U.S. patent application number 09/944223 was filed with the patent office on 2002-03-14 for pressure relief valve monitoring device.
This patent application is currently assigned to Anderson Greenwood, LP. Invention is credited to Friend, Ronald George, Jones, Michael Allen.
Application Number | 20020029808 09/944223 |
Document ID | / |
Family ID | 26768854 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020029808 |
Kind Code |
A1 |
Friend, Ronald George ; et
al. |
March 14, 2002 |
Pressure relief valve monitoring device
Abstract
A pressure relief valve monitoring device is provided. The
monitoring device includes a sensor input module located proximate
to a pressure relief valve, a microcontroller located within the
sensor input module, and a real time clock/calendar also located
within the sensor input module. The monitoring device also includes
a number of sensors, including (1) a position sensor mounted on the
pressure relief valve for measuring the position of the valve's
closure element relative to the inlet nozzle seat and for
generating a lift signal representative of such position; (2) a
pressure sensor mounted on the pressure relief valve for measuring
the pressure of the pressure system and generating a pressure
signal representative of such pressure; and (3) a leakage sensor
mounted on the pressure relief valve and positioned in close
proximity to the inlet nozzle seat and capable of detecting noise
generated by leakage of fluid between the inlet nozzle seat and the
closure element when the closure element is engaged with the inlet
nozzle seat. The microcontroller is configured to receive and store
signals from any or all of the three sensors and correlate the
receipt thereof with an indication of time from the real time
clock/calendar to determine certain characteristics of valve
performance. A method for monitoring the operation of the pressure
relief valve is also provided.
Inventors: |
Friend, Ronald George;
(Franklin, MA) ; Jones, Michael Allen; (Bristol,
RI) |
Correspondence
Address: |
William M. Merone
KENYON & KENYON
Suite 700
1500 K Street, N.W.
Washington
DC
20005
US
|
Assignee: |
Anderson Greenwood, LP
Wrentham
MA
|
Family ID: |
26768854 |
Appl. No.: |
09/944223 |
Filed: |
September 4, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09944223 |
Sep 4, 2001 |
|
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|
09285268 |
Apr 2, 1999 |
|
|
|
6283138 |
|
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|
60083021 |
Apr 24, 1998 |
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Current U.S.
Class: |
137/551 |
Current CPC
Class: |
Y10T 137/7745 20150401;
F16K 37/0083 20130101; F16K 17/06 20130101; Y10T 137/8208 20150401;
Y10T 137/8242 20150401; F16K 37/0091 20130101; Y10T 137/0396
20150401; Y10T 137/8175 20150401; Y10T 137/7738 20150401; Y10T
137/8158 20150401 |
Class at
Publication: |
137/551 |
International
Class: |
F16K 037/00 |
Claims
We claim:
1. An apparatus for monitoring the operation of a pressure relief
valve having a closure element engageable with a nozzle to block
flow of fluid through the pressure relief valve, comprising: a. a
sensor input module including a microcontroller and a real time
clock/calendar, said sensor input module located proximate to the
pressure relief valve; b. a leakage sensor for detecting leakage of
fluid between the nozzle and the closure element and generating a
leakage signal, said leakage sensor located proximate to the
pressure relief valve and proximate to the nozzle; and c. said
microcontroller configured to receive said leakage signal and
correlate the receipt thereof with an indication of time from said
clock/calendar.
2. The invention according to claim 1 wherein said leakage sensor
detects noise generated by leakage of fluid between the nozzle and
the closure element.
3. The invention according to claim 1 wherein said leakage sensor
is an acoustic sensor.
4. The invention according to claim 1 wherein said leakage sensor
is a piezo electric crystal.
5. An apparatus for monitoring the operation of a pressure relief
valve having a closure element engageable with a nozzle to block
flow of fluid through the pressure relief valve, comprising: a
leakage sensor for detecting noise generated by leakage of fluid
between the nozzle and the closure element; said leakage sensor
located proximate to the pressure relief valve and proximate to the
nozzle.
6. An apparatus for monitoring the operation of a pressure relief
valve having a closure element engageable with a nozzle to block
flow of fluid through the pressure relief valve, comprising: means
mounted on the pressure relief valve for detecting unstable
operation of the pressure relief valve.
7. A method for monitoring the operation of a pressure relief valve
having a closure element in sealing engagement with a nozzle for
blocking flow of fluid through the pressure relief valve, the
pressure relief valve being located proximate to a sensor input
module and to a leakage sensor, said method comprising the steps
of: a. detecting noise generated by leakage of fluid between the
closure element and the nozzle using said leakage sensor; b.
generating a leakage signal in response to said noise; and c.
communicating said leakage signal to said sensor input module.
