Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CHECK VALVE TESTING SYSTEM
Field of the Invention
The present invention relates generally to the field of
testing the condition of valves, and, most specifically to tes-ting of
check valves.
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Background of Invention
A check valve is a type of one-way valve used in the control of
fluid flow through conduits. The check valve permits the flow of
fluid in a first direction through a conduit and prevents fluid flow
in the reverse direction. A check valve is generally constructed with
a disk which is mounted to a pivoting hinge. When fluid is flowing in
the allowed direction, the fluid forces the disk to pivot upward to
allow passage. When there is no fluid flow or when fluid attempts to
flow in the reverse direction, the disk pivots (usually gravity drop)
down to seal the conduit and prevent reverse Flow. Typically, all of
the parts of the check valve are located inside the valve chamber with
no external parts available for visual inspection.
Since it is dif-ficult, i-f not impossible, to achieve visual
inspection of a check valve, the dangerous reality is that a user will
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- generally not know if the check valve is actually working until the
valve is needed; at which time, it may be too late. Under most
operating condi-tions, the check valve stays normally open on a
continuous basis because pumps are in constant operation and flnid is
constantly being pumped through the conduit in the allowed flow
direction. Thus, it can be seen that the disk or other parts of the
check valve may be broken and simply lying in the conduit and no one
will know of a problem; and, when the "check" function is required,
the valve can not perform. Such unfortunate events are well
documented in the industry. Furthermore, it is being more and more
appreciated that undersized valves, oversized valves and certain
turbulen-t conditions in the conduit can result in harmful, damaging
vibration and "bouncing" of the check valve disk. There are not
practical methods in the prior art to check for the existence oF these
harmful vibrations. To date, the present inventors are unaware of any
systems available for testing the condition of a check valve without
either tearing down the valve assembly or allowing reverse -fluid
Flow.
Brief Summary of the Invention
Briefly described, the present invention teaches a method and
apparatus for tes-tins the condition of a check valve while the valve
is fully assembled and operating under various flow conditions,
including no-flow. The present invention comprises the use of an
ultrasonic sound transducer -to send high frequency sound waves
through the check valve casting and through the transported fluid to
the valve disk. Reflection of the sound waves is detected and
analyzed through the use of signal recording and conditioning devices
to assist in determination of the positioning and movement of the
valve disk.
It is an object of the present invention to provide a testing
system to test and assist in analysis of the condition of check valve
componen-ts without requiring physical inspection o-f the valve compo-
nents nor requiring back flow of fluid.
Another object of the present invention is to provide a check
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- valve testing method and apparatus for determining if a check valve is
in an inoperative condition.
Still another object of the present invention is to provide a
check valve testing method and apparatus for deterlnining if a check
valve is stlll operable yet being subjected to damaging operating
conditions.
Other objects, features and advan-tages of the present inven-
tion will become apparent upon reading and understanding the follow-
ing speciFication, when taken in conjunction with the accompanying
drawings.
_rief Description of the Dra_i_gs
Fig. 1 is a schematic represen-tation o-f the check valve
testing system, in accordance with the present invention.
Fig. 2 is a cut-a-way, side view of a check valve tested by the
invention of Fig. 1, and depicting a portion of the check valve
testing system of Fig. 1.
Fig. 3 is a schematic representation of a portion of the check
valve testing system of Fig. 1, showing an alternate embodiment.
Fig. ~ is a representative view depicting various, alternate
points of placement of the transducers of the check valve testing
system of Fig. 1.
Detailed Description of the Preferred Embodiment
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Referring now in greater detail to the drawings, in which like
numerals represent like components throughout the several views, -the
check valve testing system 10 of-the present invention is seen in Fig.
