Note: Descriptions are shown in the official language in which they were submitted.
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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,
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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
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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
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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
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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;
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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
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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).
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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
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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.
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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
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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
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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
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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
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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.
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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.
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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
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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.
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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.
