Title: Double block valve with proving system
Abstract: A double block valve and a valve proving system are disclosed. The double block valve is actuated by a single actuator and includes a valve body housing a cavity. The cavity defines an upstream portion with a fluid inlet and a downstream portion with a fluid outlet. A seating assembly is interposed between the upstream and the downstream portions. A first and a second blocking element are disposed in the valve body and are both movable within the cavity between opened and closed positions. With the first and second blocking elements both contacting the seating assembly, the space therebetween defines an enclosed space with a finite volume. The proving system is used for two safety shut-off valves on a valve train, such as a double block valve. The proving system connects to an enclosed space established between the two safety shut-off valves and includes a pair of three-way valves, oppositely biased pressure switches, and a pump, all of which are interconnected through pneumatic conduits. The proving system uses pressure accumulation and timed decay to determine the integrity of the two safety shut-off valves of the valve train.
Patent Number: 6,968,851 Issued on 11/29/2005 to Ramirez, et al.
| Inventors:
|
Ramirez; James (Randolph, NJ);
Dorsey; Edward (Randolph, NJ);
Zich; Thomas (Vernon, NJ);
Wagner; Dennis (Newton, NJ)
|
| Assignee:
|
ASCO Controls, L.P. (Florham Park, NJ)
|
| Appl. No.:
|
120899 |
| Filed:
|
April 11, 2002 |
| Current U.S. Class: |
137/1; 137/312; 137/614.19; 137/565.23; 137/557 |
| Intern'l Class: |
F16K 011/20; F16K 037/00 |
| Field of Search: |
73/405 R,46
137/240,312,467.5,614.16,614.17,614.18,614.19,565.01,565.23,551,552,557,1
|
References Cited [Referenced By]
U.S. Patent Documents
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| 4458706 | Jul., 1984 | Scholes.
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| 4587619 | May., 1986 | Converse, III et al.
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| 4798223 | Jan., 1989 | Mitchell et al.
| |
| 4806913 | Feb., 1989 | Schmidt.
| |
| 4825198 | Apr., 1989 | Rolker et al.
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| 4846212 | Jul., 1989 | Scobie et al.
| |
| 4911192 | Mar., 1990 | Hartfiel et al.
| |
| 5165443 | Nov., 1992 | Buchanan.
| |
| 5190068 | Mar., 1993 | Philbin.
| |
| 5267587 | Dec., 1993 | Brown.
| |
| 5307620 | May., 1994 | Hamahira et al.
| |
| 5441070 | Aug., 1995 | Thompson.
| |
| 5621164 | Apr., 1997 | Woodbury et al.
| |
| 5699825 | Dec., 1997 | Norton.
| |
| 5781116 | Jul., 1998 | Hedger et al.
| |
| 5827950 | Oct., 1998 | Woodbury et al.
| |
| 5979488 | Nov., 1999 | Smith et al.
| |
| 6014983 | Jan., 2000 | Sondergaard et al.
| |
| 6128946 | Oct., 2000 | Leon et al.
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| 6134949 | Oct., 2000 | Leon et al.
| |
| 6216726 | Apr., 2001 | Brown et al.
| |
Other References
International Search Report for PCT Application No. PCT/US 02/11365 dated Aug.
28, 2002.
|
Primary Examiner: Lee; Kevin
Attorney, Agent or Firm: Locke Liddell & Sapp, LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority of the Provisional Application No. 60/283,030
filed Apr. 11, 2001.
Claims
1. A system for proving sealing engagement of first and second safety shut-off
valves, the first and second safety shut-off valves establishing a controlled volume
therebetween, the system comprising:
a device for determining or measuring volumetric flow rate;
a pump in fluid communication with the device for determining or measuring volumetric
flow rate;
a first selectable valve having an inlet and first and second outlets, the inlet
connectable to the controlled volume, the first outlet connected to the pump;
a second selectable valve having first and second inlets and an outlet, the first
inlet connected to the pump, the second inlet connected to the second outlet of
the first selectable valve, the outlet in communication with an outlet of the second
safety shut-off valve;
wherein the first selectable valve is selectively operable to communicate the
controlled volume with the device for determining or measuring volumetric flow
rate and the pump or with the second selectable valve, and
wherein the second selectable valve is selectively operable to communicate the
outlet of the second safety shut-off valve with the first selectable valve or with
the device for determining or measuring volumetric flow rate and the pump.
2. The system of claim 1, further comprising control circuitry operating the
first selectable valve, the second selectable valve, the pump, and monitoring the
device for determining or measuring volumetric flow rate.
3. The system of claim 1, wherein the outlet of the second safety shut-off valve
is downstream of the second safety shut-off valve.
4. The system of claim 1, wherein the proving system purges fluid from the controlled
volume to the outlet of the second safety shut-off valve.
5. The system of claim 1, further comprising a second device for determining
or measuring volumetric flow rate, wherein the devices comprise a first pressure
switch biased to attain continuity at a first threshold pressure and a second pressure
switch biased to attain continuity at a second threshold pressure.
6. The system of claim 1, wherein the proving system measures for an accumulation
of pressure in the controlled volume to a first level within a first time interval.
7. The system of claim 6, wherein a first alarm is indicated if the pressure
in the controlled volume accumulates above the first level within the first time interval.
8. The system of claim 1, wherein the pump creates a partial vacuum within the
controlled volume.
9. The system of claim 8, wherein the device for determining or measuring volumetric
flow rate measures for a change in pressure in the controlled volume to a second
level within a second time interval during creation of the partial vacuum.
10. The system of claim 9, wherein a second alarm is indicated if the change
in the pressure in the controlled volume fails to attain the second level within
the second time interval.