8. The method as recited in claim 7, wherein said sensor input
module has a microcontroller and a real time clock/calendar, said
method further comprising the steps of: generating an indication of
time using said real time clock/calendar; and correlating the
receipt of said leakage signal with said indication of time using
said microcontroller.
9. The method as recited in claim 7, further comprising the step
of: generating an indication of time using a real time
clock/calendar; and storing said leakage signal as a function of
time in said sensor input module.
10. The method as recited in claim 7, further comprising the step
of: communicating said leakage signal to an enunciating device to
activate an alarm.
11. The method as recited in claim 7, further comprising the step
of: communicating said leakage signal to a process controller to
activate an alarm.
12. The method as recited in claim 7, further comprising the step
of: detecting noise having a characteristic frequency of the fluid
leaking between the closure element and the nozzle.
Description
[0001] This Application is a continuation of application Ser. No.
09/285,268 filed Apr. 2, 1999, U.S. Pat. No. 6,283,138. This
application also claims the benefit of U.S. Provisional Application
No. 60/083,021, filed Apr. 24, 1998.
FIELD OF INVENTION
[0002] The present invention relates to pressure relief devices,
and more particularly to devices for monitoring their
performance.
BACKGROUND OF THE INVENTION
[0003] Pressure lines (e.g., pressure vessels and piping systems)
are often designed with pressure relief valves located at various
locations to protect the pressure line from excess overpressure.
The pressure relief valves are self-actuated devices set to open
when the pressure in the pressure line exceeds a specified level.
When the pressure in the pressure line exceeds the pressure at
which the pressure relief valve is set to open, the closure element
of the pressure relief valve moves away from the inlet nozzle seat
and fluid is allowed to flow out of the pressure line and through
the pressure relief valve. This flow of fluid will continue at a
sufficient rate to prevent the pressure in the pressure line from
rising above a predetermined level or above a specified
overpressure. When the pressure in the pressure line is reduced to
a level below the pressure at which the pressure relief valve is
set to open, the closure element in the pressure relief valve will
return to its closed position, i.e. into contact with the inlet
nozzle seat, preventing additional flow from the pressure line.
Under normal operating conditions, the closure element of the
pressure relief valve is in the closed position.
[0004] Prior art monitoring devices used in these pressure lines
typically employ position transducers mounted on the pressure
relief valve to sense the position of the closure element. These
position transducers transmit analog signals indicating the
position of the closure element with respect to the inlet nozzle.
These devices, however, do not store this information and apply the
information to determine operating characteristics of the pressure
relief valve, such as total flow through the pressure relief valve
during a specified time interval when the pressure relief valve is
open.
[0005] Moreover, in the prior art the presence of leakage flow past
the closure element of a pressure relief valve (i.e., flow past the
closure element when the closure element is in the closed position)
could only be determined by physically examining the valve in its
installed position, removing the valve from its installed position,
and performing a seat leakage test on a test stand, or by isolating
the valve (through the use of appropriate valving) in its installed
position, but not in active service, and performing a seat leakage
test in situ. Such techniques for determining the presence of seat
leakage, however, do not allow for continuous monitoring to detect
seat leakage past the closure element while the pressure relief
valve is both installed and in service.
[0006] In addition, unstable operation of pressure relief valves,
i.e. rapid opening and closing of the closure element, can occur
when the system pressure rises just to or slightly above the set
pressure and then drops, as a result of fluid flowing from the
system through the pressure relief valve, as soon as the closure
element lifts off the seat permitting the spring to immediately
seat the closure element. Such unstable operation, however, can
cause physical damage to components of the pressure relief valve.
It is therefore desirable to know when such unstable operation
occurs so that corrective action may be taken. The prior art
practice has been for personnel to listen for the noise, often
referred to as "valve chatter," generated by the closure element
being rapidly and repeatedly forced against its seat. This
practice, however, is ineffective if no personnel are near the
valve at the time the unstable operation occurs or if the location
of the valve is beyond earshot of attending personnel.
SUMMARY OF THE INVENTION
[0007] In light of the above, a pressure relief valve monitoring
device is provided. The monitoring device includes a sensor input
module located proximate to a pressure relief valve, a
microcontroller located within the sensor input module, and a real
time clock/calendar also located within the sensor input module.
