U.S. patent application number 09/991999 was filed with the patent office on 2002-05-02 for pressure relief device for a sealed system.
This patent application is currently assigned to BS&B Safety System. Invention is credited to Brazier, Geof, Klein, Greg, Nguyen, John.
Application Number | 20020050291 09/991999 |
Document ID | / |
Family ID | 24170822 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020050291 |
Kind Code |
A1 |
Brazier, Geof ; et
al. |
May 2, 2002 |
Pressure relief device for a sealed system
Abstract
A pressure relief device for a sealed system is provided. The
device includes a negative pressure support that is engageable with
the system. A seal is disposed between the support and the system
such that a negative pressure differential created in the system
acts on the seal to move the seal away from the negative pressure
support. A wire connects the seal to the support. The wire is
configured to break, thereby releasing the seal, when the seal is
exposed to a negative pressure differential having a predetermined
level. The device may also include a positive pressure support
disposed between the seal and the negative pressure support. The
positive pressure support prevents the seal from releasing until
the system experiences a positive pressure differential of a
predetermined level. The device may also include a sensor that
indicates when the seal has released.
Inventors: |
Brazier, Geof; (Tulsa,
OK) ; Klein, Greg; (Owasso, OK) ; Nguyen,
John; (Tulsa, OK) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT &
DUNNER LLP
1300 I STREET, NW
WASHINGTON
DC
20005
US
|
Assignee: |
BS&B Safety System
|
Family ID: |
24170822 |
Appl. No.: |
09/991999 |
Filed: |
November 26, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09991999 |
Nov 26, 2001 |
|
|
|
09544119 |
Apr 6, 2000 |
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Current U.S.
Class: |
137/68.18 |
Current CPC
Class: |
Y10T 137/1692 20150401;
Y10T 137/1684 20150401; F16K 17/16 20130101; F16K 17/403 20130101;
F16K 37/005 20130101; Y10T 137/1759 20150401; Y10T 137/1722
20150401; Y10T 137/1714 20150401 |
Class at
Publication: |
137/68.18 |
International
Class: |
F16K 017/14 |
Claims
What is claimed is:
1. A pressure relief device for a sealed system, comprising: a
support engageable with the system; a seal disposed between the
support and the system such that a negative pressure differential
created in the system acts on the seal to move the seal away from
the support; a wire connecting the seal to the support, the wire
configured to break and thereby release the seal when the seal is
exposed to a negative pressure differential having a predetermined
level; and a sensor connected to the wire and operable to indicate
when the wire connecting the seal to the support has broken and
released the seal from the support.
2. The device of claim 1, wherein the support has an arched shape
and includes three legs.
3. The device of claim 2, further comprising a button engageable
with the support and configured to house the wire.
4. The device of claim 3, further comprising a second button
disposed on the seal and configured to house the wire.
5. The device of claim 2, wherein the support is configured to
provide a flow path of at least 60% of the cross-sectional area
corresponding to the nominal size of the device when the seal is
released.
6. The device of claim 1, further comprising a knife disposed
adjacent the seal and configured to open the seal when the seal is
released.
7. The device of claim 1, further comprising a pair of safety
members configured to sealingly engage the support member and
seal.
8. The device of claim 7, wherein the ends of the wire extend
through a pressure barrier connector in one of the safety
members.
9. A pressure relief device for a sealed system, comprising: a
support engageable with the system; a seal disposed between the
support and the system such that a negative pressure differential
created in the system acts on the seal to move the seal away from
the support; and a wire connecting the seal to the support, the
wire configured to break and thereby release the seal when the seal
is exposed to a negative pressure differential having a
predetermined level, the support configured to provide a flow path
of at least 60% of the cross-sectional area corresponding to the
nominal size of the device when the seal is released.
10. The device of claim 9, further comprising a sensor connected to
the wire and operable to indicate when the wire connecting the seal
to the support has broken and the seal is released from the
support.
11. The device of claim 10, further comprising a button engageable
with the support and configured to house the wire.
12. The device of claim 11, further comprising a second button
disposed on the seal and configured to house the wire.
13. The device of claim 9, wherein the support has an arched shape
and includes three legs.
14. The device of claim 13, wherein the legs are evenly spaced from
each other.
15. The device of claim 9, wherein the flow path is at least 75% of
the cross-sectional area corresponding to the nominal size of the
device when the seal is released.
16. The device of claim 9, wherein the flow path is at least 85% of
the cross-sectional area corresponding to the nominal size of the
device when the seal is released.
17. The device of claim 9, wherein the flow path is at least 100%
of the cross-sectional area corresponding to the nominal size of
the device when the seal is released.
