Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02598949 2007-08-27
SN/. P060113 1 Dr.
Alfred Mortel
Specification
Collector line for leakage monitoring and leakage location
The invention relates to a collector line for leakage monitoring and leakage
location on a
plant such as is known from EP 0 175 219 B1. This invention moreover relates
to a
device and a method for leakage monitoring and leakage location on a plant in
which
such collector line is used.
A collector line is known from EP 0 175 219 B1, which consist of a carrier
tube which is
provided with a permeable layer on its exterior surface, through which a
substance from
a leakage in the plant, for example a pipeline, can diffuse, which escapes
into the
environment of the collector line and must be detected. The carrier tube is
impermeable
for this substance. Its wall is provided with openings so that any substance
passing
through this permeable layer can get to the inside of the collector line
through these
openings. Using a method known from DE 24 31 907 C3, the location at which the
substance has penetrated into the collector line can then be determined. This
location
corresponds to the place at which the substance has escaped from the monitored
plant
section. For this purpose, the substance which has penetrated into the
collector line is
fed with a pump connected to the collector line together with a carrier gas
contained in
the collector line to a sensor which is also connected to the collector line.
If the flow rate
is known, using the time interval between switch-on of the pump and when the
substance arrives at the sensor,
CA 02598949 2013-11-04
30146-29
2
the location at which the substance penetrates into the collector line and
thus the
location of the leakage in the plant section can be determined.
As a material for the permeable layer, ethylene vinyl acetate, EVA, was found
to be
particularly suitable in a multitude of applications. The use of EVA as a
permeable
layer is problematic under environmental conditions where very low
temperatures can
occur, however, such as during the monitoring of aboveground installed oil
pipelines,
such as is the case in arctic and subarctic areas. Because it has been shown
that the
diffusion rate of the substances to be detected though a wall of EVA
exponentially
drops with the temperature, and in practice limits the range or applications
with EVA
as a permeable layer in such collector lines to temperatures above 0 C
The object of some embodiments of the invention therefore is to specify a
collector
line for leakage monitoring and leakage location on a plant which is also
suitable for
used at low temperatures. In addition, the objectives of the invention are to
present a
device and a method for leakage monitoring and leakage location with said
connection line that is suitable for use at low temperatures.
According to an embodiment of the invention, there is provided a pipeline, the
pipeline comprising: an inner pipe conveying a material and having a
longitudinal
axis; a thermal insulation layer surrounding said inner pipe; a channel
extended in
said thermal insulation layer parallel to said longitudinal axis of said inner
pipe; an
auxiliary pipe embedded in said insulation layer, perforated with holes or
slots and
forming said channel; and a collector line disposed in said channel for
leakage
monitoring and leakage location at said inner pipe, said collector line
including: a
carrier tube being impermeable to a substance to be detected and having a wall
with
openings formed therein; and a at least one first layer closing said openings,
being
formed of silicone rubber and being permeable to the substance to be detected.
According to another embodiment of the invention, the collection line
comprises a
carrier tube in which the wall is provided with openings that are sealed with
at least
one first layer which is permeable for the substance to be detected, which
consists of
silicone rubber
CA 02598949 2007-08-27
SN/?060113 3 Dr.
Alfred MOrtel
and in particular completely covers the exterior surface of the carrier tube.
=
Consisting of silicone rubber within the meaning of the present invention
means that this
is the base matrix or the base material of the first layer to which further
fillers or additives
may have been added.
The invention is thus based upon the knowledge that silicone rubber, even
though it is
normally used as an elastic sealant, particularly has high permeability for
crude or
mineral oils and gasoline and because of its high low temperature stability
has high
permeability even at low temperatures and is therefore suitable as a permeable
layer of
a collection line also for use under environmental conditions in which low
temperatures
can occur.