The monitoring device also includes a number of sensors, including
(1) a position sensor mounted on the pressure relief valve for
measuring the position of the valve's closure element relative to
the inlet nozzle seat and for generating a lift signal
representative of such position; (2) a pressure sensor mounted on
the pressure relief valve for measuring the pressure of the
pressure system and generating a pressure signal representative of
such pressure; and (3) a leakage sensor mounted on the pressure
relief valve and positioned in close proximity to the inlet nozzle
seat and capable of detecting noise generated by leakage of fluid
between the inlet nozzle seat and the closure element when the
closure element is engaged with the inlet nozzle seat. The
microcontroller is configured to receive and store signals from any
or all of the three sensors and correlate the receipt thereof with
an indication of time from the real time clock/calendar to
determine certain characteristics of valve performance. A method
for monitoring the operation of the pressure relief valve is also
provided.
[0008] The present invention provides a monitoring device mounted
on or near a pressure relief valve and which will continuously
monitor the performance of the pressure relief valve while the
valve is in active service. The monitoring device will also convert
analog signals received from sensors attached to the valve into
digital format, will store the digital information, will detect
leakage flow through the pressure relief valve while the valve is
in active service, will calculate fluid mass flow through the
pressure relief valve when the valve is open and allowing fluid to
flow from the pressure line, will detect and warn of unstable
operation of the pressure relief valve, and will communicate with a
host computer to transmit the information stored by the valve
monitoring device and receive information regarding that particular
valve from the host computer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing objects and other attributes of this
invention, and the attendant advantages thereof, may be more fully
understood from the following description when read together with
the accompanying drawings in which:
[0010] FIG. 1 is a view of a typical pressure relief valve, shown
in vertical section, with a valve monitoring device according to
the present invention attached thereto;
[0011] FIG. 1a is an enlarged view of a portion of the pressure
relief valve shown in FIG. 1;
[0012] FIG. 1b is a view of the pressure relief valve shown in FIG.
la showing the valve in an open position;
[0013] FIG. 2 is a view similar to FIG. 1, but showing two pressure
relief valves with the valve monitoring devices connected to a host
computer; and
[0014] FIG. 3 is a schematic block diagram of the circuitry
incorporated into each valve monitoring device.
DETAILED DESCRIPTION
[0015] FIG. 1 shows a preferred embodiment of the pressure relief
valve monitoring device, indicated generally at 8, according to the
present invention. As shown, this embodiment includes a sensor
input module or SIM 10 which is connected to and receives analog
signals from a position sensor 12, a leakage sensor 14, and a
pressure sensor 15, all mounted on a pressure relief valve 13. The
pressure relief valve 13 includes an inlet nozzle 20 with an inlet
nozzle seat 25 connected in fluid communication with a pressure
system 18, and a closure element 16 which contacts the inlet nozzle
seat 25 when the pressure relief valve 13 is closed and which is
able to move away from the inlet nozzle seat 25 to allow fluid from
the pressure system 18 to flow through the nozzle 20, with a
compression spring 21 controlling the position of the closure
element 16 by opposing the force of the pressure acting on the
closure element 16. A housing 22 supports and contains the
aforementioned valve components. A spindle 17 extends through the
housing 22 and is held by the spring 21 against, and thus exactly
replicates the movement of, the closure element 16.
[0016] An enlarged view of the area of the pressure relief valve 13
where the closure element 16 contacts the nozzle seat 25 when the
valve 13 is closed is shown in FIG. 1a. With reference to FIG. 1a,
the portion of the closure element 16 that comes into contact with
the inlet nozzle 20 at the inlet nozzle seat 25 (i.e., the surface
of the closure element 16 where contact occurs) may be identified
as the closure element seat 16a. Similarly, the portion of the
inlet nozzle 20 that comes into contact with the closure element 16
(or, more specifically, with the closure element seat 16a of the
closure element 16) may be identified as the inlet nozzle seat 25.
Both the closure element seat 16a and the inlet nozzle seat 25 (and
their interaction) may be more clearly seen with reference to FIG.
1b, which shows the section of the pressure relief valve 13 shown
in FIG. 1a except that in FIG. 1b the valve 13 is open.
[0017] Referring again to FIG. 1, the pressure relief valve 13 is
designed to protect the pressure system 18 from excess pressure.
The spring 21 is pre-compressed and applies a force which holds the
closure element 16 in contact with the nozzle seat 25. In this
position, the closure element 16 forms a seal with the nozzle seat
25 and thus prevents fluid from the pressure system 18 from flowing
through the nozzle 20. Pressure in the pressure system 18 acts upon
the closure element 16 creating a force which opposes the spring
force. When pressure in the pressure system 18 reaches a
predetermined level, i.e. the set pressure of the pressure relief
valve 13, the force of the pressure acting on the closure element
16 overcomes the force exerted by the pre-compressed spring 21,
thus permitting the closure element 16 to move away from the nozzle
seat 25 to allow fluid to flow out of the pressure system 18,
through the nozzle 20, past the closure element 16, and out of the
pressure relief valve 13. The flow of fluid out of the pressure
system 18 prevents pressure in the pressure system 18 from
increasing above an allowable level above the set pressure.