18. The device of claim 9, further comprising a knife disposed
adjacent the seal and configured to open the seal when the seal is
released.
19. The device of claim 9, further comprising a pair of safety
members configured to sealingly engage the support member and
seal.
20. The device of claim 19, wherein the ends of the wire extend
through a pressure barrier connector in one of the safety
members.
21. A pressure relief device for a sealed system, comprising: a
support having a substantially circular flange and three legs, the
three legs extending from the flange and connecting at a point
substantially aligned with the center of the flange, the flange
engageable with the system; a seal disposed between the support and
the system such that a negative pressure differential created in
the system acts on the seal to move the seal away from the support;
a wire connecting the seal to the support at the point where the
legs connect, the wire configured to break and thereby release the
seal when the seal is exposed to a negative pressure differential
having a predetermined level.
22. The device of claim 21, further comprising a sensor disposed at
the connection between the seal and the support, the sensor
operable to indicate when the seal has released from the
support.
23. The device of claim 22, wherein the sensor includes a magnet
disposed on the seal and a reed switch disposed on the support such
that movement of the magnet away from the reed switch causes reed
switch to move and indicate that the seal has released.
24. The device of claim 23, further comprising a first button
disposed on the seal and configured to house the magnet and a
second button disposed on the support and configured to house the
reed switch.
25. The device of claim 22, wherein the sensor is connected to the
wire connecting the seal and support and the breaking of the wire
activates the sensor to indicate that the seal has released.
26. The device of claim 21, wherein the legs of the support are
configured to provide a flow path of at least 85% of the
cross-sectional area corresponding to the nominal size of the
device when the seal is released.
27. A pressure relief device for a sealed system, comprising: a
seal engageable with the system and configured to release from the
system to create a fluid flowpath; and a support structure
configured to prevent the seal from releasing when the seal is
exposed to a negative pressure differential until the negative
pressure differential reaches a first predetermined level, the
support structure further configured to prevent the seal from
releasing when the seal is exposed to a positive pressure
differential until the positive pressure differential reaches a
second predetermined level, the first predetermined level being
independent of the second predetermined level.
28. The device of claim 27, wherein the support structure includes
a first support and a second support, the first support having an
arched shape and connected to the seal to provide support for the
seal when the seal is exposed to a negative pressure differential,
the second support disposed for engagement with the seal to provide
support for the seal when the seal is exposed to a positive
pressure differential.
29. The device of claim 28, further comprising a wire connecting
the first support and the seal, the wire configured to break and
release the seal when the negative pressure differential reaches
the first predetermined level.
30. The device of claim 29, further comprising a sensor connected
to the wire and operable to indicate when the wire connecting the
seal to the support has broken and the seal is released from the
support.
31. The device of claim 30, further comprising a button engageable
with the support and configured to house the wire.
32. The device of claim 31, further comprising a second button
disposed on the seal and configured to house the wire.
33. The device of claim 28, wherein the first support has an arched
shape and includes three legs.
34. The device of claim 28, wherein at least one of the legs is
configured to separate when the seal releases under a positive
pressure differential.
35. The device of claim 34, wherein at least two of the legs are
configured to separate when the seal releases under a positive
pressure differential, thereby allowing the first support to pivot
about the third leg.
36. The device of claim 28, wherein the second support is made of a
flexible material and includes at least one opening adjacent the
perimeter of the second support.
37. The device of claim 36, wherein the second support further
includes a centrally located opening, the wire passing through the
centrally located opening.
38. The device of claim 27, further comprising a knife disposed
adjacent the seal and configured to open the seal when the seal is
released.
39. The device of claim 27, further comprising a pair of safety
members configured to sealingly engage the support member and
seal.
40. The device of claim 39, wherein the ends of the wire extend
through a pressure barrier connector in one of the safety
members.
41. A pressure relief device for a sealed system, comprising: a
seal engageable with the system and configured to release from the
system to create a fluid flow path; and a first support having an
arched shape and including three legs, the first support connected
to the seal to provide support for the seal when the seal is
exposed to a negative pressure differential and configured to
release the seal when the negative pressure differential reaches a
first predetermined level; and a second support disposed for
engagement with the seal to provide support for the seal when the
seal is exposed to a positive pressure differential, the second
support configured to release the seal when the positive pressure
differential reaches a second predetermined level; wherein at least
of the legs of the first support is configured to separate when the
seal releases under a positive pressure differential.
42. The device of claim 41, further comprising a wire connecting
the first support and the seal, the wire configured to break and
release the seal when the negative pressure differential reaches
the first predetermined level.
43. The device of claim 42, further comprising a sensor connected
to the wire and operable to indicate when the wire connecting the
seal to the support has broken and the seal is released from the
support.
