Note: Descriptions are shown in the official language in which they were submitted.
- FILE, ~N 11~ THIS AM~NDED ,~ 1 0 ~ 5
~ TRANSLATION ~ ~ 2
WO 92/16316 - 1 - PCT/DE92/00236
Element for sealing and monitoring a body, in
particular a refuse dump
The invention relates to an element for sealing
and monitoring a body having two seals, which at their
edges are sealingly connected together, leaving free an
inlet opening and an outlet opening for a medium, while
at least one sensor can be connected to the outlet
opening.
From DE 37 37 569 Al a device for the base
sealing of deposits is known. Two seals extending over a
large area are here sealingly connected together at their
edges, leaving free an inlet opening and an outlet
opening for a medium. The medium, which may be air, flows
through the space between. The medium passes through the
outlet opening to a sensor, in which a substance
penetrating can be identified by gas-chromatography. With
this device it can be determined whether a substance has
penetrated into the cavity through a leak in one of the
two seals. However, the leak cannot be located.
From BMT, volume 34, No. 4, April 1987, Pages 196
to 200, a simple seal consisting only of a sheet is
known. A device for locating leaks is associated with
this sheet. Since the leak locating device is situated in
a filter layer, which usually consists of sand and has no
homogeneous flow resistance, after a leak has occurred in
the sheet a substance passing through the leak can travel
through the filter layer until it is detected at an
undetermined point. The known arrangement is not a handy
element consisting of two seals, which has a reliable
sealing action and would be easy to lay. On the contrary,
it is a simple association of a sheet and a locating
system.
A similar device to that from BMT, Volume 34, No.
4, April 1987, Pages 196 to 200, can also be seen in the
Siemens leaflet "long-term refuse dump monitoring with
LEOS", Order No. A 19100-U653-A222, July 1990. From this
leaflet a device for sealing a refuse dump and for
detecting and locating leaks is known. This provides for
REPLACEMENT SHEET
~106~i82
WO 92/16316 - la - PCT/DE92/00236
the refuse dump to be equipped with a waterproof sheet,
sealing sheeting (particularly of plastic material) or
"seal". This seal may be disposed under the refuse body
(base seal), so that no noxious matter can pass into the
groundwater. The seal may however also be placed above
the refuse body (surface seal), in order to prevent the
penetration of rainwater and therefore to prevent noxious
matter from being washed out of the refuse. In order to
detect in good time a leak (damage) in this seal,
provision is made with the known device to lay so-called
LEOS hoses on the side of the seal remote from the refuse
body. The LEOS hoses, which are laid in a meander pattern
and are filled with air, and whose wall is permeable to
various substances present in the refuse, are connected
to a central monitoring system. In the case of a seal
situated under the refuse body, a damaged point in the
seal is located by detection of substances dissolved in
the leakage water, while when the seal is placed above
the refuse body, damage in it is located by detecting
rising fermentation gases.
A LEOS hose and a device serving to operate it
are known from German Patent Specification 24 31 907.
This relates to a hose which is permeable to noxious
substances. At one end of the hose a pump is disposed,
with which individual volumes of a medium, for example
individual gas volumes, can be delivered one after the
other through the hose at intervals of time. The hose is
in this way flushed for some time at regular intervals of
REPLACEMENT SHEET
2~0~582
WO 92/16316 - 2 - PCT/DE92/00236
time, that is to say with a constant flushing frequency.
Sensors sensitive to noxious substances are disposed at
the other end of the hose. If a noxious substance comes
into the vicinity of the hose, it will penetrate into the
latter and be brought to the sensors by the next medium
pumping operation. Since during this operation the medium
flows at a known speed, the difference between the moment
of time when the pump is switched on and the moment of
time when the sensors react will make it possible to
determine accurately the point where a noxious substance
entered the hose between two flushings. In addition, the
amount of noxious substance can be determined.
