figure 4c is a partial view illustrating khe cam pin of the latching trip valve in its three positions on the cam.

DESCRIPTION OF SPECIFIC EMBODIMENT

Referring now to the drawings, an emergency shut down or gate valve actuator system is generally illustrated at 100 in Figure 1. It comprises a gate valve generally shown at 101 used to open and close a pipeline 271, a pump assembly generally shown at 102 and a valve sub-assembly generally shown at 103 connected to the pump assembly 102.

The gate valve actuator system 100 includes a housing 104, a compression spring 110 within the housing 104, a piston 111, an attached valve stem 112, and an -- ~284;2~38 indicator rod 113 connected to piston 111, the indicator rod 113 only being par~ially illustrated in Figure 1. A
cylinder 114 surrounds piston 111 and a seal 120 and a backup ring 121 act between the piston 111 and cylinder 114 to define a chamber 134 in communication with fluid passage 131.

An end plate 115 retains spring 110 in the housing 104 and a seal 116 seals the end plate 115. A
retaining ring 117 retains the end plate 115 and cannot be removed unless spring 110 is appropriately compressed.

A load plate 122 is connected to a pull tube 123 which, in turn, is connected to a spring plate 124. Load plate 122 is retained on piston 111 by a shoulder 130.
Compression spring 110 acts between the end plate 115 and spring plate 124.

Hydraulic fluid passage 131 is provided in head plate 132. Head plate 132 is connected to the housing 104 by cap screws 133 and fluid passage 131 communicates between chamber 134 defined by piston 111, cylinder 114 and seal 120 and port 164 of the pressure reducing valve assembly 153 (Figure 2a).

~Z8~38 -The housing 104 (Figure 1) also acts as the hydraulic fluid reservoir. An outlet (not shown) is provided in the housing 104 and the fluid passage from the outlet extends to the pump assembly 102 (Figure 2b) where it communicates with suction port 140 (Figure 2b).

Referring to Figure 2b, the pump assembly 102 has a suction port 521 which communicates with port 252 of the pump assembly 102 (Figure 1). It further includes a suction filter 142 (Figure 2b), a removable pump handle 143, a plunger 144 movable within a cylinder 150, and a discharge valve 151 (Figure 2a). A fluid passage 152 extends from the discharge valve 151 to the pressure reducing valve assembly generally shown at 153.

The pressure reducing valve assembly 153 comprises a nozzle 154, a seat 160 within a poppet 161 which is mounted within the valve body 162. A seal 163 acts between the valve body 162 and the poppet 161. A
discharge port 164 is positioned in the valve body 162.

A compression spring 170 (Figure 2a) acts between the valve body 162 and the poppet 161 which may reciprocate within valve body 162. A fluid passage 171 in poppet 161 extends from the downstream side of nozzle 154 to cavi~y 172 between the poppet 161 and khe valve body 162. A discharge port 173 extends from the cavity 172 to the signal port 202 of the latching trip valve generally shown at 174 in Figure 4a. A discharge port 18U (Figure 2b) from the cavity 172 is provided in pressure reducing valve assembly 153 which is connected to the accumula~or 181 (Figure 3).

Referring to Figure 4a, the latching trip valve used in the embodiments illustrated in Figures 2a and 2b is shown in more detail and is generally illustrated at 174. A spool 501 is mounted for longitudinal movement within the body 505 of the latching trip valve 174. Signal port 504 communicates with the discharge port 173 (Figure 2a) o the pressure reducing valve assembly 153 and the chamber 521 (Figure 4a) between the body 505 and, spool 501. A reservoir or tank passage 510 extends from a second chamber 506 defined by the body 505 and the sleeve 502 and this tank passage 510 communicates with passage 195 (Figure 2b) in pressure reducing valve assembly 153 which communicates with a second chamber 194 defined between poppet 161 and valve body 162. Chamber 194 communicates with passage 200 and suction port 140 in pump assembly 102.

~8~
g Sleeve 502 (Figure 4a) is connected to spool 501 in the latching trip valve 174 and a removable pin 512 is inserted in the spool 501. A compression spring 507 is positioned within sleeve 502 and a keeper ring 508 and flat washer 509 together with bolt 515 retain the sleeve 50~ on the spool 501. A second compression spring 513 is mounted between a retaining ring 514 mounted on sleeve 502 and a second retaining ring 516 mounted in body 505 An operating knob 503 iS connected to spool 501 by set screw 517. Pin 512 is adapted to bear against an internal cam surface 518 on cam 500. A torsion spring 530 is mounted between the operating knob 503 and cam 500 which is mounted within body 505 and retained by set screw 519. The spring 530 acts to induce torsional force on the operating knob 503 and, therefore, pin 240 in order to retain contact with cam surface 518. Three positions are defined by the cam surface 518, namely the LATCHED, TRIPPED and ARMED positions, respectively, as illustrated diagrammatically in Figure 4c.

