WO 2007/032919 PCT/US2006/034006
PRESSURE RELIEF DEVICE
DESCRIPTION OF THE INVENTION
[001] This international application claims the priority of earlier filed United
States Patent Application No. 11/221,856, filed September 9, 2005.
Field of the Invention
[002] This invention generally relates to systems for relieving pressure from
a pressurized system. More particularly, the present invention relates to a pressure
relief apparatus for a system containing a pressurized fluid.
Background of the Invention
[003] There are many types of systems that process, transport, or use a
pressurized fluid. To ensure the safety of these types of systems, each such
system typically includes a safety device designed to prevent the over-
pressurization of the system. In an emergency situation, where the fluid in the
system reaches an unsafe level, the pressure of the fluid acts on the safety device
to create an opening to release fluid from the system. Venting fluid to the
environment or a safety reservoir through the opening reduces the pressure in the
system and prevents another portion of the system from failing due to the high
pressure of the fluid.
[004] Examples of commonly used safety devices include rupture disks and
explosion panels. These safety devices can be attached to a pressurized system to
expose a certain portion of the device to the pressurized fluid in the system. The
portion of the device exposed to the fluid is configured to rupture or tear when the
fluid reaches a predetermined pressure. The tearing or rupture of the disk or panel
creates an opening through which the pressurized fluid flows to reduce the
pressure in the system. This type of safety device is, therefore, self-destructing and
must be replaced after each use. Typically, to replace one of these safety devices,
some disassembly of the system is needed so that the disk or panel can be
properly engaged with the system.
-1-

WO 2007/032919 PCT/US2006/034006
[005] Another type of safety device for a pressurized system is a pressure
relief valve, which may be a reclosing valve or a non-reclosing valve. Typically, a
spring, a pin, or a combination of a spring and pin, is used to hold a moving plug in
sealing engagement with the housing of the device while connected to the
pressurized system. When the pressure of the fluid reaches the predetermined
safety level in such systems, the force exerted on the plug by the pressurized fluid
overcomes the bias of the spring or exceeds the resistance of the pin that holds the
plug in place. When either of these events occurs, the pressurized fluid moves the
plug to expose an opening through which fluid may escape to relieve the pressure
in the system. Reclosing valves wiii automatically reset once the pressurized fluid
at the inlet of the device has reduced sufficiently for the spring or other mechanism
to reseat the plug. Non-reclosing valves require that the device be manually reset
so that the valve plug is re-engaged with the seal and, if necessary, the pin or other
expendable component replaced.
[006] As noted above, relief valves are known that use buckling pins, or
breaking pins, to hold a sealing plug in sealing engagement to block the flow of a
pressurized fluid. The pin release device prevents the plug from venting
pressurized fluid until the output force exceeds a predetermined limit. Prior release
devices have included a pin that is subject to a compressive force and that buckles
according to Euler's Law when the output force reaches the predetermined limit or
a shearing or tensile force that causes the breaking of the pin when the output force
reaches the predetermined limit. Such a device is typically termed a "Buckling Pin
Non Reclosing Pressure Relief Device."
[007] Buckling pins are carefully manufactured components configured to
buckle at a particular predetermined compressive force. Breaking pins are carefully
manufactured components configured to fail at a particular predetermined tensile or
shear force. Such pins used for a pressure relief valve require considerable care
and control during installation. Maintenance personnel must ensure that the pin is
properly secured and tightened to properly bear the pressure exerted on the
pressure relief valve. Failure to do so may result in untimely opening of the valve.
A premature opening below the predetermined safety level leads to an unwanted
downtime for the system, while a delayed opening above the predetermined safety
-2-

WO 2007/032919 PCT/US2006/034006
level jeopardizes the physical integrity of the system. Another problem with a bare
pin is that there is a risk of pin damage stemming from maintenance personnel
having to contact the bare pin during installation or maintenance. This risk of pin
damage is especially high for a fragile, low pressure bare pin.
[008] As noted above, it order to properly function as a safety pressure
relief device, it is important that the relief device vents at, or close to, the set
pressure. Since buckling pins are designed to buckle at a predetermined
compressive force, a pressure relief system must assure that force from the
pressurized system is efficiently transferred to the buckling pin. In prior devices,
forces from the pressurized system are often improperly transferred through the
pressure relief device's structural system such that the compressive force
experienced by the buckling pin is not an accurate representation of the actual
force transmitted by the pressurized system. For example, forces transferred to the
buckling pin from the pressurized system are often lost due to bending, friction
between moving parts, and moments generated along the path of transmitted force.
[009] In some pressure relief devices, and particularly those having a low
set pressure, mishandling and improper installation of the underlying buckling pin
can interfere with the accuracy of the set pressure of the device. For example,
buckling pins can be dangerously overloaded during the pre-assembly and
installation process such that the pin activates at a much lower pressure than
desired during use.
[010] In light of the foregoing, there is a need for a pressure relief apparatus
that (1) efficiently and accurately transfers force between the pressurized fluid and
the buckling pin, (2) assures that pins are not overloaded during the pre-assembly
and installation process, and (3) can provide for resistance to back pressure while
maintaining proper positive pressure venting as a pressure relief device.
SUMMARY OF THE INVENTION
[011] Embodiments of the present invention are directed to an improved
pressure relief device fora system containing a pressurized fluid that obviates one
or more of the limitations and disadvantages of prior pressure relief devices.
-3-