If a leak in the seal does not occur in the direct
vicinity of the LEOS hose, the substance to be detected
which has escaped is distributed over a larger area before
it reaches the LEOS hose. In the event of different speeds
of propagation in this area the substance may reach the
LEOS hose simultaneously at more than one point. The
substance to be detected may also reach the LEOS hose only
at a point relatively distant from the leak. Moreover,
between two flushings the substance may reach and diffuse
into a relatively large portion of the hose. It will then
only be possible to determine that the leak is situated
somewhere in the region of that portion of the hose.
Determination of the location of the leak may consequently
be subject to relatively considerable error. With the known
device a leak in the seal cannot always be accurately
located. Furthermore, the laying of the seal and that of
the LEOS hoses constitute two operations.
The invention is based on the realization that it
is appropriate to provide increased protection by means
of a double barrier. This would be expedient both for the
base seal and for the surface seal of a refuse dump. It
is in addition based on the reflection that it is then
also appropriate to provide a configuration such that it
can be determined by measurement techniques whether one
barrier or the other has a leak and where this leak is
situated.
REPLACEMENT SHEET
~ 3 ~ 2 1 0 65 82
The problem underlylng the lnventlon ls that of
lndlcatlng an element for seallng and monltorlng a body, wlth
whlch the slte of a leak can be very accurately located and
wlth whlch double leak protectlon ls ensured by the use of two
barrlers. The element should be able to be lald qulckly and
rellably.
Accordlng to the lnventlon there ls provlded element
(2) for seallng and monltorlng a body (1), whlch element (2)
comprlses two seals (4, 5) havlng edges, whlch two seals (4,
5) are seallngly connected together leavlng free an lnlet
openlng and an outlet openlng for a medlum, whlle at least one
sensor (18) can be connected to the outlet openlng,
characterlzed ln that the two seals (4, 5) are spaced apart by
supportlng elements (6), ln that between the seals (4, 5) and
the supportlng elements (6) at least one channel (7) ls formed
whlch connects together the lnlet openlng and the outlet
openlng, and ln that the supportlng elements (6) are made of a
materlal permeable but reslstant to flow for a substance to be
detected, and havlng a known flow reslstance.
Wlth thls element the advantage ls achleved that
after a leak has occurred ln one of the seals a substance to
be detected ls passed to the channel ln a deflned manner. The
substance does not flow through an envlronment whose structure
ls unknown, but proceeds through the supportlng elements to
the channel. The flow reslstance of the supportlng elements
or of the cavltles ln the supportlng elements ls known and, at
least ln the dlrectlon of each axis of the supportlng element,
20365-3307
- 3a - 21 06582
is constant. The substance penetratlng flrst passes from the
leak ln the seal lnto the channel by the shortest route,
namely at rlght angles to the channel. Only then does the
penetratlng substance arrlve at the channel at nelghborlng
polnts. In the perlod of tlme between the occurrence of the
leak and the next flushlng a substance dlstributlon ls formed
ln the channel wlth a maxlmum whlch durlng flushlng and
detectlon lndlcates the slte of the leak. Wlth a low flow
reslstance of the supportlng element the dlfferences in tlme
between arrlval via the direct route and arrlval vla the
rather longer routes are very sllght. In the perlod of tlme
between the occurrence of the leak and the next flushlng a
wlde, flat
20365-3307
~L
~ 2106582
-- 4
distribution of substance could then build up in the
channel, with an undetectable maximum. However, owing to
the fact that according to the invention the supporting
elements are made of a material resistant to flow, the
penetrating substance moves so slowly in a supporting
element that the difference in time between arrival at
different points in the channel is measurably large even
when the difference between the paths followed is slight.
In the period of time between the occurrence of the leak
and the next flushing, with a predetermined flushing
frequency in the channel only a narrow, steep substance
distribution can be formed, the maximum of which can be
well recognized by the sensor. Consequently, it can
easily be determined where the substance first reached
the channel. The leak must then lie on a line at right
angles to this point on the channel.
Only one sensor may be provided for a determined
substance, or a plurality of sensors for different
substances may be provided.
With the element according to the invention good
location of a leak in the seal is possible.
