Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02955724 2017-01-23
RELIEF VALVE
TECHNICAL FIELD
[0001] Relief valve
BACKGROUND
[0002] Relief valves are used in fluid systems to control the internal
pressure or vacuum
within the system. Pressure relief valves are used to control or limit the
amount of pressure in a
system by allowing pressurized fluid to flow from an auxiliary passage out of
the system. Vacuum
relief valves are used to open at a predetermined pressure to admit gas into
the system to control the
amount of vacuum in a system.
[0003] A typical vacuum or pressure relief valve is a direct acting valve.
For example, a
standard vacuum relief valve design includes a pallet which is forced upwards
when pressure in the
container drops. The movement of the pallet ()pens a vent which allows
atmospheric gas to enter the
container to equalize the pressure difference between atmosphere and
container. The movement of
the pallet is directly related to the pressure differential between the
container and atmosphere.
SUMMARY
[0004] In an embodiment, there is provided a relief valve comprising a
valve body having
an interior in fluid communication with a container having a container
pressure and the valve body
having an exterior exposed to an atmosphere; a pallet assembly having a relief
pallet having a relief
pressure bearing area, a pilot pallet having a pilot pressure bearing area,
and a shaft connecting the
pilot pallet and relief pallet to space the pilot pallet from the relief
pallet; a relief pallet seat extending
from the valve body towards the interior of the valve body and configured to
seal against the relief
pallet to seal the valve body; a pilot pallet seat extending from the valve
body and away from the
interior of the valve body and configured to seal against the pilot pallet to
form a reservoir between
the pilot pallet, the pilot pallet seat and the valve body, and the reservoir
having an equalization port
to provide fluid communication between the valve body and the reservoir; a
force element connected
to and acting on the pallet assembly to maintain the pallet assembly in a
sealed position against the
relief pallet seat and the pilot pallet seat while the container pressure is
above a selected opening
pressure; wherein the pilot pressure bearing area is less than the relief
pressure bearing area, and the
pilot pallet and relief pallet are configured so that when the container
pressure is at or below the
selected opening pressure, the relief pallet and the relief pallet seat unseal
to form a relief port and the
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pilot pallet and the pilot pallet seat unseal to form a pilot port; and
wherein the pilot port and the
equalization port are configured such that when the container pressure is at
or below the selected
opening pressure, the gas flows through the pilot port into the reservoir from
the atmosphere at a
greater rate than through the equalization port from the reservoir to the
valve body.
[0005] In various embodiments, there may be included any one or more of the
following
features: the pilot pallet comprises a pilot pallet seal configured to engage
with the pilot pallet scat;
the relief pallet comprises a relief pallet seal configured to engage with the
relief pallet seat; force
element comprises a weight; the force element comprises a biasing member.
[0006] In an embodiment, there is provided a relief valve comprising a
valve body having
an interior in fluid communication with a container having a container
pressure and the valve body
having an exterior exposed to an atmosphere; a pallet assembly having a relief
pallet having a relief
pressure bearing area, a pilot pallet having a pilot pressure bearing area,
and a shaft connecting the
pilot pallet and relief pallet and spacing the pilot pallet from the relief
pallet; a relief pallet seat
extending from the valve body and away from the valve body and configured to
seal against the relief
pallet to seal the valve body; a pilot pallet seat extending from the valve
body towards the interior of
the valve body and configured to seal against the pilot pallet to form a
reservoir between the pilot
pallet, the pilot pallet seat and the valve body, and the reservoir having an
equalization port to
provide fluid communication between the reservoir and the atmosphere; a force
element connected to
and acting on the pallet assembly to maintain the pallet assembly in a sealed
position against the
relief pallet seat and the pilot pallet seat while the container pressure is
below a selected opening
pressure; and the pilot pallet and the pilot pallet seat unseal to form a
pilot port and the relief pallet
and the relief pallet seat unseal to form a relief port; wherein the pilot
pressure bearing area is less
than the relief pressure bearing area and the pilot pallet and relief pallet
are configured such that
when the container pressure is at or above the selected opening pressure, the
relief pallet and the
relief pallet seat unseal to form a relief port and the pilot pallet and the
pilot pallet seat unseal to form
a pilot port; and wherein the pilot port and the equalization port are con
figured such that when the
container pressure is at or above the selected opening pressure, the gas flows
through the pilot port
into the reservoir from the valve body at a greater rate than through the
equalization port from the
reservoir to the atmosphere.