1 as comprising an ultrasonic wave sending unit 12 connected to a wave
sending transducer 13 by wire 1~; and an ultrasonic wave receiving
unit 16 connected by wire 17 to a wave receiving transducer 1~. The
sending unit 12 is connected by signal cable 21 to a firs-t recording
device 23, such as an oscilloscope, and is also cnnnected by the
signal cable 21a to a signal conditioning device 25. The wave
receiving unit 16 is connected by signal cable 2~ to the first
recording device 23 and by cable 2~a to the signal conditioning device
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25.
The signal conditioning device 25 comprises a discriminator 2~
and a counter/delay device 27, the functions of which are described
below. The signal conditioning device 25 is connected by signal cable
30 to the first recording device and by a signal cable 31 to a second
recording device 33, such as a second oscilloscope. The signal cable
31 is connected to an analog output terminal 34 of the signal
conclitioner 25.
The transducers 13, 18 are seen as acting upon a check valve
assembly 40, which assembly is seen in deta-il in Fig. 2. The check
valve assembly 40 comprises a fluid concluit ~1 providing for normal
free flowing of fluid from an inlet ~2, in the direction of arrows A,
-to an outlet 43. Between the inlet 42 and outlet 43 of the fluid
conduit 41 is a valve chamber ~5 which houses a swinging disk assembly
~6. The swinging disk assembly 46 comprises a valve disk 98 mounted
to a hinge arm 49, which hinge arm is pivotally connected at a pin 50
which is mounted to the inner wall 51 of the valve chamber. In some
embodiments o-f the swinging disk assembly 46, the valve disk 48 and
hinge arm 49 are forged as one component. In other embodiments, as
that shown in Fig. 2, the valve disk 4~ is bolted to the hinge arm 49
by a stud nut 53 bolted to a threaded stud 54 protruding upward from
the disk ~. The check valve assembly 40 further includes a lower
valve stop 56 and a back stop 57.
The check valve testing system 10 of the presènt invention is
set-up, in the field, at the location of the check valve along the
fluid conduit system. The wave sending unit 12 is set-to generate and
deliver a pulsing, ultrasonic signal. That is, a sound wave signal is
generated repeatedly at desired, equal intervals. The interval of
time between each pulse shall be termed -the "pulse interval". The
rate at which the pulses occur shall be termed the "pulse rate". The
frequency of the ultrasonic wave is set sufficently high to assure
transmission of the sound wave through the different medium of the
valve casting, fluids, and any other materials associated with the
valve assembly 40. The user places the sending transducer 13 and
receiving transducer 18 at the valve assembly body so as to direct the
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- sound waves at the valve disk 4~ wi-thin the valve chamber 45. The two
transducers 13, 1~ are placed relative to one another such that the
receiving transducer 1~ can receive the sollnd wave from the sending
~ransduc~r 13 after the waves have been directed into the valve
chamber 45. Some examples of alternate transducer 13, l~ placement
are shown in Figs. 3 and 4. Note that the transducer location
depicted in Fig. 3 and as positions "a", "b" and "c" of Fig. 4 are
oriented such that the receiving transdllcer 1~ is receiving sound
waves from the sending transclucer 13 after the waves have been
reflected off the valve disk 4~. The position of the transducers 13,
1~ depicted as position "d" of Fig. 4 is such that the receiving
transducer l~ receives sound waves from the sending transducer 13
without reflection off of-the valve disk 4~. The significance of this
"d" position is further explained below.
With reference again to Fig. 1, the wave sending unit 12
generates a trigger signal upon the generation of each ultrasonic
pulse at the sending transducer 13. This trigger signal is delivered
along signal cable 21 to the first recording device 23. At the first
recording device, this trigger signal triggers the recording device
to begin its recording sequence. For example, in the case of an
oscilloscope, the trigger signal triggers the oscilloscope to hegin
its sweeping function. This sarne trigger signal is delivered along
signal cable 21a to the signal conti-tioner 25 where it triggers the
signal conditioner to the fact that a sound wave has been delivered by
the transducer 13 and the conditioner 25 should begin -its condi-
tioning functions as discussed below.
