Note: Descriptions are shown in the official language in which they were submitted.
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-1-
DUAL PII.OT MANIFOLD ASSEMBLY FOR
A SAFETY RELIEF VALVE
Field of the Invention
The present invention relates to a manifold assembly for actuating a safety
relief valve. More particularly, a non-flowing dual pilot manifold assembly is
provided for activating a safety relief valve in fluid communication with a
pressure
vessel.
Background of the Invention
Safety relief valves are commonly used to regulate the pressure in vessels.
In a typical installation, a main safety relief valve is mounted on a tank or
other
pressure vessel for relieving fluid from the vessel if fluid pressure rises
above a
predetermined maximum safe value. A suitable safety relief valve includes a
valve
member reciprocal within a valve body. The valve member is normally in a
closed
position, and moves to an open position to relieve pressure in the vessel. A
dome
chamber provided in the relief valve is normally at the same pressure as the
inlet
pressure to the relief valve, and pressure in the dome chamber acts on the
valve
member to maintain the relief valve closed. A decrease in dome pressure causes
the
inlet pressure to open the relief valve and relieve pressure from the vessel.
U.S.
Patent No. 4,870,989 discloses a safety relief valve, and an improved seal for
safety
relief valve is disclosed in U.S. Patent No. 5,011,116. A suitable safety
relief valve
according to this invention is manufactured by Anderson Greenwood & Co. as a
Type
727.
Pilot valves have been used to control the operation of the main safety relief
valve, and are preferred over conventional spring valves for many
applications. Early
versions of pilot valves for controlling a main pressure relief valve are
disclosed in
U.S. Patent Nos. 3,512,560 and 3,864,362. U.S. Patent No. 4,172,466 discloses
a
pressure responsive valve with a tandem pilot and stabilizing valve assembly
mounted
on a safety relief valve. U.S. Patent No. 4,672,995 discloses redundant pilot
valves
and a control system which allows each pilot valve to be independently
actuated for
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-2-
triggering the safety relief valve to open and release excess pressure. The
redundant
pilot valves are mounted on a manifold body which in turn is supported on the
housing of the main relief valve.
In many operations, a block valve cannot be used between the pressurized
vessel and either the safety relief valve or the pilot valve, since the
inadvertent
closure of the block valve would obviate the entire safety control system. A
valve
selector manifold which allows one safety relief valve and its associated
pilot valve
to remain in service while a second relief valve and its associated pilot are
removed
from service is disclosed in U.S. Patent No. 4,821,772. The solution proposed
by
the '772 patent allows for service while desirably reducing the number of
openings
to the pressure vessel, although this solution is relatively expensive since
two separate
relief valves are utilized.
One of the problems which has long plagued the use of pilot valves to control
a main safety relief valve involves the pilot valve maintenance. The pressure
in the
vessel is frequently maintained near its maximum allowable value, so that
pressure
to the pilot valve is only slightly less than that required to trigger
operation of the
main relief valve. Accordingly, the valve element in the pilot valve is not
held tightly
into engagement with the seat, and instead may "flutter" against the seat
without
opening sufficiently to activate the relief valve. This causes high wear on
the pilot
valve, and also allows debris in the flow line to the pilot valve to prevent
reliable
seating between the pilot valve element and the seat. Accordingly, two pilot
valves
and a three-way control valve have been hydraulically interconnected by
suitable flow
lines, so that one pilot valve may be taken out of service during a
maintenance
operation while the other pilot valve reliably controls the operation of the
relief valve.
This technique allows for servicing of each pilot valve without shutting down
the
system protected by the main relief valve.
A prior art safety relief system employed by Anderson Greenwood comprises
a pair of pilot valves connected hydraulically in parallel. Pairs of hand
valves are ~
connected to a manifold block, and each of the inlet control valves is spaced
upstream
from the respective pilot valve. A slidable link is movable with respect to
the manifold block, and may be positioned so that one pair of hand valves
remain open
(and are prevented from closing by a mechanical stop) in order to supply
vessel
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-3-
pressure to one of the pilot valves and then to the dome chamber of the relief
valve.
When the link is positioned so that the stop is removed to allow one pair of
hand
valves to close, the other pair of hand valves was inherently prevented from
closing.
This feature thus ensured that the vessel pressure would always be supplied to
one of
the pilot valves while the other pilot valve could be isolated from the system
and
removed during a pilot valve service operation. A test valve separate from the
pair
of hand valves allowed for testing of each pilot valve.
While the above solution is considerably less expensive than that provided by
the '772 patent, the cost of the hand valves and the separate pilot valves,
the
mechanism for mounting the pilot valves, the separate test valves, the
fittings required
to fluidly connect these valves, and the time and expertise required to
properly install
the tubing which interconnects these valves are a considerable expense to the
overall
safety relief system. While these costs are justified for many applications in
order
to obtain the benefits of a pilot operated safety relief system, a standard
spring biased
relief valve system is used in many applications to reduce costs. Also, many
of the
flow lines which interconnect the various valves in the pilot operated safety
relief
system are continually supplied with high vessel pressure. Numerous threaded
connections between these flow lines and the valves increase the likelihood of
leakage
and the resultant release of fluid to be protected by the safety relief
system. If a leak
developed in a flow line upstream from the shutoff valve to the pilot valve,
it may be
impossible to maintain the vessel pressure while repairing the leak. In some
cases,
a flow line leak may result in the premature or faulty operation of the relief
valve.
Also, the flow lines and the various valves in the pilot operated safety
relief system
are exposed and thus could be inadvertently ruptured, thereby again requiring
a
shutdown of the system which pressurized the vessel.
A related problem concerns the time and expense required to replace or repair
a pilot valve in a safety system as described above. While one of the pilot
valves
remained in service and pressure was cutoff to the other pilot valve, the
other pilot
valve member could be removed from the system, but the pilot valve body itself
typically had to be removed from both the upstream and downstream flow lines
in
order to properly readjust the blowdown pressure and replace the valve seat.
The
numerous components of the pilot valve complicate the pilot valve maintenance
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-4-
operation, and extends the off-line pilot valve replacement time. The longer
operator
time required to replace safety system components, the greater the likelihood
of
inadvertently damaging or rupturing a flow line and the longer an operator may
be
exposed to a potentially hazardous environment. Accordingly, these problems
have
limited the acceptance of pilot controlled relief valves in a safety relief
system.
