Note: Descriptions are shown in the official language in which they were submitted.
S3100
L~`AK LOCATION DE'~EC~ING APPARATUS
FOR A PRE~;SURIZED PIP:~LINE
Field o~ the Invention
The present invention relates to leak location de-
tecting apparatus, and more particularly, to leak loca-
tion detecting apParatus ~or a pressurized pipeline.
~ lost successfully, the invention can be used for
determination of leak locations in transmission and dis-
tribution lines used ~or pumpin~ fluids, ~or example, oil,
water, gaseous ~uel, gasoline, the ~luid therein being
under pressure.
Background o~ the Invention
Fluids (in either a liquid or gaseous state) ~low-
ing through transmission and distribution lines usuaLly
leak through pipe walls, and the location of the leak should
be quickly and precisely determined to reduce the ~luid
loss. Furthermore, in many instances the leaking o~ gas
is extremely hazardous since the accumulation o~ gas under
sidewalks, streets, ~oundations, in sewers, basements and
other enclosed areas can result in explosions that would
cause considerable da~lage to the property and even lead to
loss of li~e.
A variety of aPParatus has been developed to deter-
mine leak locations in a pressurized pipeline, and a com-
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~L~ 531~)0
bination of several apparatus is often used on the same
pipeline in hopes that if one apparatus fails to detect
a given leak, perhaps another apparatus will be success-
ful.
Known in the prior art is a leak location
detecting apparatus for a pressurized pipeline, that
comprises a transducer intended for conversion of
mechanical oscillation into electric signals, for example,
a microphone connected in series with an amplifier, a
bandpass filter with a variable tuning, a rectifier, and
an indicator (cf. USS~ Author's Certificate No. 62,668,
Gitis and Zolomikhin, published in 1943).
~he leak location is detected in the following
manner.
The leak location detecting apparatus is tuned
to a frequency of sound produced by the leak, that lies
within 3,000 to 4,000 Hz, then the microphone with the
bandpass filter is moved along the pipeline to be leak-
inspected, The leak location is the place where the
indicator needle deflects at a maximum.
This leak location detecting apparatus possesses
low expedition properties as a considerable time is
required to detect the leak location since it is first
necessary to define the route of the pipeline to ~e leak-
inspected and then to go all over the route of the
pipeline.
The leak location detecting apparatus does
not allow the leak place to be determined reliably
because it is practically impossible to determine
exactly the route of the
f~
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1153i~
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pressurized pipeline to be inspected.
Furthermore, the leak location detecting apparatus
does not allow the leak location to be deterlrlined with an
adequate accuracy in a pressùrized pipeline due to the fact
that the transducer has a low sensitivity and do~s not always
record the acoustic waves produced by a gas leak since the
lat-ter attenuate as they propagate through the soil.
Furthermore, the apparatus in ~uestion ~ails to pos-
sess an adequate noise immunity. As a result it does not al-
lo~ the leak location to be determined reliably in pres-
suriæed pipelines laid in regions with a high level o~ en-
vironmental acoustic noise (~or example, in the boundaries
of a city, in the neibourhood o~ railway crossin~s, main
highway crossings, industrial enterprises, airplane traf-
fic routes). '~his is explained by the ~act that in these
regions the environmental acoustic noise is o~ten consider-
ably higher than the acoustic noise produced by the leak,
and the transducer does not distinguish the use~ul acoustic
oscillation ~rom the bac'~round one.
Also known in the prior art is a leak location detect-
ing apparatus ~or a pressurized pipeline, which comprises
a concentrator mechanically connected with an electroacoust-
ic -transducer electrically associated ~ith an input o~ an
ampli~ier havin~ its output connected to an indicator (c~.
1~53~~
USSR Inventor's Certificate No. 380,910, patented ~ugust
1, 197~).
In order to detect the location o~ a leak, the in-
let end face Oe the concentrator is placed on the soil.
If acoustic waves of the soil, produced by a leak in the
pipeline being inspected, are present, the concentrator
amplifies their amplitude. ~he amplified acoustic waves
act upon the electroacoustic transducer aonverting them
into an electric signal applied further to an indicator.
~he leak location is de-termined using the maximum deflec-
tion of the indicator needle.