44. The device of claim 43, further comprising a button engageable
with the support and configured to house the wire.
45. The device of claim 44, further comprising a second button
disposed on the seal and configured to house the wire.
46. The device of claim 41, wherein at least two of the legs are
configured to separate when the seal releases under a positive
pressure differential, thereby allowing the first support to about
the third leg.
47. The device of claim 41, wherein the second support is made of a
flexible material and includes at least one opening adjacent the
perimeter of the second support.
48. The device of claim 47, wherein the second support further
includes a centrally located opening, the wire passing through the
centrally located opening.
49. The device of claim 41, further comprising a knife disposed
adjacent the seal and configured to open the seal when the seal is
released.
50. The device of claim 41, further comprising a pair of safety
members configured to sealingly engage the support member and
seal.
51. The device of claim 50, wherein the ends of the wire extend
through a pressure barrier connector in one of the safety members.
Description
BACKGROUND OF THE INVENTION
[0001] This invention generally relates to safety devices for
pressurized systems and storage systems typically maintained at or
near atmospheric pressure. More particularly, the present invention
relates to a pressure relief device for a sealed system.
[0002] There are many industries in which it is desirable to design
and build systems to hold or process 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, such
as a fire, where the pressure in the system endangers the physical
integrity of the system, the safety device will create an opening
to provide a vent path to correct the over-pressurization within
the system. The opening allows fluid to vent from the system to the
environment, or to a safety reservoir, to reduce the pressure in
the system and prevent the system from failing under the pressure
of the fluid.
[0003] In some industries, such as the food processing industry, it
is also expected that systems, which require protection from
over-pressure situations, may also be exposed to under-pressure, or
vacuum, situations. In certain systems, any vacuum within the
system can damage sensitive equipment. In the food & drug
processing industries, for example, a vacuum may be created in a
system when the system is being cleaned after a completion of a
process. Typically, these food processing systems are cleaned
and/or sterilized with a steam spray apparatus that removes any
product from the system after a processing operation is completed
and before the next processing step begins. If the system is not
properly controlled during steam cleaning, a sudden vacuum can be
developed, which may cause damage to the system. For example, if
cold water were introduced to the system while steam cleaning, the
steam would condense, thereby creating a vacuum situation.
[0004] Thus, to completely protect such a system, the pressure
release device must provide two-directional pressure relief. The
first direction of pressure relief prevents damage or safety
hazards resulting from an over-pressurization, or a positive
pressure differential situation. The second direction of pressure
relief prevents damage or safety hazards resulting from
under-pressurization, or a negative pressure differential
situation. Since the design of pressure systems and atmospheric
storage systems typically produce a design strength that is much
higher in a positive pressure differential than a negative pressure
differential, an appropriate two-directional pressure relief device
must have the ability to function at pressures that vary
significantly in each direction.
[0005] It should be noted that some systems are unlikely to
encounter an over-pressure situation and, thus, the only risk is
exposure to a negative pressure differential. In these types of
systems, a pressure relief device need only protect the system from
a negative pressure differential.
[0006] Some systems require pressure protection at very low levels,
measured in "inches of water column" rather than "pounds per square
inch." Protection may be required in both over-pressure and
under-pressure directions, or just in one direction.
[0007] A typical two direction pressure relief device includes a
sealing member that is sealingly engaged with the system. The
sealing member is surrounded by a pair of support members. One
support member is configured to permit the seal to release when the
seal is exposed to a predetermined positive pressure differential
and the other sealing member is configured to permit the seal to
release when the seal is exposed to a predetermined negative
pressure differential. To provide protection from a negative
pressure differential only, the positive pressure support member
may be omitted.
[0008] The positive pressure support member provides a backdrop for
the sealing member and is configured to withstand a predetermined
force. As the pressure in the system rises, the seal moves against
the positive pressure support. When the pressure reaches a
predetermined level, the positive pressure support releases the
seal to create a vent path and reduce the pressure in the system.
Typically, the positive pressure support member is a generally
solid unit that has a series of holes and slits or perforations.
The holes allow fluid to enter the system if the seal releases
under a negative pressure differential and the slits allow the
support member to open when the positive pressure differential
reaches a predetermined level. However, in low pressure
applications, the positive pressure support does not always fully
open, which results in an obstructed flow path for the venting
fluid.
[0009] The negative pressure support, often referred to as a
"girdle," is typically disposed between the system and the seal.
When a light negative pressure differential acts on the seal, the
seal moves towards the system and into contact with the girdle. The
girdle is configured to flex as the seal is pushed against the
girdle by the negative pressure differential. This flexing begins
at a predetermined pressure level. In most cases, however, the
force of the vacuum on the seal and girdle arrangement will not
open the seal. Thus, a knife blade is often positioned to puncture
the seal as the girdle and seal flex under the vacuum to ensure
that the seal fully opens. The positive pressure support does not
open under these conditions, which restricts the flow path for the
venting fluid to typically 50% of the pressure relief device
nominal cross sectional area.