The disadvantages of the prior art are overcome by the present invention, and
an improved dual pilot manifold assembly for activating a safety relief valve
is
hereinafter disclosed. The dual pilot manifold assembly of the present
invention has
a relatively low manufacturing cost, may be easily installed using
preassembled
components standard to a particular type of relief valve, substantially
reduces the
likelihood of vessel pressure leaking from the safety system, and reduces the
operator
time and expertise required to replace a worn pilot valve in the safety relief
system.
Summarv of the Invention
A manifold assembly is provided for controlling the operation of a safety
relief
valve. The unitary manifold block includes a block inlet port in fluid
communication
with the pressure source controlled by the safety relief valve. More
particularly, a
fluid passageway provided in an end plate of the safety relief valve provides
communication between the relief valve inlet port and the block inlet port.
The
manifold block also includes a block dome pressure port which is in fluid
communication with a dome chamber in the safety relief valve via another
passageway
in the end plate. Actuation of the manifold assembly causes the relief valve
member
to move in response to inlet fluid pressure to open the relief valve when
pressure rises
above a set pressure value.
The manifold block includes first and second control cavities each having an
inlet port and a dome pressure port. First and second inlet passageways in the
manifold block fluidly connect the block inlet port with the first and second
control
cavity inlet ports, and first and second dome pressure passageways in the
manifold
block similarly connect the block dome pressure port with the dome pressure
port in
each control cavity. Corresponding inlet control valves mounted on the
manifold
block are provided for selectively closing the inlet passageway to each
control cavity.
Corresponding dome pressure control valves also mounted on the manifold block
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-5-
selectively close off the first dome pressure passageway and the second dome
pressure
passageway. The manifold block further includes first and second test
passageways
for fluidly connecting each control cavity with a respective test port, and
first and
second test control valves mounted on the manifold block selectively close off
each
test passageway. First and second vent passageways are provided in the
manifold
block for venting pressure from the respective first and second control
cavities. Flow
passageways in the manifold block are arranged to minimize the plugging of
ports in
the manifold block. The absence of external tubing lines substantially reduces
the
likelihood of leakage, and thus ensures reliable operation of the safety
relief system.
At least one of the control cavities is provided with a pilot valve which is
responsive to pressure in the block inlet port. The pilot valve is normally
closed for
maintaining fluid communication between the respective control cavity inlet
port and
the dome pressure port for supplying vessel pressure to the dome chamber in
the
relief valve. In a non-flashing liquid application, the pilot valve opens to
establish
fluid communication between the relief valve dome pressure chamber and the
respective vent passageway in the manifold block to relieve gas from the dome
chamber and open the safety relief valve. The second control port is provided
with
an auxiliary control member, which may be a second pilot valve, a pressure
gauge,
a fluid temperature sensing gauge, a solenoid valve, or other fluid
measurement or
control device. When the manifold assembly is regulating a flashing liquid,
such as
steam, an unloader valve may be provided within the manifold block. The
unloader
valve is normally closed for prohibiting fluid communication between a dome
chamber line extending to the relief valve outlet port and the dome chamber in
the
relief valve. The unloader valve opens when the respective pilot valve opens
and
releases pressure in an unloader valve chamber to the vent passageway of the
pilot
valve. The unloader valve releases pressure from the dome chamber to the
relief
valve outlet port.
A selector mechanism is provided positionable with respect to the manifold
block for mechanically preventing closing of one of the inlet control valves
and the
corresponding dome pressure control valve while in one position, and for
preventing
closing of the opposing valves while in a second position. The selector
mechanism
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-6-
thus mechanically prevents closure of the valves to ensure that at least one
of the pilot
valves is continually on-line for regulating the relief valve.
Each of the pilot valve assemblies is preferably a cartridge assembly, wherein
the components involved in adjusting and controlling the valve set pressure
and the
components involved in adjusting and setting the blowdown pressure are
included with the pilot valve element to form a unitary cartridge assembly.
Each cartridge valve
assembly may thus be easily removed from the manifold block and replaced with
a
new or repaired cartridge valve. A bushing engages the valve body and has
external
threads for threaded engagement with the block. The bushing allows seals
between
the valve body and the manifold block to be axially raised and lowered with
respect
to the manifold block during the removal and replacement operation without
rotating
the valve body or these seals. A metal washer may be also provided for sealing
engagement between the valve body and the block, with the metal washer having
an
upper knife edge and a lower knife edge for sealing engagement with the outer
cylindrical surface of the valve body and an inner cylindrical surface of the
block,
respectively. The metal washer seal provides reliable fluid-tight engagement
between
the valve body and the block by applying a relatively small amount of torque
to the
bushing.
It is an object of the present invention to provide an improved manifold
assembly for controlling a relief valve, wherein external tubing lines which
are
normally exposed to high pressure are substantially if not completely
eliminated. A
related object of the invention is to improve the reliability of a safety
relief system
by minimizing the likelihood of leakage between the valves of the assembly
which
control the operation of the safety relief system.
Another object of the invention is to provide an improved cartridge valve
assembly for mounting to a block cavity, wherein the cartridge valve assembly
includes both a valve set pressure mechanism and a valve blowdown pressure
mechanism. The cartridge valve assembly of the present invention substantially
reduces the time and expertise required to properly install a pilot valve in a
manifold
assembly.
It is a feature of the present invention that the manifold assembly is
constructed to provide a compact design wherein the control valves are easily
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-7-
accessible, yet relatively few drilled passageways are provided in the
manifold block.
It is a further feature of the invention that the manifold assembly may
include an
unloader for increasing the speed of operating the safety valve when used in
flashing
liquid applications. It is also a feature of the manifold assembly that the
various
passageways and ports in the manifold block are arranged to provide gravity
draining
of condensate, which also assists in removing debris from the passageways
within the
manifold block.
An advantage of this invention is that the cartridge valve assembly may be
reliably installed in a manifold block using a relatively low torque. The
manifold
assembly of the present invention may be installed on existing safety valves,
such that
rework or modification of the safety valves is not required.
These and further objects, features, and advantages of the present invention
will become apparent from the following detailed description, wherein
reference is
made to the figures in the accompanying drawings.
Brief Description of the Drawings
Figure 1 is a cross-sectional side view of a pilot-operated pressure relief
valve
according to the present invention for relieving pressure from a vessel having
a vessel
flange depicted in dashed lines. The manifold assembly of the invention for
controlling actuation of the safety relief valve is illustrated in the upper
right hand
corner of Fig. 1.
Figure 2 is a front view of the manifold assembly and a portion of the relief
valve shown in Fig. 1.