This apparatus has a considerably higher sensitivi-
ty owin~ to the fact that both the amplitude and the power
of the acous-tic waves applied to the electroacoustic trans-
ducer can be materially increased as co~npared with those
in event where the electroacoustic transducer is applied
directly to the surface of earth blanket of the pipeline.
~`his is achieved by proper selection o~ the concentrator
end face areas.
However, this leak location detecting appara-tus also
possess,es low expedition properties as it requires a con-
siderable time for the leak location determination since
it is ~irst necessary to define the route of the pipeline
to be leak-inspected and then to go all over the route o~
the pipeline.
~S3~0~)
Besides, the apparatus mentioned herein above does
not possess -the adequate noise immunity as well. As a re-
sult it does not allow the leak loca-tions to be determined
reliably in the pressurized pipelines laid in regions with
a high level of environmental acoustic noise.
'~here is also known a leak location detecting appara-
tus for a pressurized pipeline, comprising a transducer
intended for conversion of mechanical oscillation into an
electric one, an amplifier, a converter of signals into
their ratio and an i~dicator, all elements being connected
in series (cf. USSR Inventor's Certi~icate No. 603,8049 pa-
tented April 25, 1978).
'Mounted within the transducer casinK are a sluggish
member linked with the casing by a resilient suspension,
a probe and two transducers, one being arranged in parallel
with the probe, while the other is arranged normall~ to the
probe axis.
~ his apparatu~ allows the leak location -to be deter-
mined more precisely due to the proper ~election of sluggish
member mass providing for the filtration of mechanical os-
cillations that are higher than a specified frequency range,
i.e. all noise signals lying over tens of kilohertzes and
hempering the leak location determination can be filtered
out,
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~i53'100
-6-
However, said apparatus possesses low expedition pro-
perties as it re~uires a con~iderable time to determine the
leak location since it is first necessary to define the ro-
ute of the pressurized pipeline and -then -to move all over
said route.
In addition, the leak location de~ecting apparatus
mentioned hereinabove does not possess the adequate noise
immunity as well. As a result it does not allow the leak
locations to be deterl~ined reliabl~ in pipelines laid in
regions with a high level of environmental acoustic inter-
ference.
r~he noise immunity of the leak location detecting ap-
paratus can be improved b~ placing the latter within the
pipeline to be leak-inspected.
Enown in the prior art is an acoustic lea~ detecting
appara-tus comprising a movable pipeline pig having at least
two resilient cups isolating at least one compartment there-
between wherein the electrica' por~ion of the apparatus is
carried (c~. U.S. Patent No. 3,413,653, patented ~ovember
20, 1968).
r~he electrical portion of the apparatus is provided
with two acoustic transducers, one being installed in the
head part of the apparatus and directed downstream while
the other bei~g installed in the back part of the appara-
tus and directed upstream. ~he electrical portion is fur-
,
~1~3~00
ther provided with suitable ~ilters ~or filtering out lowerfrequencies generated by the environment (including sounds
caused by the pig banging against the pipeline as it passes
there-through), a differential arnplifier and a multi-channel
recording system.
In order to detect the leak location, the apparatus
is placed inside the pipe, the recordi~g system recording
output signals of the difeerential amplifier. '~hen the leak
detecting apparatu5 is withdrawn from the pipeline, and the
records are processed.
However, the leak detecting apparatus possesses low
expedi-tion properties since the data are recorded cn a mag-
netic tape that is to be withdrawn ~rom the pipeline and
processed. As a result a considerable time is required for
the leak location determination in a pressurized pipeline.
Furthermore, in the apparatus in question, the dis-
tance is read off ~rom the s-tarting point o~ the acoustic
transducer displacement, causing a large error of the leak
location determination.
Moreover, the leak detecting apparatus does not make
it possible to determine reliably the leak absence since
the acoustic -transducer can receive no sound signal both
in event where no leaks are present and in event where the
acoustic transducer itsel~ is ~aulty.
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11~3~
--8--
Also known in the prior art is a leak location detect-
ing apparatus for a pressurized pipeline, com~risinK gene-
rators placed at certain di~tances along the pipeline and
an acoustic transducer with an indicator made as a record-
ing member that are located inside the pipeline (c~. USSR
Patent ~o. 310,460, patented July 26, 1971).