In an advantageous development of the invention, the carrier tube comprises a
,second
electrically conductive layer which extends in its longitudinal direction into
which the
substance may penetrate and the ohmic resistance thereof is dependent on the
level of
penetrant material therein. With such a collection line, the presence of a
substance
escaping during a leakage from the plant in large quantities can be
permanently
monitored by measuring the resistance of the electrically conductive,
substance
sensitive layer between two measuring points which are spatially far apart
from each
other. In other words: permanent leakage monitoring is possible which is
independent of
the times at which a pump connected to the collection line is switched on.
CA 02598949 2007-08-27
SN/.P060113 4 Dr.
Alfred Martel
This has the advantage that big leakages can be registered with very short
time delay. In
fact, in order to be able to register even small leakages with the known
leakage
monitoring and leakage location device, relatively long collection times are
required
which can be up to 24 hours. Only then, in view of the unavoidable
longitudinal diffusion
and the absorption that occurs inside of the collection line over an extended
section, a
sufficient quantity of the substance to be detected has penetrated into the
collection line
in order to be able to transfer it to the sensor at a concentration necessary
for detection.
Particularly with long collection lines, such as laid along pipelines, the
carrier gas is
therefore conveyed through the collection line at larger time intervals or
interrogation
intervals, for example every 6 to 24 hours, so that in the least favorable
case, a time
interval between the occurrence of the leakage and its detection can pass that
is
composed of the time interval between two consecutive measurements and the
time
which the penetrant substance requires from the start of the pump sequence
until it
arrives at the sensor. A time interval in the order of several hours can
however be
accompanied by significant irreversible damage, particularly in the case of
larger
leakages, both to the plant as well as to the environment.
This damage can be prevented by using a collection line with an electrically
conductive
second layer, since with such a collection line both a high detection
sensitivity in the
event of small leakages, as well as a high speed of response in the event of
large
leakages, can be achieved.
=
In a further development of the invention, the electrically conductive layer
consists of a
carbon black filled polymer material,
CA 02598949 2007-08-27
SNLP060113 5 Dr.
Alfred MOrtel
which preferably likewise involves a silicone rubber. This facilitates the
electrically
conductive layer to be produced in a particularly cost effective manner,
since, on the one
hand, it can likewise be applied to the carrier tube just as easily as a layer
made of pure
silicone rubber, i.e. one that is not filled with carbon black, and by filling
it with fine-
grained carbon black, in which the grain size is preferably within the nm
range, the
electrical conductivity of the carbon black particles in contact with each
other can be
brought about through the development of contact bridges between them in a
particularly
simple manner, and since, on the other hand, the electrical conductivity of
the carbon-
black filled silicone rubber largely depends upon the swelling that occurs
during the
penetration of the substance and the accompanying destruction of the carbon
black
bridges.
Since the electrically conductive layer is also permeable in this case, it can
completely
cover the exterior surface of the carrier tube. In this development, the
electrically
conductive layer can also be used to monitor the collector line with respect
to
mechanical damage, for example for fracture.
If the permeable first layer is electrically insulating and covers the
electrically conductive
second layer, the electrically conductive layer is electrically insulated from
the
environment, so that the collector line can also be installed in the ground or
in contact
with electrically conductive plant components. Moreover, in the event that the
electrically
conductive second layer is permeable and surrounds the carrier tube completely
and
thus also seals the openings contained therein,
CA 02598949 2013-11-04
30146-29
6
a decrease in the permeation rate caused by the admixture of carbon black can
be
reduced, since this electrically conductive permeable layer only has to have a
thickness
to the extent that is necessary for monitoring of the electrical resistance
and/or the
electrical conductivity.
A particularly simple embodiment provides for only one first permeable layer,
iehich is
electrically conductive through the admixture of carbon black, so that its
electrical
resistance depends on the level of penetrant material therein. In one such
development,
both a high detection sensitivity as well as a high speed of response can be
achieved
with a one-layer collector line.
. .
Particularly advantageous developments of a device and a method for leakage
detection
and leakage location using a particularly advantageous development of the
collector line
according to some embodiments of the invention. _
By measuring the electrical resistance of the electrically conductive layer
according to
an embodiment of the invention, permanent leakage monitoring is possible with
little
effort in terms of apparatus and technical measurement complexity.
