Note: Descriptions are shown in the official language in which they were submitted.
7~
:LE'AK DETr.'C~rL'lON S`~STEM FOR
SUBTERRANE:AN PIPE'LINE'S
The present invention relates to the field of pipeline
leak detection, and in particular to the protection of pipelines
containing hydrocarbon liquids or gases and the like Eor the detec-
tion and location of leakage from such pipelines before substantial
volumes of fluid have escaped, and beEore environmental damage has
occurred. The system described in the present application is de-
signed to be fitted on any subterranean pipe transporting any type
of liquid or gas. The system includes a minimal number of sensor
test points yet it is able to determine leak locations in any de-
sired length of pipeline including lengths as short as five metresections. The system of the present application utilizes a single
layer of plastic sleeve, such as high density polyethylene sheet
sealed around the pipe, with a plurality of collars installed at
desired intervals which sub-divide the interior of the plastic
sleeve into appropriate lengths depending upon the accuracy with
which leaks must be located. Leak sensors are loca-ted at intervals
along the pipe and serve to provide an indication of the leakage of
product from the pipeline.
Within the plastic sleeve, internal collars are prov~ded
which sub-divide the sleeve into discrete chambers, and depending
upon the spacing of the collars, leakage can be located to the
nearest chamber in which such a leak is occurring. Sensors may be
located at all low poin-ts on the pipeline and at approximately 1.6
kilometre intervals for example as determined by the pipeline instal-
lation requirements.
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Between every pair of collars there is a specially
designed spigot fittin~ sealed to the plastic sleeve, at a point
slightly below the centre of the pipe. This spigo-t fi-tting. is
especially designed so that it can be connected to the bottom half
of the pipe sleeve and consis-ts of a reservoir wi-th three external
connections. An inlet connects the reservoir to the interior oF
-the sleeve. The top of the reservoir is connected -to a small dia-
meter pipe which leads up to ground level, and an outlet is connected
to a collection pipe running beside the pipeline through which leak-
age can be collected and fed to a sensor reservoir by gravity.
In -the event of a leak the product from the pipeline will
be con-tained within the sleeve between two collars, until the leak-
age reaches a point where fluid will flow into the spigot and ulti-
mately from the spigot reservoir into the gathering pipe and thus
to the sensor reservoir which is fitted with a leakage sensor. The
inlet to the spigot and gathering pipe may be fitted with a plurality
of one-way valves so that leakage from the main pipeline will flow
in the direction of the reservoir to prevent the f low of liquid back
upstream to higher spigots. The leaking product will flow along the
~0 gathering pipe to the sensor test point where it will accumulate in
the sensor reservoir until it comes in contact with a sensor. At
this point an alarm is generated by the sensor indicating that leak-
age has occurred from the pipeline. Once such an alarm has been
generated, surplus leaking fluid can be fed from the sensor reservoir
to an optional second spill-over pipe leading to either a buried
storage tank or a large sludge pond or the like, so -that no product
is lost to the environment and reclamation can be readily accomplished.
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The system of the present invention also enables the
determination oE the rate of a liquid leaJ<. F3~ buildincl ~he sensor
reservoir to an appropria-te size, and providing it with two sensors,
and by detecting the time delay between the activation of these two
sensors, -the rate of leak flow can readily be determined I,eak
detection and leakaye rate can be monitored by an appropria-te cir-
cuit board mounted in the sensor test point pipe which may be con-
nected via the telephone system to an appropria-te monitor to allow
an operator at a desired location to know that there is a leak in
a given pipeline, the location of the leak, as well as the size of
the leak, within a very brief period of time after the leak has
commenced.
After leakage has been detected by the sensor, the pre-
cise location of the leak can be determined by a person walking the
section of pipeline in which the sensor is located, and using a dip-
stick to inspect each of the spigot reservoir test points to deter-
mine whether the reservoir is filled with leaking product. Because
of the particular configuration of the leak sensing system of the
present invention, only the reservoir of a leaking section will con-
tain a leaked liquid product.
After a leak has been located and repaired, the system
can readily be re-activated. Leaked product can be removed from the
system by the use of appropriate flushing fluids, such as water with
emulsifying detergents which may be pumped into the spigot test point
and which would then flow through the gathering pipe to the sensor
reservoir where the soapy water with the broken down product can be
pumped out.
Leakage in the pipeline is repaired b~ cuttiny away the
sleeve between -the two ~ollars where the leak has occ~lrred, replace-
ment or welding of -the leaking section of pipe, and a new section
of sleeve being welded around the pipe, the collars replaced and
the system re-activated. Several advantages are obtained by the
use of the system of -the present invention.
