Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
MErrHO~ 0~ IN'~ERNAL ~JTICOi.~OSIY~
PROTECTION OF PII'ELII~S
~ his invention relates to construction and ope-
ration of pipelines aad, in particular, to a method
of internal protection of pipelines against corrosion.
This invention can be used most advantageously
for protection of the internal surfacs of trunk a-nd
distribution pipelines against corrosion. It can be
used for anticorrosion protectio~ of deliv~ry and
low-pressur~ pipelines utilized in land reclamation9
public and proces s water supply systems, and in h0at
and power generation systems.
In addition9 the invention can be used for pro-
tection of pipel~nes for water supply to gas and
oil wells and ~or pumping o~ chemical products.
The invention can be used both during laying
of new pipelines and ~or protectio~ of active pipe-
lines .
At present protection of inside surface of pipe-
lines is a pressing problem in many technical fields.
Particularly urqe~t is protection o~ active pip~lines
since their internal sur~ace is constantly wetted by
some liquid, ~ter, for example Conventionally1 the
internal surface of a pipe has ~o be dried before
applying a protective coating. ~he drying pxoc~ss has
to immediately preceed the applic~tion process or~
otherwise the inter~al surface gets wet again by
- 2 ~ 3V~;~q3~
moiqture preclpitated ~rom the atmosphere.
At present, there ar~ ~no~n variou~ methods a~d
device6 far internal protection of pipelin~s ~gainst
corrosion.
Known in the art is a method ~or coating the
internal sur~`ace of a pipe b~ a cement-and-sand
mi~ture (cf., ~or ex~npleg hMER0~ Co. pamphlet, New
York 7 1978, pp 54~-601).
This method is de~icient in that it is inefficient .
si~ce one installation can coat 690 m o~ a 700 Dm
pipe .
Also Xno~Jn i~ the art is a method for i~ternal
prot~ction of a pipeline agai~st corrosion, consisting
in that a hose of a polymer material is fed lnto a
pipeline, the pipe is heated and the polymer hose
is pressed from i~side to the sur~'ace o~ the pipe,
The devic~ realizing this method comprises a
means for feedi~ the polymer hose into th~ pipeline,
a system for ~eedi~g a working medium into the
pipeline and a heater installed on the pipeline from
outside (c~, for example, U~SR Inventor's Certi-
~icate No. 1 018 729, IPC F16 L 5~/009 198~ ~n~ u.S.
Patent 4,135,958 issued January 23, 1979 to Insitu~orm
International Inc.).
s~rious disadva~kage o~ ~his method consi6ta
in that it cannot be uaed for coatin~ activ~ pipeli~es,
This method can only be uaed by the.~acturer
when the heater is mov~d alon~ ~he external su~face
of the pipe.
.~
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-- 3
It is an object of the invention to improve
the quality of protective coatin~s in actin~ pipe-
lines.
Another object o~ the invention is to ma~e the
service life of acting pipelines lo~ger~
- One more object of this invention is to make
the section of the active pipeline coated at one
setting much lon~er~
Still another object of this invention is to
make the pipeline more reliable.
And, finally, a further obaect of thi~ invention
is to cut the cost of the protective coating applied
on ac~ive pipelines.
q'hese and other objects of` the invention are
~chieved in ~hat in a method of internal anticorrosi~e
protection of` pipelines, comprisin~ the steps of
feedin~ a ~lexible hose into the pipeline, securin~
the end of said hose, whic~ is turned inside out~ to
the internal wall of the pipeline, moving the hose
along the pipeline, pressin~ said hose against the
intern~l surface of the pipeline by producin~ an
excessive pressure in the spac~ de~ined by the hose
and the pipe, and heati~g the pipe, according to the
inv~ntion, the pipe is heated ~rom inside and the
hose is silnultaneously presse~ a~airlst th~ lnt~rnal
surface of the pip~, the pressure differential on
3~
-- 4
both si~es of the hose fed into the pipeline being
suitably adjusted.
~ rlhis method provides a protective coating of active
pipelines and those under construction. This is ~chiev-
ed in that the pipeline is heated ~rom in~ide~ Simul-
taneous pressin~ of the hose to the pipe wall and its
heati~ produce a reliable bonding of the hose and
pipe. The guali~y of the coatlng thus made is extremely
high, which makes the service life of' the pipeline
much longer.
This method can be used to provide a protective
coatin~ o~ active pipelines and t~lose still being
laidg both on the sur~ace and buried ones.