11. The system of claim 8, wherein the device for determining or measuring volumetric
flow rate measures for an accumulation of pressure in the controlled volume to
a third level within a third time interval after creation of the partial vacuum.
12. The system of claim 11, wherein a third alarm is indicated if the pressure
in the controlled volume accumulates above the third level within the third time interval.
13. A device for proving sealing engagement of first and second safety shut-off
valves, comprising:
a first port communicating with a finite volume established between the safety
shut-off valves;
a second port communicating with an outlet of the second safety shut-off valve;
a first three-way valve having an inlet connected to the first port and first
and second outlets connected to a bypass conduit and a main conduit, respectively,
the first three-way valve selectively operable to communicate the first port to
either the bypass conduit or the main conduit;
one or more devices for determining or measuring volumetric flow rate, the one
or more devices being connected to the main conduit;
a pump connected to the main conduit and operable to evacuate fluid from the
controlled volume to the outlet of the second safety shut-off valve; and
a second three-way valve having a first inlet connected to the main conduit and
a second inlet connected to the bypass conduit, the second three-way valve selectively
operable to communicate the second port to either the bypass conduit or the main conduit.
14. The device of claim 13, wherein the device couples to a double block valve.
15. The device of claim 14, wherein the outlet is connected to a downstream portion
of the double block valve.
16. The device of claim 13, further comprising control circuitry operating the
first three-way valve, the second three-way valve, and the pump and monitoring
the one or more devices for determining or measuring.
17. The device of claim 13, wherein the one or more devices for determining or
measuring volumetric flow rate comprise a first pressure switch biased to attain
continuity at a first threshold pressure and a second pressure switch biased to
attain continuity at a second threshold pressure.
18. The device of claim 17, wherein the first threshold pressure is a positive
gauge pressure, and wherein the second threshold pressure is a negative gauge pressure.
19. A method for proving sealing engagement of a first safety shut-off valve
and a second safety shut-off valve, comprising the steps of:
a) closing the safety shut-off valves to establish a controlled volume therebetween;
b) purging fluid from the controlled volume;
c) measuring for a first volumetric flow rate within the controlled volume; and
d) indicating a first alarm condition if the first volumetric flow rate exceeds
a first predetermined rate.
20. The method of claim 19, wherein the step (c) comprises the step of measuring
for an accumulation in pressure within the controlled volume to a first pressure
level within a first time interval.
21. The method of claim 19, further comprising:
e) reducing pressure in the controlled volume to a predetermined level;
f) measuring for a second volumetric flow rate within the controlled volume; and
g) indicating a second alarm condition if the second volumetric flow rate in
the controlled volume exceeds a second predetermined rate.
22. The method of claim 21, wherein the step (e) comprises the step of pumping
fluid from the controlled volume to produce a partial vacuum therein.
23. The method of claim 21, wherein the step (f) comprises the step of measuring
for an accumulation of pressure in the controlled volume to a second pressure level
within a second time interval.
24. The method of claim 23, wherein the second alarm condition is indicated if
the pressure of the controlled volume fails to sustain the second pressure level
within the second time interval.
25. The method of claim 21, further comprising the step of:
h) measuring for pressure in the controlled volume to reach a third pressure
level within a third time interval while reducing the pressure in the controlled
volume to the predetermined level in step (e).
26. The method of claim 25, further comprising the step of:
i) indicating a third alarm condition if the pressure in the controlled volume
fails to reach the third pressure level within the third time interval.
Description
FIELD OF THE INVENTION
The present invention relates generally to a double block valve and, more particularly
to a double block valve, wherein the integrity of the valve seals may be tested
by a proving system.
BACKGROUND OF THE INVENTION
Most combustion gas trains are required by national and/or local codes to use
two safety shut-off valves in series on the main line to the burner. Depending
upon the capacity rating, two safety shut-off valves in series may be required
on the pilot line as well. Double block valves have been designed to meet this
requirement by providing two independent sealing members in series in a single
valve body. By eliminating the need for two separate valve bodies, the double block
valve reduces the length of the fuel train and the requisite installation costs.
Additionally, the double block valve eliminates several piping connections, which
incrementally reduces the probability of external leaks. In some prior art double
block valves, the two sealing members of the double block valve have impeded the
fluid flow through the valve body and thus reduced the valves effectiveness. Existing
double block valves may also have a substantial captured volume between the sealing
members, which holds a large amount of gas or liquid when the sealing members are sealed.
Some installations on fuel trains use a double block valve with a vent system
that places a normally open valve between the two sealing members. Any leakage
from the upstream sealing member is vented to the atmosphere. Designing the venting
system may prove to be expensive and may further complicate the proper sealing
of the two sealing members in the double block valve. Furthermore, the venting
system may expel the volatile organic compounds into the atmosphere, which is environmentally undesirable.
The same codes that require two safety shut-off valves on the burner line also
mandate that the safety shut-off valves be tested on a regular basis to insure
the integrity of the internal seals or blocks. The testing is usually performed
manually and involves removing plugs from test ports on the valve body. For example,
if a gaseous fuel is being valved, a combination of manual test cocks, rubber tubing,
and a container filled with solution may be used to check for leakage of the sealing
members in the double block valve. The appearance of gas bubbles in the solution
identifies leakage. The determination of an acceptable leakage rate is often based
upon the operator's judgement of the size and number of bubbles present.
The present invention is directed to an improved double block valve and a proving
system and method, which may be used with first and second safety shut-off valves
or with the improved double block valve.