WO 2007/032919 PCT/US2006/034006
[012] In one embodiment, a pressure relief device comprises a main valve
body including an axial passageway defining an inlet port, an outlet port, and a fluid
flowpath between the inlet and outlet ports. A valve plug is positioned to seal the
flowpath of the pressurized fluid between the inlet port and the outlet port of main
valve body and a force transmission component is connected to the valve plug. An
activation component is installed between the force transmission component and a
mounting surface and wherein the activation component is configured to prevent
axial movement of the valve until a predetermined pressure is exerted on the valve.
The force transmission component only transfers an axial force acting on the valve
piug to the activation component.
[013] In another embodiment, a pressure relief device comprises a main
valve body including an axial passageway defining an inlet port, an outlet port, and
a fluid flowpath between the inlet and outlet ports. A valve plug is positioned to
seal the flowpath of the pressurized fluid between the inlet port and the outlet port
of main valve body. A force transmission component is connected to the valve plug
and an activation component is installed between the force transmission
component and a mounting surface such that the activation component is
configured to prevent axial movement of the valve seal until a predetermined
pressure is exerted on the valve plug. The force transmission component is
incapable of transferring any moment resulting from the output force acting on the
valve plug to the activation component.
[014] Another embodiment is directed to a method of installing a pressure
relief device. The method comprises providing a main valve body including an axial
passageway defining an inlet port, an outlet port, and a fluid flowpath between the
inlet and outlet ports. The method further comprises providing a valve plug, a force
transmission component connected to the valve seal, a mounting surface, and an
activation component. The valve plug is positioned to seal the flowpath of the
pressurized fluid between the inlet port and the outlet port of main valve body. The
method further comprises installing the force transmission component such that
only an axial component of output force acting on the valve plug can be transferred
therealong and installing an activation component between the force transmission
component and the mounting surface such that the activation component is
-4-

WO 2007/032919 PCT/US2006/034006
configured to prevent axial movement of the valve plug until a predetermined
pressure is exerted on the valve plug.
[015] Additional objects and advantages of the invention will be set forth in
part in the description which follows, and in part will be obvious from the
description, or may be learned by practice of the invention. The objects and
advantages of the invention will be realized and attained by means of the elements
and combinations particularly pointed out in the appended claims.
[016] It is to be understood that both the foregoing general description and
the following detailed description are exemplary and explanatory only and are not
restrictive of the invention, as claimed.
[017] The accompanying drawings, which are incorporated in and constitute
a part of this specification, illustrate several embodiments of the invention and
together with the description, serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[018] Figure 1 is a side view of a pressure relief device for a pressurized
system according to an exemplary embodiment.
[019] Figure 2A is a general cross-sectional view of a pressure relief device
for a pressurized system according to an exemplary embodiment.
[020] Figure 2B is a general cross-sectional view of a pressure relief device
for a pressurized system according to an exemplary embodiment illustrating a
relieving of pressure from the system.
[021] Figure 2C illustrates an alternative arrangement for a component of
the pressure relief device.
[022] Figure 3A illustrates a perspective view of an activation component
installation location in a pressure relief device according to an exemplary
embodiment.
[023] Figure 3B illustrates another perspective view of an activation
component installation location in a pressure relief device according to an
exemplary embodiment.
-5-

WO 2007/032919 PCT/US2006/034006
[024] Figure 4 is a cross-sectional view of a pressure relief device for a
pressurized system according to an exemplary embodiment illustrating a device for
preventing interference from backpressure.
DESCRIPTION OF THE EMBODIMENTS
[025] Reference will now be made in detail to exemplary embodiments
illustrated in the accompanying drawings. Wherever possible, the same reference
numbers will be used throughout the drawings to refer to the same or like parts.
[026] In accordance with the present invention, there is provided a pressure
relief apparatus for a system containing a pressurized fluid. The pressure relief
apparatus includes a valve having a body that defines a fluid flow path. The body
is engageable with the pressurized system to direct pressurized fluid through the
flow path. Preferably, the body includes a flange that has a series of bolt holes
corresponding to the standard bolt pattern on a pipe flange to allow the body to be
easily engaged with the pressurized system. However, it is contemplated that the
pressure relief apparatus may be engaged with the pressurized system in any other
manner readily apparent to one skilled in the art.
[027] FIG. 1 illustrates a side view of a pressure relief device for a
pressurized system according to an exemplary embodiment. FIG. 1 illustrates a
pressure relief apparatus 10 including a main valve body 12, a bonnet assembly
enclosure 14, and a cap weldment 16. Main valve body 12 includes an axial bore
18 forming an inlet port 20 configured for engagement with a corresponding pipe
flange that is connected to a pressurized system (not shown). For example, main
valve body 12 can include an inlet flange 22 that contains a series of bolt holes (not
shown) positioned in flange 22 to conform to the standard ANSI bolt pattern (or
other standardized bolt pattern) for a pipe flange with a similar nominal size. Bolts,
or other connecting devices, may be used to engage inlet flange 22 with a
corresponding pipe flange that is connected to a pressurized system (not shown).
This structure allows for utilization of the entire ANSI standard bolt pattern when
installing the valve and is, therefore, preferable over prior art designs wherein this
was not practical.
-6-