[0010] These types of bi-directional pressure relief devices are
not conducive to industries, such as the food & drug industry,
that require a sanitary environment for processing operations. The
girdle, which is positioned between the seal and the system, tends
to pick up product during system operation. The configuration of
the systems and the pressure relief devices make it difficult to
clean the girdle, especially the space between the seal and the
girdle, which may ultimately lead to contamination and/or a spoiled
product.
[0011] The same girdle and seal combination is typically used to
provide a single direction low pressure relief device for either
positive or vacuum relief.
[0012] It is also desirable to include a sensor in the pressure
relief devices to indicate when the seal has opened. Typically, the
sensor is integrated with the seal and consists of a wire
connection that extends across the seal. In theory, when the seal
opens, the wire connection will be broken and will indicate that
the seal is open. In operation, however, the seal does not always
fully open and the wire connection is not always broken. Thus, the
seal may open without activating the sensor. For low pressure
relief devices, the sensor may be of such fragile construction to
avoid interference with the set pressure of the device, that the
sensor wire can break leading to false signals that the seal is
open.
[0013] In light of the foregoing, there is a need for a pressure
relief device that (1) provides a high flow area for both positive
and negative pressure releases; (2) includes a reliable sensor to
indicate when the seal has opened; (3) provides a sanitary seal,
(4) provides a high-flow area for single direction of operation at
low pressures, and (5) provides a two-way device that operates at
low pressures in both directions or at widely different set
pressures in each direction.
SUMMARY OF THE INVENTION
[0014] Accordingly, the present invention is directed to a one-way
or a two-way pressure relief device that obviates one or more of
the limitations and disadvantages of prior art pressure relief
devices. The advantages and purposes 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 advantages and purposes of the invention will be
realized and attained by the elements and combinations particularly
pointed out in the appended claims.
[0015] To attain the advantages and in accordance with the purposes
of the invention, as embodied and broadly described herein, the
invention is directed to a pressure relief device for a sealed
system. The device includes a support that is engageable with the
system. A seal is disposed between the support and the system such
that a negative pressure differential created in the system acts on
the seal to move the seal away from the support. A wire connects
the seal to the support and is configured to break, thereby
releasing the seal, when the seal is exposed to a negative pressure
differential having a predetermined level. A sensor is connected to
the wire to indicate when the wire connecting the seal to the
support has broken and released the seal from the support.
[0016] In another aspect, the invention is directed to a pressure
relief device for a sealed system. The device includes a support
that is engageable with the system. A seal is disposed between the
support and the system such that a negative pressure differential
created in the system acts on the seal to move the seal away from
the support. A wire connects the seal to the support. The wire is
configured to break, thereby releasing the seal, when the seal is
exposed to a negative pressure differential having a predetermined
level. The support is configured to provide a flow path of at least
60% of the cross-sectional area corresponding to the nominal size
of the device when the seal is released.
[0017] In yet another aspect, the present invention is directed to
a pressure relief device for a sealed system. The device includes a
seal that is engageable with the system and is configured to
release from the system to create a fluid flowpath. The device also
includes a support structure. The support structure prevents the
seal from releasing when the seal is exposed to a negative pressure
differential until the negative pressure differential reaches a
first predetermined level. The support structure also prevents the
seal from releasing when the seal is exposed to a positive pressure
differential until the positive pressure differential reaches a
second predetermined level. The first predetermined level is
independent of the second predetermined level.
[0018] According to another aspect, the present invention is
directed to a pressure relief device for a sealed system. The
device includes a support that has a substantially circular flange
and three legs. The three legs extend from the flange and connect
at a point substantially aligned with the center of the flange. The
flange of the support is engageable with the system. A seal is
disposed between the support and the system such that a negative
pressure differential created in the system acts on the seal to
move the seal away from the support. A wire connects the seal to
the support at the point where the legs connect. The wire is
configured to break, thereby releasing the seal, when the seal is
exposed to a negative pressure differential having a predetermined
level.
[0019] In still another aspect, the present invention is directed
to a pressure relief device for a sealed system. The device
includes a seal that is engageable with the system and is
configured to release from the system to create a fluid flow path.
The device further includes a first support having an arched shape
and including three legs. The first support is connected to the
seal to provide support for the seal when the seal is exposed to a
negative pressure differential and is configured to release the
seal when the negative pressure differential reaches a first
predetermined level. The device also includes a second support
disposed for engagement with the seal to provide support for the
seal when the seal is exposed to a positive pressure differential.