SUMMARY OF THE INVENTION
One aspect of the present invention provides a double block valve, including
a seating assembly, a first blocking element, and a second blocking element. The
seating assembly is positioned in the valve and defines a fluid passageway communicating
a valve inlet with a valve outlet. The seating assembly includes a first seat interposed
within the fluid passageway and includes a second seat distanced from the first
seat and interposed within the fluid passageway. The first blocking element is
coupled to the actuator and is movable by the actuator out of sealing engagement
with the first seat. The second blocking element is movable by the first assembly
out of sealing engagement with the second seat of the seating assembly. An enclosed
space having a finite volume is established between the first and second blocking
elements when both are sealingly engaged with the seating assembly.
Another aspect of the present invention provides a double block valve operated
by an actuator and including a seating assembly, a first blocking assembly, and
a second blocking assembly. The seating assembly is positioned in the valve and
defines a fluid passageway communicating an upstream portion with a downstream
portion of the valve. The seating assembly includes a first seat on one side of
the assembly exhibited to the upstream portion and circumscribing the fluid passageway.
The seating assembly also includes a second seat on the one side and circumscribing
the first seat. The first blocking assembly includes a first stem coupled to the
actuator and movably disposed in the downstream portion of the valve. The first
stem has a distal end extended through the fluid passageway and into the upstream
portion. The first blocking assembly also includes a first disc attached to the
distal end of the first stem and movable by the actuator out of sealing engagement
with the first seat. The second blocking assembly includes a second stem movably
disposed in the upstream portion of the valve and having a distal end. The second
blocking assembly also includes a second disc connected to the distal end of the
second stem and movable by the first assembly out of sealing engagement with the
second seat. An enclosed space having a finite volume is established between the
first and second discs when engaged with the seating assembly.
Yet another aspect of the present invention provides a double block valve having
integral prove and being operated by an actuator. The double block valve includes
first means for blocking fluid communication from a valve inlet to a valve outlet
and second means for blocking fluid communication from the valve inlet to the valve
outlet. The valve includes means for seating the first and second blocking means.
The valve also includes means for moving the first blocking means with the actuator
out of sealing engagement with the seating means and means for moving the second
blocking means with the first blocking means out of sealing engagement with the
seating means. The valve further includes means for establishing an enclosed space
with a finite volume between the first and second blocking means when sealingly
engaged with the seating means and means for communicating the enclosed space with
a port defined in the valve.
One aspect of the present invention provides a valve proving system for first
and second safety shut-off valves. The proving system includes a first selectable
valve, a second selectable valve, one or more devices for determining or measuring
volumetric flow rate, and a pump. The first selectable valve is in communication
with a controlled volume established between the first and second safety shut-off
valves. The second selectable valve is in communication with an outlet. The one
or more devices for determining or measuring volumetric flow rate are interconnected
between the first and second selectable valves. The pump is interconnected between
the first and second selectable valves and is operable to evacuate fluid from the
controlled volume to the outlet. The first selectable valve is selectively operable
to communicate the controlled volume with the one or more devices and the pump
or with the second selectable valve. The second selectable valve is selectively
operable to communicate the outlet with the first selectable valve or with the
one or more devices and the pump.
Another aspect of the present invention provides a proving device. The proving
device includes a first port, a second port, a first three-way valve, one or more
devices for determining or measuring volumetric flow rate, a pump, and a second
three-way valve. The proving device has a first port communicating with a finite
volume established between a first and a second safety shut-off valve and has a
second port communicating with a outlet. The first three-way valve is selectively
operable to communicate the first port to either a bypass conduit or a main conduit.
The one or more devices for determining or measuring volumetric flow rate are connected
to the main conduit. The pump is connected to the main conduit. The second three-way
valve is selectively operable to communicate the second port to either the bypass
conduit or the main conduit.
Yet another aspect of the present invention provides a method for proving sealing
engagement of a first safety shut-off valve and a second safety shut-off valve.
The method includes the steps of: closing the first and second safety shut-off
valves to establish a controlled volume therebetween; purging fluid from the controlled
volume to an outlet; isolating the controlled volume in communication with a pressure
sensor; measuring for a first volumetric flow rate within the controlled volume
with the pressure sensor; and indicating a first alarm condition if the first volumetric
flow rate exceeds a first predetermined rate. The method also includes reducing
pressure in the controlled volume to a predetermined level; measuring for a second
volumetric flow rate within the controlled volume; and indicating a second alarm
condition if the second volumetric flow rate in the controlled volume exceeds a
second predetermined rate.
The foregoing summary is not intended to summarize each potential embodiment,
or every aspect of the inventions disclosed herein, but merely to summarize the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention, including a preferred embodiment and other aspects, will
be best understood with reference to the detailed description of specific embodiments
of the invention, which follows, when read in conjunction with the accompanying
drawings, in which:
FIG. 1 illustrates a schematic diagram of a double block valve according to
the present invention;
FIG. 2A illustrates an embodiment, in cross-section, of a double block valve
in a closed position;
FIG. 2B illustrates a detail of the double block valve of FIG. 2A in a closed position;
FIG. 3 illustrates the embodiment of the double block valve of FIGS. 2A-B in
an opened position;
FIG. 4 illustrates an embodiment of a flange in frontal view according to the
present invention;
FIG. 5A-B illustrate an embodiment of an automated valve proving device according
to the present invention; and
FIGS. 6A-6E schematically illustrate operation of an automated proving system
according to the present invention.
While the inventions described herein are susceptible to various modifications
and alternative forms, only specific embodiments have been shown by way of example
in the drawings and will be described in detail herein. However, it should be understood
that the inventions are not to be limited to or restricted by the particular forms
disclosed herein.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, a schematic diagram illustrates a normally closed,
double block or double seal valve according to the present invention. The double
block valve includes a valve body 10, a double block assembly 20,
and an actuator 30. The double block valve may also include test ports 80,
82 and/or 84 and a proving device 90.