WO 2007/032919 PCT/US2006/034006
[028] Main valve body 12 further includes a lateral bore 24 intersecting the
axial bore 18 and forming an outlet port 26, configured for connection to the
environment or a safety reservoir for venting a pressurized fluid. The lateral bore
24 may be formed at a 90 degree angle with regard to the flow path of the inlet
bore. For example, main valve body 12 can include an outlet flange 28 configured
for connecting the flow path to a safety reservoir, a discharge path, or the
environment. Upstream along the flow path that begins at inlet port 20, main valve
body 12 includes a downstream port interface 30.
[029] The downstream port interface 30 comprises an opening 32 (see FIG.
2A) that allows for connection to the bonnet assembly 14, which is configured to
house and seat a valve sealing interface. As will be described more fully herein
below, a valve plug is positioned to close the flow path of the pressurized system
between the inlet port 20 and the outlet port 26 of main valve body 12. As noted
above, when the pressure of the fluid reaches a predetermined safety level, the
force exerted on the valve plug, or plug, by the pressurized fluid overcomes the
bias of a spring or exceeds the resistance of a pin that holds the plug in place.
When either of these events occurs, the pressurized fluid moves the valve seal, or
plug, to expose an opening through which fluid may escape to relieve the pressure
in the system.
[030] The bonnet assembly 14 encloses moveable components of the
pressure relief apparatus 10 that provide for a valve sealing interface. In addition,
the bonnet assembly 14 includes an axial sensor mount 34 for adjustably mounting
a position sensor 36 at a location along the exterior surface of the bonnet
assembly. The bonnet assembly 14 connects to the main valve body 12 over the
downstream port interface 30, for example, through a bonnet assembly flange 38.
The bonnet assembly flange 38 can connect to the main valve body 12 through a
series of bolts 40 and nuts 42 received in bolt holes formed in the flange 38. The
use of a flange connection is considered to be a non-limiting example, and other
appropriate connections could be used. Atop portion of the bonnet assembly 14 is
further enclosed by a removable cap weldment 16. As will be described more fully
herein below, cap weldment 16 encloses the portion of the pressure relief device 10
housing an activation component. As an alternative to welding, cap 16 could be a
-7-

WO 2007/032919 PCT/US2006/034006
cylinder with an end plate threaded in place. The engagement of cap 16 to the
remainder of the system can be accomplished with or without an additional element
providing a soft seal, such as a rubber or graphite gasket, to optimize leak
tightness.
[031] Referring to FIG. 2A, a general cross-sectional view of a pressure
relief device is illustrated. As will be apparent, the pressure relief device 10, of FIG.
1 has been rotated 90 degrees such that the outlet port 26 and the outlet flange 28
are directed into the page. As seen in FIG. 2A, a flow path 44 beginning at the inlet
port 20 is constituted by a nozzle 48 surrounded by the inlet flange 22 of main valve
body 12. The bonnet assembly 14 is mounted such that it encloses moveable
components of the pressure relief apparatus 10 that provide for a valve sealing
interface.
[032] The valve sealing interface includes a stem assembly 50. Stem
assembly 50 comprises a moving valve seat or plug 52, a gimballing joint 54, and a
force transmission shaft 56 extending to a protrusion member 58. Protrusion
member 58 is a spherical or other curved surface that allows a point contact with an
adjacent flat surface, thereby delivering an axial force to an opposing surface (such
as, for example, an opposing base surface 78 of a piston 72 as will be described in
more detail below). Protrusion member 58 could, for example, be a ball bearing
inserted into the end of stem assembly 50 or a surface machined directly to the end
of the stem assembly. In addition, the stem assembly 50 may further include a
sensor device 60 housed along shaft 56. The gimballing joint 54 rotatably connects
the valve plug 52, which closes the flow path 44 upon a sealing connection at a
mouth 62 of nozzle 48 to the remainder of the stem assembly 50. The stem
assembly 50, in turn, is freely, slidably housed within a central through bore/shaft
bushing 64 of a plate member 66. Plate member 66 is formed to exhibit an annular
shoulder 68 that cooperates with a reduced step portion 70 along the opening 32 of
downstream port interface 30. Accordingly, plate member 66 is dimensioned in
order for the annular shoulder 68 to cooperate with the reduced step portion 70
such that plate member 66 concentrically houses the stem assembly 50 therein. In
addition, the plate member 66 is also dimensioned to be sealingly engaged
-8-

