Note: Descriptions are shown in the official language in which they were submitted.
i CA 02473867 2004-07-13
METHOD AND MEANS OF REPAIRING A PIPE
The invention relates to a method and means of repairing a pipe more
particularly the invention relates to a method and means of repairing a
damaged pipe
without isolating the pipe or without stopping the flow of materials within
the pipe.
When pipe repairs are to be carried out, three main repair scenarios are
normally encountered. This will include (i) pipes subject to external metal
loss
(caused by corrosion or mechanical damage), (ii) pipes subject to internal
metal loss
(caused by corrosion. erosion or erosion/corrosion) and (iii) piping
components that
are leaking. In addition to these main repair scenarios, the extent of the
deterioration
or damage (i.e. localized or extensive) has also to be considered when
choosing the
repair methods and repair components.
Current repair methods include clamps (localized repairs) and specialized
connectors with sleeves (extensive repairs). It is equally possible to
encircle the
detective area with close lit metallic sleeves which are welded together.
This,
litmever. has to be seal welded. These methods could cause weld induced damage
or
material property changes on the pipe being repaired. In underwater conditions
this
may require specialist habitats to carry out hyperbaric welding. This can
prove costly
and can pose additional dangers. Welding on live pipelines poses further
additional
dangers.
Condition and extent of damage of the pipe essentially dictates the type of
repairs to be carried out. !f the external surface is damaged to the extent
that an
elastomeric seal cannot provide sufficient sealing forces in the immediate
vicinity of
the damage, or in the relatively unaffected areas adjacent to the major damage
(these
areas being used to effect the sealing forces of 'stand'-ofT repair clamps),
the external
pipe surface may need to be re-installed using some form of filler material.
Developments using epoxy-filled steel sleeves have been shown to accommodate
such
areas of extensive damage and have applications for a whole range of defects
including corrosion, non- propagating cracks, dents or. gouges in both axial
and
CA 02473867 2004-07-13
2
circumferential orientation, and girth weld associated anomalies. The epoxy-
filled
sleeve repair technique is typically recommended on areas operating below
100barg
with temperatures not exceeding 100 C. It was assumed that epoxy filled
sleeves can
be used for leak containment. However in various tests conducted it has been
found
that the sleeves were only able to contain leaks below 40barg. Additional
tests were
conducted to determine if pumping epoxy and allowing it to cure under pressure
i.e. in
equilibrium pressure (to that within the pipe) would produce better results.
The tests
prove that higher pressures are obtained but in practical terms this will
involve de-
rating the pipe or suspending production and could prove costly for operators.
There
is a need therefore to develop a method where the pipes can be repaired
without de-
rating the pipe or suspending the throughput of the pipe.
The prior art method is expensive in that heavy duty connectors dimensioned
to fit the damaged pipes, need to be provided. Such connectors are expensive
and take
substantial man-hours to design. manufacture and assemble. The prior art
composite
fibre wraps which has a pressure limit not exceeding 40 barg. When the axial
pressure
exceeds 40barg or when used in isolation are considered temporary repairs.
The invention discloses a permanent method of repairing or reinforcing a
weakened
area in a pipeline section. The method includes removing rust, old coating and
other
unwanted surface blemishes by grit blasting. Then the leaking, damaged or
weakened
surface are wrapped with at least one layer of reinforced composite wrap
material.
The composite wrap is left to cure. If necessary, to further mechanically
strengthen
the affected portion of the pipeline. the pipeline in the affected areas is
encapsulated
by sleeves. Optionally, a wear plate can be placed between the affected
portion of the
pipeline and the composite wrap material. Two half oversized steel sleeves are
installed over the pipe section and bolted together or seal welded together
and thus
forming an annular. chamber. Non gaseous matter in the annular chamber is
removed
by flushing with fresh water and followed by flushing with inert gas or
atmospheric
air. Load bearing epoxy or cementitious grout with high compressive strength
in
excess of I I OMpa or a combination of both separated by chambers is then
introduced
into annular chamber. Finally the grout / combination of gout is allowed to
cure. The
CA 02473867 2010-10-06
3
above invention is used for pipelines submerged in water or sea. Alternatively
the same
method can be done for pipelines on land except the procedures are modified
where by
the two half oversized steel sleeves can be welded together and the flushing
with fresh
water will no longer be required. The unwanted matter can be flushed out using
compressed air or inert gas.