Through the fixed connection between the seals
and the channels the element according to the invention
can be laid quickly in a single operation.
If different substances are to be expected below
and above a laid element, the type of substance detected
will make it possible to deduce whether the leak is in
the top or the bottom seal. The nature of the substance
can be detected by providing appropriate sensors. For
example, an element according to the invention may seal
a refuse dump. The penetration of almost pure water would
then permit the assumption of a leak in the top seal
facing away from the refuse dump body.
The channel may for example be in the form of a
permeable hose. The hose known from German Patent
Specification 24 31 907 may be suitable.
According to another example of embodiment the
channel in the element may be separated from neighboring
supporting elements by permeable diffusion layers. No
- ?lOfi582
hose is then necessary.
The hose may be surrounded by a filling material.
A drying agent may be used as filling material, or as a
component of the supporting elements, in order to
eliminate residual moisture in the element. The accuracy
of measurement of moisture penetrating through a leak can
thus be improved. A moisture sensor is for example used
to determine the penetration of water.
According to a further development the supporting
elements have lower flow resistance at right angles to
the channel than parallel to the channel. The advantage
is thereby gained that the substance penetrating into the
supporting element through a leak in a seal will spread
out in the shape of an ellipse and not circularly. The
longer axis of the ellipse is then directed at right
angles to the channel. A still narrower, steeper
substance distribution is consequently obtained in the
channel than when use is made of a homogeneous flow-
resistant material as supporting element, that is to say
a material permitting the same speed of flow in all
directions. The leak can thus also be located with
greater accuracy.
The material of the supporting elements, which
has lower flow resistance at right angles to the channel
than parallel to the channel, may for example be a woven
fabric directed at right angles to the channel. The
material of the supporting elements may however also be
constructed of capillaries, tubules or the like, directed
at right angles to the channel.
The two seals may be sealingly connected together
at their edges at the channel ends, but also in places
where there are no channel ends, by means of sectional
members fitted onto them. Such sectional members are easy
to handle. The two seals may however also be welded
together.
The inlet and outlet for the medium flowing
through the channel may be connected together to form a
circuit. The sensor and a pump are then disposed in the
circuit. As long as no leaks occur, the medium flowing
- 210~82
through the channel need not be continually replenished.
The circuit has for example a closable feed
opening and a closable outlet opening. Between the outlet
opening and the feed opening the circuit should be
completely or partially closable. Medium can then be
introduced and drawn off as required. The circuit can be
interrupted, so that all the medium introduced can be
drawn off again. Instead, with a partially closed
connection between the outlet opening and the feed
opening, only a part of the medium in the circuit may be
replaced.
In the outlet or in a bypass around the outlet a
filter is for example disposed, which can remove
substances penetrating into the circuit through a leak.
A filter of this kind may be a catalytic filter.
Particularly when the filter is disposed in a bypass
around the outlet, it can be replaced or cleaned without
impairing the intactness of the circuit. In certain
circumstances it is appropriate to measure the substances
removed from the filter in the cleaning operation. For
this purpose the filter may be connected to a cleaning
device and to a sensor in order to permit sensitive,
integral measurement.
In addition to immediate determination of
penetrating noxious substances by means of the sensor, it
is also possible to determine in the manner described,
the penetration of noxious substances between two filter
changes. In the event of the failure of the sensor, it
can thus at least be ascertained whether a leak existed
between two filter changes.
For the purpose of cleaning the filter to remove
retained substances, the filter may be provided with a
heating system. This heating system serves the purpose of
freeing the retained substances by heating. The filter
may also be able to be charged with water vapor or water.
By this means also the substances retained in the filter
can be freed again.
A plurality of the elements described for sealing
and monitoring a body can preferably be sealingly
2106~82
- 7 -
connected together to form a panel. In this case the
outlet opening of the channel of the one element is
connected to the inlet opening of the channel of another
element. With an arrangement of this kind the advantage
is gained that for the purpose of sealing a large area,
for example a refuse dump, it is not necessary to provide
a large one-piece cover element which would be difficult
to transport and to handle. The advantage is gained that
with simple means it is possible to form quickly, from
handy individual elements, a panel which can take over
the duty of a very large element for sealing and
monitoring a body.