The second support is configured to release the seal when the
positive pressure differential reaches a second predetermined
level. At least one of the legs of the first support is configured
to separate when the seal releases under a positive pressure
differential.
[0020] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate different
embodiments of the present invention and together with the
description, serve to explain the principles of the invention. In
the drawings,
[0022] FIG. 1 is a cross sectional view of a two-directional
pressure relief device in accordance with the present
invention;
[0023] FIG. 1a is a cross sectional view of an alternative
embodiment of a two-directional pressure relief device according to
the present invention;
[0024] FIG. 2 is a cross sectional view of a one-direction pressure
relief device in accordance with the present invention;
[0025] FIG. 2a is a cross sectional view of an alternative
embodiment of a one-direction pressure relief device according to
the present invention;
[0026] FIG. 3 is a top view of a negative pressure support
according to the present invention;
[0027] FIG. 4 is a side view of a separable leg joint of a negative
pressure support in accordance with the present invention;
[0028] FIG. 5 is a side view of a negative pressure support in
accordance with the present invention, illustrating the support in
the released position; and
[0029] FIG. 6 is a top view of a positive pressure support in
accordance with the present invention.
DETAILED DESCRIPTION
[0030] Reference will now be made in detail to the presently
preferred embodiments of the present invention, examples of which
are 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. An exemplary embodiment of a
pressure relief device of the present invention is shown in FIG. 1
and is designated generally by reference number 20.
[0031] In accordance with the present invention, there is provided
a pressure relief device for a sealed system. As used herein, the
term "sealed system" includes any system that typically uses a
pressure relief device, including, for example, systems designed to
operate at pressures above atmospheric pressure and storage systems
designed to operate at or near atmospheric pressure but may become
plugged and, thus, require a pressure relief device. The pressure
relief device includes a seal that is engageable with the system.
Preferably, the seal is disposed between a pair of safety heads
that are, in turn, sealingly engaged with the system. The present
invention contemplates, however, that the seal may be may be
sealingly engaged with the system in any similar manner, such as,
for example, sealing the pressure relief device between a pair of
pipe flanges in the system.
[0032] As illustrated in FIG. 1, pressure relief device 20 includes
a seal 22. Preferably, seal 22 is sealingly engaged between an
inlet safety head 34 and an outlet safety head 36. Each safety head
34 and 36 includes a raised surface 50 and 52, respectively, that
is configured to engage seal.
[0033] Seal 22 may be engaged between safety heads 34 and 36 by a
series of bolts (not shown) configured to connect the safety heads
together. Alternatively, safety heads 34 and 36 may be disposed
between fixtures in the system, such as pipe flanges, which are
then connected by bolts or clamps to seal safety heads 34 and 36
and seal 22 therebetween.
[0034] Pressure relief device 20 engages the system such that inlet
safety head 34 is disposed adjacent the system. Inlet safety head
34 includes a bore 30 that defines a fluid passageway. When
pressure relief device 20 is engaged with the system, bore 30
allows the fluid in the system to contact seal 22, thereby exposing
the seal to the pressure within the system.
[0035] During operation of the system, the system may be exposed to
either a positive pressure differential, where the pressure within
the system is greater than the ambient pressure (over-pressure), or
a negative pressure differential, where the pressure within the
system is less than the ambient pressure (vacuum). Preferably, seal
22 is made of a flexible material, such as TEFLON, that responds to
the respective pressure situation. Thus, when the system is
experiencing a negative pressure differential, seal 22 will tend to
move towards the system, as indicated by arrow 48. When the system
is experiencing a positive pressure differential, seal 22 will tend
to move away from the system, as indicated by arrow 46.
[0036] The seal is configured to release under either a negative
pressure differential or a positive pressure differential. When
either pressure differential exceeds a certain level, the material
of the seal will tear, or otherwise separate, thereby creating a
fluid flowpath through the pressure relief device. In the case of a
positive pressure differential, fluid will flow in the direction of
arrow 46 through bore 30 of inlet safety head 34 and then through
bore 32 of outlet safety head 36 to relieve the over pressure
situation. In the case of a negative pressure differential, fluid
will flow in the direction of arrow 48 through bore 32 of outlet
safety head 36 and then through bore 30 of inlet safety head 34 to
relieve the vacuum situation.
[0037] In accordance with the present invention, the pressure
relief device includes a negative pressure support. The negative
pressure support is connected to the seal to prevent the seal from
releasing when the seal is exposed to a negative pressure
differential until the negative pressure differential reaches a
predetermined level. Preferably, a wire connects the negative
pressure support to the seal.
