Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF RESISTING EROSION IN A PIPE
FIELD OF THE INVENTION
The present invention relates to a method of resisting erosion in a pipe
by lining a pipe to form an erosion resistant layer on an inner surface of the
pipe.
BACKGROUND
In pipes for conveying fluid or materials therethrough and in containers
for handling fluid or materials, the desirability of resisting erosion,
abrasion and
corrosion along an inner surface of the pipe or container is known for
extending the
life thereof. Conventional methods of lining pipes include spray-on coatings,
however
these tend to bond poorly and do not provide considerable resistance to
erosion. Use
of ceramic liners in pipes is also known, however this involves a complex
process in
which the liner is typically formed separately from the pipe and then later
installed in
the pipe in a time consuming and costly manner. In general, known erosion
resistant
coatings do not provide suitable resistance to erosion while being readily
applied to
pipes.
US Patent Application Publication No. 2003/0192613 by Zhen Wang
discloses a Pipe and Method of Resisting Erosion, Abrasion and Corrosion in
which a
steel pipe is lined with iron and aluminum oxide by applying aluminum and iron
oxide
as powders and igniting the powders to form an exothermic and self-propagating
reaction which fuses the resultant materials to the inner surface of the pipe.
When
applying the pipe lining in the manner described in the prior publication, it
is difficult to
efficiently ignite the powders and distribute the materials evenly to obtain a
uniform
coating, resulting in a lower quality coating. Also, in order for the pipe to
be released
from the mold as described in the prior publication, the pipe and mold must be
cooled
slowly to prevent the pipe from being lodged in the mold, however the slow
cooling
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can have a negative effect on lining quality.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a method of
resisting erosion in a pipe comprising:
providing a pipe having a tubular body;
surrounding the pipe with a pipe mold;
applying aluminum as a powder and iron oxide as a powder to an inner
surface of the tubular body;
initiating an exothermic reaction between the aluminum and the iron
oxide to form aluminum oxide and iron;
rotating the pipe about a longitudinal axis of the pipe to separate the
aluminum oxide and the iron into a layer of the iron and a layer of the
aluminum oxide;
cooling the aluminum oxide and the iron by applying a cooling fluid to
the pipe mold to solidify the layer of the iron directly adjacent the inner
surface of the
tubular body and to solidify the layer of aluminum oxide adjacent an inner
surface of
the layer of the iron; and
releasing the pipe mold from the pipe in a generally radial direction
relative to the pipe.
By providing a radially releasable mold, the mold can be tighten secured
about the pipe during formation of the coating layers and subsequent cooling
to
prevent deformation of the pipe while remaining readily releasable even when
subjected to a very rapid cooling, for example by a cooling liquid.
Accordingly, the
advantages of better quality coating layers achieved by rapid cooling with
fluids can
be achieved.
According to a further aspect of the present invention there is provided a
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method of resisting erosion in a pipe comprising:
providing a pipe having a tubular body;
surrounding the pipe with a pipe mold;
applying aluminum as a powder and iron oxide as a powder to an inner
surface of the tubular body;
rotating the pipe about a longitudinal axis of the pipe at a prescribed
speed for a prescribed duration to distribute the powders about the inner
surface of
the tubular body;
initiating an exothermic reaction between the aluminum and the iron
oxide to form aluminum oxide and iron;
rotating the pipe about a longitudinal axis of the pipe to separate the
aluminum oxide and the iron into a layer of the iron and a layer of the
aluminum oxide;
cooling the aluminum oxide and the iron to solidify the layer of the iron
directly adjacent the inner surface of the tubular body and to solidify the
layer of
aluminum oxide adjacent an inner surface of the layer of the iron.
By rotating the pipe before ignition at a prescribed speed and a
prescribed duration of rotation, a more even distribution of material can be
achieved
for forming more uniform and better quality resultant coating layers on the
pipe as
compared to prior art configurations.