A schematic diagram of the hydraulic circuit and, particularly, the pilot system is illustrated in Figure 3~ It comprises a pilot or three way solenoid valve 201 connected to the pipeline 271 using a pressure sensing lZ84~8 diaphragm (not shown), the latching krip valve 174, the pressure reducing valve assembly 153, the pump 102 and the valve actuator 311. The pilot valve 201 has two operating positions. In the first operating position, as illustrated, the high pressure fluid will pass through the pilot valve 201 and, enter the latching trip valve 174. In a second position, fluid may flow outwardly from the pilot valve 201 to tank as will be described hereafter.

OPERATION

In operation, it will initially be assumed that the gate valve 101 (Figure 1) is in its closed position as illustrated: that is, the gate valve 101 has previously been closed because of some dislocation in the fluid flow through the pipeline 271 and it is now desired to open the gate valve 101 so that normal flow can resume through the pipeline 271. In such a condition, the cam pin 512 (Figure 4c) will be in the TRIPPED position 301 on cam 500 illustrated and the spool 501, sleeve 502 and operating knob 503 will be fully to the right as illustrated in Figure 2b such that fluid may Ereely flow between ports 504 and 510 because of the access between the ports created by displacement of sleeve 502 and spool 501 such that the groove 519 allows access between cavities 521 and --ll--506 in the absence of signal fluid pressure as will be fully explained hereafter.

To open the gate valve 101, the operating knob 503 will be manually rotated such that pin 512 falls in the LATCHED position 511 (Figure 4c). Pin 512 will be rotated by knob 503 and is moved leftwardly by cam 500 as viewed in Figure 4a together with sleeve 502. As it moves leEtwardly, compression spring 513 exerts an increasing rightwardly directed force on the retaining ring 514 and, therefore, sleeve 502. Further, the spool 501 moves leftwardly, the passage between the inlet and reservior ports 504, 510, respectively, which were in communication by recess 519 when the trip valve 174 was in the TRIPPED
position, is now closed. The operating knob 503 of the trip valve 174 will now be in the LATCHED position Sll with reference to Figure 4c.

The pump handle 143 (Figure l)is then activated.
A suction is created in the reservior port 521 IFigure 2b) and fluid enters chamber 140 from the reservoir within the housing 104 (Figure 1) through the filter 142 and suction check valve 520. When pump handle 143 is pulled downwardly/ plunger 144 pushes the fluid out of chamber 140 through discharge check valve 151 IFigure 2a) and into B~

the pressure reducing valve 153 where it is discharged to chamber 134 (Figure 1) of the actuator 100 from port 164 in the pressure reducing valve 153. This fluid forces piston 111 downwa~dly thereby opening the gate valve 101.
Simultaneous with the opening of the gate valve 101, the high pressure fluid from the pump assembly 102 is passing through the nozzle 154 of the pressure reducing valve 153 and entering cavity 172 because poppet 161 will be in a leftwardly located position by the influence of compression spring 170 and absent fluid pressure in cavity 172. Poppet 161 remains in its leftwardly located position until pressure begins to build in the pilot circuit. The fluid in chamber 172 cannot travel through latching trip valve 174 because communication betweerl the inlet and reservoir ports 504, 510, respectively, is blocked by spool 501. The fluid will therefore exit from pressure reducing valve assembly 153 through por~ 180 (Figure 2b) which communicates with the pilot valve 201 (Figure 3). The pilot valve 201 is in its tripped position which blocks the flow of fluid to the latching trip valve 174. When the gate valve 101 is fully open (i.e., the poppet is again in a flowing configuration) and the proper pressure values are obtained in the pipeline 271, the pilot valve 201 will move from its tripped position into its normal operating position as illustrated -~ ~z~

in ~igure 3 whereby it communicates with signal port 522 of laching trip valve 174. Pressure, therefore, will commence to increase in cavity 523.

As the pressure increases in cavity 523, the sleeve 502 and spool 501 (Figure 4a) are moved leftwardly such that the pin 512 will move out of its LATCHED
position (Figure 2c) and into its ARMED position 523 as illustrated in Figure 2c under the influence of torsion spring 530. Thus, an equilibrium position has been reached throughout the circuit with the pipeline 271 open and flowing.

Assuming that the pipeline pressure returns to a value within the predetermined limits set on the pilot valve 201 (Figure 3) when the gate valve 101 has been opened, signal pressure of about 100 p.s.i. is provided to the signal port 522 (Figure 4a) by the operation of the pressure reducing valve 153. As the pressure increases in cavity 523, the sleeve 502 and spool 501 ~Figure 4a) are moved leftwardly such that pin 512 will move out of its LATCHED position (Figure 4c) and into its ARMED position 523 under the influence of torsion spring 530. Thus, an equilibrium position has been reached throughout the circuit with the pipeline 271 open and flowing. This is the normal operating condition.

