Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD FOR CLEANING AND
RENOVATING PIPELINES
FIELD OF THE INVENTION
The present invention relates to a method for
cleaning and renovating pipelines, in particular for
cleaning and renovating pipelines which are difficult to
access, such as pipelines buried underground, installed in
walls, and the like.
BACKGROUND OF THE INVENTION
As is well known, after pipelines have been in use
for some time incrustation accumulates therein, which
arises partly from salts in the fluids passing therethrough
and partly from corrosion of the pipelines. The
incrustation usually further includes thick and tough
deposits of micro-organisms such as algae, bacteria, etc.,
which steadily increase over time. The pipelines can be
cleaned by chemical cleaning, knocking and mechanical
cleaning. These cleaning methods have their disadvantages
and negative affects on the pipelines, or have limited
applicabilities. A popularly used method is to clean the
inner surface of the pipelines by supplying a fluid stream
containing abrasive agents such as sand, through the
pipelines so that the abrasive agents impinge upon the
inner surfaces of the pipelines to remove the deposits
thereon.
Examples of applying this method for pipeline
cleaning are described in United States Patent 1,890,164,
entitled SAND BLASTING METHOD AND APPARATUS and issued to
Rosenberger on December 6, 1932, United States
Patent 2,087,694, entitled CLEANING PIPE and issued to
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Malmros on July 20, 1937, United States Patent 3,073,687,
entitled METHOD FOR THE CLEANING OF PIPELINES and issued to
McCune on January 15, 1963 and United States
Patent 5,924,913, entitled PROCESS FOR RENOVATING PIPES and
issued to Reimelt on July 20, 1999.
More especially, in United Kingdom patent
application 2,140,337, which is entitled CLEANING AND
LINING A PIPE and published on November 28, 1984, Shinno
describes a method for renovating a pipe which comprises
l0 cleaning an internal surface of the pipe by supplying a
fluid stream containing at least entrained abrasive agents
and thereafter lining the pipe by introducing into the pipe
a mixed stream of paint and air to deposit paint on the
cleaned internal surface of the pipe. The mixture stream
used in Shinno's cleaning and lining process is subjected
to pulsations in a predetermined cycle and at a
predetermined pulsation rate. Shinno states that in a
conventional system, when a flow speed of the mixture
stream reaches 30-100m/sec, the air current is turbulent,
and the flow speed near the inner surface of the pipe is
slower than the flow speed at the center portion of the
pipe. Shinno therefore suggests using a rotating vane as a
pulsation-generating apparatus installed within the
pipeline to be cleaned in order to reduce ~ the f laid speed
difference between the flow through the center of the pipe
and the flow near the inner surface of the pipe. The
suggested flow speed is 20-100m/sec. Shinno's system is
relatively complicated and it is not convenient to install
the pulsation-generating apparatus in pipelines. The
pulsation-generating apparatus installed in the pipelines
can cause fluid flow resistance which is not desirable.
The length of the pipelines which can be cleaned according
to Shinno is about 30-100 meters, therefore more than 10
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vertical holes would have to be dug in streets when, for
example a one kilometer length of pipeline buried
underground is to be cleaned. This is not satisfactory.
Therefore a simple and efficient method for cleaning and
renovating pipelines is desirable.
SUN~ARY OF THE INVENTION
One object of the present invention is to provide a
pipeline cleaning and renovating method in order to clean
and renovate pipelines effectively.
In accordance with one aspect of the present
invention, a method of cleaning a pipeline having open
entry and exit ends, comprises the steps of: introducing a
flow of pressurized air into the entry end of the pipeline;
introducing a plurality of abrasive particulates into the
flow of pressurized air at the entry end of the pipeline by
means of a balancing pressure of air; controlling the flow
of pressurized air at the entry end of the pipeline such
that the flow of pressurized air has a speed of between
40m/sec and 100m/sec, preferably to induce a substantially
helical flow pattern along an inner surface of the
pipeline, thereby causing a substantial amount of the
abrasive particulars to move along the inner surface of the
pipeline; and introducing a liquid with a limited quantity
and a controlled rate into the flow of pressurized air at
the entry end of the pipeline, generating or increasing
moisture content of and thereby increasing a density of the
flow of pressurized air to drive the abrasive particulates
powerfully to remove deposits on an inner surface of the
pipeline.