(1) Rapid leak detection is possible depending on the size
of the leak. A small leak will obviously take longer for the
product to reach the sensor but there is no loss to the environ-
ment, so the length of time is not important for this size of
leak. For a larger leak, time to alarm will be a matter of
minutes, no ma-tter what the product might be, even crude oil;
(2) The product is no longer lost to -the environment but is
contained within the piping system associated with the present
invention. Leak location can be determined to the nearest sec-
tion between collars (which can be as short as five metres).
While it is hoped that there will never be a leak in the pipe-
line and that the spigot test point fittings will be redundant,
in the event o~ a leak i-t is desirable to be able to determine
the leak location to the nearest five-metre interval;
~3~ Protection against corrosion (cathodic protection) would
be optional;
(~) Damage to the pipeline by outside agents, for example
contractor's earth moving equipment causing a leak may be quickly
detected;
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(5) For locations highly sensitive to product loss, a
secondary retention sys-tem can easily be provided;
(6) The system is economical. A simple monitor and sensors
at 1.6 kilometre intervals make this system inexpensive com~
pared to other systems on the market wi-th respec-t to the
equivalent abillty for time of leak detection, leak location,
leak containment, and ability to determine rate of the leak;
(7) Reclamation of lost product: With the secondary piping
system, the overflow of the sensor test points is contained
within the piping system and directed to a reservoir for re-
clamation.
Thus in accordance with the invention a pipeline leak
cletection and leak location system comprises a sealed plastic sleeve
surrounding the pipe, which is sub-divided into discrete segments
which are separated from each other b~ internally positioned collars,
with each segment being connected to a spigot including a reservoir
for the collection of leaked product from the pipe, a small diameter
pipe or tube leading to the surface from the reservoir, and a
gathering pipe connecting each spigot to a sensor reservoir con-
taining a sensor for detecting the presence of leaked product from
the pipeline.
In drawings which illustrate an embodiment of the present
invention;
Figure 1 is a general diagram illustrating a buried pipe-
line equipped with the applicant's leak detection and location system,
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Figure 2 is a cross-sect:ion oE the plpeline of FlcJure 1
through one of the cruciEorm spl~o-ts,
Figure 3 is a cross-section of the pipeline of Figure 1
through the sensor reservoir,
Figure 4 is a sec-tion of an a]ternative form of spi~ot,
and,
Figure 5 is a plan view of a pipeline pro-tected by
applicant's leak detection system.
Referring to Figure 1 there is shown a pipeline 10 fitted
with a plastic sleeve for example of High Density Polyethylene 11
the interior of which is internally sub-divided by a plurality of
collars 12. Between each pair of collars 12 there is located a test
spigot 13. A pipe 14 connects the spigot 13 to a surface pipe sec-
tion test point 14 located at ground level 15. The spigot 13 is
connected in a manner which will be more clearly explained in rela-
tion to Figure 2, to a gathering pipe 16 through which product from
a pipeline leak passes to a sensor reservoir 17 containing a sensor
18. Overflow from the reservoir 17 can pass through the overflow
pipe 19 to a recovery reservoir (not shown). The gathering pipe 16
preferably is fitted with directional flow control valves 20 to
ensure that flow occurs only toward the reservoir 17. Although
not illustrated in Figure 1, it is clear that several reservoirs 17
may be connected together and via the overflow pipe 19 to a suitable
reservoir (not shown).
Referring to Figure 2 there is shown in cross~section a
pipeline construc-ted in accordance with the invention consisting of
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a cylinclrical pipe l0 wrapped :in a po:Lyethylene sleeve 11 to which
is welded at 21 ~ cr~lciform spigot 13. The spigot 13 is p:rovided
with four arms, the first being a reservoir portion 22, a top portion
23 connected to a pipe 2~ which in turn is connected to the surface
test point 14 illustrated in Figure 1. A third arm 25 is welded to
the sleeve 11 and -the fourth arm 26 of the cruciform spigot is con-
nected to the gathering pipe 16. As previously described, in -the
event of a leak, the product leaking from the pipe 10 will be
retained by the retainer sleeve Ll between the two collars, and
when the product reaches the level of the arm 25, will flow into
the reservoir 22. The reservoir will then fill, and flow will con-
tinue via the arm 26 of the cruciform spigot 13 into the gathering
pipe 16 and from there will flow to the sensor reservoir 17 (Fig. 1).