WO 2007/032919 PCT/US2006/034006
between the main valve body 12 and the bonnet assembly enclosure 14 upon the
application of nuts 42 and bolts 40 through the bonnet assembly flange 38.
[033] As seen in FIG. 2A, the plate member 66 houses the stem assembly
50 such that the valve plug 52 is aligned to close the flow path 44 by sealingly
engaging mouth 62 of nozzle 48. Valve plug 52, as illustrated in FIG. 2A,
comprises a moving valve seat disk providing a face seal at the mouth 62 of nozzle
48. It is to be understood that the illustrated face seal between the valve plug 52
and the valve mouth 62 of the flow path 44 is merely exemplary, and the sealed
closure of flow path 44 can be achieved through alternative seals or plug
configurations as would be apparent to one having ordinary skiii in the art. For
example, valve plug 52 could comprise a plug structure sealingly engaged within
the nozzle 48 using a perimeter "O" ring seal. In addition, the valve plug 52 may
have alternative configurations, including a single plate design or a multiple plate
design. Alternatively the nozzle 48 could be omitted and the valve plug 52
designed to seat directly into a mating surface prepared in the internal body 12 of
the valve.
[034] In some situations the plug 52 can experience a back pressure from
the direction of outlet port 26 and acting in a direction opposite the flow path 44. In
order to avoid any unwanted influence of a back pressure on the valve plug 52,
both the plate member 66 and the bonnet assembly 14 may include one or more
apertures 71 therein forming a vent path to the outside environment.
[035] With continued reference to FIG. 2A, the movable components
comprising a valve sealing interface further include a piston pin 72 slidably housed
within a throughbore 74 along a top surface of the bonnet assembly enclosure 14.
The piston pin 72 includes a platform 76 at one end and a base surface 78 along
the opposite end. The top surface of the bonnet assembly enclosure 14 includes a
mounting block 80, which houses a mounting surface, such as adjuster screw 82, in
opposed relation to the piston pin 72, and a pre-loading mechanism 84, to be
described more fully in detail below. An activation component, such as, for
example, a buckling pin 86, is configured for placement between adjuster screw 82
and the piston pin platform 76. It may be desirable for the buckling pin 86 to insert
-9-

WO 2007/032919 PCT/US2006/034006
into an appropriately dimensioned recess in both the adjuster screw 82 and the
piston platform 76 in order to achieve proper alignment.
[036] For purposes of following description, the term "activation component"
refers to any device configured to maintain a valve in a first configuration until a
predetermined pressure is exerted on the valve or until a predetermined
temperature is experienced whereupon the particular device will allow the valve to
move to a second configuration. By way of non-limiting examples, activation
components include pressure sensitive elements such as buckling pins, shear pins,
tensile pins, springs and other equivalent structures. It is also contemplated that
the activation component may include a temperature sensitive element such as
fusible alloys and other equivalent structures. It is further contemplated that the
activation component may reset automatically to allow the valve to return to the first
configuration once the pressure exerted on the valve has been decreased below
the predetermined pressure. Such an activation component may include a spring.
[037] Because activation components are designed to actuate at a pre-
determined parameter threshold, proper performance for a pressure relief device
requires that the relief device vents at, or close to, the set pressure (or other
desired parameter, such as for example, temperature). Therefore, it is important for
the pressure relief system to assure/facilitate an efficient transfer of force from the
pressurized system to the activation component.
[038] During assembly and field installation of the pressure relief device 10,
fluid flow path 44 is closed upon a sealing connection at mouth 62 of nozzle 48
through the following arrangement. Plate member 66 is positioned to seat within
the opening 32 of downstream port interface 30, as described above. Valve plug
52 is positioned to close the flow path 44 through a sealing connection (such as, for
example, the use of a rubber gasket at the outer perimeter at mouth 62) or through
metal to metal connection between small polished flat surfaces on the valve plug 52
and the mouth 62. The remainder of the stem assembly 50 is positioned such that
the protrusion member 58 at the opposite end of shaft 56 contacts the base surface
78 of piston pin 72. The components of pressure relief device 10 are dimensioned
such that upon installation of stem assembly 50 and bonnet assembly 14, piston
pin platform 76 is raised to extend above the top surface of the bonnet assembly
-10-

WO 2007/032919 PCT/US2006/034006
enclosure 14. This arrangement provides a manufacturing benefit. Since the
distance between adjuster screw 82 and the piston pin platform 76 is adjustable,
the stem assembly 50 can be manufactured to fit a range of distances so long as
upon proper installation of stem assembly 50, the piston pin platform 76 extends
above the top surface of the bonnet assembly enclosure 14. Therefore the stem
assembly 50 does not need to be manufactured according to particular unique
dimensions and instead can be manufactured to fit a range of distances for an
underlying pressure relief device.
[039] Accordingly, upon (1) sealing engagement of the plate member 66
between main valve body 12 and bonnet assembly 14 and (2) when sealing valve
plug 52 is positioned to close the flow path 44 (as seen in FIG. 2A), an activation
component can then be installed as a load bearing member included in the
transmission path of the output force generated by the pressurized system at valve
plug 52.
[040] As seen in FIG. 2A, an activation component, such as buckling pin 86,
is installed between adjuster screw 82 and piston pin platform 76, thereby
experiencing an output force transmitted by the pressurized fluid system. Referring
to FIG. 2B, when the output force exceeds the predetermined force of the buckling
pin 86, the material of the buckling pin 86 will deform, or buckle. Upon the
activation of buckling pin 86, the pressurized fluid of the underlying system can
then vent (by unseating valve plug 52) through outlet port 26 to a safety reservoir,
for example.
[041] With reference to FIGS. 2A and 2B, pressure relief device 10 may
include a sensor or sensor activating device 60 housed along shaft 56 of stem
assembly 50. The sensor device 60 can be positioned to rest, upon proper
installation, a predetermined axial distance relative to a corresponding position
sensor 36 mounted along the axial sensor mount 34 at the exterior surface of the
bonnet assembly 14. For example, the sensor 36 may comprise a magnetically
activated proximity switch 88 and the sensor activating device 60 may include a
permanent magnet 90. Upon the activation of buckling pin 86 due to an
overpressure situation, the unseating of sealing valve plug 52 will result in axial
displacement of the stem assembly 50, which in this case includes permanent
-11-