As each sound wave is generated and directed by -the sound
transducer 13 into the valve chamber 45, the wave receiving trans-
ducer 1~ begins to receive reflected and refracted sound waves from
various components of the valve assembly 40. For example, a portion
of each wave generated at the sending transducer 13 is reflected or
refracted by the metal casting of the valve assembly 40~ a portion of
the wave is reflected and refracted by the fluitl within the valve
chamber 45 and a portion of the wave is reflected by the valve disk 4~.
Various other materials and components within the valve assembly 40
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- and valve chamber ~5 may also reflect and refract portions of each
wave generated by the sending transducer 13. Thus, for each wave
(each pulse) generated at the sending transducer 13, a plurality of
waves are received by the receiving transducer 1~. Whether reflected
or refracted, the waves received by the receiving transdllcer 1~ shall
be referred to in this disclosure as "reflected waves". As each
reflected wave is received by the receiving transducer 1~, the wave
receiving unit 16 acknowledges receipt of the wave and generates a
signal which is sent along signal cable 2~3 to l:he first recnrding
device 23. The signal is recorded by the recortling device 23. In the
example o-f an oscilloscope, each signal corresponding to a received,
reflected wave is recorded in the form of a spike. Since the
reflected waves are received at the receiving unit 1~ at different
times, a series of signals, separated in time, are sent by the
receiving unit 16 to the oscilloscope 23. Thus, the series of signals
appear as a plurality of spikes spaced across the screen of the
oscilloscope. The Amplitude of the spikes corresponds to the energy
of the respective, reflected wave received at the receiving trans-
ducer 1~. An example of such a sweep is given by trace "f" of Fi~. 1.
The pulse ra-te of the sending unit 12 is adjusted by the user
to assist in receiving a good sweep trace at the oscillnscope 23.
That is, the pulse rate is set so that a substantial number of -the
reflected waves from the first generated sound wave are received at
the receiving unit 1~ before the second generated wave is sent at-the
sending transducer 13. Each time a new wave is generated at the
sending transducer 13, a trigger signal is sent from the sending unit
along signal cable 21 to the oscilloscope triggering the oscilloscope
to begin a new sweep. As explained above, during the new sweep, the
oscilloscope records input from the receiving unit 16 corresponding
to the received, reflected waves relating to the respective generated
sound wave pulse. Analysis of each recorded trace during each sweep
familiarizes the user with a pattern of spikes which correspond to
"noise" 60 corresponding to waves reflected or refracted off of -the
valve casting, the fluid, or other miscellaneous materials; and also
familiarizes the user with a particular target spike 61 corresponding
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- to the wave portion reflected off the valve disk 4~3. The pulse rate
of the sending unit 12 is adjusted to assure clear generation of the
target spike 61 during each sweep of the oscilloscope 23.
At the same time that the series of signals is sent hy the
receiving unit to the oscilloscope 23, the same series of signals are
delivered alon~ signal cable 2)3a to the signal conditioner~ The
signal conditioner~l25 performs two main functions: (1) isolating of
the target spike'~ during each single sweep of l:he first recording
device 23; and (2) convertin~ the digital signal associated witt) each
sweep of the first recor(ling device 23 to an analog signal which
signal is delivered to the second recording device 33 along signal
cable 31. The isolating function is accomplished as follows: each
time the sending unit 12 generates a pulse, the trigger signal is
delivered along cable 21a to the counter/delay device 27 of the signal
conditioner 25. This trigger signal resets the counter of the
counter/delay device 27 to "zero" to begin counting the relative time
since the respective pulse was sent by the sending unit 12. The delay
mechanism of the counter/delay device 27 further affects the counter
by delaying the counter's beginning time by an increment of time
selected by the user. In this way, -the user adjusts the delay such
that the counter does not begin counting until a substantial portion,
if not all, of the reflected waves which resulted in the "noise" 60
have been received by the receiving uni-t 1~. The signal conditioner
25 also comprises a discriminating device 26. The function of the
discriminating device 26is to command the signal conditioner 25 to
recognize only signals from the receiving unit 16 which have
amplitudes in excess of a selec-ted minimum arnplitude. Thus, in
practice, the user adjusts the discriminator device 26 such that the
signal conditioner 25 discriminates in favor of certain, high
amplitude signals. Thus, it can be seen, that by selectively
adjusting the delay device 27 and the discriminator device 26, the
user is able to effectively isolate the -target spike 61 from all of
the noise spikes 60. The signal conditioner discriminately seeks
signals during each pulse interval which signals are generated after
the delay interval and which signals exceed or equal the minimum
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- discriminating amplitude. Such isolated signals are conveyed by
signal cable 30 to the first recording device 23 where they are
recorded. When an oscilloscope is used, the isolated signal is
displayed on the lower trace "9" during each sweep of the oscillo-
scope.