The adjoining elements may for example be welded
together to form a panel. They may however also be joined
in other ways. For example, a sectional member, which is
disposed on the edge of one element and which holds the
two seals of that element, may also be provided with
devices for holding the seals of the adjoining element.
Only one sealing sectional member is thus then situated
between two adjoining elements. In order to ensure a
particularly leakproof connection, a weld seam may
nevertheless be necessary.
The channels of adjoining elements may for
example be joined together by means of plug-in
connections. However, other forms of connection, for
example welded joints, are also possible.
The individual elements can be joined together to
form a panel in such a manner than only one channel
passes through the entire panel, covering the whole panel
in a meander pattern. The entire panel then has only one
feed inlet and only one outlet and needs, for all the
elements, only one common sensor, which may also be in
the form of a double sensor, for example for water and
methane gas.
With an element according to the invention the
advantage is achieved that a leak in one of its seals can
be detected and accurately located. In addition, kncwing
which substance has penetrated makes it possible to
ascertain whether the substance detected comes from the
~lQ6582
interior of the space monitored or comes from outside.
For this purpose sensors responding to different
substances or a plurality of sensors for different
substances, for example for noxious substances or gases
such as methane gas and for water, are necessary.
Examples of embodiment of the invention will be
explained more fully with reference to the drawing, in
which:
Figure 1 shows a refuse dump sealed at top and
bottom, for which respective flexible panels composed of
sealing and monitoring elements are used;
Figure 2 is a section through an element
according to the invention;
Figure 3 shows another embodiment of an element
according to the invention;
Figure 4 shows a device with a channel lead-
through for connecting together two elements, the drawing
being turned by 90~ relative to Figure 2;
Figure 5 shows a connection, without a channel
lead through, between two adjoining elements;
Figure 6 shows a panel comprising a plurality of
elements, with an appertaining installation for its
operation, and
Figure 7 shows the flow pattern starting from a
leak in an element.
According to Figure 1, a refuse dump comprising
a refuse body 1 is sealed at the top and at the bottom by
a device having a configuration according to the
invention. This device comprises a top panel Fl and a
bottom panel F2, each panel consisting of monitorable
double seals, which hereinbelow will be referred to as
~elements" 2. These elements 2, each of which has two
parallel longitudinal channels 7, are connected together
at respective joints 50. By means of the upper panel F1
the penetration of water from above into the refuse body
1 and the escape of refuse gas in the upward direction
from the refuse body 1 are monitored, and a corresponding
leak is located. By means of the bottom panel F2 the
escape of refuse gas from the refuse body 1 in the
21Qfi582
g
downward direction and the penetration of moisture from
below upwards into the refuse body 1 are monitored, and
a corresponding leak is indicated. Each panel F1, F2
comprises two barriers for gas and moisture, as will
become clear later on. The monitorable upper panel F1 is
covered with earth and the monitorable panel F2 rests on
a mineralogical sealing layer.
According to Figure 2 an element 2 consists of a
bottom seal 4 and a top seal 5. The two impermeable
sheets, sealing sheetings, coverings or seals 4 and 5,
which for example consist of polyethylene or other
plastic material, are spaced apart by supporting elements
6. Between the seals 4 and 5 and the supporting elements
6 a channel 7 is left free, which extends through the
element 2 at right angles to the plane of the drawing.
Two (see Figure 1) or more channels 7 could also be
provided in each element. Except for the inlet opening
and the outlet opening of the channel 7, the element 2 is
sealingly closed on all sides at its edges, the top seal
5 being for example welded to the bottom seal 4. The weld
joint is designated 45. In Figure 2 a permeable hose 8 is
laid in the channel 7 and corresponds to the hollow duct
according to German Patent Specification 24 31 907. It
consists in particular of a LEOS hose. It can effectively
convey gas and water vapor over great lengths. The hose
8 is surrounded by a filling material 8a, for example
sand or a drying agent.