[0018] A lift or position sensor 12, which preferably is a high
impedance variable resistor (or other means of indicating lift)
such as a 50 k Ohm potentiometer sold by Betatronix, Inc., is in
contact with the spindle 17 which moves with the closure element
16. The resistance generated by the position sensor 12 is an
indication of the position of the closure element 16. This position
information is transmitted to the sensor input module 10. When the
closure element 16 moves, the change in resistance of the sensor 12
indicates a change in the position of the closure element 16 and
the magnitude of that change, which information is stored in the
sensor input module 10 as a function of real time--i.e., the time
at which movement of the position sensor 12 occurred, the extent of
that movement, and the elapsed time the closure element 16 remained
in that position are recorded. The information so recorded, along
with corresponding information from the pressure sensor 15, permits
a determination of the quantity or mass of fluid that has escaped
through the pressure relief valve 13 under critical flow conditions
when the fluid is compressible. When the fluid flow through the
pressure relief valve is compressible and subcritical, both the
inlet and the outlet pressure may be used to determine the total
mass flow. When the fluid flow through the pressure relief valve is
noncompressible, the differential pressure between the inlet and
outlet may be used to determine the total mass flow. The pressure
sensor 15, which preferably is a thin film strain gauge such as
sold by Strain Measurement Devices, Inc., is connected to the inlet
pressure line 18 and provides a signal which is representative of
the magnitude of the pressure in the pressure line 18. This
pressure signal is transmitted to the sensor input module 10, where
it is recorded in relation to real time.
[0019] Additional sensors may be provided which measure outlet
pressure, differential pressure, fluid or ambient temperature, or
other parameters. Information from such additional sensors may
also, in a similar manner, be transmitted to and stored in the
sensor input module 10.
[0020] When the magnitude of the pressure in the inlet pressure
line 18 is reduced to a specified level below the opening pressure
of the pressure relief valve 13, the force of the spring 21
overcomes the pressure force on the closure element 16 and the
closure element 16 moves back into contact with the nozzle seat 25
stopping further flow of fluid from the inlet pressure line 18.
When the closure element 16 comes in contact with the nozzle seat
25, movement of the closure element 16 ceases. When this occurs,
storage of additional inlet pressure data and closure element
position data in the sensor input module 10 may be
discontinued.
[0021] Under normal operating conditions, the closure element 16
remains in contact with the nozzle seat 25. This is the closed
position of the pressure relief valve 13. While there should be no
flow past the closure element when the closure element 16 is in its
closed position, such "leakage flow" can occur and it is often
important to know when it does. A leakage sensor 14, preferably a
piezo electric crystal, such as that sold by Massa Products Corp.,
is attached to the housing 22 of the pressure relief valve 13 and
protrudes through the housing 22 in close proximity to the
interface between the inlet nozzle seat 25 and the closure element
16. When the closure element 16 is not in perfect sealing
engagement with the nozzle seat 25, or when either the closure
element seat 16a or the inlet nozzle seat 25 is damaged, or when
solid particles are present on the nozzle seat 25 or on the closure
element seat 16a, there may be leakage flow between the closure
element seat 16a and the inlet nozzle seat 25. Such leakage creates
a noise having a characteristic frequency, which frequency is a
function of the fluid within the system. The leakage sensor 14 is
capable of detecting noises in this range of frequencies and, upon
detection, sends a signal to the sensor input module 10 indicating
the presence of leakage flow. This signal, as a function of time,
is stored in the sensor input module 10. This signal may also be
transmitted from the sensor input module 10 to an enunciating
device or to a process controller to activate an alarm indicating
the presence of leakage flow in the pressure relief valve 13 in
installations where the device is connected to such a network.
[0022] As shown in FIG. 3, which represents a preferred
arrangement, the circuitry incorporated into the SIM 10 is provided
with a microcontroller 30, such as Phillips 80CL 580. This
particular microcontroller has integrated analog to digital (A/D)
conversion capability, but a microcontroller without such
capability may be used if separate A/D conversion is provided. Each
of the sensors 12, 14, and 15 is connected to the microcontroller
30 through a signal conditioner 32, which amplifies and conditions
the signals from their respective sensors for A/D conversion by the
microcontroller 30, which signals are representative of the
magnitude of the parameter being measured by each of the sensors
12, 14, and 15. A real time clock/calendar 34 is also connected to
the microcontroller 30 to provide an accurate indication of the
time the signals are generated by each of the sensors 12, 14, and
15. The input connections for each sensor also provide power to the
respective sensors 12 and 15.