~ o determine the leak location in a pressurized pipe-
line, the acoustic transducer with the indicator is caused
to be moved in side the pipeline to be inspected. At the
same time, -the ge~erators arranged at certain distances along
the route o~ the pipeline are turned on. ~he generators pro-
duce external sound signals that are received by the mov-
ing acoustic transducer. ~he acoustic signals produced as
a result o~ a leak are received by -the moving acoustic trans-
ducer as signals transmitted in intervals between adjacent
signals transmitted by the generators.
~ hus, in order to determine the leak location, the
distance is read o~ not from the starting point of the aco-
ustic transducer displacement, but ~rom adjacent generators,
arranged along the pipeline. This reduces the error o~ leak
location.
I~ no leak signals are available on the recording memb-
er o~ the movable device, the good condition o~ the acoustic
transducer is judged from correctly recorded signals of the
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'
~153100
generators arranged along the pipeline since the absence o~
signals indicates only that no leaks are present and is not
an indication that the moving acoustic transducer is ~ault~.
However, all leak location detecting apparatus in-tended
to be installed inside a pressurized pipeline require compli-
cated means ~or their ins-tallation in the pipeline and their
~urther withdrawal.
Furthermore, resilient cups used to translate t~e appa-
ratus inside the pipeline make slapping noises as they pass
over welded seams, joints and other internal projections
inside the pipeline. These are often just the places where
the leak is located since no method is as yet developed
to pr-oduce seams o~ a 100 per cent reliabili-ty.
The acoustic waves produced by the cups can completely
override the acoustic waves caused by the leak, and the de-
tector will record spurious waves instead o~ the useful ones.
As a result, it becomes impossible to determine leak loca-
tion.
There is also known a leak location detecting appara-
tus for a pressurized pipeline,comprising two measuring
channels, each including a transducer intended ~or conver-
sion o~ mechanical oscillation into elec-tric signals and
having its output connected to a respective amplifier, am-
plifier outputs being connected to an indicator which is a
loop oscillograph (cf. USSR Inventor's Certi~icate No.827,425,
patented January 26, 1972).
llS310~
--10--
To determine the leak location, the transducers in-
tended for conversion of mechanical oscillation into elect-
ric signals are installed on the pipeline body at the beginn-
ing and a-t the end o~ the pipeline portion to be leak-in-
spected.
The acoustic waves produced by a leak propagate ~rom
the leak place at the speed o~ sound, e~ect upon the trans-
ducers converting these waves into electric sigrlal~ which
are then amplified by the ampli~iers and are recorded on
an oscillogram by the oscillograph loops.
~ he oscillograms are then processed visually to de-
termine and to measure phase shi~ts between typical peaks
of the acoustic waves. ~he distance to the leak place is
determined ~rom the phase shift between the acoustic waves.
~ owever, the visual processing o~ the data recorded
by the oscillograph lowers the accuracy of the acoustic
wave phase shi~t determination, and, as a result, the accu-
racy o~ determination o~ leak location.
Furthermore, the leak location detecting apparatus
mentioned above has a low speed o~ operation due to the
~act that oscillograms recorded by the oscillograph are
processed manually.
Summary of the Invention
It is an object o~ the present invention to provide
a leak location detectin~ apparatus enabling the time re-
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3~00
quired to determine the leak location in a pressurizedpipeline to be reduced.
Another object of the present invention is to
provide a leak location detecting apparatus improving the
accuracy of leak location determination in a pressurized
pipeline,
In accordance with a particular embodiment of
the invention there is provided a leak location detecting
apparatus for a pressurized pipeline. The apparatus
includes a first transducer intended for conversion of
mechanical oscillation into electric signals and having
an output, A first amplifier, which has an input and an
output, has the input connected to the output of the first
transducer, Also included is a first limiter having a
first input, a second input, and an output, the first
input being connected to the output of the first amplifier.
A first limiting level control unit has an output, the
output being connected to the second input of the first
limiter. A first pulse shaper has an input and an output,
the input being connected to the output of the first
limiter, and a variable delay unit, having an input and
an output, has the input connected to the output of the
first pulse shaper. The first transducer taken in con-
junction with the first amplifier, the first limiter,
the first limiting level control unit, the first pulse
shaper, and the variable delay unit forming a first
measuring channel. The apparatus also includes a second
transducer intended for conversation of mechanical
oscillation into electrical signals and having an output.