In the method according to an embodiment of the invention, the time interval
between
the occurrence of a leakage and leakage location is reduced by using an
increase in
resistance as tripping or triggering signal for performing a measurements to
locate the
leakage, in that a fluid carrier medium is pumped through the collector line
and analyzed
with a sensor for a substance that escapes during the leakage.
CA 02598949 2007-08-27
SN/ .P060113 7 Dr.
Alfred MOrtel
A leakage location is therefore no longer exclusively performed at fixed
specified time
intervals but in addition or only when the occurrence of a leakage is detected
by
resistance measurement.
A collector line of the type mentioned at the outset, in particular a
collector line as taught
by the invention, is particularly suited for monitoring of a pipeline carrying
the substance.
In one particularly suitable development for use of a collector line of the
type mentioned
at the outset, a pipeline comprises an inner pipe conveying the substance,
which is
surrounded by an insulation layer in which a channel for accepting a collector
line is
arranged parallel in relation to the longitudinal axis of the inner pipe.
=
Such pipeline can be particularly easily provided with a collector line of the
type
mentioned at the outset. Through this measure, the collector line is moreover
protected
against environmental effects.
If the channel is formed by an auxiliary pipe embedded into the insulation
layer, the
subsequent introduction of the collector line is simplified and the risk of
damaging the
insulation layer during the installation of the collector line is decreased.
The channel is preferably arranged at a distance from the inner pipe. As a
result, the
entire exterior surface of the inner pipe contacts the insulation layer, and
its adhesion to
the inner pipe is not impaired by the channel.
CA 02598949 2007-08-27
SN/ PO60113 8 Dr.
Alfred MOrtel
For further explanation of the invention, reference is made to the exemplary
embodiments of the invention, as follows: =
Fig. 1 and 2 present a collector line as taught by the invention as a
longitudinal section
and/or cross-section,
Fig. 3
presents an alternative embodiment of the openings made in the collector
line,
Fig. 4 ¨ 7
presents further advantageous developments of a collector line as taught
by the invention in their respective schematic cross-section,
Fig. 8
presents a collector line as taught by the invention which is provided with
pressure resistant braiding, as an isometric view,
Fig. 9
presents a device with a collector line according to Fig. 4 - 7, also as a
schematic diagram,
Fig. 10, 11
presents a particularly advantageous arrangement of a collector.line as
taught by the invention in a pipeline carrying crude oil, as a schematic,
partially longitudinal and/or cross-section.
According to Fig. 1 and 2, a collector line 1 comprises a carrier tube 2, for
example from
polyvinyl chloride PVC, in particular from polyvinylidene fluoride PVDF or
polyether
ketone PEEK, in which the wall is provided with a multitude of radial openings
4. On the
carrier tube 2, a permeable contiguous first layer 6 consisting of silicone
rubber for a
substance L to be detected is arranged, which completely covers the carrier
tube 2 and
seals the openings 4 in this manner. Particularly suitable are cross-linked
silicones,
organopolysiloxanes, particularly wide-meshed cross-linked silicone rubbers
(diorganopolysiloxanes)
CA 02598949 2007-08-27
SN/ P060113 9 Dr.
Alfred Mortel
with particularly high absorptivity of the substance L to be detected, i.e.
polysiloxanes,
which exhibit high swelling in the presence of substance L, particularly the
commercially
available MVQ HTV silicone rubber (HCR silicone rubber) SX 70 W which consists
of a
mixture of polynnethylvinylsiloxanes and highly dispersed silicic acids or
alternatively of a
mixture of polydimethylsiloxanes, polyvinylmethylsiloxanes,
polyphenylmethylsiloxanes,
polyphenylvinylmethylsiloxanes and silicic acids.
Fig. 3 represents an embodiment in which the openings 4 have a conical shape
and
taper toward the inside of carrier tube 2 and are filled with a porous filler
material, which
practically does not impede the diffusion of the substance L into the inside
of carrier tube
2. This facilitates the covering of the carrier tube 2 with a permeable first
layer 6 which
consists of silicone rubber, since this can in this case also be applied in a
low viscosity
liquid condition, without filling the openings 4 or flowing into the inside of
carrier tube 2.