In another aspect, the invention discloses a means to seal the terminal ends
of the
two half oversized sleeves, positionable on the external circumferential side
of affected
riser pipes. The means comprises of a pair of flange bodies integral to the
two half
oversized sleeves and a pair of terminator bodies. Each flange body includes a
semi-
circular collar with a plurality of bores thereon and a semi-circular lip. The
terminator
body includes a semi-circular collar with a plurality of bores thereon, and a
semi-circular
recess structured and configured to receive the semi-circular lip. A graphite
body is
introduceable into the semi-circular recess. The terminator body is secured
against the
flange body by tightening of nuts and bolts introduced between the bores
(apertures) in
the flange body and the terminator body.
In another aspect, the flange ends of the two half oversized steel sleeves are
serrated along the longitudinal axis and sheets of PTFE body is placed between
the two
steel sleeves before the steel sleeves are bolted together by nuts and bolts.
Accordingly, in one aspect of the present invention there is provided a method
of
repairing a leaking, damaged or weakened area in a pipeline section
comprising: a)
removing rust, old coating and other unwanted surface blemishes on the
leaking, damaged
or weakened surface area and the surface beyond the leaking, damaged or
weakened
surface portion of the pipeline; b) wrapping the leaking, damaged or weakened
surface
portion of the pipeline referred in step (a) above by having at least one
layer of reinforced
composite wrap material; c) allowing the reinforced composite wrap material to
cure; d)
enclosing total surface areas referred to in step (a) with two half oversized
steel sleeves; e)
sealing terminal annulus ends of sleeves; f) removing non-gaseous matter in
annular
chamber formed by sleeves, pipe and seals formed in step (e); g) introducing a
load bearing
epoxy or cementitious grout or a combination of both into the annular chamber;
h)
allowing the load bearing epoxy or cementitious grout to cure, wherein at
least one wear
plate is placed between the pipeline and the reinforced composite wrap
material; the
CA 02473867 2010-10-06
3a
reinforced composite wrap material consists of fiber reinforced material pre-
impregnated
with a resin that can be activated by one of fresh water and salt water; the
reinforced
composite wrap is wrapped in a spiral manner on the external surface of the
pipeline; the
non-gaseous matter is removed by flushing the non-gaseous matter with fresh
water
followed by flushing with inert gas or atmosphere air; the terminal annulus
ends are sealed
by hermetically securing a pair of terminator bodies to a pair of flange
bodies, said flange
bodies integral to the two half oversized steel sleeves; and the pair of
terminator bodies are
compressed against the pair of flange bodies by means of a plurality of nuts
ad bolts.
In one embodiment, the reinforced composite method of repairing a leaking,
damaged or weakened area in pipeline, section as claimed in claim 1 wherein
the reinforced
composite wrap material of fiber reinforced material pre-impregnated with a
resin that can
be activated by salt or fresh water for underwater applications or UV or
catalyst cured for
above water applications.
The invention will be described in reference to a preferred embodiments of the
invention with reference to the following diagrams:
Figure 1 shows a leaking. damaged or weakened surface area and the area
beyond the leaking, damaged or weakened surface portion of pipeline is to be
grit
blasted.
Figure 2 shows a leaking, damaged or weakened surface area wrapped with fibre
reinforced wrap.
Figure 3A shows longitudinal cross-sectional views of a pipe being repaired
with
a wear plate and wrap around fibre reinforced wrapped. Figure 3B shows a cross
sectional view of pipe in Figure 4.
CA 02473867 2009-09-01
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Figure 4 shows an enclosure of the surface area with two half oversized steel
sleeves with
inlet and outlet port. (Details of bolts and nuts or welds not shown).
Figure 5 shows diagrammatic longitudinal and cross-sectional views of a pipe
being
repaired with a wear plate (optional) wrapped around fibre reinforced wrap,
enclosed in
sleeves with annular chamber filled with grout.
Figure 6 shows a cut away perspective view of a pipe being repaired with half
sleeves and
terminating means
Figure 7 shows a radial cross-sectional view of the pipe shown in Figure 6.
Figure 8 shows a detailed partial sectional view of the seal wings of the
sleeves.
Figure 9 shows a sectional view of the terminating means.
Figure 10 shows details of graphite ring splice.
The surface of a damaged/deteriorated pipe (20) is prepared first by grit
blasting
to remove rust and remnants of old coating. Grit blasting is known as one of
abrasive
blasting. The blasting of the pipe (20) is carried out by sweep blasting using
fine abrasives
not containing iron (e.g. garnet, aluminum oxide), glass pearls or stainless
steel shot.
Maximum speed and most effective cleaning is obtained by systematic blasting.
Work is
blocked out in 30cm squares and each square blasted evenly until complete. A
minimum
of 25mm into any adjacent coated area is continued by blasting and the edges
are
feathered.
