Note: Descriptions are shown in the official language in which they were submitted.
CA 02198103 1997-04-03
Translation
PCTDE95/01152
WO 96/06710
PROCESS FOR RENOVATING PIPES
The invention relates to a process for
renovating pipes, which comprises the steps of removing
internal deposits in the pipe by flowing abrasives and
applying an inside coating of a viscous curing material.
Basically, it should be remarked at this point
that the pipes to be renovated are already installed
lines, which may carry gas, vapor, or liquid. Thus, the
pipes may include, for example, feed and/or drain pipes
for water or gas in residential, industrial, and municipal
areas. This also includes residential and industrial
sewer lines. All of these lines tend to form
incrustations, which result primarily from calcareous
deposits from the water, corrosion on the inside wall of
the pipe, precipitates from the flow medium, products of
reaction between the flow medium and entrained substances
as well as the material of the pipe, etc., and from a
combination of effects resulting therefrom. The foregoing
phenomena lead to leaks or very considerable reductions of
the inside cross sections of the pipes, whereby the
transportation of the flow medium is disturbed, if not
even prevented. .
The presently claimed process for renavating
pipes assists in avoiding a total replacement of. the
pipes, which turns out to be especially advantageous with
respect to completely installed plumbing equipment. In
this instance, the pipes are more or less freely
accessible after removal of the fixtures, so as to permit
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application of the claimed cleaning and coating process.
Essential is at any rate that a pipe be accessible at
least at two open ends, so as to be able to carry out the
individual steps of the process. The claimed process does
not preclude an at least partial conventiona:L repair of
the pipes, so that it is also quite possible to replace
complete pipe systems in part and to renovate same in part
by the claimed process.
Processes of the aforesaid kind have been known
from practice for quite some time. only as an example,
reference is made in this context to EP 0 29:9 134. This
European Patent discloses a process of this ',kind, in which
the removal of internal deposits in the pipes and internal
coating of the pipes occurs exclusively by means of
compressed air. In other words, in the known process,
compressed air is forced as a carrier medium through the
pipe. When removing internal deposits, the transportation
of the abrasive, which occurs exclusively by compressed
air, leads to cloggages of the pipe, especially in the
case of substantial internal deposits and, thus, requires
quite considerable efforts to remove the cloggages. Flat
parts that have been torn off by the compressed air are
prone to accumulate just in the region of elbows or bends.
Eventually, these accumulations will lead to a total
blockage of the pipe.
Furthermore, the known method has the great
disadvantage that while carrying out the process or during
the application of compressed air, it is practically
impossible to detect leaks. Consequently, there exists
the risk that despite enormous leaks the inside wall is
coated, which practically prevents a stopping of the
leaks. In this respect, a large leak or hole in the pipe
is virtually "improved" by the coating, and can no longer
be effectively closed.
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It is now the object of the present invention to describe a process for
renovating
pipes, which allows to obtain with simple technical means a conveying quality
that is
comparable with new piping, while avoiding cloggages by internal deposits
which
become detached during the treatment.
The above and other objects and advantages of the present invention are
achieved
by the provision of a process for renovating pipes comprising the steps of
introducing an
abrasive material into the pipe by means of a pressure drop between the two
ends of the
pipe, then alternately producing a pressure drop between the two ends of the
pipe so as to
cause the abrasive material to reciprocate within the interior of the pipe,
and then causing
the abrasive material and any loosened internal deposits to exit from the pipe
by means of
a pressure drop between the two ends of the pipe. Finally, a coating may be
applied to
the interior of the pipe, which is subsequently cured.
In accordance with the invention, as soon as an adequate quantity of the
abrasive
is in the pipe, the abrasive effect is promoted in that the abrasive is caused
to reciprocate
in the pipe as a result of an alternating pressure drop. This measure of the
present
invention helps ensure that no cloggages develop inside the pipe as a result
of detaching
internal deposits. In particular, in the region of pipe elbows or bends, the
pipes are
effectively prevented from clogging. The advance of the abrasive as a result
of an
alternating pressure drop, i.e. the alternating motion of the abrasive inside
the pipe
continues until the pipe is totally freed from internal deposits, however at
least until the
abrasive is able to flow unhindered through the pipe. Once such a situation is
reached,
the further "cleaning process" can be accomplished even without an alternating
pressure
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simply by a predetermined pressure drop and the therefrom
resulting advance of the abrasive through 'the pipe. In
other words, the abrasive is finally caused to exit from
the pipe as a result of a pressure drop between the two
ends of the pipe. This may be a continuous operation, in
which additional abrasive is sucked in by the pipe or
blown thereinto at the inlet end.