[0023] The digital signals so generated are correlated with the
data from the clock/calendar 34 by the microcontroller 30 and
stored in on-board random access memory (RAM) 36. The
microcontroller 30 also converts the digital information into
readable information for display on any suitable readout device,
such as a liquid crystal display (LCD) 38, provided on the valve
monitoring device 8. The microcontroller 30 will generate messages
for display on the readout device which (i) indicate leakage flow
through the pressure relief valve 13 has or is occurring, (ii) warn
of unstable operation whenever the opening and closing of the
closure element 16 in a given time interval exceeds a predetermined
limit, which indicates that valve chatter has occurred, and (iii)
indicate that the valve 13 has opened permitting escape of fluid
from the system, the pressure at which it opened, the time at which
it opened, and the length of time it was open, and may also
calculate the mass or volume of fluid that escaped from the system
through the valve 13. The microcontroller 30 may also be programmed
to send correlated data to a host computer 19, as shown in FIG. 2,
upon receipt of a command from the host computer 19.
[0024] Electric power may be provided to the SIM 10 by means of a
battery (e.g., for stand alone applications), an external power
source, or a 4-20 mA current loop powered from a process control
network or similar source. The 4-20 mA connection also provides a
convenient means for transmitting information to a direct connected
network host computer. Communication between the SIM 10 and a host
computer 19 (shown in FIG. 2) may be provided via a conventional
RS-232 port or a modem 40 supporting commonly-used communication
protocols, such as HART.
[0025] With reference again to FIG. 1, in some cases it is
desirable to sense the difference in pressure between the inlet
pressure system 18 and the pressure in the pressure line at the
outlet 26 of the pressure relief valve 13. In such cases, a
differential pressure sensor 24 is connected to the inlet pressure
line 18 and the outlet pressure line 26 and the signal from the
differential pressure sensor 24 is sent to the sensor input module
10 in addition to, or in lieu of, the signal sent from a pressure
sensor 15 in the inlet pressure line 18. Alternatively, an outlet
pressure sensor 23, which is similar to the pressure sensor 15, may
be connected to the outlet 26 of the pressure relief valve 13. The
signal generated by the sensor 23 is sent to the SIM 10 so that the
microcontroller 30 can calculate the pressure difference.
[0026] FIG. 2 shows two pressure relief valves 13 mounted on a
pressure line 18, each with a valve monitoring device 8 in
communication with a host computer 19, which arrangement is
representative of what may be a plurality of valves, each of which
may be mounted on separate and independent pressure lines.
Communication between the host computer and each of the valve
monitoring devices 8 may be provided by means of a permanent
connection therebetween or by temporarily connecting the host
computer to each of the valve monitoring devices 8 periodically for
the purpose of data transfer. The host computer 19 may be arranged
to extract stored data from each valve monitoring device 8 and
utilize such data to determine present operating characteristics of
the pressure relief valve 13, such as total flow through the
pressure relief valve 13 during a specified time interval that the
pressure relief valve 13 was open. When the valve monitoring device
8 is continuously connected to a host computer, a real time
indication of lift or of the presence of leakage may be
communicated as an alarm signal. The host computer 19 is arranged
to analyze the information provided to it and to output information
useful in determining the operational readiness of each valve, and
may be used, when in constant communication with any particular
valve monitoring device 8, to sound an alarm or otherwise indicate
when the corresponding pressure relief valve 13 is leaking and/or
open. The host computer 19 may also be used to receive, update, and
store data such as valve configuration, maintenance history, or
other useful information.
[0027] One of the advantages of the present invention is that it
provides a monitoring device that continuously monitors the
performance of the pressure relief valve while the valve is in
active service, including detecting leakage flow through the
pressure relief valve, calculating fluid mass flow through the
pressure relief valve when the valve is open and allowing fluid to
flow from the pressure line, and detecting and warning of unstable
operation of the pressure relief valve. The monitoring device of
the present invention may also communicate with a host computer to
transmit the information stored by the monitoring device and
receive information regarding that particular valve from the host
computer. Of course, other objects and advantages of the present
invention will become readily apparent to those skilled in this art
from the above-recited detailed description. Accordingly, the
drawings and descriptions are to be regarded as illustrative in
nature, and not as restrictive.
* * * * *