According to a further aspect of the present invention there is provided a
method of resisting erosion in a pipe comprising:
providing a pipe having a tubular body;
surrounding the pipe with a pipe mold;
applying aluminum as a powder and iron oxide as a powder to an inner
surface of the tubular body;
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applying molten tungsten to the powders so as to initiate an exothermic
reaction between the aluminum and the iron oxide to form aluminum oxide and
iron;
rotating the pipe about a longitudinal axis of the pipe to separate the
aluminum oxide and the iron into a layer of the iron and a layer of the
aluminum oxide;
and
cooling the aluminum oxide and the iron to solidify the layer of the iron
directly adjacent the inner surface of the tubular body and to solidify the
layer of
aluminum oxide adjacent an inner surface of the layer of the iron.
Use of molten tungsten provides an accurate control of the ignition of
the powders and provides a sufficiently elevated ignition temperature that
fast and
complete ignition of the material results in a more uniform and thus an
improved
quality of coating layers as compared to the prior art.
In one embodiment, the mold comprises an outer frame surrounding the
pipe, spaced radially outwardly from the pipe and a plurality of support
members
spanning radially inwardly to support pipe an inner ends centrally in the
outer frame.
In this instance, the support members are preferably releasable in radial
direction of
pipe relative to outer frame and the pipe.
The support members may comprise screws for releasing the mold by
rotating the screws.
The support members are preferably located at circumferentially spaced
positions about the pipe and at axially spaced positions along the pipe.
According to an alternative embodiment, the mold comprises a plurality
of sections each extending along a length of the pipe and extending only
partway
about a circumference of the pipe such that the plurality of sections together
fully
surround the pipe about the circumference thereof. The pipe is preferably
released
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from the mold in this instance by releasing at least some of sections in the
radial
direction from the pipe.
The method may further include rotating the pipe about the longitudinal
axis of the pipe until the powders are uniformly distributed about the pipe
prior to
5 igniting the powders.
The molten tungsten may be applied to the powders by inserting a
tungsten wire into pipe and heating the tungsten wire until molten tungsten
forms by
passing an electrical current through the tungsten wire.
There may be provided an elongate conductive member supporting the
tungsten wire at a free end thereof. In this instance, the conductive member
is
preferably inserted into the pipe prior to passing an electrical current
through elongate
conductive member to heat the tungsten wire so that the molten tungsten is
formed
and applied to the powders at a location in the pipe spaced inwardly from one
end of
the pipe towards a central portion of the pipe.
Some embodiments of the invention will now be described in
conjunction with the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an end view of a pipe which has been lined.
Figure 2 is an end view of the pipe shown supported in a mold for
rotating the pipe.
Figure 3 is a side elevational view of the pipe shown supported in the
mold.
Figure 4 is a flow chart illustrating the order of operations for lining the
pipe.
Figure 5 is a sectional elevational view of an ignition system for igniting
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the powders in the pipe.
Figure 6 is an end view of further embodiment of the pipe mold
supporting the pipe therein.
Figure 7 is an end view of another embodiment of the pipe mold
supporting the pipe therein.
In the drawings like characters of reference indicate corresponding parts
in the different figures.
DETAILED DESCRIPTION
Referring the accompanying drawings there is illustrated a pipe
generally indicated by reference numeral 10. The pipe 10 includes a lining 12
coating
an inner surface 14 thereof to prevent erosion of the inner surface while also
providing
a durable corrosion and abrasion resistant layer.
The pipe 10 includes a generally tubular body surrounding a longitudinal
axis of the pipe. Respective ends 16 of the pipe are open for communication
with
adjacent sections of pipe when connected in a pipeline. The pipe is thus
suitably
arranged for conveying fluids and the like therethrough. The tubular body of
the pipe
has a steel composition.
The lining 12 of the inner surface 14 of the pipe includes a layer of iron
18 and a layer of aluminum oxide 20. The layers are fused onto the pipe such
that the
layer of iron 18 is located directly adjacent the inner surface 14 of the
tubular body of
the pipe while the aluminum oxide layer 20 is positioned radially inwardly in
reEation to
the iron layer adjacent an inner surface of the iron layer.