[0007] In various embodiments, there may be included any one or more of the
following
features: the pilot pallet comprises a pilot pallet seal configured to engage
with the pilot pallet scat;
2
the relief pallet comprises a relief pallet seal configured to engage with the
relief pallet seat; the
force element comprises a weight; the force element comprises a biasing
member.
[0008] In an embodiment, there is provided a relief valve comprising: a valve
body having an
interior in fluid communication with a container having a container pressure
and the valve body
having an exterior exposed to an atmosphere; a pallet assembly having a relief
pallet having a
relief pressure bearing area, a pilot pallet having a pilot pressure bearing
area, and a shaft
connecting the pilot pallet and relief pallet to space the pilot pallet from
the relief pallet; a relief
pallet seat extending from the valve body away from valve body and configured
to seal against
the relief pallet to seal the valve body; a reservoir attached to the valve
body and separated by the
pallet assembly, the reservoir having a pilot pallet seat configured to seal
against the pilot pallet,
and the reservoir having an equalization port to provide a fluid connection
between the valve
body and the reservoir; a force element connected to and acting on the pallet
assembly to
maintain the pallet assembly in a sealed position against the relief pallet
seat and the pilot pallet
seat while the container pressure is below a selected opening pressure; and
wherein the pilot
pressure bearing area is less than the relief pressure bearing area and the
pilot pallet and relief
pallet are configured such that when the container pressure is at or above the
selected opening
pressure, the relief pallet and the relief pallet seat unseal to form a relief
port and the pilot pallet
and the pilot pallet seat unseal to form a pilot port; and wherein the pilot
port and the
equalization port are configured such that when the container pressure is at
or above the selected
opening pressure, gas flows through the pilot port from the reservoir into the
atmosphere at a
greater rate than through the equalization port from the valve body into the
reservoir.
[0009] In various embodiments, there may be included any one or more of the
following
features: the pilot pallet comprises a pilot pallet seal configured to engage
with the pilot pallet
seat; the relief pallet comprises a relief pallet seal configured to engage
with the relief pallet seat;
the force element comprises a weight; the force element comprises a biasing
member; the
equalization port is formed by a channel extending through the shaft; the
equalization port is
formed by a connecting element which provides a fluid connection between the
valve body and
the reservoir;
[0010] These and other aspects of the device and method are set out in the
claims.
BRIEF DESCRIPTION OF THE FIGURES
[0011] Embodiments will now be described with reference to the figures, in
which like reference
characters denote like elements, by way of example, and in which:
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[0012] Fig. 1 is a perspective view in cross-sectional of an embodiment of
a vacuum relief
valve, the valve shown in a closed configuration.
[0013] Fig. 2 is a cross-sectional view of an embodiment of a vacuum relief
valve, the valve
shown in a closed configuration.
[0014] Fig. 3 is a cross-sectional view of the embodiment of the vacuum,
relief valve of Fig.
1 combined with direct acting pressure valve;
[0015] Fig. 4 is a detail view of the embodiment of the vacuum relief valve
of Fig. 3 within
line A;
[0016] Fig. 5 is a cross-sectional view of an embodiment of the vacuum
relief valve of Fig.
1 in a closed position;
[0017] Fig. 6 is a cross-sectional view of the embodiment of Fig. 1 in a
partially open
position;
[0018] Fig. 7 is a cross-sectional view of the embodiment of Fig. 1 in a
fully open position;
[0019] Fig. 8 is a cross-sectional view of an embodiment of a pressure
relief valve;
[0020] Fig. 9 is a cross-sectional view of an embodiment of a pressure
relief valve;
[0021] Fig. 10 is a cross-sectional view of an embodiment of a pressure
relief valve; and
[0022] Fig. 11 illustrates an exemplary use of a pressure relief valve.
DETAILED DESCRIPTION
[0023] Immaterial modifications may be made to the embodiments described
here without
departing from what is covered by the claims. In the claims, the word
"comprising" is used in its
inclusive sense and does not exclude other elements being present. The
indefinite articles "a" and
"an" before a claim feature do not exclude more than one of the feature being
present. Each one of
the individual features described here may be used in one or more embodiments
and is not, by virtue
only of being described here, to be construed as essential to all embodimenfs
as defined by the
claims.