As an alternative to this, it is also possible to incorporate the openings 4
through suitable
manufacturing methods, for example laser drilling, in large numbers into the
carrier tube
2 and with a very small diameter, so that the silicone rubber, even when it is
applied in
electric condition, can practically not penetrate into these openings 4.
In the exemplary embodiment according to Fig. 4, an electrically conductive
second
layer 8 has been applied to the exterior surface of the carrier tube 2, which
is surrounded
by a permeable first layer 6, which, in this development, is electrically
insulating. This
electrically conductive second layer 8 is equally permeable
CA 02598949 2007-08-27
SN/ P060113 10 Dr.
Alfred MOrtel
for the substance L to be detected and moreover reacts sensitively to
substance L in
such a manner, that its (specific) electrical resistance is dependent upon the
presence of
substance L.
The electrically conductive second layer 8 in the exemplary embodiment consist
of a
polymer material filled with electrically conductive particles, which in this
case involves
an electrically isolating polymer base material in particular also a silicone
rubber, to
which, in order to bring about electrical conductivity, conductive particles
have been
admixed which are carbon black, in the example.
Because of the substance L entering and passing through it, the electrically
conductive
second layer 8 experiences a change in its structure, such as swelling. In
this manner,
the bridges between the electrically conductive particles break open and the
electrical
conductivity which is based upon these bridges in the silicone rubber to which
these
=
conductive particles have been added, deteriorates.
The proportion of carbon black needed in practice depends on the length of the
collector
line, in order to achieve electrical resistance values in the range of several
mC2 that can
be registered using little technical measurement complexity.
In the exemplary embodiment, the layer thicknesses of layers 6 and/or 8 are 1
mm in
each case. The wall thickness of carrier tube 2, which preferably consist of
PVDF or
PEEK, is approximately 1 mm with an inside diameter of approximately 10 mm.
CA 02598949 2007-08-27
SN/ P060113 11 Dr.
Alfred MOrtel
The exterior, electrically insulating permeable first layer 6 is moreover
surrounded by
permeable, elastic protective braiding, which is not shown in the figure, for
protection
against mechanical damage.
The carrier tube 2 can moreover be provided with a coating on its internal
surface area,
which consist of a material that has only a low absorption capacity for
substance L, in
order to extensively reduce the signal attenuation by absorption in carrier
tube ? which
develops if the distance between the leakage location and the detection sensor
is large.
This coating, for example from Teflon PTFE, is applied to the internal surface
area,
before the radial openings 4 are made in the carrier tube.
According to Fig. 4, a single-layer structure is provided in which the first
layer 6, which is
permeable for substance L, is electrically conductive through admixture of
carbon black.
In other words: only one single layer is provided which combines both the
properties of
the first layer 6, that is the good permeability for the substance L to be
detected, as well
as the properties of the electrically conductive second layer 8, that is the
change in the
electrical resistance, if substance L penetrates into it.
In principle, it is also not mandatory that the electrically conductive second
layer 8 in the
presence of an electrically insulating permeable first layer 6 which
completely surrounds
carrier tube 2 covers said tube completely. In the exemplary embodiment
according to
Fig. 6, the electrically conductive second layer 8 covers only a band-shaped
subarea of
the exterior surface of the carrier tube 2 which extends in a longitudinal
direction.
CA 02598949 2007-08-27
SN/ P060113 12 Dr.
Alfred MOrtel
In other words: the electrically conductive second layer 8 and the permeable
first layer 6
are arranged side-by-side on carrier tube 2. In this exemplary embodiment, it
is also not
mandatory that the second layer 8 is permeable for the substance L.
In the embodiments illustrated in Fig. 5 and 6, the collector line 1 is
suitable for
installation in an electrically insulating environment.