[0038] It should be noted that the device of the present invention
may be connected to the system in a reverse fashion such that a
positive pressure differential will cause seal 22 to move in the
direction of arrow 48 and a negative pressure differential will
cause seal to move in the direction of arrow 46. Thus, the negative
pressure support of the preferred embodiment may act to support the
seal under a positive pressure differential under these
circumstances.
[0039] As illustrated in FIG. 1, a negative pressure support 24 is
positioned between safety heads 34 and 36. Negative pressure
support 24 includes an arched section 23 and a circular flange 25.
Preferably, flange 25 is disposed between seal 22 and outlet safety
head 36.
[0040] In the embodiment illustrated in FIG. 3, negative pressure
support 24 includes three legs 60. Preferably, legs 60 are equally
spaced around support 24 and form a generally arched shape. Legs 60
join at a point at the top of the arched section 23 that is
substantially aligned with the center of the flange. Preferably, a
circular opening 64 is defined at the top of arched section 23.
[0041] As also shown in FIG. 1, a wire 28 connects negative
pressure support 24 with seal 22. Wire 28 extends from a support
button 42 that is engaged with opening 64 in arched section 23 to a
seal button 40 disposed on seal 22. Preferably, each button 40 and
42 is made of plastic, although other materials may be used. Each
button 40 and 42 is configured to securely hold wire 28 to maintain
the connection between seal 22 and support 24.
[0042] Wire 28 is configured to break under a predetermined force.
When a negative pressure differential is exerted on seal 22, which
acts on seal 22 to move seal 22 away from support 24, a
corresponding force is transmitted through wire 28 to support 24.
When the magnitude of the force reaches the predetermined level,
the wire breaks, thereby releasing the seal. The magnitude of the
force at which the wire breaks may be adjusted by varying the size
and/or material of the wire and the number of wire elements
used.
[0043] As illustrated in FIGS. 1 and 2 a knife blade 38 is
preferably positioned in bore 30 of outlet safety head 34. Knife
blade 38 includes a point configured to ensure that seal 22 opens
fully under a negative pressure differential. Preferably, the knife
blade point is offset from seal button 40 to ensure that only seal
22 engages knife blade 38. After wire 28 releases seal 22 in
response to a negative pressure differential, seal 22 moves towards
bore 30. If material of seal 22 does not tear under the force of
the pressure differential, seal 22 will strike knife blade 38,
which will puncture seal 22 to ensure that the seal opens to create
a vent path.
[0044] Alternatively, as illustrated in FIGS. 1a and 2a, in an
embodiment where the pressure relief device is engaged with a
system without the use of the safety heads, the pressure relief
device may include a separate knife ring 53 to ensure seal 22
opens. Knife ring 53 includes a spacer 56 that extends from a
flange 54. Spacer 56 supports a series of teeth 58 that are
configured to engage seal 22. Spacer 56 provides room for seal 22
to flex under the pressure differential without engaging teeth 58
until wire 28 breaks to release seal 22.
[0045] The present invention contemplates that the wire connection
between support 24 may be extended, as illustrated in FIG. 1, such
that seal 22 extends directly across bore 30 of inlet safety head
34 and is spaced from support 24. Alternatively, as illustrated in
FIG. 2 the wire connection may be shorter, such that seal 22
extends toward and is in closer physical proximity to support 24.
The embodiment illustrated in FIG. 2 is the preferred embodiment
for a device to relieve a negative pressure differential only,
where protection from a positive pressure differential (explained
in greater detail below) is not required.
[0046] In a pressure relief device for relieving only negative
pressure differentials, such as illustrated in FIG. 2, the negative
pressure support of the present invention provides for high flow
vacuum relief. Preferably, legs 60 and 61 of support 24 are
configured to provide a vacuum relief flow area of at least 60% of
the cross-sectional area corresponding to the nominal size of the
device, compared to typically 50% for prior art relief devices.
More preferably, the legs provide a vacuum relief flow area of at
least 75% of the cross-sectional area corresponding to the nominal
size of the device when the seal is released. Still more
preferably, the legs provide a vacuum relief flow area of at least
85% of the cross-sectional area corresponding to the nominal size
of the device when the seal is released. In the illustrated
embodiment, the domed shape created by the legs has an area that is
greater than the cross-sectional area corresponding to the nominal
size of the device. Thus, the configuration of the legs in the
preferred embodiment allows the flow area to be approximately equal
to the cross-sectional area corresponding to the nominal size of
the device.
[0047] Preferably, wire 28 is configured to make a circuit, such
that both ends of wire 28 extend outside of pressure relief device
20. Preferably, a pressure barrier connection 44 is provided in
outlet support member 36. The ends of wire 28 exit the pressure
relief device 20 through barrier connection 44.