Depending on the properties of the fluid being controlled, the valve body
10 may be composed of various materials, including metals or composites
known in the art for use with the given system. The valve body 10 houses
a cavity 11. The cavity 11 is divided into an upstream portion 12
with a fluid inlet 14 and a contiguous downstream portion 16 with
a fluid outlet 18. An external connection 15 of the fuel train connects
to the inlet 14 and carries the controlled fluid into the upstream portion
12 of the valve body 10. A second external connection 19 connects
to the outlet 18 and carries the controlled fluid out of the downstream
portion 16 to a device, such as a burner (not shown).
Two, independent safety shut-off valves, referred to herein as the double block
assembly 20, are disposed in the cavity 11 of the valve body 10
between the upstream portion 12 and the downstream portions 16. The
double block assembly 20 provides two "blocks" or safety shut-off valves
for sealing the upstream portion 12 from the downstream portion 16.
In particular, the double block assembly 20 includes a first shut-off valve
or blocking assembly 40, a second shut-off valve or blocking assembly 50,
and a seating assembly 60. To create a double block, the first and second
blocking assemblies 40, 50 contact the seating assembly 60,
which is interposed between the upstream portion 12 and the downstream portion 16.
The first blocking assembly 40 includes a first blocking element 42,
a seal 44, a stem 46, and a biasing member 48. The first blocking
element 42 is positioned on an end of the stem 46. The blocking element
42 and stem 46 construction is moveable between a first, closed and
a second, opened position within the cavity 11. A portion of the stem 46
is disposed in a receiver 47 in the valve body 10, which guides the
first blocking element 42 from the first position to the second position.
The seal 44 is preferably located adjacent to the outer periphery of the
first blocking element 42. The seal 44 creates a seal with a first
seat 64 on the seating assembly 60 when the first blocking element
42 is in the first or closed position. Depending on the properties of the
controlled fluid used in the valve 10, the seal 44 may be composed
of various materials, such as an elastomer, copolymer, metal, or other type of
seal material known in the art for use with the controlled fluid.
The biasing member 48 is disposed about the stem 46, and in the
absence of other forces, the biasing member 48 urges the first blocking
element 42 into sealing engagement with the first seat 64. With the
first blocking element 42 sealingly engaging the first seat 64, the
seal 44 closes off the upstream portion 12 of the cavity 11
from the downstream portion 16 and creates a first block or safety shut-off
valve for the double block valve of the present invention.
The second blocking assembly 50 includes a second blocking element 52,
a seal 54, a second stem 56, and a second biasing member 58.
The second blocking element 52 is positioned on an end of the stem 56.
The blocking element 52 and stem 56 construction is movable between
a first, closed and a second, opened position within the cavity 11. A portion
of the stem 56 is disposed in a sealed receiver 57 in the valve body
10. The stem 56 guides the second blocking element 52 between
the closed and opened positions. The seal 54 is preferably located adjacent
to the outer periphery of the second blocking element 52. The seal 54
creates a seal with the second seat 65 when the second blocking element
52 is in the first or closed position.
The biasing member 58 is disposed about the stem 56, and in the
absence of other forces, the biasing member 58 urges the second blocking
element 52 to sealing engagement with a second seat 65 of the seating
assembly 60. With the second blocking element 52 engaging the second
seat 65, the seal 54 closes off the upstream portion 12 from
the downstream portion 16 and creates a second block or safety shut-off
valve for the double block valve of the present invention. When both the first
blocking element 42 and the second blocking element 52 are closed,
as shown in FIG. 1, an enclosed space 70 of fixed volume is defined therebetween.
The double block valve of the present invention is preferably operated using
a single actuator 30. The actuator 30 may employ a solenoid valve
or a hydraulic, electric, or pneumatic motor, among other devices known in the
art to actuate valves. When activated, the actuator 30 provides a motive
force on the second stem 56, which overcomes the closing force of the biasing
member 58. The actuator 30 moves the second blocking element 52
away from the second seat 65. Consequently, the sealing engagement between
the seal 54 and the seat 65 is broken, and the enclosed space 70
communicates with the downstream portion 16.
With further activation, the distance between the second blocking element 52
and the first blocking element 42 decreases until the second blocking element
52 contacts the first blocking element 42. The actuator 30
overcomes the additional closing force of the first biasing member 48 and
fuel pressure and moves the first blocking element 42 away from the first
seat 64. Therefore, the sealing engagement between the seal 44 and
the seat 64 is also broken. Thereafter, the upstream portion 12 is
in open communication with the downstream portion 16, and fluid may flow
through the valve 10.
In the event that the controlled fluid is a compressible gas, contact between
the first and second blocking elements 42, 52 will be relatively
unhindered by the compressible gas. On the other hand, if the controlled fluid
is an incompressible or viscous liquid, a thin layer of fluid may form between
the first and second blocking elements 42, 52. Essentially, the thin
layer may act as a solid contact between the first and second blocking elements
42, 52. The contact surfaces 43 and 53 of the respective
blocking elements 42, 52 are preferably uniform and may include soft
pads or bumpers if necessary.
The double block valve 10 may include test ports 80, 82,
and 84 for testing the integrity of the seals 44 and 54 within
the double block assembly 20. The test ports 80, 82 and 84
may be used with conventional methods for testing the seals of the double block
valve 10. As such, the double block valve 10 may further include
a manual or automated proving device 90 for testing the integrity of the
seals 44 and 54 within the double block assembly 20.