WO 2007/032919 PCT/US2006/034006
magnet 90. In FIGS 2A-2B, the axial movement of two magnets 90 will result in the
activation of two proximity switches 88, thereby providing dual electronically
signaling of the actuation of the underlying pressure relief device 10. The two
sensors 88 and sensor activating devices 60 could be placed in different positions
on shaft 56 to provide electronic signaling of different valve positions.
[042] The use of a non-contact sensor, such as the above-mentioned
magnets 90 and proximity switch 88 arrangement, is advantageous in that the
sensor configuration does not contribute to any corruption of valve activation at a
predetermined set pressure. For example, in low pressure situations (i.e. in a
system where an "over-pressure" situation occurs at a relatively low pressure
condition) corruption may result where sensor actuation requires that a force be
overcome, such as in a dry contact switch or burst sensor arrangement. The use of
a non-contact sensor therefore removes any potential for the actuation condition of
the sensor to interfere with the predetermined activation condition of the pressure
relief device. Accordingly, sensing of valve activation is more accurate. Alternative
non-limiting examples of suitable non-contact sensors include hall-effect
transducers and photo-detector/photo-emitter sensor arrangements.
[043] The arrangement of the valve sealing interface of pressure relief
device 10 provides an efficient transfer of output force between the valve plug 52
and buckling pin 86. Upon proper installation, the output force of the pressurized
system directly acts upon the valve seal 52. From valve plug 52, force is
transferred through gimballing joint 54, along force transmission shaft 56, and
extends to protrusion member 58. Protrusion member 58 may be provided in the
form of protruding ball bearing 92. Output force is then transferred to the buckling
pin 86 through the point of contact between ball bearing 92 and base surface 78 of
piston pin 72.
[044] As noted above, in past valve systems, forces transferred to the
buckling pin from the pressurized system are often poorly transmitted due to,
bending, poor alignment of component parts, friction between moving parts, and
moments generated along the path of transmitted force. For example, in a valve
where output force is transferred to a buckling pin along a single, unitary shaft
member extending through a bushing enclosure, output forces may be lost due to
-12-

WO 2007/032919 PCT/US2006/034006
bending moments stored in the shaft, as well friction between the bushing and the
shaft member during pin failure. This problem of improper force transfer is often
exacerbated when the single shaft member and bushing enclosure are misaligned
due to either differences in manufacturing tolerances and bending of the shaft
member over time.
[045] The inclusion of gimballing joint 54, which acts a universal ball joint
connector, allows the force transmission shaft 56 to rotate a certain amount relative
to the sealing plug 52. At the other end of stem assembly 50, ball bearing 92
provides a point contact for transferring force to the piston pin 72. The
arrangement of gimballing joint 54, force transmission shaft 56, and ball bearing 92,
provides the structural equivalent of a pin ended link, where no moment can be
transferred along the connection. Since force transmission shaft 56 is free (within
limits) to rotate relative the valve seal 52, no moment can be transferred therealong
and therefore, only force coincident with the direction of the shaft 56 will be
transmitted. In addition, since there is no direct connection (i.e., no positive
engagement) between ball bearing 92 and the base surface 78 of piston pin 72,
only the axial component (and, therefore, no lateral component) of force along shaft
56 can be transferred. Accordingly, in this arrangement there is no mechanical
connection other than contact. This arrangement also allows easy removal of the
stem assembly for resetting an activation component and maintenance.
[046] Accordingly, the stem assembly 50 efficiently transfers the output
force to the activation component, thereby assuring that pressure relief device more
accurately opens at the predetermined pressure. While FIGS. 2A and 2B illustrate
stem assembly 50 including a gimballing joint 54 and a ball bearing 92, the present
invention should not be limited to this structure. Alternative arrangements include,
but are not limited to, any transmission structure that prevents, or reduces the
transfer of moments therealong.
[047] FIG. 2C, for example, illustrates an alternative arrangement for a joint
54'. Joint 54' includes a connection between valve plug 52' and the end of
transmission shaft 56'. The end of shaft 56' can be rounded to a point or protrusion
55, which correspondingly engages and is seated within a recessed divet 59
formed in the upper surface of the valve plug 52'. A recess 61a can be formed at a
-13-

