PIPE COATING PROCESS

PROCESSUS DE REVETEMENT DE TUYAU

English Abstract

Resin soaked fiberglass strands are applied to abrasively cleaned steel pipe
to
increase the hoop stress. Steel pipe that is abrasively cleaned is preheated
and a primer coat
is applied. Fiberglass strands that are soaked with heated resin are then
applied in a helical
method to the pipe to induce an accelerated cure of the resin. Followed by a
polyethylene
wrap to protect the ouside of the composite. Allowing the coated pipe to be
driven over a
conveyor line. This process is continuous in which the steel pipe is wrapped
from end to
end, on pipe that is connected with a come-along (steel or plastic).

Claims

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THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. ~A method for coating pipe, comprising the steps of:
surface treating a pipe to enhance adhesion of the pipe surface to resin
soaked fibers;
continuously winding resin soaked fibers in a helical fashion onto the surface
treated
pipe to form a continuous pipe coating made up of multiple layers of the resin
soaked fibers;
and
curing the resin.
2. ~The method of claim 1 in which the pipe is heated before winding the resin
soaked
fibers onto the pipe to a temperature that promotes curing of the resin.
3. ~The method of claim 2 in which the resin soaked fibers are heated before
winding the
resin soaked fibers onto the pipe to a temperature that promotes curing of the
resin.
4. ~The method of claim 1 in which surface treating the pipe comprising
roughening the
pipe surface.
5. ~The method of claim 4 in which surface treating the pipe comprises
applying a
primer to the pipe surface.
6. ~The method of claim 1 in which the resin soaked fibers are coated with a
heated film
to enhance curing.
7. ~The method of claim 6 in which the film is a thermal setting plastic film.

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8. ~The method of any one of the preceding claims in which the resin soaked
fibers are
arranged into a web before being wound onto the pipe.
9. ~The method of claim 8 in which the web is formed of a single layer of
parallel fibers
and the web is advanced along the pipe in a spiral with sufficient overlap
between adjacent
flights of the spiral to produce multiple layers of resin soaked fibers.
10. ~A method for coating pipe, comprising the steps of:
surface treating a pipe to enhance adhesion of the pipe surface to resin
soaked fibers;
winding a single layered web of resin soaked fibers in a helical fashion onto
the
surface treated pipe to form a pipe coating made up of multiple layers of the
resin soaked
fibers; and~
curing the resin.
11. ~The method of claim 10 in which the web is formed of parallel fibers and
the web is
advanced along the pipe in a spiral with sufficient overlap between adjacent
flights of the
spiral to produce multiple layers of resin soaked fibers.
12. ~The method of claim 11 in which the pipe is heated before winding the
resin soaked
fibers onto the pipe to a temperature that promotes curing of the resin.
13. ~The method of claim 12 in which the resin soaked fibers are heated before
winding
the resin soaked fibers onto the pipe to a temperature that promotes curing of
the resin.
14. ~The method of claim 13 in which surface treating the pipe comprising
roughening the
pipe surface.
15. ~The method of claim 14 in which surface treating the pipe comprises
applying a
primer to the pipe surface.

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16. The method of claim 15 in which the resin soaked fibers are coated with a
heated
film to enhance curing.

Description

CA 02329444 2000-12-21
TITLE OF THE INVENTION
Pipe Coating Process
NAME OF INVENTOR
Glen R. Garneau
FIELD OF THE INVENTION
This invention relates to processes for the coating of pipes.
BACKGROUND OF THE INVENTION
Conventionally, fiber coating of pipes is carried out by winding a continuous
resin
soaked fiber bundle back and forth along a section of pipe until multiple
layers of the fiber
bundle are formed. Once one section of pipe is completed, another section is
started. This is
a time consuming process, and produces a relatively thick coating in a few
passes. At the
ends of the pipe, fibers of successive layers cross-over each other, resulting
in stress points
in the fiber bundle. This method is not practical for coating long sections of
pipe.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for applying
resin soaked
2 0 fiber strands to surface treated pipe to increase the hoop stress, which
is t the maximum
operating pressures of the steel pipe.
It is also an object of the invention to provide a method for accelerating the
cure of
the resin by heating the pipe, fiber and resin in order to increase the
production rate.
There is therefore provided in accordance with an aspect of the invention, a
method
2 5 for coating pipe. A pipe is first surface treated, such as by abrasive
cleaning and application
of primer, to enhance adhesion of the pipe surface to resin soaked fibers.
Resin soaked fibers
are continuously wound in a helical fashion onto the surface treated pipe to
form a
continuous pipe coating made up of multiple layers of the resin soaked fibers.
The resin is
then cured. preferably heat cured. Preferably, the pipe, resin, primer and
fibers are all pre-
3 ~ heated before winding the resin soaked fibers onto the pipe to a
temperature that promotes