Then the thinned down, leaking or affected area is wrapped around with a
fibre reinforced composite wrap (21) capable of curing under water and
standing
pressure. Example of a wrap is a fiberglass cloth pre-impregnated with a resin
that can
be activated by salt or fresh water. (Fig. 2) Optionally, wear plates (23) can
be used in
addition to the fiberglass wrappings to reduce the risk of damage due to
corrosion and
erosion. (see Fig. 3). The fiberglass as sourced is packaged in a hermetically
sealed
foil pouch, it is ready to use and does not require any measuring or mixing.
It has an
initial settling time of only 30 minutes (24 C). Preferably the fiberglass
should be
spirally wrapped with overlapping layers. The number of wraps depends upon the
operating pressure desired; the greater the pressure the more wraps. Once the
wrap is
CA 02473867 2009-09-01
cured, it is preferable to control blast to create an anchor pattern for the
epoxy or grout to
be subsequently injected.
The above described embodiment is acceptable for temporary repairs of affected
5 riser pipes. To provide a more permanent solution, a further strengthening
of the affected
area of the riser is required.
Two half oversized matingly engageable steel sleeves (22) are then installed
covering and extending to beyond the deteriorated part of a pipe (20) (Fig.
5). The
extension of the sleeves (22) beyond the deteriorated part of the pipe is to
cater for axial
loads of the material transported within the pipe. The sleeves are welded or
bolted
together around and beyond the damaged/deteriorated or corroded area. When the
sleeves are secured together by nuts and bolts, then one surface of the flange
of each
sleeve is serrated all along one side of the length of the sleeves (see Fig.
8). A strip of
PTFE is placed between the serrated surface before the sleeves are secured
together. The
ends of the sleeves are capped. The sleeves are with inlet (16) and outlet
(18) port at the
ends. The sleeves are dimensioned to allow an annular chamber (25) between the
original
pipe(20) and the sleeves(22). Upon installation of the sleeves the ends are
capped using
either fast epoxy curing resins or elastomeric seals (27) which are compressed
when the
sleeves are bolted or welded together or secured by other known means in the
art.
The annulus gap typically will range from 12.7mm to perhaps maximum of
76.2mm and will be dependent upon surface condition of the effected area i.e.
dents,
weld protrusions, out of dimension pipe etc. The size of the annulus shall be
calculated
to provide sufficient sheer and axial load carrying capacity. In addition
grout (29) can be
formulated with additives or aggregates to either insulate the pipe (reduce
thermal shock
especially at the splash zone) or to reduce shrinkage of the epoxy.
All ambient water present in the annular chamber (25) should be discharged
by means of the application of compressed air or other inert gas with a
pressure not
CA 02473867 2004-07-13
6
exceeding 9.7 bar (I 40ps)) entering through the inlet port (16) and allowing
discharge
through the outlet port (18). The maximum pressure stated is for indicative
purposes
only and is dependent upon the capacity of the end seals.
Upon removal of all ambient water from the annular chamber (25) by means
of compressed air or inert gas, the annular chamber (25) is flushed with fresh
water:
The fresh water is injected from the inlet port (16) and allowed to exit at
the outlet
port (18). The fresh water is pumped at a pressure not exceeding 9.7bar
(140psi). The
procedure is continued until complete discharge of all contaminants. Upon
completion
of the above, the fresh water is discharged by means of introduction of inert
gas. This
procedure is continued until all moisture is discharged from the annular
chamber (25).
The pressure in the annular chamber (25) during the injection of the inert gas
shall not
exceed 9.7 bar (140psi).
Finally a load bearing grout capable of curing under water is then injected
into
annular chamber (25) of the sleeves through the pre-installed inlet and outlet
port (16,
18). The maximum injection pressure shall not exceed 9.7bar (140psi).
Load bearing filler material used in this present invention is either epoxy
based or cementitious grout. The epoxy should have low viscosity, designed for
application with automatic meter, mix and dispense pressure injection
equipment. The
physical properties allow its use in applications requiring high load bearing
strength
and excellent adhesion under adverse application conditions. It should have a
long
working life and low exotherm reaction (minimal heat generation during cure
that
make it suitable for applications where a relatively large mass of adhesive is
employed. Preferably the epoxy should have a high degree of chemical and
radiation
resistance attainable in the ambient temperature. The injected epoxy is left
to cure in
accordance with manufacturer's recommendations.
The cementitious grout should have high compressive strength and should be
pumpable and similarly should be left to cure as per manufacturer's
recommendations. The epoxy / grout completely integrates the sleeves (22) and
the
existing pipe (20) providing additional structural reinforcement. The sleeves
(22)
CA 02473867 2004-07-13
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isolate the pipe thus preventing further external corrosion and being bonded
to the
pipe (20) further strengthens the pipe. The fibre reinforced wrap (21)
contains leaks
within corroded area and in conjunction with the load bearing grout (29)
contains the
hoop stresses experienced by the pipe. The axial loads are contained by making
sleeves longer than the affected area.