The lining is applied to the pipe by an apparatus 22 arranged for coating
the inner surface of the pipe. The apparatus includes a mold 24 which is
supported on
a suitable rotating mechanism 26. The mold 24 is arranged to snuggly receive
the
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pipe 10 to be coated therein. The rotating mechanism 26 includes a drive wheel
28 for
engaging an outer surface of the mold to rotate the mold and an idler wheel 30
for
supporting the mold 24 rotatably thereon.
The mold is sufficiently rigid to resist pipe deformation when the pipe is
heated as the coating is being applied to the inner surface thereof. The mold
includes
a tubular portion 32 which snuggly receives the pipe 10 therein and a pair of
end
portions 34 capping respective ends of the tubular portion. Each end portion
34
generally comprises an annular flange which spans radially inwardly from the
ends of
the tubular portion 32 about a full circumference of the tubular portion so as
to abut
respective ends of the pipe 10 when the pipe is received within the tubular
portion 32
of the mold. The end portions are suitably arranged for containing a small
amount of
liquid adjacent an inner surface of the pipe 10. The mold includes a cooling
mechanism for cooling the mold to resist deformation when the pipe is heated.
The method of operating the apparatus 22 for coating the inner surface
14 of the pipe 10 begins by first mixing aluminum powder and iron oxide powder
in a
ratio of 8 Al to 3 Fe304. The pipe is received within the mold 24 and capped
by the
end portions 34 thereof. The aluminum and iron oxide powders are distributed
evenly
about the inner surface 14 of the pipe within the mold which is rotated about
the
longitudinal axis of the tubular body of the pipe 10 prior to igniting the
powders. The
pipe is rotated at a prescribed speed arranged to distribute the powders and
for a
prescribed duration prior to igniting the powders corresponding to a duration
required
to evenly and uniformly distribute the powders about the circumference of the
pipe.
Heating and igniting the powders within the pipe initiates a self-
propagating exothermic reaction to produce aluminum oxide and iron in the
ratio of 4
A1203 to 9 Fe. The self-propagating reaction generates sufficient heat to melt
the
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products of the reaction so that the aluminum oxide and iron flow freely about
the
inner surface 14 of the pipe as a fluid. Despite the high temperatures, the
rigid
insulated mold resists deformation of the pipe.
Continued rotation of the mold about a longitudinal axis of the pipe and
the mold causes the heavier iron particles to be displaced radially outwardly
in relation
to the aluminum oxide by the centrifugal spinning forces. The iron thus
deposits itself
in an iron layer directly adjacent the inner surface 14 of the pipe while the
lighter
aluminum oxide forms a harder layer adjacent an inner surface of the layer of
iron.
Rotation of the mold continues until the iron and aluminum oxide layers
have sufficiently cooled so as to mostly solidify. The pipe 10 may then be
removed
from the mold 24.
Turning now to Figure 5, an ignition system is disclosed for igniting the
powder. The ignition system uses a tungsten wire 50 which is heated inside the
pipe
to form a molten tungsten which serves to ignite the powder when the molten
tungsten comes into contact with the powder. The molten tungsten is applied to
the
powder at a location within the pipe spaced inwardly from one end of the pipe
towards
or near a centre of the pipe in the longitudinal direction thereof.
The ignition system comprises an elongate conductive member 52
which supports the tungsten wire 50 at a free end thereof. The tungsten wire
is
supported electrically in series with the conductive member so that passing an
electrical current through the conductive member from a source 54 serves to
sufficiently heat the wire that the tungsten becomes molten tungsten. The
source 54
comprises a suitable portable source for providing an electrical current to
the elongate
conductive member. As illustrated, the source is supported on wheels for ease
of
portability.