As noted above, the space between the first and second blocking elements 42,
52 and the seating assembly 60 defines the enclosed space 70.
If the seals 44 and 54 are properly seated, the enclosed space 70
establishes a controlled and fixed volume by which the integrity of the first and
second blocking elements 40 and 50 may be tested independently of
each other. In one embodiment, the device 90 may include an automated proving
system, which monitors changes in volumetric flow rate over a fixed period. The
device 90 may include pressure transducers, pressure switches, valves, pumps,
control circuitry or relays. Because the volume in the enclosed space 70
is fixed and may even be evacuated of fluid to form a vacuum, any positive or negative
changes in pressure can be monitored at pre-set time increments. The increments
may be calculated to check for leakage across the first and second blocking assemblies
40 and 50 at rates that meet current industry requirements. In a
preferred embodiment, the device 90 may include an automated valve proving
system as disclosed herein.
Communicating with the enclosed space 70, a first test port
80 routes from the enclosed space 70 though the valve body 10
and couples to the pressure-testing device 90. The device 90 may
measure the pressure in the enclosed space 70 using a pressure sensor (not
shown) in the device 90. Additionally, the device 90 may purge fluid
from the enclosed space 70 or create a vacuum within the enclosed space
70 using valves and a pump (not shown). A second test port 82 may
communicate the device 90 with the upstream portion 12 of the valve
body 10. Using the second test port 82, the device 90 may
measure the pressure of the controlled fluid in the upstream portion 12
or the differential pressure between the upstream portion 12 and the enclosed
space 70. Similarly, a third test port 84 may communicate the device
90 with the downstream portion 16 of the valve body 10. Using
the third test port 84, the device 90 may measure the pressure of
the controlled fluid in the downstream portion 16, a differential pressure
or purge fluid from the enclosed space 70 to the downstream portion 16.
Turning now to FIG. 2A, an embodiment of a double block valve 100
according to the present invention is illustrated in cross-section. The double
block valve 100 includes a valve body 110, a bonnet 120, and
a double block assembly 130. The valve body 100 is preferably composed
of aluminum and may be used as a double block safety valve for a gas fuel train
to a burner (not shown). The valve body 110 defines a cavity 111
therein. The cavity 111 is divided into an upstream portion 112 with
a fluid inlet 114 and a contiguous downstream portion 116 with a
fluid outlet 118. The bonnet 120 connects to the valve body 110
and encloses the downstream portion 116 of the cavity 111. The removable
bonnet 120 provides for assembly and replacement of the double block assembly
130 within the valve body 110.
The double block assembly 130 is disposed in the cavity 111 of
the valve body 110 between the upstream portion 112 and the downstream
portions 116. The double block assembly 130 provides two blocks for
sealing the upstream portion 112 from the downstream portion 116.
In particular, the double block assembly 130 includes a first blocking element
140, a second blocking element 150, and a seating assembly 160.
Referring concurrently with the detailed illustration in FIG. 2B, the seating
assembly 160 is interposed between the upstream portion 112 and the
downstream portion 116 at a throat 102 in the valve body 110.
The seating assembly 160 preferably defines a removable ring disposed in
the throat 102. The throat 102 includes a widened, annular side 104
accommodating the seating assembly 160 and a ledge 106 for positively
supporting and locating the seating assembly 160 in the throat 102.
The seating assembly 160 includes two annular seats 164, 165
projecting from a first side 161 a of the ring and preferably toward the
inlet portion 112 of the valve 100. The seating assembly 160
also includes a fluid passageway or orifice 166 for fluid to flow therethrough
from the inlet portion 112 to the outlet portion 116.
To hold the seating assembly 160 within the throat 102, a plurality
of balancing stems 122 project from the bonnet 120 and contact the
seating assembly 160 on a second side 161
b. In one embodiment,
three balancing stems 122 are used to hold the seating assembly 160
in the throat 102. Each of the three stems 122 may be spaced approximately
every 120° around the seating assembly 160 to compression fit the seating
assembly 160 within the throat 102.
Seals 162
a-b, preferably O-ring seals, seal the contact of the
seating assembly 160 with the side 104 of the throat 102 such
that the only avenue of fluid communication between the upstream portion 112
and the downstream portion 116 is through the orifice 166. The seals
162
a-b seal the exterior surface of the seating assembly 160
to the throat 102 and further seal an annular passageway or gallery 174
formed around the periphery of the seating assembly 160. The sealed annular
passageway or gallery 174 communicates with a first test port 190
in the valve body 110.
The first blocking element 140 is preferably a first disc with a first
diameter D1. The first disc 140 is mounted on a first stem 144,
which is partially disposed in a receiver 145 in the valve body 110.
A biasing member or spring 146, disposed on the first stem 144, contacts
the first disc 140 and the valve body 110 and provides a closure
force on the first disc 140.
The first disc 140 includes seals 142
a-b to provide a first
block between the upstream portion 112 and the downstream portion 116
of the double block valve 100. The seal 142
a is preferably
a flat, annular seal, while the seal 142
b is preferably an O-ring.
The flat seal 142
a is located on a shelf 143
a around
the perimeter of the first disc 140 for engaging the distal end of the first
seat 164 of the seating assembly 160. The O-ring seal 142
b
is disposed in an annular groove 143
b around the periphery of
a shoulder on the first disc 140 for engaging the inner side of the first
seat 164.