Within the scope of a particularly advantageous
generation of the pressure drop it will be of advantage,
when the abrasive is caused to enter into 'the pipe from
one end by a vacuum.
In this connection, it has been recognized that
on the one hand the compressed air used in the state of
the art may lead to damage of the pipe being renovated, or
that is causes cloggages in the pipe. On the other hand,
it will bring along <:onsiderable environmental stress,
unless specific measures are taken, since the compressed
air that is blown into the pipe under over:pressure may
exit, at the outlet end -- under very high pressures --
into the environment together with harmful substances.
Accordingly, special collection and filter devices are
required irrespective af, or aside from the compressed-air
generation at the inlet end, which requires additional
apparatus and, thus, involves also considerable costs.
Other than for the vacuum generation, additional equipment
is no longer needed as a result of the advantageous
layout, inasmuch as suction occurs only at one end of the
pipe, and the sucked-in air is collected or received,
together with particles or the like, in an apparatus
preceding the suction device. Added to this is the
special advantage that, with a suction occurring on one
side, the process can be carried out from one side of the
pipe, namely from the suction side. It is only necessary
to enter the viscous coating material at the free end,
which may occur prior to the suction, so that again a
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single operator can start and carry out the actual coating
operation at the suction end.
Furthermore, the advantageous layout of the
process in accordance with the invention brings along the
considerable advantage that the vacuum generated at the
suction end drops toward the open end of the pipe.
Consequently, as the distance from the outlet end or
vacuum end decreases, detached particles are pulled along
to a greater extent, so that as a result of. the drop
occurring in direction toward the outlet end, cloggages
are effectively prevented, inasmuch as same are detached
and entrained respectively to a greater extent with a
decreasing distance from the outlet end. Finally, the
process of the present invention facilitates detection of
leaks, in that in the presence of a leak a lesser vacuum
adjusts at the outlet end. When this drop of the vacuum
occurs suddenly, same indicates a hole that has suddenly
been torn open in the pipe.
Advantageously, the motion of the abrasives
inside the pipes is generated in that the <~brasive is
caused to reciprocate in the pipe by alternating vacuum
and overpressure. In other words, ance it is accomplished
that vacuum alternates with overpressure in the pipe, the
abrasive is alternatingly sucked and blown therethrough.
Likewise however, it is possible to cause the abrasive to
reciprocate in the pipe by alternately applying a vacuum
to both ends of the pipe. In this case, the above-
described advantages are given. Finally, it is also
possible to cause the abrasive to reciprocate in the pipe,
in that overpressure is alternatingly applied to both ends
of the pipe. Tn this instance, the overpressure is
effectively used for advancing the abrasive only in the
absence of substantial leaks in the pipe.
A regards a special, environment-protective
realization of the process, it will be of advantage, when
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the preheated air that is used to dry the pipe is not
simply sucked off', but rather sucked respectively out of,
or through the pipe via a filter device. This filter
device may directly precede the compressor, so that no
special tools are needed.
The abrasive serving to remove the internal
deposits could be particles of any kind treat are carried
by flowing air. However, these particles would have to be
harder than the internal deposits that are to be removed.
In this connection, particles having a grain size in the
range from 0.3 mm to 6 mm have shown to be' satisfactory,
in particular in the renovation of water 1_ines. A
specific weight of more than 3.0 g/cm' has likewise been
found advantageous. In this case, air is used as carrier
medium. In the concrete case, the abrasive particles
could be corundum or quartz sand. It: would likewise be
possible to provide the abrasive particles in the form of
metallic particles, in particular ferromagnetic particles.
These particles will permit a subsequent magnetic
separation of the abrasive particles from the detached
internal deposits, which consist, as aforesaid, of rust
and/or lime.
The application of the coating rnaterial and,
thus, on the one hand a satisfactory wett_lng with the
inside wall of the pipe and, on the other hand, a rapid
subsequent curing are favored in particular in that, after
removal of the internal deposits, the pipe is heated to a
temperature above room temperature. In this connection, a
temperature of about 40°C has'shown to be especially
satisfactory. The heating of the pipe could again occur
by sucking therethrough heated air, which is sucked
through the pipe until the desired temperature is reached
at the outlet end. This temperature could again be
determined via the temperature drop 'between the inlet end
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and the outlet end of the pipe. Anyhow, it. is essential
that the heating of t:~e pipe occur by :aucki.ng therethrough
heated air and not by forcing therethrough compressed air.