For leak location purposes, a suitable dip-stick may be inserted
down pipe 24 into the reservoir 22 to detect the presence of product
in the reservoir, whence leakage from the section of pipe will be
indicated, and the individual section in which the leakage has
occurred may be repaired.
Figure 3 is a cross-section through the pipeline at the
sensor reservoir 17. The cruciform member 13 is shown in phantom
lines merely to indicate the manner in which the flow occurs from
the retaining sleeve 11 through the cruciform spigot 13 to the
gathering pipe 16, and hence into the sensor reservoir 17. The
continuing flow of product from the gathering pipe 16 into the
reservoir 17 will ultimately result in the reservoir 17 being
filled to the point that Elow occurs out through the outlet to the
overflow pipe 19 and from -here to the recovery reservoir ~not
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illustra-ted). The sensor reservoir 17 is fitted with a sensor 1~
connected to a sensor test point 27 ~Fig. 1) and is also connected
to a main power line or control cable 28 which :is positioned in a
suitable enclosed duct positioned parallel to and below ground
level 15. The test point 27 is connected to the sensor reservoir
17 by a suitable form of duc-t 29 through which the appropriate
wiring may be run to connect -the sensor 18 to a suitable form o~
monitor. It will be appreciated that the sensor 18 may be one of
a variety of devices depending upon equipment requirements, such as
a Leak-X~type sensor cable, an infrared sensor, a fibre optic sensor,
a conductive llquid monitor, a photoelectric cell or the like. The
sensor may also be of the type in which swelling of a plastic insu-
lating material causes contacts to close thereby completing an
electrical circuit.
~ n accordance with an alternative embodiment of the
invention, it is possible to fit the sensor reservoir 17 with a
plurality of sensors 18 and 18a whereby with a sensor reservoir 17
of known dimensions, and with a known spacing between the sensors
18 and 18a, the time difference between the operation of the lower
sensor, and the upper sensor, can be utilized to determine the
rate of leakage of product from the pipeline 10.
Figure 4 is a cross-section through a pipeline and an
alternative form of spigot in accordance with the present invention.
As before the pipe 10 is encased in a sleeve 11 to which is adhered
a spigot fitting 13a, consisting of a reservoir 22a with a vertical
arm 23a, an inlet arm 25a and an outlet arm 26a connected to the
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gatherin~ pipe 16. The spigot 1.3a :i.s connectecl to the sleeve 1.1
as by welding at 40. As i.llustrated in Figure 4 the inlet arm 25a
may optionally include a one-way valve shown as 41.
In certain instances it is desirable to insulate the
pipeline, and Figure 4 illustrates the use o~ the leak detection
and location apparatus of -the present invention on a pipeline
which has been insulated with foam insula-tion 42. As illustrated
in Figure 4 a strap ~3 may be adhered to the exterior of the pipe-
line for the purpose of positioning the gathering pipe 16.
Figure 5 illustrates in plan view a pipeline fitted with
a leak detection and location system in accordance with the present
invention utilizing spigots 13a as illustrated in Figure 4. The
gathering pipe 16 which is positioned adjacent the pipe 10 is illus-
trated in dotted lines in Figure 5 since the gathering pipe 16 is
in fact located partially beneath the pipe 10. The sensor reservoir
17 is positioned beside the pipe 10, and is connected to over~low
pipe 19 through which the leaked product may be sent to a holding
reservoir. The collars 12 in accordance with one form of the inven-
tion may comprise, ~or example, 3 inch wide pieces o~ polyethylene
foam wrapped about the pipe 10 inside the sleeve 11, and sealed
between the pipe and the sleeve by a twisted stainless steel wire 44.
As before, leakage from individual sections of the pipeline is con-
tained between the collars, and exists the sleeve through the spigots
13a where it is directed through the gathering pipe 16 to the sensor
reservoir 17 in which an appropriate form of sensor is mounted to
detect the presence of leakage and/or to measure the rate of leakage
from the pipeline.
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The sleeve of the present invention may be Eormed of
material other than high density polyethy:Lene, Eor example the
shrink wrap material currently used on gas pipelines is suitab:Le
for use as the sleeve material. The sleeve may also be sealed
to the pipe either by welding or the use appropria-te adhesives.
Also, in accordance with a preferred form of the invention as
illustrated in Figure 4, a purge valve is located in the inlet
to the spigot preventing the accidental reversal of flow in the
system in the event that leaked product should attempt to flow
through the inlet back into the sleeve.