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The method preferably comprises a further step
after the pipeline is cleaned, of introducing a coating
material into the pipeline by, for example an air flow in a
substantially helical flow pattern along the inner surface
of the pipeline, thereby moving a substantial amount of the
coating material in the substantially helical flow pattern
on and along the inner surface of the pipeline.
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The substantially helical flow pattern is
preferably obtained by controlling the speed of the air
flow. In accordance with Applicant's test results, the
flow speed through a pipeline reaches about
40m/sec-l0om/sec the air flow is rotated to create a
substantially helical flow patterN, although other flow
patterns may jointly exist. The substantially helical flow
pattern in the pipeline causes a substantial amount of the
abrasive particulates or the coating material to move along
the inner surface of the pipeline such that the inner
surface of the pipeline is effectively cleaned or coated.
The pipeline cleaning and renovating method of the
present invention advantageously provides very effective
cleaning results for a relatively long length of pipelines
at one time and uniform coating to the inner surface of the
cleaned pipelines in order to protect the surface from
incrustation for a relatively long period of time. The
pipeline cleaning and renovating process is relatively easy
to conduct which results in less labour and time
consumption and thereby, lowers costs.
Other advantages and features of the present
invention will be better understood with reference to the
preferred embodiment of the present invention described
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the
present invention, reference will now be made to the
accompanying drawings, showing by way of illustration the
preferred embodiments thereof, in which:
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Figs. 1-3 are schematic illustrations showing air
flow patterns within a section of a pipeline when the speed
of the air flow is controlled within various predetermined
speed ranges; and
Fig. 4 is a schematic illustration showing an
apparatus used in a preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The pipeline cleaning and renovating method will
now be described in detail, as embodiments of the present
invention. The pipelines to be cleaned can be, for example
water pipes buried underground, installed in the walls of a
high-rise building, or in other locations. Therefore,
preliminary planning is needed prior to pipeline cleaning
and renovating on site. During the preliminary planning
stage, the layout of the pipelines, including switches,
branches, etc. should be defined according to the
construction drawings. The sections of the pipelines to be
cleaned at one time are to be divided to have open ends
according to the layout of the pipelines. For a straight
pipeline buried underground, the length of the pipeline to
be cleaned at one time can be several hundred meters to
more than one kilometer depending on the diameter of the
pipeline, which can vary from l3mm to 300mm. The entry end
and exit end as well as the flow direction through the
pipeline section are also determined together with the
determination of pipeline sections. The type of
pressurized fluid used for cleaning and renovating
pipelines can vary. Nevertheless, the most convenient and
inexpensive pressurized fluid is pressurized air. A final
step of the preliminary planning stage is to select
pressure air volume, air flow speed and the air pressure to
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be used in the pipeline cleaning and renovating process.
The air flow speed is selected from a range of
between 40m/sec and IOOm/sec, preferably 70m/sec-80m/sec
and the air pressure is selected from a gressure range of
between 2-8kg/cm2 depending on the length and diameter of
the selected section of the pipeline and on other
considerations, to ensure that the air flow reaches the
selected flow speed. For example, the air pressure should
be increased 0.5kg per 10 meters of rise when the pipeline
is substantially in a vertical condition, such as in a
high-rise building. The determined volume of the
pressurized air depends on the diameter of the selected
section of the pipeline to be cleaned.
The type of abrasive particulates is also selected
during this planning step, for example the abrasive
particulates from sands including quartz, iron or steel
particulates. When a coating of the inner surface of the
section of the pipeline after cleaning is required, the
type of coating material is also selected. The coating
material must be harmless to health, water resistant,
preferably wear resistant and quick-drying material such as
rosin.
The next stage is site preparation. The water
supply to the pipelines is shut down and a first section of
the pipeline to be cleaned according to the preliminary
planning, is located and cut from the pipeline. The
terminal equipment, if any, is removed such that the
section of the pipeline has two open ends and is ready to
be cleaned. The pipeline section is connected at its
predetermined entry end to an apparatus for controllably
supplying the pressurized air and the abrasive particulates
to generate an air flow mixed with the abrasive
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particulates in the desired substantially helical flow
pattern, through the section ~of the pipeline. The
apparatus will be described below with reference to Fig. 4.
A flexible pipe is preferably connected to the exit end of
the section of the pipeline in order to direct the exhaust
flow of the mixture for the waste collection. A safety
check is conducted for a safe operation of the cleaning and
renovating process. For example, all valves installed in
the section of the pipeline to be cleaned must be open, or
removed if the valve cannot be fully opened, such as
butterfly valves.