CA 02329444 2000-12-21
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curing of the resin. The composite pipe thus formed is preferably coated with
a film, such as
polyethylene or other thermosetting plastic film before curing.
The resin soaked fibers are preferably arranged into a web before being wound
onto
the pipe. The web is preferably formed of a single layer of parallel fibers
and the web is
advanced along the pipe in a spiral with sufficient overlap between adjacent
flights of the
spiral to produce multiple layers of resin soaked fibers.
These and other aspects of the invention are described in the detailed
description of
the invention and claimed in the claims that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
There will now be described preferred embodiments of the invention, with
reference
to the drawings, by way of illustration only and not with the intention of
limiting the scope
of the invention, in which like numerals denote like elements and in which the
figure shows
a schematic of a process for carrying out a method according to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In this patent document, "comprising" means "including". In addition, a
reference to
an element by the indefinite article "a" does not exclude the possibility that
more than one of
the element is present. The word "continuously" is used in the claims to
indicate that a pipe
2 0 made of several sections is being continuously coated, without pausing to
allow resin to cure
on a particular section of pipe.
The invention provides an improved accelerated method for curing and applying
resin soaked fiberglass strands to an abrasively cleaned steel substrate to
increase the hoop
stress. First, the steel substrate of the pipe 10 is abrasively cleaned with a
blast media to a
2 5 near white sspc-sp 10 finish, anchor pattern 40-100 microns. The substrate
is preheated at
heating unit 12 to 215-235°f and a primer layer 14 of 0.001-0.003" is
applied using a
conventional primer applicator 14a at 65-75°f just to cover the
surface.
Resin is mixed with catalyst and preheated in resin tank 13. The resin is
selected in
accordance with principles generally known in the art of composite manufacture
for the

CA 02329444 2000-12-21
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intended application. The resin is delivered to a soaking trough 15 where the
preheated
fiberglass strands are dragged through at high velocities The fiberglass
strands are preheated
at preheat unit 19 before use and additional heating comes prior to the
soaking trough at a
waffle iron 17. The resin is preheated to 100-120°F in the tank 13 and
is delivered to the
soaking trough as a web 21 of heated fiberglass strands. The web 21 is formed
of wide band-
single layer parallel strands pre-heated to at least 120-150°F prior to
soaking. The web 21 of
strands is dragged through at high speeds (150-600 ft/min). These resin soaked
fiberglass
strands are wrapped helically to the steel substrate to form a composite
coated pipe. The pipe
travels on a conveyor line at set angle of travel per rpm. The preheated
primered pipe 10 is
externally wrapped in multiple helical layers of heated resin soaked
fiberglass strands at
wrapping unit 16 and squeegeed by squeegees 16a & 16b to remove excess resin
to insure
the correct resin to glass ratio in accordance with known principles for
composite
manufacture. Surplus resin may be reclaimed at the end of the trough 15 and
returned to the
resin tank 13. The web 21 is applied to the pipe 10 at an angle that results
in adjacent flights
of the resulting helical wrap overlapping, such that a desired number of
layers, for example
12 or more, may be formed.
This combination of heated pipe, primer, resin, and fiberglass causes the
resin to
setup (cure) extremely quickly as compared with room temperature cure. While
composite is
being wound onto the pipe at wrapping unit 16, a heated film 18 is wrapped
onto the coated
2 0 pipe at a wrapping unit 18b sufficiently downstream in the process that a
set time period
(less than about 2 minutes for the example described here) has elapsed between
coating and
film wrapping. The exterior of the composite is wrapped with polyethylene or
equivalent
thermo-setting plastic film 18 while the composite is still tacky on the
surface. This heated
film 18 cures the resin from the heat of the polyethylene, which may be at
200°C or more,
2 5 the higher the better, and as high as the polyethylene will permit. The
film is produced as a
sheet of polyethylene 18 produced from a extruder 18a. The film wrap allows
the end
product to be driven on conveyor wheels 22.
The composite coated pipe 20 is driven over wheels 22 on a conventional pipe
conveyor line. This process allows the steel pipe 20 to be advanced
continuously by the

CA 02329444 2000-12-21
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conveyor line, with the pipe sections joined via conventional come-alongs 24.
The
composite is wrapped from end to end pipe after pipe. The produced composite
coated pipe
may be tested for glass to resin ratio, percentage of void (air pockets)
content, hardness
inside and outside and percentage of cure of resin in a differential scanning
calorimeter.
The use of the continuous coating process including resin soaked fiber supply
unit
(elements 13, 15, 17 and 19), pipe heating unit 12, primer applicator 14a and
film wrapping
unit 18b may all be installed easily as a stand alone unit in a coating plant.
The modularized
system allows simple set up and control of the individual units making up the
continuous
coating process. Resin tanks, waffle irons, fiber strand supply, soaking
troughs, film
extruders and applicators, primer applicators, pipe rotation equipment,
squeegees and
abradors are all known in themselves in the art of pipe coating and do not
need to be further
described here.
Immaterial modifications may be made to the invention described here without
departing from the essence of the invention.

Representative Drawing