Figure 3 is a side view of the manifold assembly shown in Fig. 2, illustrating
particularly the selector mechanism for preventing closure of the control
valves.
Figure 4 illustrates a pair of pilot valve assemblies and a portion of a
manifold
block as shown in Fig. 2. A pictorial view of a cartridge valve assembly on
the left
side of Fig. 4 is depicted prior to insertion of the cartridge valve assembly
in the
manifold block, while the cartridge valve assembly illustrated in cross-
section on the
right side of Fig. 4 is shown in its installed position within the manifold
block.
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-8-
Figure 5 is a simplified schematic view of the manifold assembly according
to the present invention, illustrating particularly the positioning of the
flow lines and
the valves within the assembly.
Figures 6A, 6B, and 6C sequentially depict the positioning of a portion of the
valve body of the cartridge valve assembly within the manifold block, and
particularly
illustrate movement of the wedge ring seal for sealing engagement between the
cartridge valve body and the manifold block.
Detailed Description of Preferred Embodiments
Figure 1 illustrates a suitable manifold assembly 10 mounted on a safety
relief
valve 12. As discussed hereafter, the manifold assembly 10 controls the
operation
of the safety relief valve 12 to prevent excessive build up of fluid pressure
within a
pressurized tank, flow line, or other fluid containing vessel. Accordingly,
valve 12
is normally closed, but opens to automatically relieve excess pressure in the
fluid
system. While the valve 12 may be used for various applications, it will be
discussed
hereafter in an exemplary installation wherein the valve 12 is mounted on a
flange 14
of a vessel containing high pressure steam. A particular feature of the
present
invention is that the manifold assembly is able to withstand temperatures in
excess of
500 F, so that the manifold assembly may be reliably used to control pressures
in
fluid systems housing steam and other high temperature gasses. Port 16 in the
vessel
flange 14 is thus exposed to pressurized steam in the vessel. If the steam
pressure
rises above an acceptable predetermined level, the manifold assembly 10
automatically opens the safety relief valve 12 to release excess pressure from
the
vessel and prevent a possible catastrophic explosion.
The manifold assembly 10 may be used for controlling various types of safety
valves. An exemplary safety valve 12 depicted in Fig. 1 includes a housing 13
having a lower inlet flange 18, an outlet flange 20, and an end cap or cover
22. The
inlet port 24 is continually exposed to steam pressure in the vessel, while
the outlet
port 26 is connected to a conventional vent line or other system for venting
high
pressure gas. Suitable seals (not shown) ensure reliable sealing engagement of
the
safety valve housing 13 with the upstream vessel and the downstream vent
system.
The pressure relief system as shown in Fig. 1 is particularly well suited for
use in
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-9-
fluid systems handling high temperature fluids in excess of 350 F, and may be
utilized in systems containing steam, air, or other fluids maintained at a
temperature
of from 500 F to 1000 F.
Metal annular seat ring 28 is fixed within the housing 13, and includes a
planar seating surface 30 thereon. Piston valve member 32 is reciprocal within
the
housing 13 for engagement and disengagement with sealing surface 30. Sleeve 34
defines a bore for slidably receiving the valve member, and a split ring 38
and seal
ring 36 ensure reliable sealing engagement between the sleeve 34 and the
reciprocating valve element 32. The valve element 32 as shown in Fig. 1 is
normally
in a closed position, and may move to the right to pass steam from the inlet
24 to the
outlet 26. The left end of the valve element 32 adjacent sealing surface 42 is
solid
in cross-section, so that fluid cannot pass from the dome chamber 44 in the
housing
to the outlet port 26. The valve element 32 may be provided with a flexing
disk seat
and a cushioning sleeve 40 as discussed in U.S. Patent No. 4,865,074, which
also
discloses additional features of a suitable safety relief valve.
The end plate 22 is connected to housing 13 by threaded fasteners 46, thereby
allowing removal of the end plate 22 during periodic relief valve service
operations
to facilitate repair or replacement of the seals and other internal components
within
the relief valve. An inlet passageway 48 in the housing 13 and a mating
passageway
50 in the end plate 22 provide continual fluid communication between the inlet
port
24 and the manifold assembly 10. A conventional sealing member 52 ensures
reliable
sealing between the housing 13 and the end plate 22. Another passageway 54 in
the
end plate 22 maintains fluid communication between the dome chamber 44 in the
housing 13 and the manifold assembly 10. Lower planar face 62 of the metal
block
60 is thus mounted directly on the upper planar face 56 of the end cap 22 (see
Fig.
2). A pair of sealing members 58 and 59 may be used for reliable sealing
between
the manifold block 60 and the end plate 22.
The manifold assembly 10 as shown in Figs. 1, 2 and 3 includes first and
second pilot valves 70 and 80 each extending upward from an upper planar face
63
of the manifold block 60. A first inlet control valve 74, mounted directly to
the
manifold block and extending from a first side 64 of the block, may be
manually
operated by a handle to open and close off pressure from passageway 50 to the
first
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-10-
pilot valve 70. The first dome pressure valve 76 is similarly mounted on the
manifold block and controls pressure between the dome chamber 44 and the first
pilot
valve 70. A first test control valve 78 is mounted to the manifold block and
extends
through a planar front face 66 of block 60. Valve 78 controls fluid pressure
between
the first pilot valve and test line 79 extending from the first face 64 of the
block 60.
Manifold 10 is generally symmetrical about centerline 75 as shown in Fig. 2,
and
pressure to the second pilot valve 80 is similarly controlled by valves 84 and
86 each
mounted to the manifold block and extending from the second side 65 of the
block.
A second test control valve 88 is mounted to the block and extends from the
front
face 66 to control fluid pressure between the test line 81 and the second
pilot valve
80. Figure 3 illustrates a vent cap 72 extending from the rear face 67 of the
manifold
block 60. Vent cap 72 is provided for venting fluid from the first pilot
valve, and
a similar vent cap (not shown) is provided for venting fluid from the second
pilot
valve 80.
Figures 1, 2 and 3 also illustrate a selector mechanism 89 which is
positionable for preventing closure of the inlet control valve and the dome
pressure
control valve associated with one of the pair of pilot valves 70 and 80.
Selector
mechanism 89 includes a plate 90 slidably positioned between a pair of plates
91 and
92 (see Fig. 1) each fixed to the block 60 by bolts 94. The slidable plate 90
includes
a pair of slots 96 which allow sliding movement of plate 90 with respect to
the block
60 from a second, right side position as shown in Fig. 2 to a first, left side
position.