The cleaning and renovating process begins with
introducing the pressurized air supply into the entry end
of the section of the pipeline to be cleaned. This is a
preliminary air cleaning step without the abrasive
particulates to be used later in this step. The section of
the pipeline to be cleaned usually contains some water
remaining therein. The pressurized air flow will blow the
remaining water out of the section of the pipeline.
Furthermore, the inner surface of the section of the
pipeline to be cleaned may be heavily encrusted at some
points and will clog easily when a certain amount of
abrasive particulates or the removed deposits pass through
those heavily encrusted points. Therefore, the air flow
under pressure without the mixed abrasive particulates
first removes those deposits which are relatively easy to
dislodge, and increases the passage cross-section,
particularly at those heavily encrusted points. Thus, the
risk of clogging the section of the pipeline to be cleaned
when the abrasive particulates are introduced is
significantly reduced.
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During the preliminary air cleaning step, a mixed
stream of air and water under pressure can replace the air
flow to be introduced into and through the section of the
pipeline being cleaned, which will be referred to below as
a wet operation. The mixed stream. of air and water is
heavier than the air flow and thereby carries a greater
amount of inertia, which makes the fluid flow more powerful
for dislodging the deposits. Furthermore, the water
contained in the mixed stream provides lubrication when the
dislodged deposits are blown through the inner passage of
the section of the pipeline while being discharged, and
thereby further reduces the risk of clogging the section of
the pipeline.
After the preliminary air cleaning step, the air
flow introduced into the section of the pipeline being
cleaned is adjusted to reach the selected flow speed,
between 40-100m/sec, preferably 70-80m/sec, and the
abrasive particulates are controllably introduced into the
entry end of the section of the pipeline being cleaned, in
order to ensure that the air flow with the mixed abrasive
particulates is generated in the desired substantially
helical flow pattern. Tests show that different flow
patterns through a pipe can be achieved when the flow speed
is varied, as illustrated in Figs. 1-3. The flow pattern
under a relatively low air pressure and at a low air flow
speed produces a moderate turbulence in a wave-shaped
pattern, as illustrated in Fig. 1. When the air pressure
is increased and the air flow speed reaches the range of
between 40-100m/sec, the air flow through the pipe produces
a substantially helical flow pattern as illustrated in
Fig. 2, although other flow patterns may jointly exist.
When the air pressure is further increased and the air flow
speed exceeds 100m/sec, the substantially helical flow
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pattern through the pipe no longer occurs and a smog-shaped
straight flow pattern is produced, as illustrated in
Fig. 3. These flow patterns can be observed when the
exhaust flow is discharged from the exit end of the pipe,
particularly if the flow is mixed with a coloured coating
material such as rosin. The cleaning and renovating method
of the present invention uses the substantially helical
flow pattern to cause a substantial amount of the abrasive
particulates to move along the inner surface of the
pipeline section, thereby impinging upon the deposits
adhering to the inner surface and removing the same
therefrom. The removed deposits are then blown out of the
exit end of the pipeline section by the air flow.
It is optional to heat the section of the pipeline
being cleaned prior to the abrasive particulates cleaning
step in order to dry the encrustation on the inner surface
of the section of the pipeline being cleaned. The heating
step is conducted by introducing hot airflow through the
section of the pipeline. The temperature of the hot air
can be selected from a temperature range of between 30°C
and 40°C. Neverthless, in a wet operation, there is no
need for drying the section of the pipeline being cleaned.
After the abrasive particulates cleaning step is completed,
a quality check is conducted to ensure the fineness and
cleanness of the inner surface of the section of the
pipeline which has been cleaned.
It is preferable to introduce a liquid, for example
water in most applications, which are called wet
operations, into the section of the pipeline from the entry
end thereof, thereby generating or increasing moisture
content in the flow of the pressurized air. Similar to the
water included in the mixed stream of air and water used in
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the preliminary cleaning step, the moisture in the air flow
increases the density of the air flow and thus, the air
flow in the substantially helical flow pattern more
powerfully drives the abrasive particulates to impinge upon
the incrustation adhering to the inner surface of the
section of the pipeline. The moisture also provides
lubrication to the abrasive particulates and the dislodged
deposits when they are blown through the section of the
pipeline. This wet operation further eliminates the need
for heating the section of the pipeline. As an overall
result, the cleaning process reaches a high level of
efficiency.