Use of the two seals 142
a-b on the first disc 140 provides
redundant sealing engagement of the disc 140 with the first seat 164
on the seating assembly 160. For the present embodiment of the double block
valve 100 intended for a gas fuel train, the seals 142
a-b are
preferably NITRILE (BUNA-N) seals, which are composed of a copolymer of Butadiene
and Acrylonitrile. NITRILE (BUNA-N) seals typically have a high acrylo-content,
which makes them resistant to petroleum base oils and hydrocarbon fuels over a
temperature range of -40° F. to +250° F. In addition, the seals 162
a-b
discussed above for the seating assembly 160 are also preferably NITRILE
(BUNA-N) seals.
The first disc 140 is movable between a first, closed position and a second,
opened position. As best shown in FIG. 2A, the stem 144, partially disposed
in the receiver 145 in the valve body 110, guides the first disc
140 to the first seat 164. The spring 146, disposed on the
stem 144, urges the disc 140 to the closed position. In the closed
position as shown in FIGS. 2A and 2B, the first disc 140 engages the first
seat 164 and seals the upstream portion 112 from the downstream portion
116. In the absence of contrary forces, the spring 146 urges the
first disc 140 to engage the first seat 164 on the seating assembly
160. Moreover, any fluid pressure in the upstream portion 112 may
additionally urge the first disc 140 against the first seat 164.
With the first disc 140 engaged with the first seat 164, the seals
142
a-b provide a first block and redundant seal to close the upstream
portion 112 from the downstream portion 116.
The second blocking element 150 is adjacent to the first blocking element
140 and defines a second disc with a second diameter D2. The second
diameter D2 is preferably less than the first diameter D1 of the
first disc 140, although such need not be the case. The second disc 150
is mounted on a second stem 154 that axially opposes the first stem 144
of the first disc 140. The second stem 154, partially disposed in
a sealed receiver 124 of the bonnet 120, guides the motion of the
second disc 150 within the valve cavity 111. A second biasing member
or spring 156 is disposed on the stem 154 and provides a closure
force on the second disc 150.
As best shown in FIG. 2B, the second disc 150 includes seals 152
a-b
to provide a second redundant seal between the upstream portion 112
and the downstream portion 116 of the double block assembly 130.
The seal 152
a is preferably a flat, annular seal, while the seal
152
b is preferably an O-ring. The flat seal 152
a is
located on a shelf 153
a around the perimeter of the second disc 150
for engaging the distal end of the first seat 165 of the seating assembly
160. The O-ring 152
b is disposed in an annular groove 153
b
on a shoulder around the periphery of the second disc 150 for engaging
the inner side of the second seat 165. As before, the seals 152
a-b
are preferably NITRILE (BUNA-N) seals.
The second disc 150 is also movable between a first, closed position and
a second, opened position. In the closed position as shown in FIGS. 2A and 2B,
the second disc 150 engages a second seat 165 on the seating assembly
160 and seals the upstream portion 112 from the downstream portion
116. In the absence of other forces, the spring 156 urges the second
disc 150 to engage the second seat 165. With the second disc 150
engaged with the second seat 165, the seals 152
a-b provide
a second block and redundant seal to close the upstream portion 112 from
the downstream portion 116.
In the closed position, the first and second discs 140, 150 engage
the first and second seats 164, 165 respectively by the closure forces
of the springs 146, 156. Each disc 140 or 150 prohibits
fluid from passing from the upstream portion 112 to the downstream portion
116. In general, the pressure in the downstream portion 116 is less
than the upstream portion 112. The pressure differential for the present
embodiment may be up to 25 psi. Consequently, the pressure differential on the
sides of the first disc 140 may further urge the first disc 140 to
seal on the first seat 164. If the seals 142
a-b fail, fluid
may enter the enclosed space 170, causing pressure to rise in the enclosed
space 170. The increased pressure may additionally urge the second disc
150 against the second seat 165, further ensuring a secure seal of
the double block valve 100.
To provide representative dimensions for the present embodiment, the first diameter
D1 of the first disc 140 may be approximately 2.7 inches with the
shelf 143
a defining a further diameter of approximately 2.9 inches.
The second diameter D2 of the second disc 150 may be approximately
2.2 inches with the shelf 153
a defining a further diameter of approximately
2.4 inches. The relative thickness of both discs 140, 150 may be
approximately 0.40 inches. The seating assembly 160 may provide a diameter
of 2.25 inches for the fluid passageway or orifice 166. The discs 140,
150 and the seating assembly 160 may all be composed of aluminum,
while the stems 144, 154 may be composed of stainless steel.
When the first disc 140 and the second disc 150 are closed, as
shown in FIG. 2A-B, the first disc 140 is at a fixed distance from the second
disc 150. The finite distance between the discs 140, 150 may
be approximately 0.06 inches. The finite distance preferably establishes a required
separation, whereby the valve meets code requirements as two safety shut-off valves
in series within a single valve body. The space contained by the discs 140,
150 and the seating assembly 160 defines an enclosed space 170.
In the present embodiment, the enclosed space 170 may have a volume of approximately
15 cc.
As best shown in FIG. 2B, a pathway 172 in the seating assembly 160
communicates the enclosed space 170 to the sealed annular passageway or
gallery 174. The pathway 172 may be a 1/16
th-inch hole
made in the seating assembly 160. As noted above, the O-ring seals 162
a-b
seal the contact of the seating assembly 160 with the side 104
of the throat 102 so that the annular passageway or gallery 174 formed
around the periphery of the seating assembly 160 is also sealed. In this
way, when assembling or replacing the seating assembly 160 within the valve
body 110, the pathway 172 need not be aligned with the test port
190 to allow fluid communication between the enclosed space 170 and
the test port 190. Fluid pressure within the enclosed space 170,
if any, may be communicated through the pathway 172 and into the sealed
annular passageway or gallery 174. The annular passageway or gallery 174
may then communicate fluid or pressure to the test port 190.