~-z~

Referring now to Figure 3, the pilot valve 201 will be in the position illustrated under normal operating conditions; that is, when the pressure in pipeline 271 is within operating tolerances as sensed by the pilot valve 201. In the event the pipeline pressure rises or falls to pressures outside those limits, the pilot valve 201 is tripped, the signal fluid will exhaust to reservior 531 through port 252 and the signal pressure at port 522 (Bigure 3 and 4a) will fall to zero. The latching trip valve 174 (Figure 4a) will thereupon be affected by the sleeve 502 and spool 501 immediately moving rightwardly under absence of signal pressure by compression spring 513, Pin 512 moves on cam 500 as it rotates to the TRIPPBD position 301 (Figure 4c). The recess 532 in spool 501 will allow communication between inlet port 504 and reservior port 510 and the fluid will flow freely through the latching trip valve 174.

Referring to Figure 2b, the poppet 161 will move leftwardly under the influence of compression spring 533 with the result that fluid will flow freely between port 272 and port 173 which allows the fluid in cavity 134 to flow outwardly thus closing valve 101 and terminating fluid to the pipeline.

An accumulator 181 (Figure 3) is provided in the hydraulic circuit and cooperates with the operation of the pressure reducing valve 153 which acts as a pressure relief valve. The ratio between the area of the left end of the poppet 161 exposed to the low pressure of the circuit in cavity 172 and the area of the hole in seat 160 exposed to the high pressure fluid in nozzle 154 is of a value such that when the pressure of the fluid in the actuator cylinder cavity 134 increases due to thermal expansion, the force on the seat 160 of the poppet 161 exceeds the force on the left hand end of the poppet 161.
The poppet 161 is thus moved leftwardly allowing a small amount of fluid to flow into the accumulator 181 to relieve the excess pressure in the actuator cylinder cavity 134.

In the event it is desired to manually dump the fluid circuit and thereby to close the gate valve 101, the operating knob 503 is merely pushed inwardly. This has the effect of allowing communication between the inlet and reservoir ports 504, 510, respectively.

A further embodiment of a latching trip valve 174 is illustrated in Figure 4b. In this embodiment, the spool 501 in the latching trip valve 174 illustrated in Figure , . 1~

4a is replaced in favour of a spool 182 which is connected to operating knob 233 by set screw 234 and has a cam 241 bearing against a pin 240. The pin 240 is connected to the sleeve 204 which is movable relative to the body 183.
A compression spring 210 is mounted in the cavity 534 of the sleeve 204 and acts against a seat 301 which contains a hole 540 against which nozzle 303 acts~ Nozzle 303 is threadedly adjustable within body 183 and a keeper ring 302 in sleeve 204 prevents seat 301 from exiting sleeve 204. A torsion spring 243 acting between a sleeve 310 and the operating knob 233 acts to move the knob to the ARMED
position as illustrated. Before the ARMED position is reached, the LATCHED position has the spool 204 slightly leftwardly from the position shown. Inceeasing the signal pressure moves the sleeve 204 rightwardly into the ARMED
position shown. In this embodiment, the circuit can be manually dumped very quickly by rotating the knob and thereby moving the pin 240 and cam 241 towards the TRIPPBD
position as seen in Figure 4c and then pulling the knob 233 and pin 240 leftwardly whereas the seat 301 will be removed from nozzle 540 which creates direct communication between the inlet and reservoir ports 184, 192 respectively. This embodiment of the latching trip valve 174 also acts as a pressure relief valve through the effect of the actions of nozzle 303, seat 301 and the hole in seat 301.

:~2~

Specific embodiments of the invention have been described which should be construed as illustrative only and not as limiting the scope of the invention. Other embodiments may be clearly envisioned by those skilled in the art, which embodiments will fall within the spirit and scope of the invention as defined in accordance with the accompanying claims.

Claims (4)

1. A pressure monitoring system for a pipeline, said system comprising a signal circuit having hydraulic fluid at a first pressure, an actuator circuit having hydraulic fluid at a second pressure and an accumulator, said hydraulic fluid flowing between said signal and actuator circuits, said accumulator being operable to receive fluid from and discharge fluid to said signal circuit, said first pressure being lower than said second pressure.

2. A monitoring system as in claim 1 wherein said accumulator is connected directly to said signal circuit.

3. A monitoring system as in claim 2 and further comprising a pressure reducing valve, said fluid moving between said signal and actuator circuits through said pressure reducing valve.

4. A shut down system for a pipeline comprising valve means in said pipeline, hydraulic fluid to actuate said valve means, circuit means to monitor the pressure in said pipeline, said circuit means including a signal circuit having hydraulic fluid at a first pressure and a high pressure circuit having hydraulic fluid at a second pressure, said second pressure being higher than said first pressure, said hydraulic fluid being circulated between both said signal and high pressure circuits, actuator means including reservoir means, said reservoir means being operable to hold said hydraulic fluid and spring means in said reservoir means to actuate said valve means.