[0024] Embodiments of a relief valve 20 arc shown in Figs. 1 ¨7. The relief
valve 20
comprises a valve body 22, a pallet assembly 24, a relief pallet seat 26, a
pilot pallet seat 28 and a
force element 30. The valve body 22 has an interior 32 in fluid communication
with a container 34
and the valve body 22 has an exterior 36 exposed to an atmosphere 38. The
container 34 has a
container pressure. The pallet assembly 24 has a relief pallet 40 having a
relief pressure bearing area
42, a pilot pallet 44 having a pilot pressure bearing area 46, and a shaft 48
connecting the pilot pallet
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44 and relief pallet 40 to space the pilot pallet 44 from the relief pallet
40. The relief pallet seat 26
extends from the valve body 22 towards the interior 32 of the valve body 22
and is configured to seal
against the relief pallet 40 to seal the valve body 22. The pilot pallet seat
28 extends from the valve
body 22 and away from the interior 32 of the valve body 22 and is configured
to seal against the pilot
pallet 44 to form a reservoir 50 between the pilot pallet 44, the pilot pallet
seat 28 and the valve body
22. The reservoir 50 has an equalization port 52 to provide fluid
communication between the valve
body 22 and the reservoir 50. The force element 30 is connected to and acts on
the pallet assembly 24
to maintain the pallet assembly 24 in a sealed position against the relief
pallet seat 26 and the pilot
pallet seat 28 while the container pressure is above a selected opening
pressure. The pilot pressure
bearing area 46 is less than the relief pressure bearing area 42 and the
relief pallet 40 and pilot pallet
44 are configured such that when the container pressure is at or below the
selected opening pressure,
the relief pallet 40 and the relief pallet seat 26 unseal to form a relief
port 54 and the pilot pallet 44
and the pilot pallet seat 28 unseal to form a pilot port 56. The pilot port 56
and the equalization port
52 are configured such that when the container pressure is at or below the
selected opening pressure,
gas flows through the pilot port 56 into the reservoir 50 from the atmosphere
38 at a greater rate than
through the equalization port 52 from the reservoir 50 to the valve body 22.
[0025] The relief pressure bearing area 42 is the area of the relief pallet
40 and the pilot
pressure bearing area 46 is the pilot pallet 44.
[0026] The embodiment of a relief valve 20 shown in Figs. 1 ¨ 7 operates to
relieve vacuum
pressure in the container 34. In a first stage, shown in Figs. 1 ¨5, the
relief valve 20 is closed and
both the relief pallet 40 and the pilot pallet 44 are sealed. The force caused
by the vacuum in the
container 34 and valve body 22 acts on both pallets 40 and 44 in opposite
directions. Because the
pilot pressure bearing area 46 is smaller than the relief pressure bearing
area 42, the resultant force
acts on the pallet assembly 24 in a direction tending to urge the relief
pallet 40 and pilot pallet 44
away from, respectively, the relief pallet seat 26 and pilot pallet seat 28.
This resultant force is less
than the opposing force generated by the force element 30. At this stage, the
pressure in the reservoir
50 is equal to the pressure in the container 34 and valve body 22.
[0027] In a second stage, shown in Fig. 6, the container pressure has
dropped to the selected
opening pressure (also known as the set pressure), and the force on the pallet
assembly 24 due to the
vacuum in the container 34 is equal to or slightly greater than the force of
the force element 30. Set
pressure may be set as or close to the maximum allowable working vacuum of the
container 34
relative to the atmosphere 38. The seals of both pallets 40 and 44 are broken
and the pallet assembly
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24 begins to lift. Gas begins to flow through the pilot port 56 from the
atmosphere 38 to the reservoir
50 and to the valve body 22 from the atmosphere 38 through the relief port 54.
The inflow of gas
begins to relieve the vacuum in the valve body 22, container 34 and the
reservoir 50. Since the rate of
gas flow through the pilot port 56 into the reservoir 50 from the atmosphere
38 is greater than the
outflow of gas through the equalization port 52 from the reservoir 50 to the
valve body 22, the
pressure within the reservoir 50 increases.
[0028] In a third stage, the pressure in the reservoir 50 has equalized
with atmospheric
pressure. The force across the pilot pressure bearing area 46 caused by the
vacuum drops to almost
zero due to the rapid increase in pressure in the reservoir 50, and the force
generated by the pressure
in the reservoir 50 rapidly overcomes the force of the force element 30 and
the force of the vacuum
pressure across the relief pressure bearing area 42 of the relief pallet 40.