Nevertheless, the introduction of water in this
cleaning step must be conducted with a limited quantity and
a controlled rate such that the water added into the air
flow will be blown into fine particles suspended therein,
to generate or increase the moisture content of the air
flow. Excess water will form drops and bond the abrasive
particulates to form large pellets, which create a high
risk of clogging the section of the pipeline being cleaned,
and must be avoided.
A coating step is similar to the abrasive
particulate cleaning step. The coating material, for
example rosin, is introduced into the entry end of the
section of the pipeline which has been cleaned by an air
flow under the predetermined pressure flowing through the
section of the pipeline. The air flow under the
predetermined pressure is controlled to reach a
predetermined flow speed of between 40-100m/sec, preferably
70-80m/sec in order to induce a substantially helical flow
pattern through the section of the pipeline. Thus, the
semi-liquid rosin is blown into the section of the pipeline
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and a substantial amount of rosin is brought by the
substantially helical flow pattern to move on and along the
inner surface of the section of the pipeline, thereby
forming a rosin film of 0.2-0.3mm thick, covering the
entire inner surface of the section of the pipeline. The
rosin coating can be allowed to dry naturally or can be
dried by introducing a hot air flow through the section of
the pipeline. After the rosin coating is completely dried,
the apparatus which is used to introduce the pressurized
air flow and the abrasive particulates as well as the
coating material, is then disconnected from the entry end
of the section of the pipeline. The flexible tube
connected to the exit end of the section of the pipeline is
also disconnected. This cleaned and renovated section of
the pipeline is then ready to be re-coupled to the
pipelines when adjacent sections of the pipelines have been
cleaned and renovated.
The substantially helical flow pattern is imprinted
on the inner coating of the cleaned and renovated section
of the pipeline, which can be observed from one end of a
section of the pipeline if this section is straight.
When the section of the pipeline to be cleaned has
small cracks or tiny holes, those defects can be
automatically repaired during cleaning and renovating
procedures. The abrasive particulates driven by the air
flow in the substantially helical flow pattern through the
section will move into the fine cracks and tiny holes in
the pipe wall and will lodge there. The rosin coating will
adhere those abrasive particulates to the pipe wall and
further cover the same. The rosin coating becomes very
solid after drying and will also protect the mended
defects.
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In a further embodiment of the present invention,
other types of liquid can be selected to replace water, to
be introduced into the section of pipeline, especially when
the incrustation adhering to the inner surface of the
section of pipeline to be cleaned is solid or semi-solid
and very sticky to clean, such as asphalt-type
incrustations accumulated in an oil pipeline. The liquid
is selected such that the liquid can at least partially
dissolve the solid or semi-solid material included in the
deposits accumulated in the section of the pipeline to be
cleaned. This selection can be determined according the
results of tests conducted prior to the preliminary
planning of the cleaning and renovating process. Once the
liquid selection is determined from the test results, this
liquid can be used in both the preliminary air cleaning
step and the abrasive particulates step, which are similar
to the wet operation with water and will not therefore be
redundantly described.
As illustrated in Fig. 4, the apparatus used in the
above described embodiment of the present invention,
generally indicated by numeral 10 includes a section of a
connection pipe 12 having a first end 14 for connection to
a pressurized air source, such as an air compressor or
pressurized air container (not shown), and a second end 16
for connection to an entry end of the section of a pipeline
to be cleaned (not shown). The diameter of the connection
pipe 12 is preferably equal to the diameter of the section
of pipeline to be cleaned. The connection pipe 12 is
provided with a first main control valve 18 positioned near
the first end 14 of the connection pipe 12, and a second
main control valve 20 downstream of the first main control
valve 18. Air pressure indicators 22 and 24 are installed
in the connection pipe 12 for measuring the air pressure
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inside of the connection pipe 12. The air pressure
indicator 22 is positioned between the main control
valves 18 and 20, and the air pressure indicator 24 is
positioned downstream of the second main control valve 20.