Since the pressure dif`ferenc~ o~ both sides of
the hose fed into the pipeline can be adjusted, the
feeding speed can be controlle~, and the ~orce with
which the hos~ is pres~ed against the wall of the
pipe can be regulated~ This rules out ruptures of the
hose and adds to the better qual~ty of the pipe coat-
ing~
In the pre~erred embodiment o~ the i~ventio~
the pipeline is heated simultarleously with the hose
being fed lnto the pipe. The guality of the coating
this formed i~ much better because the temperature
in the zone where the hose i8 pr~ssed against the
internal sur~ace o~ thc pipe is constant.
It is advis~ble that the pxessure dif~erential is
re~ulated by re~ulatin~ the pressure ol' the working
medium in the pipeline before the hose fed into the
pipe.
~ his permits prevention o~ hydraulic and pheumatic
shocks on the hose in the pipeline~
ln one o~ the embodiments of the invention the
pressure differential is regulated by lowering the
pressure in the pipeline be~ore the moving hose and
simultaneous communication of the space between the
hose and pipe with atmosphere. In thiS manrler ruptures
of the hose can be prevented, if they are due to
irregular movement of the hose. Ilhe vacuum produced
in the pipeline in front of the hose provides better
conditions for ~rying the walls of the pipe, th~ ad-
hesion of the hose to the wall of the pipe is substan-
tially improved. ~ower is also sa~ed since the pressure
crop is localized ~ithin the pipeline.
~ hîs protects the hose against ruptures and
improves the quality of th~ protective coati~g.
It is ad~isable that protectors made of a
material capable of prod~cing9 in combination with
the pipe metal, an electrochemical potential are
installed into the annular gap between the hose and
p~pe ~imultaneously with the feddin~ o~ the hose
into this pipe.
~3
This makes the pipelin~ more reliable since the
mechanical protection of the pipeline is supplemented
by the additional electrochemical protection ~hich
can ward off corrosion ~ven wh~n the hose is not
tight.
In one OI` the embodiments of the invention,
after the polymer hose is introduced into thc ~ipe-
line, anotner hose made of a no~-ther~oplastic material
is introduced in this pipeli~e. ~hen the pipe is
heated, the polymer ho.se melts.
'l'his produces a durable and corrosion-proof`
protective coating made o~, for example a carbon-
filled plastic or glass ~iber.
In another embodiment oY this invention, blip is
applied on ~he internal su~face of the pipe before
the hose is fed into it, and, after the glass cloth
hose has been placed into the pipe, it is heated
until the slip ~elts.
This embodiment provides a stronger and more
reliable coating ~or protection of the pipeline
agains t corrosi on in ~;re ss ive me di a .
When the ~lip melts, pores are f ormed i~ the
coatin~, But the pressure buil~ up in the glass
cloth hose in the process of heating the slip comple-
tely prevents ~ormation oY pores in the coatin~ andt
consequently 7 improves the reliability of the
pipeline .
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It is advi~able that the pipeline is h~ated from
inside by purnpin~ heated gas thro~h the internal hose
made from a non-thermoplastic rnateri~l.
In this manner the processes of drying and
heating the internal surface o~ the pipellne can be
combined and made simplier.
It is also advisable that the heated gas should
be fed in the pipeline to meet the hose introduced
into the pipe and released throu~h the pipe into
atmosphere. This embodiment of the invention makes
drying of the pipe and regulation of the pressure
di~ferential on both sides of the hose a much ~implier
task.
In accordance with another embodiment of the
invention, the pipe is heated simultaneously with the
introductio~ of the hose into it by ~eedi~g a co~bu~-
tible mixture into the pipe and igniting it khereafter.
I'his method pxovi~es a built-up o~ pressure
inside the pipeline. '~his ma~es the device realizing
the method much simplier.
The hose i5 heated and pressed against the pipe
wall at the same ti~e. '~he guality of the coating
becomes better since the ho~e fills all pores and
pits in the pipe wall. The wall of the pipeline cools
o~ practically simultaneously throughout the leng~h
o~ the pipeline. Relaxation stresses in the coating
are reduced and its guality becomes better. In this
way the cost of the coatin~ is cut down and the coat-
in~ application process becomes mole e~fective sinc~
the hose is pushed forward and pressed against the
pipeline walls by the force o~ the combustible mixture~
In accordance with one of the embodiments of the
invention a protective alloy is applied onto the
internal surface o~ the pipeline before the hose is
pressed thereto,
This provides an a~ditional electrochemical
protection of the pipeline in case the hos~ is ruptur -
ed. Besides, t~he dissolution products of the prot~ctive
alloy, for example~ an ~l~minum-Gallium allo~, are
deposited on the wall o~ the pipeline and form an
oxide film which protects the pipeline a~ainst corrosi-
on for many years-to come.
Other objects and advanta~es of the invention
will become apparent from the following description
of preferred embodiments theresf, ta~en in conju~ction
with the accompanying drawings.