The relief valve 20 moves to
the fully open position, shown in Fig. 7, in which the relief port 54 allows
gas to flow into the
container 34 rapidly to relieve the vacuum in the container 34. Gas flows
almost unrestricted into the
reservoir 50 from the atmosphere 38 and slowly leaks through the equalization
port 52 into the valve
body 22 but not fast enough to decrease the pressure in the reservoir 50. The
fully open position may
be reached when the container pressure is near the set pressure.
[0029] In a fourth stage, shown in Fig. 6, as the pressure in the container
34 increases and
the pressure differential between the container 34 and atmosphere 38
decreases, so too does the gas
flow into the container 34 through the relief port 54. As a result the pallet
assembly 24 gradually
lowers until it reseats. The container pressure at which it reseats is the
closing pressure and occurs
when the force due to stagnation pressure on the relief pallet 40 decreases
until it is equal to the force
of the force element 30 acting on the pallet assembly 24. Gas flow into the
reservoir 50 is gradually
restricted, but this does not significantly affect the pressure in the
reservoir 50 until the pilot pallet 44
is almost seated since the flow into the valve body 22 through the
equalization port 52 is so small.
[0030] In a fifth stage, shown in Fig. 5, the valve 20 has reseated and the
container 34 is at
the closing pressure. There is no flow through the relief port 54 or into the
reservoir 50 from
atmosphere 38. Gas flows from the reservoir 50 into the container 34 and drops
the pressure of the
reservoir 50 from near atmospheric pressure to the closing pressure. This
increases the sealing force
on the pallet assembly 24. This results in the relief valve 20 being reset to
the same state in the first
stage before it opened. The difference between the opening pressure and
closing pressure
(blowdown) of the valve 20 is non-zero, and may be equal to the ratio of the
pilot pressure bearing
area 46 and the relief pressure bearing area 42.
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[0031] Embodiments of a relief valve 120, 220 for relieving pressure are
shown in Figs. 8-
10. The pressure relief valves of Figs. 8-10 operate on the same principals as
the vacuum relief valve
of Figs. 1-7.
[0032] In the embodiment of Fig. 8, the relief valve 120 comprises a valve
body 122, a
pallet assembly 124, a relief pallet seat 126, a pilot pallet seat 128, and a
force element 130. The
valve body 122 has an interior 132 in fluid communication with a container
(not shown) having a
container pressure and the valve body 122 having an exterior 136 exposed to an
atmosphere 138. The
pallet assembly 124 has a relief pallet 140 having a relief pressure bearing
area 142, a pilot pallet 144
having a pilot pressure bearing area 146, and a shaft 148 connecting the pilot
pallet 144 and relief
pallet 140 and spacing the pilot pallet 140 from the relief pallet 144. The
relief pallet seat 126 extends
from the valve body 122 and away from the valve body 122 and is configured to
seal against the
relief pallet 140 to seal the valve body 122. The pilot pallet seat 128
extends from the valve body 122
towards the interior 132 of the valve body 122 and is configured to seal
against the pilot pallet 144 to
form a reservoir 150 between the pilot pallet 144, the pilot pallet seat 128
and the valve body 122.
The reservoir 150 has an equalization port 152 to provide fluid communication
between the reservoir
150 and the atmosphere 138. The force element 130 is connected to and acts on
the pallet assembly
124 to maintain the pallet assembly 124 in a sealed position against the
relief pallet seat 126 and the
pilot pallet seat 128 while the container pressure is below a selected opening
pressure. The pilot
pallet 144 and the pilot pallet seat 128 unseal to form a pilot port 144 and
the relief pallet 140 and the
relief pallet seat 142 unseal to form a relief port 154. The pilot pressure
bearing area 146 is less than
the relief pressure bearing area 142 and the pilot pallet 144 and relief
pallet 140 are configured such
that when the container pressure is at or above the selected opening pressure,
the relief pallet 140 and
the relief pallet seat 126 unseal to form a relief port 154 and the pilot
pallet 144 and the pilot pallet
seat 146 unseal to form a pilot port 156. The pilot port 156 and the
equalization port 152 are
configured such that when the container pressure is at or above the selected
opening pressure, the gas
flows through the pilot port 156 into the reservoir 150 from the valve body
122 at a greater rate than
through the equalization port 152 from the reservoir 150 to the atmosphere
138.