The apparatus 10 further includes a first
container 26 containing for example, sand, which will be
referred to below as the sand container. The sand
container 26 is preferably positioned above the connection
pipe 12 and is removeably attached to the connection
pipe 12 via an output pipe 28 with a control valve 30 for
controllably delivering the sand from the sand container 26
into the connection pipe 12. The output pipe 28 is
connected to the connection pipe 12 downstream of the
second main control valve 20. The sand container 26 has an
input pipe 32 with a control valve 34. A balancing
pressure pipe 36 with a valve 38 is provided to
interconnect the connection pipe 12 and the sand
container 26. The balancing pressure pipe 36 at its one
end is detachably connected to the input pipe 32 and at its
other end is connected to the connection pipe 12 at a
position between the two main control valves 18 and 20.
Optionally, a second container 40 is provided,
preferably positioned above the connection pipe 12. The
second container 40 is removeably attached to the
connection pipe 12 via an output pipe 42 with a control
valve 44. The output pipe 42 is connected to the
connection pipe 12 close to the second end 16 thereof. The
second container 40 further includes an input pipe 46 with
a valve 48. A balancing pressure pipe 50 with valve 52 is
provided to interconnect at one end thereof the input
pipe 46 and at the other end thereof to the connection
pipe 12 at a position between the main control valves 18
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and 20. The connection of the balancing pressure pipe 50
to the input pipe 46 is detachable.
In operation, the apparatus 10 is connected at its
second end 16, perhaps via an extension pipe, to the entry
end of the section of the pipeline to be cleaned and at its
first end 14 to the air compressor. The air compressor is
enabled to provide 2m3/min to 30m3/min under a pressure
range of from 2-8kg/cm2, depending on the preliminary
planning of the cleaning and renovating process. If the
pressurized air supply is not sufficient, an additional
pressurized air container can be used. It is preferable to
remove the second container 40 prior to the cleaning step.
Before starting the cleaning and renovating
process, all valves of the apparatus 10 are tightly closed.
After the air compressor is turned on and begins to supply
pressurized air, the first main control valve 18 is opened.
The air pressure indicator 22 indicates the desired air
pressure. The second main control valve 20 is then
gradually opened, until preferably being one-third open for
the first step. The air flow under pressure passes through
the section of the pipeline being cleaned at increasing
speeds so that the deposits which are relatively easy to
remove from the incrustation are removed, and together with
the water remaining therein are blown out gradually, in
order to avoid clogging. The operation of the second main
control valve 20 is carefully manually conducted to
correspond with the exhaust flow discharged from the exit
end of the section of the pipeline being cleaned. When no
significant amount of waste material mixed with the exhaust
flow is observed, the second main control valve 20 is
gradually further opened to a position about its two-thirds
opening and then still further to be fully open. During
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this step, the first main control 18 is closed and reopened
several times and this close and reopen operating pattern
causes the pressurized air to suddenly surge which helps
clear the removed deposits away from the sections of the
pipeline being cleaned.
When a wet operation, for example with water is
desired, the second container 40 is installed prior to the
preliminary air cleaning step and the valve 48 is opened
for the addition of water through the input pipe 46 into
the container 40. After the valve 48 is closed, the valve
52 is opened to provide a balancing pressure to the second
container 40. The valve 44 is then opened to allow water
to be delivered into the connection pipe 12 when the first
and second main control valves 18, 20 are operated to
conduct the preliminary air cleaning step, as described
above. The valve 44 can be closed and reopened several
times, corresponding to the operation of the first main
control valve 18.
After this preliminary air cleaning step, the
remaining deposits adhering to the inner surface of the
section of the pipeline being cleaned are those which are
relatively difficult to remove. Nevertheless, the internal
passage of the section of the pipeline being cleaned now
has a larger cross-section than it had prior to the
preliminary cleaning step, which facilitates the subsequent
sand cleaning step.
After the preliminary air cleaning step, the
valve 34 is opened and sand particles sized from lmm to 5mm
is added through the input pipe 32 into the sand
container 26. The valve 34 is closed immediately after the
sand loading process is completed. The second main control
valve 20 is closed during the sand loading process. Before
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the second main control valve 20 is opened again to begin
the sand cleaning step, the valve 38 is opened first to
provide a balancing pressure to the sand container 26. The
second main control valve 20 is then fully opened to induce
a substantially helical flow pattern through the section of
the pipeline being cleaned. The air pressure is selected
to generate an air flow having a preferable flow speed of,
for example 70-80m/sec. The valve 30 is controlled to
gradually open such that the sand is released from the sand
container 26 gradually in order to avoid clogging in the
section of the pipeline being cleaned. Optionally,
valve 30 and the main control valves 18 or 20 may be closed
and reopened several times during the sand cleaning step.