WO 2007/032919 PCT/US2006/034006
position along the outside of the shaft 56". A snap ring 61 b fits within the recess
61a and provides a maximum distance "D" for movement between shaft 56' and the
remainder of valve plug 52'. Just as in the embodiment described above,
transmission shaft 56' is free (within limits) to rotate relative the valve plug 52'.
Again, no moment can be transferred therealong and therefore, only force
coincident with the direction of the shaft 56' will be transmitted. There is no
mechanical connection (i.e., no positive engagement) between shaft 56' and valve
plug 52'. Engagement is maintained solely due to the transmission of force from
the pressurized system to the valve plug 52' and then through the shaft 56', which
is free (within limits) to move within the recessed divet 59.
[048] The capability of sealing plug 52 to rotate relative to the transmission
shaft 56 also provides the additional benefit of allowing the valve plug 52 to
sealingly close the flow path 44 at mouth 62 of nozzle 48 when the center of flow
path 44 and shaft 56 are not perfectly aligned. As a result of these arrangements,
the stem assembly 50 does not need to be manufactured according to particular
unique dimensions. Instead, stem assembly 50 can be manufactured to fit a range
of distances other than one where the valve plug 52 is perfectly aligned with the
mouth 62 or the stem assembly 50 perfectly aligned with the mouth 62.
[049] As noted above, the top surface of the bonnet assembly enclosure 14
includes a mounting block 80, which houses an adjuster screw 82 in opposed
relation to the piston pin 72, and a pre-loading mechanism 84. In one embodiment,
the preloading mechanism 84 comprises rotatable arm assembly 94. The use of a
pre-loading feature for the buckling pin 84 is advantageous in that buckling pin 86
will not be subject to corrupting compression forces imparted from over-tightening
of the adjuster screw 82 (or other corrupting handling forces). For example, in low
pressure situations, corruption may result where a buckling pin 86 is overloaded
during the initial installation process. The use of a pre-loading feature therefore
removes any potential for improperly loading the pin 86 prior to the actual loading of
the system by the pressurized fluid generated output force (as is intended).
[050] FIG. 3A illustrates a perspective view of an activation component
installation location in a pressure relief device 10 according to one exemplary
embodiment. FIG. 3A illustrates a mounting block 80, which houses an adjuster
-14-

WO 2007/032919 PCT/US2006/034006
screw 82 in opposed relation to the piston pin platform 76, and a pre-loading
rotatable arm assembly 94. The upper face of piston pin platform 76 is configured
to receive an activation component, such as, for example, a buckling pin 86.
Preferably, adjuster screw 82 has a threaded shank portion and a pin seat hole.
The pin seat hole receives and secures a buckling pin to adjuster screw 82. In
addition, piston pin platform 76 also has a pin seat hole similar to the pin seat hole
in adjuster screw for receiving the buckling pin 86. Alternatively, the activation
component can be installed through the use of a cartridge assembly, or through
any of the methods and arrangements described in U.S. Patent No. 6,484,742,
which is hereby incorporated by reference in its entirety.
[051] As noted above, the components of pressure relief device 10 are
dimensioned such that upon proper initial installation of stem assembly 50 and
bonnet assembly 14, piston pin platform 76 is raised to extend above the top
surface of the bonnet assembly enclosure 14. With reference to FIG. 3B, pre-
loading of the piston pin 72 can thereby be achieved through the application of a
pre-loading force through rotatable arm 94. Accordingly, the rotatable arm 94
prevents corruption and overloading of the activation component during installation.
The description of rotatable arm 94 is intended to be a non-limiting example of a
preloading feature. Alternative configurations include any structural mechanism
configured to removably provide a sufficient load to piston pin platform 76 such that
piston pin platform 76 maintains contact with protrusion member 58 prior to the
installation of an activation component. Particularly where a soft valve seat is
employed at the valve plug 52 or mouth 62, preloading ensures that the sealing
arrangement is appropriately energized without risk of overloading the buckling pin
86.
[052] Referring to FIG. 4, a cross-sectional view of a pressure relief device
for a pressurized system according to an exemplary embodiment is illustrated. As
noted above, in some situations the valve plug 52 can experience a back pressure
from the direction of outlet port 26 and acting in a direction opposite the flow path
44. Many valves are applied in cases where the discharge line leading to a safety
reservoir (or the environment), for example, carries multiple relief devices
sequentially along the outlet discharge path. When one such relief device is
-15-

WO 2007/032919 PCT/US2006/034006
relieving pressure, the others further upstream in the chain are subject to a level of
back pressure. Any relief device that is sensitive to differential pressure can have
its set point temporarily affected by such back pressures. Some pressure systems
may even have a permanent back pressure that must be accounted for. In the
design of pressure relief devices there is a need for technology that can function
independent or somewhat independent of back pressure.
[053] FIG. 4 illustrates an pressure relief device 10' similar to the pressure
relief device 10 of FIG. 2A and including a feature for facilitating back pressure
independence. In FIG. 4, plate member 66 and central through-bore/shaft bushing
64 of FIG. 2A is replaced with a seai plate 66' within which exhibits an enlarged
central opening 98. An extended chimney 96 is provided which extends from the
valve plug 52 and passes through the opening 98 in seal plate 66' between the
main valve body 12' and the bonnet assembly 14'. A seal is provided between the
components of the chimney's outer diameter and the inner surface of opening 98 in
seal plate 66'. Accordingly, any back pressure from outlet port 26 cannot reach the
backside of valve plug 52 because that path is sealed due to the presence of
chimney 96. Any back pressure or vacuum from bonnet assembly 14', for example,
that induced by temperature change can be safely vented without interference with
valve plug 52 through one or more apertures 71' in the bonnet assembly 14'.
[054] The difference in area between the inlet of plug 52 and the chimney
96 cross section determines the load transmitted through the stem assembly 50. If
the chimney 96 cross sectional area equates to the inlet area of the valve plug 52,
the influence of back pressure on the load transmitted through the stem assembly
50 is zero, making the set pressure of the valve independent of back pressure. For
a low pressure device, even the changes in pressure within a sealed bonnet
assembly 14 due to change in ambient temperature can corrupt the set pressure of
the valve.
[055] As an addition, or as an alternative, to the above-described elements
for addressing system back pressure, a bellows can be provided extending from the
valve plug 52. The bellows is provided and configured to prevent back pressure
from reaching the downstream side of the valve plug through the outlet port. In
addition, the valve plug itself may extend through the main body into the valve
-16-