[0033] In a first stage, the relief valve 120 is closed and both the relief
pallet 140 and the
pilot pallet 144 are sealed. The force caused by the pressure in the container
and valve body 122 acts
on both pallets 140 and 144 in opposite directions. Because the pilot pressure
bearing area 146 is
smaller than the relief pressure bearing area 142, the resultant force acts on
the pallet assembly 124 in
a direction tending to urge the relief pallet 140 and pilot pallet 144 away
from, respectively, the relief
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pallet seat 126 and pilot pallet seat 128. This resultant force against the
pallet assembly 124 is less
than the opposing force generated by the force element 130. At this stage, the
pressure in the
reservoir 150 is equal to the pressure in the atmosphere 138.
[0034] In a second stage, the container pressure has risen to the selected
opening pressure
(also known as the set pressure), and the force on the pallet assembly 124 due
to the pressure in the
container is equal or slightly greater than the force of the force element
130. Set pressure may be set
as or close to the maximum allowable working pressure of the container
relative to the atmosphere
138. The seals of both pallets 140 and 144 are broken and the pallet assembly
124 begins to lift. Gas
begins to flow through the pilot port 156 from the valve body 122 to the
reservoir 150 and through
the relief port 154 from the valve body 122 to the atmosphere 138. The outflow
of gas begins to
relieve the pressure in the valve body 122, container and reservoir 150. Since
the rate of gas flow
through the pilot port 156 out of the valve body 122 to the reservoir 50 is
greater than the outflow of
gas through the equalization port 152 from the reservoir 150 to the atmosphere
138, the pressure
within the reservoir 150 increases.
[0035] In a third stage, the pressure in the reservoir 150 has equalized
with the pressure in
the container. The force against the pilot pressure bearing area 146 caused by
the pressure in the
container drops to almost zero due to the rapid increase in pressure in the
reservoir 150, and the force
generated by the pressure in the reservoir 150 against the pilot pallet 144
rapidly overcomes the force
of the force element 130 and pressure in the container across the pilot
pressure bearing area 146. The
relief valve 120 moves to a fully open position in which the relief port 154
allows gas to flow out of
the container rapidly to relieve the pressure in the container. Gas flows
almost unrestricted out of the
container into the reservoir 150 and slowly leaks through the equalization
port 152 into the
atmosphere 138 but not fast enough to decrease the pressure in the reservoir
150. The fully open
position may be reached when the container pressure is near the set pressure.
[0036] In a fourth stage, as the pressure in the container decreases and
the pressure
differential between the container and atmosphere 138 decreases, so too does
the gas flow out of the
container through the relief port 154. As a result the pallet assembly 124
gradually lowers until it
reseats. The container pressure at which it reseats is the closing pressure
and occurs when the force
due to the stagnation pressure on the relief pallet 140 decreases until it is
equal to the force of the
force element 130 acting on the pallet assembly 124. Gas flow into the
reservoir 150 is gradually
restricted, but this does not significantly affect the pressure in the
reservoir 150 until the pilot pallet
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146 is almost seated since the flow into the atmosphere 138 through the
equalization port 152 is so
small.
[0037] In a fifth stage, the valve 120 has reseated and the container is at
the closing
pressure. There is no flow through the relief port 154 or through the pilot
port 156. Gas flows from
the reservoir 150 into the atmosphere 138 and decreases the pressure of the
reservoir 150 from near
the container pressure and closing pressure to atmospheric pressure. This
increases the sealing force
on the pallet assembly 124, and results in the relief valve 120 being reset to
the same state in the first
stage before it opened. The difference between the opening pressure and
closing pressure
(bloN,vdown) of the valve 120 is non-zero, and may be equal to the ratio of
the pilot pressure bearing
area 146 and the relief pressure bearing area 142.