Such an operation can be repeated until no waste material
is observed in the exhaust flow discharged from the exit
end of the section of the pipeline. The pressure
indicators 22, 24 are observed. The readings of both
indicators 22, 24 are significantly below the predetermined
air pressure and indicate a pressure differential
therebetween when the air flow passes the section of the
pipeline being cleaned. Otherwise, the section of the
pipeline being cleaned is clogged and the sand cleaning
step must be stopped immediately. The sand cleaning step
begins again after actions have been taken to unclog the
section of pipeline being cleaned.
In a wet operation with water, after the valve 52
is opened to provide a balancing pressure to the second
container 40, the valve 44 is gradually opened, and may be
closed and reopened several times, corresponding to the
operation of valve 30. Thus, the water addition into the
section of the pipeline being cleaned is well controlled
and is substantially synchronized with the addition of the
sand particles.
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When the sand cleaning step is completed the
valves 30 and 38, as well as the second main control
valve 20 are closed and then the sand container 26 is
removed. If the second container 40 was installed and used
for a wet operation, the valves 44 and 52 are closed and
then the second container 40 is removed. The second main
control valve 20 is then fully reopened to provide the
pressurized air through the section of the pipeline to
thoroughly clean the inner surface of the section of the
pipeline.
In order to conduct the coating step, the second
container 40 is emptied and cleaned, and is then installed.
The valve 48 is then opened for addition of rosin through
the input pipe 46 into the container 40. After the
valve 48 is closed, the valve 52 is opened to provide a
backpressure to the second container 40. The valve 44 is
then fully opened to allow the rosin to be delivered in its
total amount at one time into the connection pipe 12, after
which the valve 44 is immediately closed. The second main
control valve 20 is then fully opened to apply the selected
air pressure which was observed on the pressure
indicator 22 prior to the opening of the second main
control valve 20. Thus, the rosin is blown into the
section of the pipeline and is mixed with the air flow in a
substantially helical flow pattern, and thus the rosin
moves on and along the inner surface of the section of the
pipeline, thereby forming a thin film of rosin evenly
covering the entire inner surface of the section of the
pipeline.
After the coating step is completed, the second
main control valve 20 is partially closed to maintain an
air flow at a relatively low flow speed passing through the
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section of the pipeline until the rosin coating on the
inner surface thereof is completely dry. At this stage,
the air compressor is switched off and all valves are
closed. The apparatus ZO can be disconnected and removed,
and then the cleaned and renovated section of the pipeline
is ready to be reconnected to the pipeline.
Nevertheless, it is preferable in the coating step
to add the rosin material directly into the connection
pipe 12. The rosin material can be added through the input
pipe 42 and the valve 44 into the connection pipe 12 or the
rosin material can simply be added into the entry end of
the section of the pipeline, or into the extension pipe
connected to the connection pipe 12, which requires
disconnection of the entry end of the section of the
pipeline from the connection pipe 12, or from its extension
pipe, for the addition of the rosin material. Thus, the
second container 40 should not be used for containing rosin
which is difficult to clean, because the rosin residue may
mix with water and be inadvertently added into the section
of the pipeline during the preliminary air cleaning or sand
cleaning steps when the second container 40 is re-used for
containing water for a subsequent wet operation. This can
cause clogging, and therefore is not desirable.
If hot air is needed to dry the section of the
pipeline prior to the preliminary air cleaning step or the
sand cleaning step, and to dry the rosin coating after the
coating step, an electric heating device (not shown) may be
additionally connected either between the apparatus 10 and
the entry end of the section of the pipeline, or between
the air compressor and the apparatus 10. The heating
device has connection pipes which have a diameter
preferably similar to the diameter of the section of the
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pipeline being cleaned. Nevertheless, in the wet
operation, the section of the pipeline to be cleaned need
not be dried and therefore, the electric heating device is
not needed.
The pipeline cleaning and renovating method of the
present invention can be broadly applied for various
pipelines such as water, gas, oil pipelines.
Modifications and improvements to the
above-described embodiments of the present invention may
become apparent to those skilled in the art. The foregoing
description is intended to be exemplary rather than
limiting. The scope of the invention is therefore intended
to be limited solely by the scope of the appended claims.