In performance of its second function, the counter of the
counter/delay device 27 begins counting upon expiration of the delay
interval, and continues counting until the signal cond-itioner 25
receives a signal from the receiving unit 16 which signal exceeds or
equals the d;scriminating amplitude (i.e. the target spike). Once
the counter has stopped counting, the digital output from this
digital counter is input -to a digital-to-analog converter within the
signal conditioner 25. The output of this D/A converter is delivered
through the analog output terminal 34 to the second recording clevice
33. The D/A converter output is, preferrably, in the form of an
equivalent voltage such that a low count on the counter results in a
low voltage and a high count on the counter results in a high voltage.
The counter is reset by the trigger signal from the wave sending unit
12 each time a new wave pulse is generated by the sending transducer.
Thus, the counter begins a new count for each new generated wave and
a separate analog signal is generated-for each pulse interval. It can
be seen that the counter is counting a relative time span over which
the sound wave of a given pulse travels-from the sentling transducer 13
to the valve disk 4~ and then to the receiving transducer 1~ (the
"critical distance"). If it took a long time for the wave to travel
this critical distance, then the count of the digital counter will be
high and the analog output voltage will be high. Conversely, if it
took a relatively short -time for the wave to travel the critical
distance, then the count of the digi-tal counter will be low and the
analog outpu-t voltage will be low. Since the time it takes for the
sound waves to travel the critical distance is directly related to the
distance of the valve disk 4~ away from the transducers 13, 1~, the
output voltage relates in a relative manner to the position of the
valve disk ~ within the valve chamber ~5.
The analog output voltage is sent along cable 31 to the second
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- recording device 33 where the voltages correspondin~ to each of the
pulse intervals of the sending unit 12 are collected and recorded.
Preferrably, the second recording device 33 performs one or more of
the functions of collecting, storing, correlating, recording and
analyzing of the signal condi-tioner output. In the preferre~
embodiment, the second recording device 33 is a storage oscilloscope
in which the voltages correspon(ling to the successive pulse intervals
of the sending unit 12 are converted to a (ligital number and stored.
The storage oscilloscope 33 also functions to successively plot the
collected data with respect to time; and to generate and display a
time (distance) versus real time curve. This time related corre-
lation of the collected data can be used to diagnose the condition and
functioning of the check valve. By way of example, and with reference
to Fig. 1, two representatlve traces are depicted as output of the
second recording device 33. In each trace, the vertical axis
represents the "relative time" which is a factor which relates
directly to the distance of the valve disk 48 from the transducers 13,
1~ (voltage). This parameter is termed "relative time" becallse that
time relates separately to each pulse interval of the sending unit
and, more specifically to the relative time during which the counter
was counting within each pulse interval of the sending unit 12. The
horizontal axis of each trace depicts real time. This parameter is
called "real time" because it is not reset with each pulse in-terval oF
the sendiny unit 12, but is continuous time spanning the accumulation
of a plurality of pulse intervals.