[0038] In the embodiment of a relief valve shown in Figs. 9 and 10, the
relief valve 220 is a
pressure relief valve. The relief valve 220 comprises a valve body 222, a
pallet assembly 224, a relief
pallet seat 226, a reservoir 250 and a force element 230. The valve body 222
has an interior 232 in
fluid communication with a container (not shown) having a container pressure
and the valve body
222 has an exterior 236 exposed to an atmosphere 238. The pallet assembly 224
has a relief pallet
240 having a relief pressure bearing area 242, a pilot pallet 244 having a
pilot pressure bearing area
246, and a shaft 248 connecting the pilot pallet 244 and relief pallet 240 to
space the pilot pallet 244
from the relief pallet 240. The relief pallet seat 226 extends from the valve
body 222 away from
valve body 222 and is configured to seal against the relief pallet 240 to seal
the valve body 222. The
reservoir 250 is attached to the valve body 222 and separated by the pallet
assembly 224. The
reservoir 250 has a pilot pallet scat 228 configured to seal against the pilot
pallet 244 and an
equalization port 252 to provide a fluid connection between the valve body 222
and the reservoir 250.
The force element 230 connects to and acts on the pallet assembly 224 to
maintain the pallet
assembly 224 in a sealed position against the relief pallet seat 226 and the
pilot pallet seat 228 while
the container pressure is below a selected opening pressure. The pilot
pressure bearing area 246 is
less than the relief pressure bearing area 242 and the pilot pallet 244 and
relief pallet 240 are
configured such that when the container pressure is at or above the selected
opening pressure, the
relief pallet 240 and the relief pallet seat 226 unseal to form a relief port
254 and the pilot pallet 244
and the pilot pallet seat 228 unseal to form a pilot port 256. The pilot port
256 and the equalization
port 252 are configured such that when the container pressure is at or above
the selected opening
pressure, gas flows through the pilot port 256 from the reservoir 250 into the
atmosphere 238 at a
greater rate than through the equalization port 252 from the valve body 222
into the reservoir 250.
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[0039] In a first stage, the relief valve 220 is closed and both the relief
pallet 240 and the
pilot pallet 244 are sealed. The force caused by the pressure in the container
and valve body 222 acts
on both pallets 240 and 244 in opposite directions. Because the pilot pressure
bearing area 246 is
smaller than the relief pressure bearing area 242, the resultant force acts on
the pallet assembly 224 in
a direction tending to urge the relief pallet 240 and pilot pallet 244 away
from, respectively, the relief
pallet seat 226 and pilot pallet seat 228. This resultant force against the
pallet assembly 224 is less
than the opposing force generated by the force element 230. At this stage, the
pressure in the
reservoir 250 is equal to the pressure in the container and valve body 222.
[0040] In a second stage, the container pressure has risen to the selected
opening pressure
(also known as the set pressure), and the force on the pallet assembly 224 due
to the pressure in the
container is equal or slightly greater than the force of the force element
230. Set pressure may be set
as or close to the maximum allowable working pressure of the container
relative to the atmosphere
238. The seals of both pallets 240 and 244 are broken and the pallet assembly
224 begins to lift. Gas
begins to flow through the pilot port 256 from the reservoir 250 to the
atmosphere 238 and from the
valve body 222 to the atmosphere 238 through the relief port 254. The outflow
of gas begins to
relieve the pressure in the valve body 222, container and the reservoir 250.
Since the rate of gas flow
through the pilot port 256 from the reservoir 250 to the atmosphere 238 is
greater than the rate of gas
flow through the equalization port 252 from the valve body 222 to the
reservoir 250, the pressure
within the reservoir 250 decreases.
[0041] In a third stage, the pressure in the reservoir 250 has equalized
with atmospheric
pressure. The force across the pilot pressure bearing area 246 caused by the
gas pressure within the
reservoir 250 drops to almost zero due to the rapid decrease in pressure in
the reservoir 250, and the
force generated by the container pressure against the relief pressure bearing
area 242 rapidly
overcomes the force of the force element 230 and the force of the reservoir
pressure on the pilot
pallet 244. The relief valve 220 moves to the fully open position in which the
relief port 254 allows
gas to flow out of the container to rapidly relieve the pressure in the
container. Gas flows almost
unrestricted between the reservoir 250 and the atmosphere 238 and slowly leaks
from the interior 232
of the valve body 222 through the equalization port 252 into the reservoir 250
but not fast enough to
increase the pressure in the reservoir 250. The fully open position may be
reached when the container
pressure is near the set pressure.
[0042] In a fourth stage, as the pressure in the container decreases and
the pressure
differential between the container and atmosphere 238 decreases, so too does
the gas flow out of the
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container through the relief port 254. As a result the pallet assembly 224
gradually lowers until it
reseats. The container pressure at which it reseats is the closing pressure
and occurs when the force
due to the stagnation pressure on the relief pallet 240 decreases until it is
equal to the force of the
force element 230 acting on the pallet assembly 224. Gas flow into the
reservoir 250 is gradually
restricted, but this does not significantly affect the pressure in the
reservoir 250 until the pilot pallet
256 is almost seated since the flow into the reservoir 250 through the
equalization port 252 is so
small.