[0048] As illustrated in FIG. 3, circular opening 64 that receives
button 42 preferably includes a notch 66. Notch 66 is sized to
allow wire 28 to return from seal button 40 and extend to pressure
barrier 44 without having to transverse seal button 42. In this
manner, a single strand of wire 28 provides the support connection
between the seal and the negative pressure support.
[0049] In the preferred embodiment, wire 28 also operates as a
sensor to indicate when the seal has released. An electrical
current may be passed through wire 28. When wire 28 breaks in
response to a negative pressure differential, the current is
interrupted. The interruption of the current is used to generate a
warning, such as an indicator light, that the seal has broken. The
present invention contemplates that the breaking of the wire may
generate any type of warning, such as an alarm, or, through a
relay, generate a system control signal that could be used to shut
down system equipment. The breaking wire sensor stores no
electrical energy and can be operated at intrinsically safe power
levels as a `simple device.`
[0050] The present invention contemplates that other types of
sensors, such as a reed switch, may be integrated into the pressure
relief device. To integrate a reed switch sensor in the embodiment
illustrated in FIG. 2, a magnet (not shown) is positioned in seal
button 40 and a reed switch (not shown) is positioned in support
button 42. Under normal operating conditions, the magnet will hold
the reed switch in a first position. When wire 28 breaks and seal
button 40 and the magnet move away from the reed switch, the reed
switch moves to a second position, which indicates that the seal
has released. The movement of the reed switch can therefore be used
to generate a warning as described above.
[0051] In accordance with the present invention, a positive
pressure support is provided. The positive pressure support
prevents the seal from releasing until the seal is exposed to a
positive pressure differential having a predetermined level.
Preferably, the positive pressure support is independent of the
negative pressure support.
[0052] As illustrated in FIG. 1, a positive pressure support 26 is
positioned adjacent seal 22. Preferably, positive pressure support
26 is disposed between seal 22 and negative pressure support 24. In
this position, when seal 22 is exposed to a positive pressure
differential, seal 22 will contact positive pressure support 24.
Positive pressure support will prevent seal 22 from releasing until
the positive pressure differential reaches a predetermined
level.
[0053] As shown in FIG. 6, positive pressure support 24 includes a
body 98 that defines a series of openings 92. Preferably, openings
92 are located along the perimeter of body 98, although it is
contemplated that the openings may be positioned elsewhere on the
body. A narrow strut 93 of support material is left between
openings 92. In the illustrated embodiment, body 98 includes three
openings 92 that define two struts 93.
[0054] When seal 22 is exposed to a positive pressure differential,
the force of the fluid pressure moves seal 22 into contact with
body 98 of positive pressure support 26. Body 98 will prevent seal
22 from releasing until the positive pressure differential reaches
a predetermined level. When the predetermined pressure level is
reached, the material of positive pressure support 26 will tear
across struts 93. Body 98 of positive pressure support 26 will then
bend in response to the positive pressure and allow the material of
seal 22 to tear and create a vent path for fluid to escape the
system.
[0055] Preferably, openings 92 surround the majority of the
perimeter of body 98. Thus, when struts 93 tear to release body 98,
the majority of body 98 will be free to bend out of the flow path.
In this manner, a large opening is created to vent fluid from the
system.
[0056] In addition, openings 92 also serve the purpose of allowing
fluid to enter the system (in the direction of arrow 48 in FIG. 1)
under a negative pressure release. Thus, the larger openings 92
are, the greater the flow rate into the system to relieve a vacuum
situation. The present invention also contemplates that additional
openings 99 may be disposed in body 98 to provide additional flow
area for a negative pressure release.
[0057] The size and/or thickness of struts 93, along with the
tensile strength of the material of construction of body 98,
determines the pressure at which the positive pressure support will
release seal 22. As the size and/or thickness of the strut
increases, so does the pressure at which the positive pressure
support will release the seal. Preferably, each strut 93 includes a
pair of holes 96. The size and location of holes 96 is selected to
further control the pressure at which the positive pressure support
will release the seal.
[0058] As illustrated in FIG. 6, positive pressure support 26
includes a central opening 94. Wire 28 connecting negative support
24 to seal 22 passes through central opening 94 (referring to FIG.
1). This configuration allows both the positive and the negative
pressure supports to be located on the opposite side of seal 22
from the system. Thus, the positive and negative supports are not
exposed to the fluid in the system under normal operating
conditions. In a food and drug industry processing application,
this configuration will prevent product from becoming lodged in one
of the supports. Thus, this configuration provides for a sanitary
pressure relief device.