In another embodiment of the present invention, the recording
device is a computer or a combination of oscilloscope and computer in
which the computer performs various opera-tions on the analog output
of the signal conditioner 25. The computer performs spectrum
(frequency) analysis of the voltage/time traces. Furthermore, the
computer, using known mathematical formulas and additional input such
as the known velocities of so~nd through the various materials9
calculates the position of the valve disk 4~ within the valve chamber
~5 at any given point in "real time". In still another embodiment,
the second recording device 33 is an instrumentation analog tape
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- recorder which collects, records and stores the analog signals. The
stored data from this tape recorder are subsequently conveyed to an
oscilloscope for display and analysis or to a computer for detailed
analysis.
An example of analysis of the traces "h", "i" generated by the
second oscilloscope 33, is given here. Trace "h" is a representative
trace depicting position, and nlovement of position of the valve disk
4~ un(ler fluid flow conditions. It can be seen that, over a period of
real time, the voltage, which relates to relative time and to clistance
of the disk 4~ from the transducers 13, 1~, fluctuates from higher to
lower voltages. This indicates that, at each pulse of the sound wave,
the valve disk 4~ was at a dif-ferent distance from the transducer 13,
18. Thus, the trace "h" is indicative oF a vibrating or "bouncing"
valve disk 4~. This condition is indicative of a poorly sized valve,
or some other detrimental condition which will result, in the long
term, in failure of the valves. Trace "i" shows a gradllal increase in
voltage depicting movement o-F the valve disk 98 From an open position
(low voltage = short relative time = short distance to transducer),
gradually closlng to a closed position (high voltage = long relative
time = far distance from the transducers). Analysis of such a trace
as trace "i" assists in determining: if the valve disk 9~ moves
freely or binds at some point in -the swing; if the vaive moves fully
from the open to closed position; and if the disk is stable during
normal and various fluid flow conditions. Analysis of the output oF
the first recording device 23 aids in immediate determination of:
whether or not the valve disk 4~3 is actually in place (i.e. broken off
or still in place); the relative position of -the valve disk 9~; and
the ability of the swinging ~isk assembly 96 to -Fully swing from its
open to its closed position.
A user, using the sys-tem of the present invention, can test the
valve condition under various flow conditions. For example, a firs-t
test of the check valve assembly 40 is conducted with full flu-id flow
through the conduit 41. Analysis of the recordings taken during this
first test is used to determine if the valve is (or seems to be) open
and if the valve disk is subjected to vibrating or bouncing during the
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- full flow condition. Next, the test is run with the fluid flow set at
various flow rates less than the full flow rate. As a result of this
second set of tests, the user can record and analyze the position of
the valve disk 48 during various flow rates ancl can record and analyze
the effect of lesser flow rate on the vibrating or bollncing of the
valve disk 4~. Finally, the user can stop fluid flow throllgh the
respective fluicl condl1it 41 and, during this test, locate the
position of the valve disk 48 and record and analyze the swin~
characteristics of the swing-ing disk assembly 46 (i.e. Does i-t
bind?).
In an alternate embodiment of the present invention, the
transducers 12, 13 are positioned at the locations indicated as "d" in
Fig. 4. With the transducers 13, 18 in this location the user seeks
to identify whether or not the valve disk 48 has achieved its fully
closed position. Thus, if the valve disk 48 is not fully closed, the
sound wave generated at sending transducer 13d will be received (in
large portions) at the receiving transducer 18d. ~lowever, if tl~e
valve disk 48 is fully sea-ted, the valve disk 48 will inter-Fere with
the sound wave generated at the sending transducer 13d; and none of
the wave, or only a small portion of the wave will be received at the
receiving transducer 18d.
~Ihereas this invention has been described in detail with
particular re-ference to preferred embodiments thereof, i-t will be
understood that variations and modifications can be effected within
the spirit and scope of the invention, as described herein~eFore and
as defined in the appended claims.
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