The supporting elements 6 consist of a material
permeable but resistant to flow. By this is meant a
material which leads to not too rapid but also not too
slow spreading-out of water vapor and/or refuse gas. The
supporting elements 6 may also consist of a material
which has a lower flow resistance at right angles to the
channel 7 than parallel to the channel 7. Such a material
may be an aligned woven fabric. The material may also
consist of capillaries or tubules extending parallel and
aligned at right angles to the channel 7. It may for
example be made of polyethylene or other plastic
material. The filling material 8a is a material which
~Ofi58~
- 10 -
retains moisture. The filling material 8a is however not
completely indispensable.
The width b of the elements 2 according to Figure
2 may for example amount to from three to five meters.
Its length may for example amount to 50 meters. Such
sheets are flexible and relatively simple to lay and then
to join to one another.
According to Figure 3 it is also possible to
dispense with the hose in the channel 7. The channel 7 is
then separated from the adjoining supporting elements 6
by permeable diffusion layers or diffusion walls 9. The
channel 7 then corresponds to the hollow ducts according
to German Patent Specification 24 31 907. In principle
the walls 9 can also be dispensed with.
According to Figure 4 the two seals 4 and 5 of a
first element 2A are connected together at their right-
hand edge by a sectional member 10 having a central
opening and fitted onto said seals. The sectional member
10 serves at the same time to hold the seals 4 and 5 of
an adjoining identical second element 2B. The sectional
member 10 thus joins together the left-hand edges of the
seals 4 and 5. The elements 2A, 2B are thus also joined
together at the joint 40. In this way a plurality of
elements 2 can be joined together in modular fashion to
form an array or a panel. For the purpose of connecting
the channels 7 or hoses 8 of the two elements 2A and 2B
which are to be joined together, the sectional member 10
has a through opening 11. A rigid sleeve 12 is disposed
therein. Said sleeve is welded fast in the through
opening 11. The hoses 8 can be connected on both sides to
the sleeve 12, for example by means of clips 13. In this
way the outlet opening 8A of the channel 7 of the left-
hand element 2A is connected to the inlet opening 8B of
the channel 7 of the right-hand element 2B. A medium,
such as air, for example, can now flow from left to
right, as indicated by arrows, through intermittent
suction or pressure action. In the structure shown in
Figure 4 weld seams 14 are necessary for sealing purposes
at top and bottom.
~10678~
- 11 --
Where no connection is necessary between
adjoining channels 7, adjoining elements 2 can be coupled
or connected together at a joint 50 also by means of a
simple weld seam 52, as shown in Figure 5. Figure 5 thus
shows such a weld joint between adjoining elements 2A, 2B
outside a channel leadthrough. Instead of a weld seam 52
directly at the connection of the seals 4 and 5, the
joint 50 may also consist of a cover plate 54 which is
sealingly welded at the ends of the two adjoining
elements 2A and 2B. The weld seams necessary for this
purpose are designated 56. Instead of this, however, a
sectional member 10 not provided with a through opening
11 may also be used (not illustrated).
According to Figure 6 an arrangement may be
selected in which the elements 2 are joined together to
form a panel F. The channels 7 are passed through the
panel F in a meander pattern. For this purpose U-shaped
connectors 16 are required for the rows of elements 2A,
2B. In principle, the channels 7 may also be disposed in
a meander pattern in each element 2A, 2B. The channels 7
are components of a circuit for a suitable medium, which
for example is dry air. A pump 17 and one or more
detectors or sensors 18 for substances to be detected are
arranged in the circuit. In the case of a plurality of
sensors 18, these respond to different substances. Two
sensors 18, which are for example connected in series,
are preferably provided, as illustrated. One sensor 18
responds to gas (refuse gas, particularly methane gas),
and the other sensor 18 detects moisture (water). In
addition, a pressure gauge 19, a flow meter 20, a safety
valve 21 and also a pressurizer 22 may be provided.