When in the first, left side position, end 98 of plate 90 extends past the
first face 64
of the block 60 to prevent rotation of swing plate 100. Plate 100 pivots about
bolt
101 as shown in Fig. 3 from a stop position (as shown in dashed lines) to a
release
position (as shown in solid lines). When plate 90 is in the first, left side
position,
swing plate 100 must be in the stop position, and is prevented from rotating
to the
release position by mechanical engagement with end 98. When in the stop
position,
the U-shaped cutouts 102 and 104 in the swing plate 100 are positioned between
the
block 60 and the respective caps 106 of valves 76 and 74, respectively,
thereby
mechanically preventing closure of these valves. Only when the opposing swing
plate
101 on the right side of block 60 is moved to its stop position may the plate
90 be
slid to its second, right side position, thereby ensuring that the second
swing plate
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-11-
101 prevents closure of the valves 86 and 84. Only when the plate 90 is moved
to
the second, right side position may the first swing plate 100 then be manually
moved
to its release position, as shown in solid lines in Fig. 3, thereby allowing
closure of
the valves 76 and 74. A pair of holes 108 and 109 may be provided in the plate
92
for receiving a padlock or other conventional locking member to prevent
inadvertent
movement of the plate 90 with respect to the block 60.
A preferred embodiment of the manifold assembly 10 includes an unloader
valve discussed subsequently when the pilot valve is exposed to a flashing
liquid, such
as steam, which may condense within the main valve dome chamber. The manifold
assembly need not include this unloader valve, however, when used to maintain
non-
flashing gasses at a safe pressure within the vessel. The operation of the
selector
mechanism 89 and the purpose served by the dual pilot valves may be understood
without reference to the unloader valve. With the selector mechanism 89
positioned
as shown in Fig. 2, valves 84 and 86 must be open, and pressure in the inlet
port 24
of the safety relief valve 12 is thus supplied to the pilot valve 80. The
pilot valve 80
may be set to open at, for example, 800 psi. As long as vessel pressure is
less than
800 psi, pressure in the inlet port 24 of the relief valve is passed through
the manifold
assembly 10 and then to the dome chamber 44. The substantial force of the
pressure
in the chamber 44 acting on the piston-like valve element 32 thus maintains
the safety
relief valve closed. If vessel pressure arises above 800 psi, the pilot valve
80 is
actuated to block flow from the passageway 50 to the passageway 54, and
simultaneously to release the pressure in the dome cavity 44 to the vent line
associated with pilot valve 80. Venting of the chamber 44 thus allows the
valve
element 32 to move right from the position shown in Fig. 1, thereby releasing
pressure from the vessel. If vessel pressure drops below a blowdown pressure
of, for
example, 750 psi, the pilot valve 80 will again close to block flow between
the dome
chamber 44 and the vent line, and simultaneously establish fluid communication
between the fluid lines 50 and 54 in the end cap, thereby again pressurizing
the dome
chamber 44 and returning the safety relief valve element 32 to its closed
position.
It should be understood that, while the selector mechanism 89 is in this
position and the pilot valve 80 is "on-line", the swing plate 100 will
normally be
moved to a release position, and the valves 74 and 76 will be closed.
Accordingly,
CA 02230480 1998-02-25
WO 97/09553 PCT/QJS96/13253
-12-
the first pilot valve 70 may be removed from the block 60 and serviced. Also,
a
pressure transducer or other pressure gauge, a temperature sensing transducer
or other
temperature sensing gauge, or a solenoid valve may be inserted into the
manifold
block at a position previously occupied by the first pilot valve. Any time an
auxiliary
control member other than a pilot valve is mounted on the manifold block, it
is
preferable that the selector mechanism 89 be locked out, as previously
described, to
prevent sliding movement of the selector mechanism. The manifold block of this
invention accordingly allows a pressure gauge to be substituted for the pilot
valve,
and the valves 74 and 76 thereafter reopened. The second pilot valve 80
reliably
controls operation of the safety relief valve 12, while the pressure to the
safety relief
valve may be simultaneously monitored by the pressure gauge. While the second
pilot valve 80 remains on-line, the pressure gauge may be replaced with a
temperature
sensing gauge or solenoid valve. Those skilled in the art will appreciate that
an
electric, pneumatic, or hydraulically operated solenoid valve permits the
desired
actuation of the relief valve independent of the vessel pressure. It should be
understood that with both first and second pilot valves mounted on the
manifold
assembly and the valves 74, 76, 84 and 86 open, the selector mechanism 89 may
be
moved to the first, left side position so that swing plate 100 prevents
closing of valves
74 and 76. The swing plate 101 may then be moved to the release position,
allowing
the valves 84 and 86 to be closed. The pilot valve 80 may then be serviced, or
as
explained above, or replaced with a pressure gauge, sensing gauge, or solenoid
valve.
The dual pilot design for the manifold assembly allows a spare pilot to be
available
to replace an on-line pilot without interrupting safety protection.
Accordingly, at
least one active or on-line pilot is always available to safely control system
pressure,
even during pilot switch-over operations.
Figure 1 depicts a suitable unloader valve 202 within the manifold block 60
of the manifold assembly 10. The passageway 54 in the end plate 22 is in fluid
communication with the left side of unloader piston 204, while the unloader
chamber
206 to the right of the unloader piston is normally pressurized by inlet fluid
pressure
from passageway 50 transmitted through one of the pair of pilot valves 70 and
80.
Unloader line 208 fluidly interconnects the manifold assembly 10 with the
outlet port
26 of the safety relief valve 12. During normal operations, passageway 54 is
sealed
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
- 13-
from the unloader line 208 by unloader valve element 210 in sealed engagement
with
bushing seat 212. Inlet fluid pressure in the unloader chamber 206 thus
maintains the
unloader valve closed while the respective pilot valve is closed. Inlet fluid
pressure
is also supplied to the dome chamber 44 through the fluid passageway 214 in
the
safety valve element 32. The passageway 214 in piston valve member 32 ensures
that
inlet fluid pressure will act on the left side of the unloader piston 204 and
on the pilot
valve to allow venting of chamber 44 through the manifold assembly 10 and
through
the unloader line 208 to the outlet port 26 in the event the inlet fluid
pressure in line
50 to the manifold assembly should become plugged.