In the exemplary embodiment illustrated in Fig. 7, the electrically conductive
second
layer 8 has the shape of a band that is embedded in the first layer 6, which
in this
exemplary embodiment is electrically insulating and insulates the band-shaped
second
layer 8 electrically insulated from the environment, in order to facilitate
the use of the
collector line 1 in an electrically conductive environment. In addition, a
band-shaped
return conductor 9 is embedded into the first layer 6, which only occupies one
sector of
the carrier tube 2 circumference, the electrical resistance of which is not
affected by
substance L. This return conductor 9 is electrically connected on one end of
collector
line 1 with the second layer 8, which enables its resistance to be measured.
Alternatively
to this, return conductor 9 can also consist of the same material as the
second layer 8,
so that its resistance is likewise affected by substance L.
The collector line 1 can in all exemplary embodiments according to Fig. 1 to
Fig. 7 in
addition be enveloped on the outer periphery with a permeable braiding 11, as
illustrated
in Fig. 8. This braiding 11 which can consist of polyethylene PE for example,
serves both
as protection against mechanical
CA 02598949 2007-08-27
SN/ P060113 13 Dr.
Alfred MOrtel
damage as well as for mechanical stabilization, if excess pressure exists on
the inside of
carrier tube 2 for conveying the carrier gas, which would result in a
destruction of the
silicone rubber layer 6 which covers openings 4.
According to Fig. 9, the collector line 1 is laid along a pipeline 10 between
a pomp 12
and a sensor 14 for the substance to be detected. An evaluation and control
unit 16
measures the electrical resistance of the electrically conductive layer 6, 8
along a
section s permanently, i.e. it is also measured even when pump 12 is not
activated, i.e.
when a fluid carrier medium M inside carrier tube 2 is at rest. In an example
for this, a
separate return conductor 18 is installed along the collector line 1. If the
resistance of the
electrically conductive second layer 8 exceeds a specified threshold value
because of a
leakage of an escaping substance L in the environment of the collector line 2
(shown by
a dotted line), a control signal 20 is generated in the control and evaluation
unit 16 in
order to start up the pump 12 and perform a leakage location in accordance
with the
known method discussed at the outset.
Depending upon the installation location of collector line 1 it can also be
possible that a
separate return conductor 18 or a return conductor 9 integrated into the
collector line 1
(Fig. 4) is not necessary, in that, for example, a ground contact is
established at the
terminal point of the section, as is indicated in this figure by dotted lines.
CA 02598949 2007-08-27
SN/ P060113 14 Dr.
Alfred Martel
According to Fig. 10, a pipeline 30 conveying substance L, for example crude
oil,
comprises an inner pipe 32 of steel, which is surrounded by an insulation
layer 34
consisting of polyurethane. A channel 36 is introduced into the insulation
layer 34 at a
small distance to the exterior surface of the inner pipe 32, which runs
parallel to the
longitudinal axis 38 of the inner pipe 32 and in which a collector line 1 is
installed as
schematically illustrated.
In the exemplary embodiment according to Fig. 11, a channel 36 is formed by an
auxiliary pipe 40 embedded in the insulation layer 34, into which the
collector line 1 can
be inserted. The auxiliary pipe 40 is perforated with holes or slots and is
thus open for
substance L to pass through, which is conveyed in pipeline 30 and which
escapes from
the inner pipe 32 in case of leakage.
With a pipeline 30 configured in this way and a collector line 1 installed
therein, any
leakages occurring in the inner tube 32 can be detected already before they
escape into
the environment of pipeline 30, since the escaping substance L initially
reaches the
insulation layer 34, where it accumulates and diffuses into the collector line
1.
CA 02598949 2007-08-27
14a
SN/ P060113 Dr.
Alfred Miirtel
List of references
1 Collector line
2 Carrier tube
4 Openings
6 First layer
8 Second layer
9 Return conductor
11 Braiding
Pipeline
12 Pump
14 Sensor .
16 Evaluation and control unit
18 Separate return conductor
Control signal
Pipeline
32 Inner pipe
34 Insulation layer
38 Longitudinal axis
Auxiliary pipe
L Substance