In the circuit the medium is passed through the
elements 2A, 2B at regular intervals (intermittent
operation), as is known from German Patent Specification
24 31 907. For this purpose pumping is continued for some
time and then a waiting period follows until any material
has accumulated through diffusion in the channel 7 of a
defective element 2A, 2B. In the event of a leak in one
of the elements 2A, 2B the penetrating substance is
?1 Qfi~82
- - 12 -
detected in the double sensor 18 in the next pumping
phase. The circuit has, for example, an inlet 23 for air
and an outlet 24 for air, which are provided with valves
23a and 23b respectively. Between the inlet 23 and the
outlet 24 the circuit can be partly or completely closed
by means of another valve 25. A closed circuit, a partly
open circuit or an open circuit are thus available at
choice. The pump 17, instead of being a pressure pump
downstream of the inlet 33, may also be disposed as a
suction pump 17a upstream of the outlet 34. A filter 26
is disposed in a bypass in order to clean the medium in
the circuit. The filter 26 may be a mechanical filter, a
filter having an absorptive action (molecular sieve,
carbon filter, silica gel, etc.) or a filter working with
catalytic combustion. For cleaning purposes this filter
26 can be disconnected from the circuit by means of
fittings 26a, 26b, 26c. A heating means 27 is provided
for the filter 26 for cleaning purposes. The substances
removed are taken off via a flushing line 28 or fed to
other sensors for integral measurement. The flushing line
28 may also be fed with hot water or steam in order to
drive off the substances which are to be detected.
Since the medium is passed through the circuit at
fixed intervals of time (flushings), the moment of time
when a substance is detected in the sensor 18 will enable
the site of the leak in one of the elements 2A, 2B to be
deduced. In the case of a leak in a seal 4 or 5 of the
element 2A or B, the penetrating substance will after a
certain period of time pass into the channel 7 and will
be conveyed from the latter with the medium to the sensor
18. In addition, when two sensors 18 are used it can be
determined whether the top seal 4 or the bottom seal 5 of
an element 2 is defective. From the nature of the
substance penetrating (for example gas or water) it can
be determined whether this substance comes from above or
from below.
Figure 7 shows that because of the supporting
elements 6, which are made of material resistant to flcw,
the penetrating substance spreads out from a leak 29
~ t O fi ~ ~ 2
- 13 -
slowly in the form of a circle (see circle a) and
uniformly. It is thereby ensured that the substance which
penetrated at the leak 29 first reaches the channel 7 via
the shortest route, that is to say at right angles to the
channel 7. In addition, it is ensured that between the
appearance of the leak and the next flushing of the
channel 7 only a small portion of the channel will
receive the substance. Directly before the next flushing
a distribution 30 of the substance as as [sic] shown in
Figure 7 will be obtained in the channel 7. K is here the
concentration of the substance in the channel 7, and z is
the place in the channel 7. This distribution K(z) passes
to the single or double sensor 18 (Figure 6), in which,
with a relatively wide distribution 30, the maximum and
hence the location of the leak can be determined only
relatively accurately. The accuracy can be improved if
the material of the supporting elements 6 has a lower
resistance to flow at right angles to the channel 7 than
parallel to channel 7. The substance penetrating through
the leak 29 will in fact then spread out in the form of
an ellipse (see ellipse b), the longer axis of which lies
at right angles to the channel 7. It follows therefrom
that in the space of time between the occurrence of the
leak and the next flushing of the channel 7 the substance
reaches and acts on only a relatively small portion of
the channel 7. Directly before the next flushing a
distribution 31 having a sharp maximum is obtained in the
channel 7. This maximum can be more accurately determined
in the sensor 18 (Figure 6). The location of the leak can
be determined with equal accuracy.
With an element 2 according to the invention a
leak (or a plurality of leaks) in a seal 4, 5 can be
located very accurately. Depending on the composition of
the penetrating medium, it can also be distinguished
whether the leak has occurred in the top seal 5 or in the
bottom seal 4. The point in the channel 7 lying closest
to the leak 29 can be determined.