A method of internal anticorrosion protection of
pipelines consists in introducing a flexible hose
into the pipeline, securing the forward end o~ the
hose, which is turned inside ou~, on the internal
surface o~ the pipeline, and then moving the hose
and pressing it against this internal surface of the
pipeline. The hose is pushed along the pipeline and
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pressed against its walls by the excess pressure
built up i~ the space between the turncd out end o~
the hose and the pipe. ~lhe pipeline is heated at the
same time as the hose is presse~ against the wall
thereo~`~
~xample 1
A polyethylene hose i5 introduced into a pipeline~
the leadin~ end of the hose being tur~ed inside out
and secured to the internal surface of the pipeline.
Air compres~ed to 0.3 ~a is pumped into the space
between the hose and the pipe. A heater is installed
into the pipe in front of the hose which pushes it
alon~ the pipe. In this way the hose and the heater
are moving simultaneously in the pipe.
The internal surface o-~ the pipeline is heated
to 150C. Compressed air presses the hose to the wall
o~ the pipe and welds it reliably to this wall. As the
hose is pushed along the pipeline, a pressure of
0.15 MPa is produced in the space before the hoso.
This pressure is produced by compressed air fed into
the pipe space be~ore the hose end. '~he air is re-
leased to atmosphere through an opening made in the
pipe at the end of the coated se~tion. '~he pressure
can be built up by pumpin~ the air out of the pipe
space i~ ~ront of the hose. Prior to installation?
the hose is rein~orced with wire made of an alumi~um
30~3
alloy. The pip~line is hr~ated by supplying a not ~as
through the hose a~d, consequently, the pipeline. The
hot gas can be either supplied at the end of the pipe-
line in the direction opposite to the movement of the
hose or at the beginnirlg o~` the pipeline in the same
direction. In botr. cases the hot gas is released to
atmosphere throu~h the hose.
Example 2.
A polyethylene hose is introduced into a pipeline,
a carbon-~illed plastic hose bein~ inserted inside the
~irst hose. The leadin~ ends of both hoses are turned
inside out and secured to the internal surface of the
pipeline. After that, air heated to 150C at a pressure
o~ 0.2 MPa is pumped into the hose and it starts
moving along the pipeline drying and heating the
walls. The polyethylene hose melts as it is heated
further o~ and, ~hen cooling, it welds tlle internal
hose to the wall of the pipeline.
~ ot air can also be pumped into the pipeline in
the opposite directio~ to tne movement of the hose
and released throu~h the internal hose.
E~ample 3
Initially, slip is pumped through the pipeline.
~fter that~ using the method described in EXample 2 9
two hose~ are introduced into the pip~line. 'I`he external
hose is made o~ polyethylene, the intcrnal one of
glass cloth.
v~hen two hoses are introduced into the pipeline,
the i~ternal ~Jall thereof is heated to 500C.
Tne heat- melts the .51ip and welds both hoses to
the wall of the pipe.
~ xample 4,
lnitially, slip is pulQped throu~h the pipeline.
'l`herl, t~o hoses are introduced into the pipeline es
described in Example 3. 'l'he workin~ medium pumped into
the pipeline i~ a mixture of oxygen and propane taken
in ~ proportion 1 to 4 by wei~ht. After tne hoses are
in the pipeline, the mixture is ignited.
`The heat produced by the burnin~ mixture heats the
internal ~all of the ~ipeline ~nd the hoses are welded
thereto.
Example 5
A polyethylene hose is introduced into the pipe~
line as in Example 1.
Prior to introducing the polymer hose into the
pipeline, a layer of a protective alloy is sprayed
over the internal su~face of the pipe~ 'l'he protective
alloy comprises the ~olloY/in~, parts bg weight:
Magnesium 1 ;
Gallium - 0,5 ;
The balance - Aluminum~
This alloy is preheated to a temperature of 950C.
~hen the melt i~ sprayed over the wall of thc p~peline
'
.
3~8
1~ --
usin~ approximately 80 ~ o~ the melt for one syuare
meter o~ the internal surface. 'llnen a polyethylene hose
is introduced into the pipelin~. The ho~e is melte~
and a protective coating i9 formed through the heat
of ~he wall o~ the pipeline.
~xample 6
A polyethylene hose is introduced into the pipe-
line as described in Exampl~ 1~
i~hen the hose is manuf~ctux~d~ it is rein~orced
with wire made of a protective alloy, Al-Ga alloy,
for example, as described in Example 5.
ln case the hose is ruptured, an electrochemical
potential is produced between the metal of the pipe
wall and the wires. ~his potential protects the pipe-
line against corrosio~
The wire in the place of rupture is dissol~ed and
the dissolution products are deposited on the pipe
wall as an oxide ~ilm which protects the pipeline
against corrosion.