Unloader 202 is thus triggered by actuation of the pilot valve 70 or 80, and
in turn causes actuation of the safety relief valve 12. During operation of
the safety
relief valve 12, the unloader allows fluid in the chamber 44 to be vented to
the
downstream port 26 of the safety valve, and only the relatively small amount
of fluid
in the unloader chamber 206 is vented through the pilot valve. Those slcilled
in the
art will appreciate that the pressure in the dome chamber 44 need only be
maintained
at approximately 40% of the inlet pressure 24 in order to maintain the safety
relief
valve closed. The use of an unloader 202 is particularly important when the
relief
valve 12 is provided in a steam system, since the speed of actuating the
safety relief
valve is substantially shortened by providing the unloader. Also, only a small
amount
of steam is vented from the chamber 206 of the unloader during opening of the
safety
relief valve, thereby desirably minimizing the venting of steam from the
manifold
assembly.
With the selector mechanism 89 positioned for supplying vessel pressure to
one of the pilot valves, the relief valve pressure setting of the other pilot
valve may
be easily tested and adjusted without removing the pilot valve from the
manifold body
60. The inlet control valve and the dome pressure control valve associated
with the
pilot valve to be pressure tested may be closed, thereby isolating that valve.
The test
control valve 78 or 88 associated with the valve to be tested may then be
opened, and
a pressurized gas source connected to the respective fitting 108. Nitrogen or
another
gas of a selected pressure may then be supplied to the pilot valve, and the
pilot valve
conventionally adjusted so that pilot valve opens so that the supplied gas is
vented to
the vent cap 72 at the desired pressure setting.
CA 02230480 1998-02-25
WO 97/09553 PCTIUS96/13253
-14-
Another purpose of the test valve 78 and 88 is to ensure that the safety
relief
valve 12 may be opened at any time, regardless of the level of pressure in the
inlet
cavity 24. An operator may wish to temporarily open the safety relief valve 12
even
though the pressure in the vessel is significantly less than the maximum
allowable
pressure. To open the relief valve 12, the respective test valve 78 or 88
associated
with the on-line pilot valve may be opened, thereby releasing pressure from
the dome
chamber 44 and opening the relief valve. Once proper operation of the relief
valve
has been assured, the respective test valve 78 or 88 may be closed, thereby
resuming
normal operations of the safety relief system.
Referring to Fig. 4 and particularly pilot valve 80, each of the pilot valves
used in the manifold assembly 10 may be cartridge valves suitable for high
temperature operation. Each pilot valve may be a "no flow" valve so that no
substantial amount of fluid flows through the valve during normal operation. A
non-
flowing pilot valve is substantially less effected by orifice sizes and is
thus more
responsive to pressure changes than a flowing pilot valve. Pilot valve 80
includes a
valve body 110 having a central bore therethrough. Passageway 50 in the end
plate
22 is in fluid communication with the lower portion of cavity 116 in the
manifold
block 60, thereby providing vessel pressure to the inlet chamber 114. A metal
0-ring
118 is carried by the valve body 110, and provides an essentially fluid-tight
seal
between the valve body and the manifold block 60. A slight leakage around seal
118
does not adversely effect the operation at the pilot valve. Annular chamber
120
between the valve body 110 and the block 60 is in fluid communication with the
passageway 54 in the end cap 22. Wedge seal ring 122 provides sealing
engagement
between valve body 110 and block 60; it is important that the seal 122 remain
fluid-
tight to prevent leakage from cavity 120. Cavity 124 between the valve body
110 and
the block 60 is provided above wedge seal ring 122, and is in fluid
communication
with the vent cap 72.
Bushing 126 is retained on the valve body 110 by snap ring 128. Bushing 126
includes a stop surface 130 for forced engagement with the body 110, and
external
threads 132 for threading engagement with mating threads on the block 60.
Bushing
126 is important to the installation and removal of the cartridge valve
assembly 80,
as described subsequently.
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-15-
Bonnet 134 is threaded to the valve body 110 at threads 136. Spring 138 is
housed within the bonnet 134 between an upper spring follower 140 and a lower
spring follower 142. An adjustment screw 144 acts on the upper spring follower
140
to adjust the compression of the spring in a manner conventional to pilot
valves. A
lock nut 146 prevents inadvertent rotation of the adjustment screw 144, and a
cap 150
acts as a cover to protect the adjustment screw 144.
Guide 152 engages nozzle 154, and both the guide and the nozzle are retained
in a fixed position by the bonnet 134 pressing downward on the guide and
forcing the
nozzle into sealing engagement with the support ledge 156 of the body 110.
Guide
152 receives a spindle 158 which moves along pilot valve axis 160 with respect
to the
guide. The spindle 158 is biased downwardly by the spring 138, thereby forcing
seal
member 159 into sealing engagement with nozzle 154. Ball member 161 serves to
maintain the seal member 159 concentric within the spindle 158 for reliable
sealing
engagement with the nozzle 154, and also ensures uniform seating of the nozzle
154
and the seal member 159. Nozzle 154 has a central port for receiving rod 162
therein
while providing fluid communication between the chamber 114 and the seal
member
159. Valve body extension 170 is threaded to sleeve 166, which guides axial
movement of piston 164. The pilot valve as shown in Fig. 4 is in its normal
closed
position, so that the chamber 114 is in fluid communication with the chamber
120.
Fluid flows around the piston 164 and between the rod 162 and blowdown seat
168
to pass inlet fluid pressure in chamber 114 through the pilot valve and to the
unloader
valve.
Upon an increase in vessel pressure above a predetermined set pressure
required to compress the spring 138, the increased fluid pressure lifts the
seal
member 159 off the nozzle 154. This increased pressure also moves piston 164
upward toward blowdown seat 168, thereby forcing the rod 162 upward as the
seal
member 159 lifts off the nozzle 154. The lifting of seal member 159
establishes fluid
communication between the chamber 120 and the chamber 124. When the piston 164
seals against the lower face of the blowdown seat 168, fluid communication
between
the chamber 114 and the chamber 120 is blocked. All the components of the
relief
valve set pressure mechanism, including adjustment screw 144 and spring 138,
and
the set pressure valve components, including spindle 150, seal member 159, and
CA 02230480 1998-02-25
WO 97/09553 PCTIUS96/13253
-16-
nozzle 154, are thus carried by the valve body 110 and are removed as a
cartridge
assembly with body 110.
The blowdown pressure for the pilot valve may be adjusted by rotating the
sleeve 166 relative to the body extension 170. This rotation selectively
raises or
lowers the axial position of blowdown seat 168, thereby controlling the amount
the
piston 164 may axially move before sealingly engaging the blowdown seat 168.