Finally, the preheated air serving to heat the pipe could
also be sucked off via a filter device, which may likewise
precede directly the compressor that i.s use:d for the
suction.
Furthermore, in a very advantageous manner, the
heating of the pipe could occur exclusively or
additionally by means of a heating device which is sucked
into the pipe after the cleaning and before: applying the
inside coating. In this respect, it. would not be
absolutely necessary that the heated air be' sucked in,
should the heating device that is sucked unto the pipe
have an adequate capacity. Just in the care of extremely
long pipes, the heating device would at least be capable
of preventing a cooling of the air that is sucked in at
one end, so that the heating process is quite considerably
accelerated. In a further advantageous manner, the
heating device used to this end could be a heating wire,
in particular a self--regulating heating wire. Such a
heating wire could be constructed in the fashion of a
resistance heater with a ceramic insulati0I1 Of the heating
conductor. However, in principle it is possible to use
all devices that can be inserted or sucked into a pipe.
As regards an effective heating of the pipe, it
will be of further advantage, when the heating wire
extends through the pipe substantially over the entire
length thereof. An even heating of the pipe is thus
guaranteed.
With respect to inserting the heating wire, it
will be especially advantageous, when same is sucked into
the pipe by means of a tow system. The tow system could
include a kind of parachute or the like, which is engaged
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by the air flow that develops as a result of the vacuum,
and which pulls along the heating wire.
After the pipe is adequately heated, the heating
wire is again pulled out of the pipe, advantageously
before applying the inside coating. In so doing, the
heating wire could be pulled out both from the inlet end
and from the outlet end, i.e., from the vacuum side. In
the latter case, it would be necessary to disconnect the
power terminals at the inlet end.
Thereafter, the coating materia7L is fed into the
heated pipe. Also in this instance, a vacuum is generated
at the outlet end. As a result of this vacuum, the
coating material is sucked together with the ambient air
into the pipe. In this process, the different viscosity
between the air and the coating material causes the
viscose coating material to come into contact with the
pipe and to wet same. With the use of resin, synthetic
resin, or plastic as coating material, the inside wall of
the pipe receives a seamless coating. The' pressure
difference necessary to pull in the coating material is
generated exclusively by the vacuum at the outlet end.
In the case of substantial leaks, the coating
material may contain embedded fibers, in particular short-
staple fibers, which may very advantageously be glass
fibers. Due to the irregularly shaped openings, the glass
fibers will come to lie crosswise or interlace thereat,
and provide the viscous coating material with an adequate
hold for stopping the leak. In this respect, it would be
possible to close at least small holes and stop leaks.
Furthermore, in particular for preventing
further environmental stress or necessary waste disposal,
it would be very advantageous to measure the quantity of
the coating material supplied to the free end of the pipe
such that the inside wall of the pipe as <~ whole is
entirely coated, however without substantial quantities of
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the coating material exiting from the pipe at the suction
end. In other words, based on the normally resulting
coating thickness and the length of the pipe being coated,
it would be possible to predetermine the required quantity
of coating material at least approximately, without having
quantities of coating material exit at the suction end and
without having to dispose of same.
Furthermore, the process of the present
invention permits a temporary closing of t=he free end of
the pipe, while suction occurs at one end. In this
instance, the gradually developing vacuum will facilitate
detection of possiba.e leaks. When hardly any vacuum is
obtained, the pipe system being renovated has a
substantial leak.
Should it be desired to check, for example, the
already cleaned pipe for its condition before the actual
coating operation, or should it be desired to examine the
quality of the coating after same is applied, it would
likewise be possible to suck, to this end, into the pipe
an optical means for inspecting the pipe or for a quality
control of the inside coating. Likewise in this instance,
it would be possible to use a tow system as an auxiliary
means. In the simplest case, the optical means could be a
fiber glass line capable of bringing light into the pipe
on the one hand, and of bringing out from the pipe light
beams that have been reflected therein. It is possible to
provide for this purpose fiber bund~.es ox' different fiber
lines with different functions. A very particular
embodiment of optical means could carnpris;e a kind of
endoscope, i.e., a miniature camera that can be sucked
into the pipe with a corresponding illumination, and even
with a miniaturized, remote-control tool for taking
samples, or the like.
Finally, it should be emphasized that the
claimed process may comprise numerous, further
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advantageous process steps, without departing from the spirit of the invention
as set forth
in the appended claims.