If the seals 142
a-b, 152
a-b and 162
a-b are
properly seated, the enclosed space 170 establishes a controlled and fixed
volume. Communicating with the enclosed space 170, the first test port 190
routes though the valve body 110 to the outside of the valve 100.
The entire route of the first test port 190 is not shown in FIG. 2A. A second
test port (not shown) may communicate the upstream portion 112 to the outside
of the valve 100, and a third test port (not shown) may communicate the
downstream portion 116 to the outside of the double block valve 100.
The test ports allow for individually testing and verifying the integrity of the
seals 142
a-b, 152
a-b and 162
a-b. A device
(not shown) may couple to one or more of the test ports to test the integrity of
the seals 142
a-b, 152
a-b, and 162
a-b.
The device may be a manual device or an automated device, which monitors changes
in volumetric flow rate or pressure drop over a fixed period. The device may include
pressure transducers, pressure switches, valves, pumps, control circuitry or relays.
Because the volume in the enclosed space 170 is fixed and may even be evacuated
of fluid to form a vacuum, any positive or negative changes in pressure can be
monitored at pre-set time increments. The increments may be calculated to check
for leakage across the first and second blocking elements 140 and 150
at rates that meet current industry requirements. In a preferred embodiment, the
device may include an automated proving system as disclosed herein.
To move the first disc 140 and the second disc 150 between open
and closed positions, the present invention uses a single actuator (not shown).
The actuator may be a solenoid valve, motor, or other device known in the art for
actuating a valve. The actuator contacts a coupling end 155 of the second
stem 154. When activated, the actuator provides an axial, motive force on
the second stem 154. The spring 156 is compressed and the second
disc 150 is dislocated from the second seat 165. Consequently, the
seals 152
a-b are broken and the enclosed space 170 communicates
with the downstream portion 116. If a small amount of fluid is contained
within the enclosed space 170, it will escape into the downstream portion
116 without significant effect. If a vacuum is contained, the enclosed space
170 will equalize pressure with the downstream portion 116.
With further axial motion, the distance between the second disc 150 and
the first disc 140 decreases until the second disc 150 contacts the
first disc 140. In the event that the valve is used with a compressible
gas, contact between the first and second discs will be relatively unhindered by
the controlled fluid. On the other hand, if the valve 100 is used with an
incompressible or viscous liquid, a thin layer of liquid may form between the first
and second discs 140, 150 when they contact. Essentially, the thin
layer may act as a solid contact between the first and second discs 140,
150. The contact surfaces 141 and 151 of the respective discs
140, 150 are preferably uniform and may include soft pads or bumpers
if necessary.
Turning now to FIG. 3, the embodiment of the double block valve 100
of FIGS. 2A and 2B is illustrated in an opened position. The actuator (not shown)
has forced the second disc 150 against the first disc 140 and has
overcome the biasing of the first spring 146. The first spring 146
has compressed, and the first disc 140 has dislocated from the first seat
164. Therefore, the seals 142
a-b have also been broken and
the upstream portion 112 may communicate with the downstream portion 116.
With further axial motion by the actuator, the contacting discs 140 and
150 have positioned further into the upstream portion 112.
In this open position, any fluid in the upstream portion 112 may pass by
the contacting discs 140, 150, pass through the orifice 166,
and enter the downstream portion 116. With the first and second discs 140,
150 moved significantly from the orifice 166, the fluid is relatively
unhindered and may flow through the orifice 166 without significant resistance
from the discs 140 and 150.
When the axial force of the actuator is removed, the energy stored in the springs
146, 156 returns both discs 140, 150 to the closed
position. The first and second discs 140, 150 preferably move in
tandem with one another within the cavity 111, until the first disc 140
contacts the first seat 164. The O-ring seal 142
b on the first
disc 140 engages the inner surface of the first seat 164 and stops
the flow of fluid through the orifice 166. The first disc 140 continues
to travel until the flat seal 142
a engages the distal end of the
first seat 164. Consequently, the first disc 140 forms a redundant
seal against the first seat 164 and creates the first block of the double
block valve 100.
Prior to complete sealing engagement of the first disc 140 with the
first seat 164, the second disc 150 has yet to seal against the seating
assembly 160. Any fluid beyond the first disc 140 may escape to the
downstream portion 116. Consequently, a pressure differential is established
across the first disc 140. The pressure on the upstream side of the first
disc 140 may be up to 25 psi above ambient, while the pressure on the enclosed
space side of the disc 140 may be at the ambient pressure of the downstream
portion 116. The second disc 150 passes the finite distance between
the first and second seats 164, 165. Immediately, the O-ring seal
152
b on the second disc 150 engages the inner surface of the
second seat 165. The flat seal 152
a then engages the distal
end of the second seal 165. Consequently, the second disc 150 forms
another redundant seal against the second seat 165 and creates the second
block of the double block valve 100. Closure of the first and second discs
140, 150 is made independently of each other as the stems 144
and 154 are not connected and each disc 140, 150 is biased
by separate springs 146, 156.
If a controlled deactivation of the actuator is used to close the valve 100,
the closing of the first and second discs 140, 150 may be controlled.
Controlled closing by the actuator may insure that the first disc 140 contacts
the first seat 164 before the second disc 150 contacts the second
seat 165. On the other hand, the springs 146 and 156 may have
disparate spring constants. In the event of power failure or the immediate release
of motive force from the actuator, the first spring 146 may, for example,
return the first disc 140 to the closed position at a greater rate of return
than the second spring 156 returns the disc 150 to the closed position.