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The conductive member 52 has a suitable cross sectional area and
resistance so that the conductive member itself does not substantially
overheat when
passing electrical current therethrough to heat the tungsten wire at the free
end of the
conductive member. Ignition of the powder occurs by inserting the conductive
member into the pipe from one end thereof so that the tungsten wire at the
free end of
the conductive member is located centrally within the pipe. When the
electrical current
is applied, and the wire forms molten tungsten, the molten tungsten will
ignite the
powder upon contact. When subsequently used, the tungsten wire is replaced
with
another tungsten wire for each ignition.
Turning now to Figures 6 and 7, further embodiments of the mold 24 are
illustrated. In each instance the mold is arranged to be released in a radial
direction
relative to the pipe when removing the pipe from the mold, however the mold
serves
to tightly constrain the pipe in the radial direction about the full
circumference thereof
during the ignition of the powder and the subsequent cooling and
solidification of the
coatings on the inner surface of the pipe to prevent any deformation of the
pipe. By
permitting the mold to be released in a radial direction from the pipe, the
material
forming the coatings on the inner surface of the pipe can be cooled more
quickly
using a coolant fluid 56, for example water which is applied directly to the
outside of
the mold 24. Accordingly the mold and coatings cool much quicker than in prior
art
configurations to form a better quality lining without encountering subsequent
problems of the deformation of the pipe and subsequent removal of the pipe
from the
mold as in prior art attempts.
Turning now more particularly to Figure 6, the mold in this instance
comprises two separate mold portions 58 which are arranged to be readily
releasable
from one another. Each of the mold portions extends a full length of the pipe
in the
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longitudinal direction while being arranged to extend only partway about a
circumference of the pipe. The two mold portions are substantially equal in
dimension
in the circumferential direction so that each spans approximately half of the
circumference of the overall circumference of the pipe. Opposing side edges of
the
5 two mold portions are arranged to mate with one another in an interlocking
and
overlapping configuration in which one of the mold portions overlaps the other
in a
circumferential direction about the full length of the pipe to ensure that the
mold can
be constrained in a radial direction about the pipe during the formation of
the coatings
on the inner surface of the pipe. After cooling using a coolant fluid 56 as
described
10 above, one or both of the mold portions is removed from the pipe in a
radial direction
of the pipe to permit the pipe to be released from the mold.
Turning now to figure 7, the mold 24 may alternatively comprise an
external frame 60 which is generally tubular in shape and fully surrounds the
pipe, but
has an internal diameter which is greater than the external diameter of the
pipe to
define an annular gap therebetween with the external frame being spaced
radially
outward from the pipes.
A plurality of support members 62 are mounted on the external frame to
span radially inward therefrom to a respective inner end 64 which engages the
outer
circumference of the pipe. The support members 62 are provided at a plurality
of
circumferentially and axially spaced positions relative to one another and
relative to
the pipe to fully surround and engage the pipe about the circumference thereof
and
along the length thereof for resisting deformation of the pipe during the
formation of
the coating on the inner surface thereof.
Each of the support members 62 is a threaded member or screw which
is threadably received through a respective threaded bore in the external
frame so
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that rotation of 'each support member 62 about its respective longitudinal
axis causes
the support member to be screwed inwardly and tightened in a radial direction
inwardly towards the pipe when rotated in one direction while also being
permitted to
be screwed outwardly or loosened in a radially outward expanding direction
relative to
the pipe when rotated in the opposite direction.
Accordingly a pipe can be initially positioned within the external frame
with the support members 62 being tightened about the pipe to constrain the
pipe in
the radial direction during formation of the coating thereon. After cooling of
the
external side of the mold using a coolant fluid 56 as noted above, the support
members 62 can be turned to be released in a radially outward direction
relative to the
surrounding external frame which remains fixed and relative to the pipe so
that the
pipe can then be readily removed from the mold.
The method described herein may be adapted for various types of pipes
or containers or other appliances for the similar purpose of resisting erosion
by
improving wear characteristics of the product being coated. Corrosion and
abrasion
resistant benefits of the aluminum oxide coating are also recognized.
Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
within the spirit and scope of the claims without department from such spirit
and
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