WO 2007/032919 PCT/US2006/034006
bonnet 14' preventing back pressure from reaching the downstream side of the
valve plug through the outlet port. In such an embodiment, the plug may be formed
to exhibit a cylindrical shape extending through the main valve body.
[056] With regard to the foregoing description of exemplary embodiments, it
is noted that, while a 90 degree angle is illustrated in the figures, this representation
is considered to be non-limiting and alterative flow paths could be provided without
departing from the scope of the invention. Other embodiments of the invention will
be apparent to those skilled in the art from consideration of the specification and
practice of the invention disclosed herein. It is intended that the specification and
examples be considered as exemplary only, with a true scope and spirit of the
invention being indicated by the following claims.
-17-

WO 2007/032919 PCT/US2006/034006
WHAT IS CLAIMED IS:
1. A pressure relief device for a system containing a pressurized fluid,
comprising;
a main valve body including an axial passageway defining an inlet port, an
outlet port, and a fluid flowpath between the inlet and outlet ports;
a valve plug positioned to seal the flowpath of the pressurized fluid between
the inlet port and the outlet port of main valve body;
a force transmission component connected to the valve plug;
an activation component installed between the force transmission
component and a mounting surface, the activation component configured to
prevent axial movement of the valve until a predetermined pressure is exerted on
the valve; and
wherein the force transmission component only transfers an axial force
acting on the valve plug to the activation component.
2. The device of claim 1, wherein the axial passageway terminates within the
main valve body at a mouth within the main valve body.
3. The device of claim 2, wherein the valve plug comprises a disk shaped valve
seat providing a seal at the mouth.
4. The device of claim 2, wherein the valve plug comprises a component
sealingly engaged within the axial passageway downstream of the mouth.
5. The device of claim 1, wherein the valve plug comprises a single plate valve
plug.
6. The device of claim 1, wherein the activation component is a buckling pin
configured to buckle when the pressurized fluid of the system reaches the
predetermined pressure.
-18-

WO 2007/032919 PCT/US2006/034006
7. The device of claim 1, wherein the activation component is a pin configured
to break when the pressurized fluid of the system reaches the predetermined
pressure.
8. The device of claim 1, further comprising a piston slidably housed within the
relief device between the force transmission component and the activation
component.
9. The device of claim 8, wherein the distance between the mounting surface
and the piston is adjustable to accommodate installation of the activation
component.
10. The device of claim 8, wherein the piston and force transmission component
are dimensioned such that when the valve plug is positioned to seal the flowpath,
the force transmission component is positioned to slidably displace the piston.
11. The device of claim 1, further comprising a pre-loading mechanism
configured to axially load the force transmission component such that the valve
plug is positioned to seal the flowpath prior to the installation of the activation
component.
12. The device of claim 11, wherein the pre-loading mechanism comprises a
rotatable arm.
13. The device of claim 1, wherein the force transmission component includes at
least one gimballing joint.
14. The device of claim 13, wherein the at least one gimballing joint is connected
to the valve plug.
-19-

WO 2007/032919 PCT/US2006/034006
15. The device of claim 1, wherein the force transmission component comprises
a gimballing joint connected to the valve plug, a protrusion member, and a shaft
extending therebetween.
16. The device of claim 15, wherein the protrusion member comprises a ball
bearing.
17. The device of claim 1, further comprising a sensor activating device
positioned along the force transmission component and a sensor fixed relative to
the main valve body configured to monitor axial movement of the sensor activating
device and the force transmission device.
18. The device of claim 1, further comprising a plurality of sensor activating
devices positioned along the force transmission component and a plurality of
sensors fixed relative to the main valve body configured to monitor several axial
positions of the force transmission device.
19. The device of claim 1, wherein the outlet port exits the main valve body at an
angle approximately 90 degrees relative to the axial passageway.
20. The device of claim 1, wherein a chimney extending from the valve plug
prevents back pressure from reaching the valve plug downstream side through the
outlet port.