An external flange 180 connects to the valve body 110 at the inlet
114, and another external flange 180′ connects to the valve
body 110 at the outlet 118. The flanges 180-180′
provide the needed interface to connect the valve body 110 to external piping
(not shown) of the fuel train. The flanges 180, 180′ are symmetrical
and bolt on the sides of the valve body 110. The flanges 180, 180′
are further sealed to the valve body 110 with O-rings seals 182, 182′.
Referring to FIG. 4, an embodiment of a flange 180 is illustrated
in frontal view. The flange 180 is substantially square and defines an orifice
181 therein for the connection to piping (not shown). An annular well 183
for receiving an O-ring seal (not shown) circumscribes the orifice 181.
One edge 184
a of the flange 180 contains two, slotted mounting
holes 186
a-b. The opposing edge 184
b also contains
two, slotted mounting holes 186
c-d. Bolts (not shown) are used to
attach the symmetrical flange 180 to the side of the valve body (not shown).
The symmetry of the flange 180 and the orientation of the slotted mounting
holes 186
a-d at opposing quadrants allows the flange 180 to
be installed either horizontally or vertically to the valve body. In this way,
the flange 180 greatly simplifies the effort required to connect or disconnect
the valve body to the fuel train. In particular, the valve body may be unbolted
from the flange 180 and removed from the fuel train without disconnecting
the external piping from the flange 180. Additionally, the valve body may
be installed in or removed from the fuel train either vertically or horizontally,
which provides for easy installation, removal, or replacement of the valve body
in the field.
Referring to FIG. 5A, an embodiment of an automated proving device 200
is illustrated in cross-section. In the discussion following herein, the device
200 may be used in conjunction with two independent safety shut-off valves
on a fuel train or with a double block valve on the fuel train. It is particularly
advantageous to use the device 200 with the embodiment of a double block
valve as described above. As such, the device 200 may mount directly to
the valve body of a double block valve as embodied herein. The device 200
may connect to the test ports for the upstream portion, the downstream portion,
and the enclosed space of the double block valve as embodied in FIGS. 1-3.
The device 200 includes an enclosure 202, a cover 204, and
watertight connectors 206, 206′. The enclosure 202
pad mounts to the outside of a valve body VB with a plurality of mounting bolts
203, and the cover 204 attaches to the enclosure 202. The
watertight connectors 206, 206′ are conduits into the enclosure
202 for the passage of wires (not shown). The enclosure 202 and cover
204 are further sealed with O-ring seals 205.
The enclosure 202 contains an automated valve proving system 210.
The valve proving system 210 is used for proving the individual integrity
of the seals for the safety shut-off valves on the fuel train. The valve proving
system 210 includes control circuitry 220 and a fluid module 230.
The control circuitry 220 may include a microprocessor, relays, or timing
circuits, among other electronics for controlling the automated valve proving system
210. The control circuitry 220 mounts to a PC board assessable with
the removal of the cover 204 and may have a terminal connector 222
and a regulated power supply. In addition, a double-pole, single-throw start-up
relay (not shown) may be provided to interface with a monitoring system (not shown)
for the main burner flame.
The fluid module 230 may be a hydraulic or pneumatic module. The fluid
module 230 includes a miniature vacuum pump P, a pair of three-way solenoid
valves V3 and VX, and two pressure sensors SW1 and SW2. The
pressure sensors SW1, SW2 may be pressure switches or transducers.
Turning to FIG. 5B, a bottom view of the device 200 is illustrated.
The bottom of the enclosure 202 includes ports 209
a-c for
connecting to test ports (not shown) on the outside of the double block valve (not
shown). The enclosure 202 also includes the mounting holes 207
a-d
and the larger bolt holes 207
e-f. The corner port 209
a
is designated for communicating with the enclosed space of the double block
valve. The adjacent port 209
b is designated for communicating with
the downstream portion of the double block valve, and the adjacent port 209
c
is designated for communicating with the upstream portion of the double block valve.
The ports 209
a-c are arranged with respect to the mounting holes
207
a-d and the bolt holes 207
e-f so that the pressure-testing
device 200 of FIGS. 5A-B may be mounted on either side of the double block
valve. Furthermore, the arrangement insures that the ports 209
a-c properly
connect with the test ports on the valve so that the pressure testing device 200
may not be improperly connected to the test ports of the valve.
Referring to FIGS. 6A-6E, operation of an automated valve proving system
210 is schematically illustrated according to the present invention. In
the discussion following herein, the automated valve proving system 210
may be used in conjunction with two independent safety shut-off valves on a fuel
train or with a double block valve on the fuel train. It is particularly advantageous
to use the automated valve proving system 210 with the embodiment of a double
block valve as described above. It is further advantageous to use the automated
valve proving system 210 with the proving device embodied in FIGS. 5A-B above.
In FIGS. 6A-6F, the proving system 210 connects to a valve train 300.
The valve train 300 couples a feed line 302 to a burner line 304.
The feed line 302 brings fluid fuel from a source (not shown), which may
be at pressure of 0 to 25 psi above ambient, to the valve train 300. The
burner line 304 carries the fluid fuel from the valve train 300 to
a burner (not shown), which may be at ambient pressure of approximately 14.7 psia.
In general, the valve train 300 may include two, separate safety shut-off
valves V1 and V2 having a connection, such as a pipe, between them
that establishes a controlled volume CV. In the present embodiment, however, the
valve train 300 may define a double block valve as disclosed herein. In
such an implementation, the safety shut-off valve V1 defines a first blocking
assembly; the safety shut-off valve V2 defines a second blocking assembly;
and the controlled volume CV defines an enclosed space established between the
first and second blocking assemblies.
For the purposes of simplicity, representative values are provided below relating
specifically to the use of the proving system 210 with the double block
valve embodied i