The
spacing between the upper end of the rod 162 and the seal member 159 may thus
be
varied. The increase in this spacing results in a lower blowdown pressure and
a
decrease in the spacing results in a higher blowdown pressure. All the
components
of the blowdown pressure setting mechanism and the blowdown valve components,
including sleeve 166, rod 162, blowdown seat 168, and piston 164 are also
carried
by the valve body and are removed as a cartridge assembly with the valve body.
Blowdown adjustment is conventional for pilot valves controlling a safety
relief valve,
and upon blowdown the pilot valve returns to the closed position. Normally,
the pilot
valve is set with a blowdown pressure of about 5% to 7% less than the set
pressure
which causes the valve to open and depressurize the dome chamber. When the
blowdown pressure is reached, the vessel pressure is again diverted by the
pilot valve
to the dome chamber, and the valve element in the safety relief valve housing
returns
to its closed position. The operation of the pilot valve as disclosed herein
is
functionally similar to the operation of the pilot valve disclosure in U.S.
Patent No.
4,865,074.
Figure 5 depicts schematically one embodiment of a manifold assembly 10
according to the present invention. Although shown schematically, the same
reference numerals will be used to refer to components previously discussed
and
graphically shown in Figs. 1-3. The unitary manifold block 60 has a
rectilinear
configuration, with top and bottom planar surfaces 63 and 62, side surfaces 64
and
65, and front and rear planar surfaces 66 and 67, respectively. The block 60
contains
first and second generally cylindrical control cavities 220 and 222 each
formed about
a respectively vertical control cavity axis 224 and 226, respectively. Bach
control
cavity is sized to receive the lower end of a respective pilot valve 70 and
80. In one
embodiment, manifold assembly 10 is provided with a first pilot valve 70, and
a
auxiliary control member 80 is selected from a group consisting of a second
pilot
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
- 17-
valve, a pressure transducer or other pressure gauge, a temperature transducer
or
other pressure gauge, and a solenoid valve. Each of these auxiliary control
members
80 may thus be selectively mounted within the second control cavity 222.
The manifold block 60 includes a block inlet port 230 and a block dome
pressure port 232 each within a lower planar block surface 62 for fluid
communication with passageways 50 and 54, respectively, in the end plate 22 of
the
safety control valve 12. Since flow passageways are provided in the end plate
22 and
the manifold block 60 is mounted directly on the plate 22, no tubing is
required to
connect the manifold block with either the inlet fluid port or the dome
chamber in the
safety relief valve 12. The manifold block also includes a first test port 234
in the
first side 64 and a second test port 236 in the opposing second side 65. Each
test
port is in fluid communication with a respective test line 79 and 81 as shown
in Fig.
2. The block 60 further contains vent ports 238 and 240 in the rear block
face. Each
of these vent ports is in fluid communication with a respective vent cap 72 as
shown
in Fig. 3.
Block 60 contains a common inlet passageway 242 extending from the port
230 to both first and second inlet passageways 244 and 246 each drilled from a
respective side face of the block to intersect passageway 242. Short inlet
paths 252
and 254 are each drilled downward through the lower end of the respective
control
cavity 220 and 222 for fluidly connecting the respective passageways 244 and
246
with the inlet port 248, 250 to the respective control cavity. First and
second control
valves 74 and 84 are each mounted on the manifold block for selectively
closing off
the first and second inlet passageways 244 and 246, respectively, to the first
and
second control cavities 220 and 222. No flow lines external of the block 60
and no
permanent passageway plugs for drilled flow lines in the block need thus be
provided
to connect the block inlet port 230 with the first and second inlet ports 248
and 250
to the respective first and second control cavities 220 and 222.
A common dome pressure passageway 256 drilled upward from the lower
block face 62 connects the block dome pressure port 232 with the unloader
chamber
258, which houses the unloader valve 202 as shown in Fig. 1. A common
horizontal
passageway 260 drilled from the rear planar face 67 connects the chamber 258
with
the first and second dome pressure passageways 262 and 264 each drilled from a
side
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
- 18-
face 64 and 65 to intersect passageway 260. A portion of the dome chamber
relief
line 208 as shown in Fig. 1 is schematically depicted in Fig. 5. It should be
understood that the unloader valve may be eliminated from the manifold
assembly for
applications other than flashing fluids, in which case the bushing 212 as
shown in
Fig. 1 may be replaced with a plug. Short flow lines 266 and 268 may each be
drilled from the front face 66 to fluidly connect the respective dome pressure
passageways 262 and 264 with a respective dome pressure port 270 and 272 to
the
control cavities 220 and 222. Each of the passageways 266 and 268 may be
provided
with a standard plug (not shown) in the front face 66 of the block 60. The
plugs and
the portion of each drilled passageway between the front face 66 and the
passageways
266 and 268 are not depicted in Fig. 5 for clarity of the remaining
components.
Dome pressure control valves 76 and 86 mounted on the manifold block 60 extend
through the respective block side 64 and 65 to control fluid pressure
transmitted along
the respective first and second dome pressure passageways 262 and 264. Each of
the
control valves 74 and 76 thus extend through a first side 64 of the manifold
block,
while the corresponding valves 84 and 86 similarly extend through the second
side
65 of the manifold block. Each control valve includes a standard handle for
moving
a respective valve element into sealing engagement with a seat provided within
the
manifold block.
Test ports 234 and 236 are each connected to a respective control cavity 220
and 222 by a first and second test passageways 274 and 276 each drilled from a
front
face 66 to a respective control ca.vity. Connecting passageways 278 and 280
are each
drilled through a side 64 and 65 to connect the ports 234 and 236 with the
test
passageways 274 and 276, respectively. Respective test valves 78 and 88 are
each
mounted on the manifold block and extend through the front face 66 for opening
and
closing the first and second test passageways 274 and 276, respectively. In an
alternate embodiment of the invention, flow passageways 274 and 276 do not
extend
into the control cavities, and instead intersect flow lines 266 and 268
provided =
between each control cavity and the respective valves 76 and 86. This fluid
connection requires drilling one more flow line (not shown) from the lower
block face
62 upward to connect horizontal passageways 274 and 266, and another flow line
(not
shown) through the lower block face upward to connect horizontal passageways
276
CA 02230480 1998-02-25
WO 97/09553 PCTIUS96/13253
- 19-
and 268. While this alternate embodiment requires the drilling and then the
plugging
of two more passageways, the direct fluid connection of the passageway 266
with
274, and 268 with 276, ensures the reliable manual operation of the relief
valve by
opening the respective test valve 78 or 88 to vent fluid pressure in the line
260 and
thus open the relief valve without requiring the fluid to flow through the
control
cavities, where fluid flow may be substantially restricted by the pilot
valves.