21. The device of claim 1, wherein a bellows extends from the valve plug and
prevents back pressure from reaching a downstream side of the valve plug through
the outlet port.
22. The device of claim 1, wherein the valve plug extends through the main valve
body beyond the axial passageway such that the valve plug prevents back
pressure from reaching a downstream side of the valve plug through the outlet port.
-20-

WO 2007/032919 PCT/US2006/034006
23. A pressure relief device for a system containing a pressurized fluid,
comprising;
a main valve body including an axial passageway defining an inlet port, an
outlet port, and a fluid flowpath between the inlet and outlet ports;
a valve plug positioned to seal the flowpath of the pressurized fluid between
the inlet port and the outlet port of main valve body;
a force transmission component connected to the valve plug;
an activation component installed between the force transmission
component and a mounting surface, the activation component configured to
prevent axial movement of the valve plug until a predetermined pressure is exerted
on the valve plug; and
wherein the force transmission component is incapable of transferring any
moment resulting from the output force acting on the valve plug to the activation
component.
24. The device of claim 23, wherein the force transmission component
comprises a gimballing joint connected to the valve plug, a protrusion member, and
a shaft extending therebetween.
25. The device of claim 23, wherein the axial passageway terminates within the
main valve body at a mouth within the main valve body.
26. The device of claim 25, wherein the valve plug comprises a disk shaped
valve seat providing a seal at the mouth.
27. The device of claim 25, wherein the valve plug is sealingly engaged within
the axial passageway downstream of the mouth.
28. The device of claim 23, wherein the valve plug comprises a single plate
valve plug.
-21-

WO 2007/032919 PCT/US2006/034006
29. The device of claim 23, wherein the activation component is a buckling pin
configured to buckle when the pressurized fluid of the system reaches the
predetermined pressure.
30. The device of claim 23, wherein the activation component is a spring
configured to compress when the pressurized fluid of the system reaches the
predetermined pressure.
31. The device of claim 23, further comprising a piston slidably housed within the
relief device between the force transmission component and the activation
component.
32. The device of claim 31, wherein the distance between the mounting surface
and the piston is adjustable to accommodate installation of the activation
component.
33. The device of claim 23, further comprising a pre-loading mechanism
configured to axially load the force transmission component such that the valve
plug is positioned to seal the flowpath prior to the installation of the activation
component between the force transmission component and the mounting surface.
34. The device of claim 33, wherein the pre-loading mechanism comprises a
rotatable arm.
35. The device of claim 23, further comprising a sensor activation device
positioned along the force transmission component and a sensor fixed relative to
the main valve body configured to monitor axial movement of the sensor activation
device and the force transmission device.
36. The device of claim 23, further comprising a plurality of sensor activating
devices positioned along the force transmission component and a plurality of
-22-

WO 2007/032919 PCT/US2006/034006
sensors fixed relative to the main valve body configured to monitor several axial
positions of the force transmission device.
37. The device of claim 35, wherein the sensor activation device comprises a
magnet and the sensor comprises a proximity switch.
38. The device of claim 35, wherein the sensor is integral to or connected to a
wireless transmitter.
39. The device of claim 23, wherein a chimney extending from the valve piug
prevents back pressure from reaching the valve plug downstream side through the
outlet port.
40. The device of claim 23, wherein a bellows extends from the valve plug and
prevents back pressure from reaching a downstream side of the valve plug through
the outlet port.
41. The device of claim 23, wherein the valve plug extends through the main
valve body beyond the axial passageway such that the valve plug prevents back
pressure from reaching a downstream side of the valve plug through the outlet port.
42. A method of installing a pressure relief device for a system containing a
pressurized fluid, comprising;
providing a main valve body including an axial passageway defining an inlet
port, an outlet port, and a fluid flowpath between the inlet and outlet ports;
providing a valve plug, a force transmission component connected to the
valve seal, a mounting surface, and an activation component;
positioning the valve plug to seal the flowpath of the pressurized fluid
between the inlet port and the outlet port of main valve body;
installing the force transmission component such that only an axial
component of output force acting on the valve plug can be transferred therealong;
and
-23-

WO 2007/032919 PCT/US2006/034006
installing an activation component between the force transmission
component and the mounting surface such that the activation component is
configured to prevent axial movement of the valve plug until a predetermined
pressure is exerted on the valve plug.
43. The method of claim 42, further comprising prior to installing an activation
component, pre-loading an axial force to the force transmission component such
that the valve plug is positioned to seal the flowpath prior to the installation of the
activation component between the force transmission component and the mounting
surface.
44. The method of claim 42, further comprising installing the force transmission
component such that the force transmission component is incapable of transferring
any moment resulting from the output force acting on the valve plug to the
activation component.
45. The method of claim 42, wherein positioning the valve plug further comprises
preventing back pressure from reaching the valve plug through the outlet port by
providing a chimney extending from the valve plug beyond the axial passageway.
46. The method of claim 42, wherein positioning the valve plug further comprises
preventing back pressure from reaching the valve plug through the outlet port by
providing a bellows extending from the valve plug beyond the axial passageway.
47. The method of claim 42, wherein positioning the valve plug further comprises
preventing back pressure from reaching the valve plug through the outlet port by
having an extended valve plug that extends beyond the axial passageway.
48. The method of claim 42, wherein providing a force transmission component
comprises providing a gimballing joint connected to the valve plug, a protrusion
member, and a shaft extending therebetween.
-24-

A pressure relief device is disclosed for a system containing a pressurized fluid. The device includes a main valve
body (12) having inlet (20) and outlet flow (26) ports and a valve plug (52) positioned to seal the flowpath of the pressurized fluid
between the inlet port and the outlet port of main valve body. A force transmission component (72) is connected to the valve plug
and an activation component (86) is installed between the force transmission component and a mounting surface. The activation
component is configured to prevent axial movement of the valve plug until a predetermined pressure is exerted on the valve plug.
The force transmission component more efficiently transfers the output force acting on the valve plug to the activation component.