A second amplifier, having an input and an output, has
its input connected to the output of the second trans-
ducer. A second limiter, having a first input, a second
input, and an output, has the first input connected to
the output of the second amplifier, and a second limiting
level control unit having an output, has the output con-
nected to the second input of the second limiter. Also
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~15~100
_ 12 --
provided are a second pulse shaper having an input and an
output, the input being connected to the output of the
second limiter. The second transducer taken in combin-
at:Lon with the second amplifier, the second limiter,
the second limiting level control unit and the second
pulse shaper form a second measuring channel. A pulse
coincidence circuit having a first input, a second input
and an output, has the first input connected to the out-
put of the variable delay unit, the second input being
connected to the output of the second pulse shaper. A
pulse coincidence counter has an input and an output,
the input being connected to the outpub of the
coincidence circuit. An indicator, having an input,
has the input connected to the output of the pulse
coincidence counter, and a delay time indicator is
operably connected to the variable delay unit. Wherein,
in order to determine the leak location, the first trans-
ducer is disposed at one point on the pipeline on one
side of the leak location, and the second transducer is
disposed at a second point on the pipeline along the
pipeline axis and on the other side of the leak location,
and the leak location is determined in accordance with
the following formula:
1 - vr
X = 2
wherein:
1 = distance between said first and second
transducers along said pipeline axis,
V = speed of acoustic wave propagation in the
fluid being pumped,
r = delay time as indicated on said delay time
indicator, and
XO = distance measured along the axis of the
pipeline from said first transducer to said
leak location.
U~!
1153~0
- 12a -
The acoustic waves produeed by a leak cover the
distances from the leak location to the transdueers in
different time intervals.
The variable delay unit introduced into one of
the channels allows the signals passing through this
channel to be time-delayed. One can make the signals of
both measuring channels to coineide by changing the delay
time. This means that the variable delay unit may be used
for an automatic determination of the acoustic wave phase
shift and, hence, for a quick and precise determination
of the distance to the leak location.
It is advisable to introduce a delay time indi-
eator into the leak location detecting apparatus so that
an output of the delay time indieator be conneeted to an
input of the variable delay unit.
These and other objects and advantages of the
present invention will beeome fully apparent from the
following description taken in conjunetion with the
aeeompanying drawing.
The drawing is a bloek diagram of the leak
loeation detecting apparatus for a pressurized pipeline
in aecordanee with the present invention,
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~L-153101
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Detailed Description o~ the Invention
Referring now to the accompanying drawing, the leak
location detecti~ apparatus ~or a pressurized pipeLine
comprises transducers I and 2 intended for conversion o~
m~chanical oscillation into electric signals. An output
of the transducer I is connected to an input o~ an ampli-
~ier 3, while an output o~ the transducer 2 is connected
to an input of an amplifier 4. An output o~ the ampli~ier
is connected to one of inputs of a limiter 5 whereas an
output of the ampli~ier 4 is connected to one of inputs
of a limiter 6.
~ he other input of the limiter 5 is connected to an
output of a limiting level control unit 7, whereas the
other input o~ the limiter 6 is connected to an output o~
a limiting level control unit 8. An output o~ the limiter
5 is connected to an input o~ a pulse shaper 9,and an out-
put o~ the limiter 6 is connected to an input of a pulse
9 haper 10.
Used as the pulse shapers 9, 10 can be one-shot multi-
vibrators generating similar pulses as to the duration and
amplitude.
The pulse shaper 9 has its output connected to one o~
two inputs o~ a variable delay unit II havin~ the other în-
put ~onnected to an output o~ a delay time indicator 12.
31~
-14-
~ he transducer I,the amplifier 3, the limiter 5, the
limiting level con-trol unit 7, the pulse shaper 9, the va-
riable delay unit II, and the delay time indicator 12 form
one measuring channel, whereas the -tra~sducer 2, the ampli-
fier 4, the limiter 6, the limiting level control unit 8,
the pulse shaper 10 form the other measuring channeL.
An output of the pulse shaper 10 and an output of the
variable delay unit II are connected to respective inputs
of a pulse coincidence circuit 13 having i-ts output con-
nected to an input of a pulse coincidence counter 14 whose
ou-tput is connected to an input o~ an indicator 15.
~ pressurized pipeline 16 with a breack or leak 17
is diagrammatically illustrated in the accompanying drawing.
'~he proposed leak location detecting apparatus operates
in the following manner.