[0043] In a fifth stage, the valve 220 has reseated and the container is at
the closing
pressure. There is no flow through the relief port 254 or into the reservoir
250 from atmosphere 238.
Gas flows from the interior 232 of the valve body 222 into the reservoir 250
and raises the pressure
of the reservoir 250 from near atmospheric pressure to the closing pressure.
This increases the sealing
force on the pallet assembly 224, and results in the relief valve 220 being
reset to the same state in
the first stage before it opened. The difference between the opening pressure
and closing pressure
(blowdown) of the valve 220 is non-zero, and may be equal to the ratio of the
pilot pressure bearing
area 246 and the relief pressure bearing area 242.
[0044] In Figs. 9 and 10, a connecting element 260 may also support the
reservoir 250 at a
fixed distance from the valve body 222. As shown in Fig. 9, the equalization
port 252 may be formed
by a channel 258 extending through the shaft 248. As shown Fig. 10, the
equalization port 252 may
be formed by the connecting element 260 which provides a fluid connection
between the valve body
222 and the reservoir 250.
[0045] In each embodiment, the relief pallet 40, 140, 240 may comprise a
relief pallet seal
62, 162, 262 configured to engage with the relief pallet seat 26, 126, 226 and
the pilot pallet 44,144,
244 may comprise a pilot pallet seal 64, 164, 264 configured to engage with
the pilot pallet seat 28,
128, 228.
[0046] In each embodiment, the force element 30, 130, 230 may be a weight
or a biasing
element and may be integral to the pallet assembly 24, 124, 224. For example,
the shaft 48, 148, 248
may be weighted to provide gravitational force to sealingly engage the pilot
pallet 44, 144, 244 and
relief pallet 26, 126, 226 respectively with the pilot pallet seat 64, 164,
264 and the relief pallet seat
26, 126, 226, as in Figs. 1 and 3 - 8. The force element 30, 130, 230 may be a
biasing element 66
such as a spring, shown in Fig. 2. The force element 30, 130, 230 may be
adjusted to change the set
pressure of the relief valve 20, 120, 220.
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CA 02955724 2017-01-23
[0047] An embodiment of a vacuum relief valve of Figs. 1 ¨ 7 may be
combined with a
pressure relief valve to form a pressure and vacuum relief vent which acts to
relieve excess
differential between a container and the atmosphere. The pressure relief valve
may be any one of the
embodiments of a pressure relief valve shown in Figs. 8 ¨ 10 or any other
pressure relief valve. For
example, in Fig. 3, the embodiment of a vacuum valve of Fig. 1 is combined
with a standard pressure
relief valve 68. Similarly, the embodiment of a pressure relief valve of Figs.
8 ¨ 10 may be combined
with a vacuum relief valve, including the embodiment of a vacuum relief of
Figs. 1 ¨ 7, to form a
pressure and vacuum relief valve.
[0048] The relief valve 20, 120, 220 may be used on oilfield storage tanks
to keep the
internal container pressure within a safe range. The atmosphere 38, 138, 238
may be contained within
a fluid receptacle 76, as shown for example in Fig. 11 for relief valve 120
and atmosphere 38. The
relief valve 20, 120, 220 may maintain a prescribed pressure differential
between the container 34
and the fluid receptacle 76. In each of the embodiments, reference to the
valve body 20, 120, 220
being connected to a container 34 may include the valve body 22, 122, 222
being connected to the
headspace 78 of the container 34. For example, the container 34 may be
partially filled with liquid 80
such as oil. The container 34 may be a tank, for example an oil tank. The
container 34 may be a first
compartment of a tank and the fluid receptacle 76 may be a second compartment
of a tank. The relief
valve 20, 120, 220 may be located inline in a pipe system.
[0049] As shown in Fig. 3, relief valve 20 may have a valve inlet/outlet
70. The relief valve
20 may have a weather hood 72 and inlet screen 74 to protect the relief valve
20 from weather
damage and to prevent matter from clogging the valve 20, as shown in Figs 3
and 4. Relief valves
120, 220 may also have a weather hood and inlet screen.
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