Vent passageways 282 and 284 each connect the respective control cavities 220
and 222 with the vent ports 238 and 240. Each vent passageway vents the
respective
control cavity to the atmosphere during operation of the pilot valves, as
explained
above. These passageways 282 and 284 could extend through the pilot valve
assembly 70 and 80 to vent above the upper block face 63, although preferably
the
passageways 282 and 284 are provided within the manifold block so that venting
inherently occurs through the rear block face 67 of the manifold block,
thereby
venting in a direction away from the operator.
The manifold assembly as shown in Fig. 5 provides a compact design with a
minimal number of access ports. By positioning the passageways and the control
valves as disclosed herein, a substantially compact, minimal manufacturing
cost
design is obtained without drilling an excessive number of passageways, and
without
plugging numerous passageways. The design as shown in Fig. 5 in combination
with
the flow lines 50 and 54 in the end plate of the safety valve thus
significantly reduces
the chance of leakage in the safety relief system. Each of the block inlet
port 230 and
block dome pressure port 232 are desirably provided in the lower face of the
manifold
block for mounting the block directly on the end plate 22, while each of the
first and
second control cavities 220 and 222 has a vertical axis and opens through the
upper
face of the block, thereby permitting the vertical mounting of the pilot
valves and/or
auxiliary control members. The manually operated control valves 74, 76, 78,
84, 86,
and 88 are each located for easy operator accessibility. The porting as shown
in Fig.
5 also provides a self-draining feature, so that any liquids which accumulate
within
the block 60 will be automatically drained from the block, thereby preventing
freezing
of condensate within the block when the steam system is shut down. When the
manifold assembly 10 is mounted on a safety valve as shown in Fig. 1, all flow
passageways in the manifold block are either horizontal, inclined slightly
downward
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-20-
for drainage to ports 230 or 232, or are substantially vertical for drainage
to these
ports. This self-draining feature also tends to remove solid contaminates from
the
flow passageways which otherwise might accumulate within the block.
The function of the pilot valves may be understood by reference to Fig. 5.
When the first pilot valve is closed, the pilot valve essentially maintains
open the flow
path illustrated by dashed line 290 in Fig. 5, and simultaneously closes the
flow path
illustrated by dashed line 292. Accordingly, the first pilot valve normally
operates
to provide inlet fluid pressure from passageway 244 to passageway 262, and
closes
off the flow to vent passageway 282. When the first pilot valve opens, the
flow path
290 is closed off and the flow path 292 is automatically opened, thereby
interconnecting flow paths 262 and 282, and venting fluid from the manifold.
When
the first pilot valve is open, the closing off of flow path 290 prevents inlet
fluid
pressure from passing to the unloader valve or to the dome chamber 44 in the
relief
valve. The second test pilot valve similarly operates to control flow of fluid
along
the corresponding flow paths 294 and 296 within the second control cavity 222.
The control pilot valve assemblies 70 and 80 as shown in Fig. 4 are complete
assemblies in the sense that all components of the valve set pressure
mechanism and
the valve blowdown pressure mechanism, including the pressure adjustment
members,
the valve elements, and the seats, are carried on and supported by the valve
body.
Accordingly, the complete assembly 70 may be installed within the control
cavity 116
as shown on the left side of Fig. 4 which corresponds to the control cavity
220
schematically shown in Fig. 5. For high temperature applications, the seal 118
preferably is a metal 0-ring, and may be pressed on the valve body 110. By
providing a complete cartridge assembly for the pilot valves, and the time
required
to remove a worn pilot valve and install a refurbished pilot valve is
minimized. Since
all components of the assembly with the exception of the wedge ring seal 122
are
supported on the valve body 110, the likelihood of improperly installing
components
is substantially eliminated.
To install the pilot valve assembly, only the wedge ring seal 122 need be
inserted within the cavity 116 and lowered on the shoulder 312. The bushing
126
may then be lowered until threads 132 engage corresponding threads 314 on the
manifold body 60. Further rotation of the bushing 126 will thereafter lower
the valve
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-21-
body, compressing the seal 122 as described subsequently. The metal 0-ring 118
is
lowered but does not rotate during this assembly operation, thereby preventing
galling
or other damage to the 0-ring or to the sidewalls of the cavity 116. Most
importantly, the seal 122 which is highly compressed between the valve body
and the
manifold block does not rotate during this assembly operation, thereby
minimizing
damage to the seal, the valve body and the manifold block. The use of bushing
126
rotatable with respect to the body 110 is also important for facilitating
removal and
replacement of the pilot valve assembly. In high temperature applications, the
metal
0-ring 118 may tend to seize in position between valve body 110 and the
manifold
block 60. To remove the pilot valve assembly, the bushing 126 may be
unthreaded,
thereby pressing upward on the clip 128 and exerting a substantial upward
force on
the valve body 110 to break the connection between the valve body and the
manifold
block due to 0-ring 118. During removal of the pilot valve assembly, the valve
body
110 and the 0-ring 118 are lifted vertically upward by rotation of the bushing
126,
so that again damage to the 0-ring 118 and to the interior walls of the
control cavity
116 are minimized.
As explained above, it is important that the wedge ring seal 122 provide a
reliable high temperature, high pressure seal between the chambers 120 and 124
as
shown in Fig. 4. As depicted in Fig. 6A, this wedge ring seal comprises a
metal
washer body 320 having a planar frustoconical upper surface 322 and a planar
frustoconical lower surface 324 prior to being compressed into sealing
engagement
between the valve body 110 and the block 60. Prior to compression, the metal
washer has a generally cylindrical interior surface 326 and a generally
cylindrical
exterior surface 328 each formed about at an axis coaxial with the central
axis 160
of the valve assembly. These surfaces thus form an upper knife edge 330 for
sealing
engagement with an outer cylindrical surface 332 of the valve body 110, and a
lower
knife edge 324 for sealing engagement with an inner cylindrical surface 336 of
the
block. Prior to compression, the radial spacing between cylindrical surfaces
326 and
328 is purposefully less than the radial spacing between surfaces 332 and 336,
so that
the seal 122 may be easily dropped in place on the planar support ledge 312 of
the
manifold body.