The transducers I and 2 intended for conversion of
mechanical oscillation in-to electric signals are installed
on the body of t~e pressurized pipeline 16 where the leak
location is to be determined.
If a Leak is formed in the pipeline 16, acoustic waves
are generated in place of the fluid escape, the acoustic
waves propagatin~ i~ the fluid being pumped to the ends of
the pipeline 16 at the speed of sound. ~hese acoustic wave~
are detected by the transducers 1, 2 and converted into elect-
:` :
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11531(~1
--15--
ric signals that are respectivel~ amplified by the ampli-
fiers ~, 4 of the measuring channels.
In each ~easuring channel the amplified signals are
applied to the respective limiter 5, 6. The limiting level
can be adjusted by the limiting level control uni~s 7, 8
and is, as a rule, pre-set,
'~he limi-ted signals are a train of pulses having
indefinite shapes and various amplitudes. These signals
are fed ~rom the output o~ the limiter 5 to the pulse shaper
9 and from the output of the limiter 6 to the pulse shaper
10, which shapers shape square pulses of similar duration
and amplitude.
Then the shaped pulses are supplied from the pulse
shaper 9 to the variable delay unit II that time-delays
them. From the variable delay unit II the pulses are ap-
plied to the pulse coincidence circuit 13, whereas from
the pulse shaper 10 the shaped pulses are fed to the pulse
coincidence circuit 13 without any delay.
If the pulses ~ed ~rom the pulse shaper 10 and from
the variable delay unit II coincide, a pulse is produced
at an output o~ the pulse coincidence clrcui-t 13, -that is
further applied to the pulse coincidence counter 14. 'rhe
ma~imum number of pulse coincidences per unit time is ob-
tained by varyin~ the delay time of pulses in the variable
.,
li~i3iO~
-16
delay unit II.
~ hen the delay time is smoothly varied in the vari-
able delay unit II, for example, is increased, and i~ the
needle of the indicator 15 deflects in the increase direc-
tion, the delay time is continued to be increased until
the needle o~ the indicator 15 starts deflecting in the
decrease direction.
The maximum dellection of the needle of -the indicator
15 corresponds to the maximum number o~ coinciding pulses.
r~he time delay corresponding to -the maximum number
o~ coinciding pulses is read o~ on the time delay indi-
cator 12. ~hen if the distance between -the transducers I,
2 and the speed of acoustic wave propagation in the ~luid
being pumped in the pipeline are known, the di~tance to
the leak location can be determined using the following
formula:
X - 1 - V~
o
where 1 - distance between the transducers 1, 2 along
the pipeline axis;
V - speed of acoustic wave propagation in the ~luid
being pumped;
- delay time;
XO = distance measured along the axis of the pipeline
16 from the transducer I whose signals are fed 'GO the pulse
coincidence circuit 13 through the variable delay unit II
1153100
--17--
to the leak 17 .
~he invention will be further described with refe-
rence -to the followinK illus-trative Example.
lS~amPle
The tran~ducers intended for conversion of mechanical
oscillation into electric signals are installed at the ends
of a pressure pipeline portion.
The distance between the transducers, 1: 182 m
The speed o~ acoustic wave propagatio~
in this pipeline, V: I,281.69 m/9
~he indicator needle shows the maximum
of pulse coincidences per unit time
with the delay time, ~ : 0.0075 s
The distance measured alon~ the pipeline a~is from
the transducer whose si~nals are fed to the pulse coin-
cidence circuit through the variable delay unit to the
leak is
X = 1 - ~ 182 - 1281 69 0-0075 = 86.2 (m)-
While a particular embodiment of the invention has
been shown and described, various modifications thereo~
will be apparen-t to those skilled in the art and there~ore
it is not intended that the invention be limited to the
1153~00
--18--
disclosed embodiment or to the detail~ thereo~ and the de-
partures may be made -therefrom within the spirit and scope
o~ the invention as defined in the appended claims.
The advantages o~fered by the present invention stem
~rom the fact that the apparatus of the present invention
allows the distance to the leak location to be determined
quickly and precisely, thus minimizing the loss of a ~luid
being pumped and the interruptions in supply o~ near consum-
ers with the products being pumped.
Another advantage is that the time required to
minate -the emergency is reduced.
A ~urther advantage is a decrease i~ the environment
contamination in case o~ pumplng of toxic fluids due to the
reduction in the time required to eliminate the emergency.
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