[0059] Preferably, as illustrated in FIGS. 3 and 4, two legs 60 of
support 24 include a separable joint 68. As illustrated in FIG. 4,
each leg 60 is separated into an upper segment 82 and a lower
segment 86. Joint 68 includes a bracket 80 that is disposed on the
upper end of lower segment 86. Bracket 80 slidably receives one end
84 of the upper leg segment 82. Bracket 80 will provide support for
upper leg segment 82 when a force (F) acts to compress leg 60, such
as would be encountered under a negative pressure differential. If,
however, a reverse force, such as would be applied by a released
positive pressure support, is applied to upper leg segment 82,
bracket 80 will release upper leg segment 82.
[0060] As also shown in FIG. 3, the remaining leg 61 preferably
includes a pair of notches 70. Notches 70 form a relatively
narrower area in leg 60. When a reverse force F.sub.r, as would be
experienced when seal releases under a positive pressure
differential, is exerted on negative pressure support 25, brackets
80 will release two of the three legs 60. As illustrated in FIG. 4,
remaining leg 61 of support 24 will bend about notches 70. Thus,
button 42 and top portions 82 of legs 61 will move out of the flow
path created when the seal releases under a positive pressure
differential. In this manner, the area of the flow path is
maximized to provide a quick reduction of pressure within the
system.
[0061] The operation of the aforementioned pressure relief device
will now be described with reference to the attached drawings.
[0062] In operation, pressure relief device 20 is engaged with a
system (not shown). As mentioned previously, the system may be a
sealed system and designed to operate at pressures above
atmospheric of the system may be a vented system whose ventilation
passage has become plugged. Engagement of pressure relief device 20
with the system exposes seal 22 to the pressure of the fluid within
the system. Preferably, pressure relief device 20 forms a fluid
tight seal with the system to prevent any fluid from leaking into
or out of the system.
[0063] The system is then operated in its normal fashion. If an
emergency situation is encountered and the system experiences an
over-pressure situation, the force of the fluid within the system
acts on seal 22 to move seal 22 against positive pressure support
26. Body 98 of positive pressure support 26 prevents seal 22 from
releasing until the positive pressure differential reaches a
predetermined level.
[0064] When the predetermined pressure level is reached, the force
of the fluid acting on the positive pressure support 26 through
seal 22 will overcome the material strength of the positive
pressure support. The material in struts 93 of body 98 will tear,
thereby allowing the force of the fluid to bend the body away from
the system. The material of seal 22 will also tear, creating a vent
path for the fluid to escape.
[0065] The continued force of the fluid moves seal 22 and body 98
into contact with negative pressure support 24. Legs 60 of negative
support 24 release at brackets 80. Negative pressure support 24
bends around notches 70 in remaining leg 61. Thus, the force of the
fluid will move seal 22, positive pressure support 26, and negative
pressure support 24 out of the fluid flowpath. Thus, a large vent
path will be created to quickly reduce the over-pressure situation
within the system.
[0066] If the system is exposed to a negative pressure
differential, the resulting force on seal 22 will act to move the
seal away from negative pressure support 24. Wire 28 connecting
negative pressure support 24 and seal 22 prevents seal 22 from
releasing until a predetermined negative pressure differential is
experienced. When the predetermined level is reached, wire 28
breaks, thereby releasing seal 22.
[0067] Seal 22 moves away from negative pressure support 24 and
into contact with knife blade 38. If the material of seal 22 does
not tear initially, contact with knife blade 38 will puncture seal
22 to initiate a tear. The continued force of the negative pressure
differential continues to open seal 22 to create a vent path. In a
vacuum relief only embodiment, fluid flows between legs 60 and 61
of negative support and through the vent path in the seal to
relieve the negative pressure differential. In a bi-directional
pressure relief embodiment, fluid flows also flows through openings
92, 94 and 99 in positive pressure support 26 to relieve the vacuum
situation.
[0068] The pressure relief device of the present invention is
therefore a sanitary device, which provides great flexibility in
determining the minimum and maximum allowable negative and positive
pressure differentials. Because both the positive and negative
pressure supports are not exposed to the fluid of the system under
normal operating conditions, the relief device does not pose a
contamination risk by providing dead space between component
surfaces in the system. In addition, the positive pressure support
and the negative pressure support are configured to support the
seal independently of the other. Thus, the negative pressure
differential of the pressure relief device is not dependent upon
the positive pressure differential. This allows the pressure relief
device of the present invention to be used with any number of
systems, including those that are designed to handle a high
positive pressure differential but only able to withstand a low
negative pressure differential, and those that require a low
positive and negative pressure differential.
[0069] It will be apparent to those skilled in the art that various
modifications and variations can be made in the assembly of the
present invention without departing from the scope or spirit 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.
* * * * *