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-22-
During threaded rotation of the bushing 126 into the block 60, the planar
shoulder surface 338 of the valve body 110 engages the upper knife edge 330,
thereby
exerting a downward "tipping" force on the body 320 for causing the upper
knife
edge 330 to engage the annular corner provided by the intersection of
cylindrical
surface 332 and planar shoulder surface 338, and for causing the lower knife
edge
334 to engage the corner provided by the intersection of cylindrical surface
336 and
planar support surface 312 (see Fig. 6B). The corners formed by these
intersecting
surfaces cooperate with the knife edges to ensure reliable sealing of the
knife edge
330 with the cylindrical surface 332 adjoining the shoulder surface 338, and
at the
knife edge 334 with the cylindrical surface 336 adjoining the support surface
312, as
explained further below. This design preferably results in each of the
surfaces 326
and 328 being inclined with respect to the centerline 160 at an angle of from
about
8 to about 15 when the knife edges first engage the respective intersecting
surfaces,
as shown in Fig. 6B. In order to form a reliable seal, the dimensions of the
metal
washer 320 are controlled such that, as the bushing 126 is further rotated to
bring the
surface 324 into planar engagement with the support surface 312 and to bring
the
surface 322 into planar engagement with the surface 338, the knife edge
surfaces 330
and 334 are slightly deformed, as shown in Fig. 6C. A reliable seal is
provided due
to the concentration of a large force generated by the bushing rotation being
distributed over a relatively small area as the knife edges 330 and 334 are
forced into
sealing engagement with the valve body and the manifold block.
A significant advantage of the seal design as shown in Figs. 6A, 6B and 6C
is that a reliable high pressure seal may be formed with relatively low torque
exerted
on the bushing 126. In a typical application, the bushing 126 may be torqued
to a
level only slightly greater than that provided by hand-tightening the bushing.
This
action will compress and deform the wedge ring seal 122 so as to provide
reliable
sealed engagement between the valve body and the manifold block to withstand
gas
pressures of several thousand psi. While the bushing 126 is unthreaded from
the
block, the wedge ring seal 122 returns to a configuration substantially as
shown in
Fig. 6A, and may thus be reused with a new valve cartridge. After repeated
use, the
seal 122 may be easily removed and replaced.
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
- 23 -
The cartridge valve assembly as disclosed herein has particular utility as a
pilot valve assembly 80 suitable for controlling actuation of a pressure
relief valve.
The pilot valve assembly includes a valve element 159 and the seat 154
normally seal
between the block cavity 120 and the block cavity 124, but unseal to
established fluid
communication between the flow lines 266 and 282 (see Fig. 5) when the set
pressure
of the pilot valve is reached. The seal 122 separating cavities 120 and 124 is
forced
into reliable static sealing engagement between the cartridge valve body 110
and a
manifold 60 by axial threading of bushing 126 to the manifold block. The
cartridge
valve set pressure may be adjusted by increasing or decreasing the biasing
force of
spring 138 exerted on the valve element 159, as previously described.
The pilot valve assembly also includes a blowdown valve element 164 which
normally is unsealed with blowdown seat 168. Fluid communication between
cavities
114 and 120 normally occurs, thus providing fluid communication between the
flow
lines 252 and 266 in the manifold block (see Fig. 5). The blowdown valve
element
164 and the seat 168 fluidly isolate cavities 114 and 120 when the cavities
120 and
124 are in fluid communication. The metal sealing ring 118 substantially seals
between the cavities 114 and 120, as previously discussed.
The inlet control valves, the dome pressure control valves, and the test
valves
each include valve elements which close off respective passageways within the
manifold block. While each of these control valve elements is preferably
provided
within the manifold block, the test valve element could be provided external
of the
block. When the pilot valve or the auxiliary control member is on-line, only
one side
of the normally closed test valve associated therewith is pressurized, while
both the
inlet and dome pressure valves associated therewith each have pressurized
fluid on
both sides of their respective valve elements. If the test valve elements were
mounted
external of the manifold block, additional expense would be incurred for the
required
fluid-tight fittings, and there is an increased risk of leakage between the
valve block
and the test valves. The pilot valves each are preferably at least partially
mounted
within the respective control cavities within the manifold block, thereby
controlling
pressure entirely within the manifold block between the respective control
cavity inlet
port and the control cavity dome pressure port. This configuration desirably
reduces
the number of seals required to seal between the manifold block and the pilot
valves,
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
-24-
and also reduces the number of fasteners required to support the pilot valve
from the
manifold block.
Those skilled in the art will appreciate that representative auxiliary control
members have been disclosed herein, and that various types of auxiliary
control
members could be provided for either sensing a desired characteristic of the
fluid
within the control cavity or for controlling operation of the relief valve.
The pressure
gauges and fluid temperature sensing gauges discussed above are thus
representative
of sensors which measure a desired characteristic of the fluid within the
control
cavity. The additional pilot valve and the solenoid valve are representative
of devices
for controlling actuation of the relief valve.
While a safety relief valve according to the present invention with metallic
valve elements, seats, and seals has been particularly described herein for an
application wherein the vessel fluid is high temperature fluids, it should be
understood
that a cartridge valve assembly and a manifold assembly with the pilot valves
having
elastomeric or "soft" seats may alternatively be used in applications where
the high
temperature characteristics of metal seats and seals is not required. The
manifold
assembly may be subjected to various types of fluids, and an unloader is
preferably
included in the manifold block for flashing fluid applications.
The selector of mechanism 89 as disclosed above is suitable for mechanically
preventing the closing of one of the pair of control valves and dome pressure
control
valves. However, other types of selector mechanisms could be used for
mechanically
or hydraulically preventing closure of these valves.
A particular advantage of the present invention is that the manifold assembly
may be used in conjunction with an existing relief valve provided that the end
cap 22
is replaced to provide the desired planar mounting surface for the manifold
assembly.
Accordingly, the manifold assembly as described herein may be used to control
an
existing relief valve without replacing or modifying the relief valve
components other
than the end cap. It is a particular feature of the invention that no tubing
external of
the manifold block is provided, with the exception of the dome chamber line
208 as
shown in Fig. 1 and the test lines 79 and 81 as shown in Fig. 2. As explained
earlier, both of these lines are not normally pressurized. Normally
pressurized lines
external of the relief valve body and the manifold block are thus avoided.
CA 02230480 1998-02-25
WO 97/09553 PCT/US96/13253
- 25 -
Those skilled in the art will appreciate that various modifications and
adaptations to the preferred embodiments of the invention as discussed above
may be
made utilizing the novel concepts of this invention. Various changes in the
manifold
assembly and in the pilot valve assemblies may be made without departing from
the
scope of the invention as set forth in the following claims.