In another aspect of the invention, there is disclosed a pair of end flanges
integrally secured to the pair of matingly engageable steel sleeves and a pair
of
independent terminal flanges, which are matingly engageable to the said end
flanges
(see Fig. 6). It will be appreciated that instead of terminal ends of the
matingly
engageable steel sleeves being sealed by means of curing resins or elastimeric
Seals,
metal flanges are used to provide more secure end sealing effect.
Referring to Fig 6, there is shown a sectional view of a riser/pipeline (20)
to
which is secured a pair of half sleeve pipes (22). Each half sleeve pipe (22)
is a
diameter larger than the diameter of the intended riser / pipeline (20) which
it is
proposed to cover. The half sleeve includes a flange (24) at the terminal
edges, said
flange extending throughout the length of the half sleeve. Each of the half
sleeve
pipes includes a longitudinal serrated strip (26) extending throughout the
length. The
longitudinal serrated strip is designed to secure a longitudinal seal (28),
such as an
elastomeric seal (such as PTFE), copper sea] or any other seal capable of
being
compressed between the two half sleeves to prevent leakage of materials
contained
within the two half sleeves when assembled together. The flanges include a
plurality
of spaced apart apertures (28) to accommodate nuts and bolts which are used to
connect the two half sleeves.
Instead of the two half sleeves being secured together by means of flanges
(24), it is possible to secure the half sleeves by welding along the edges. In
this
embodiment, there is no need for flanges at the half sleeves, neither is there
a need for
longitudinal serrated strips on the flanges.
CA 02473867 2004-07-13
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Each terminal end of each half sleeve includes an end-flange body (32)
integrated with the rest of the half sleeve. The end-flange body (32) includes
a semi-
circular collar (34) with spaced apart apertures (36). It further includes two
flange
portions (38,44) co-planar to the flange (24) in the rest of the sleeve. The
said flange
(38) includes apertures (40) to accommodate nuts and bolts when securing the
end-
flange body (32) to its appropriate end-flange body of the matingly engageable
terminator body. Integral to the end-flange body is semi-circular lip (42)
extending
forward from the semi-collar (34).
The invention further includes a terminator body (45) structurally configured
to be secured to the end-flange body (32). The terminator body (45) is
independent
and comprises of two identical halves to be secured to the two end-flange
bodies (32).
Each terminator body (45) includes a semi-circular collar (46) with spaced
apart
apertures (48). It also includes two pairs of flanges (50, 52) each with an
aperture
(53). The flanges (50) are positioned in a manner such that two terminator
bodies
placed in mirror image to each other are securable to each other by nuts and
bolts. The
terminator body further includes semi-circular recess (54) dimensioned and
configured to receive the semi-circular lip (42) from the end-flange body
(32).
The working of the end connector comprising of the end-flange body and the
terminator body will be described now. The half sleeve with the end-flange
body (32)
is positioned on the pre determined position of the riser pipe (20). The
longitudinal
seals (28) are placed in position along the longitudinal serrated strips. A
graphite ring
(56) formed by two semi-circular graphite strips is placed in the semi-
circular recess
(54). Preferably the terminal edges of semi-circular graphite strips is
obliquely cut to
provide a more effective seal (see Fig. 10). Three mild steel rings (60, 62,
64) are
positioned adjacent to graphite ring. The rings are provided to prevent any
extrusion
of graphite while compressing the graphite seal to activate. The half sleeves
and the
end-flange bodies are secured together by nut and bolt means (or alternatively
are
welded together).
CA 02473867 2004-07-13
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After positioning the graphite ring (56), the terminator bodies (45) are
placed
in registration with the end-flange bodies and are compressed against the end-
flange
body to a desired compression value to activate the graphite ring as a seal.
The
graphite ring will change its shape during external compression and fill up
voids and
gaps if any in that area. At the same time, the density of the graphite ring
will increase
due to additional compression. The additional compression force required to
compress
the graphite ring is calculated based on the graphite manufacturer's
recommendation
and on field requirements. It will be appreciated that the terminator bodies
(45) are
compressed against and secured to the end- flanges by means of the plurality
of nuts
and bolts (58).
It will be appreciated that the provision of a semi-circular recess and a
matingly engageable semi-circular lip can be present in the flange body and in
terminator body respectively instead as described above.
This invention is developed to solve problems presented by large, high
temperature risers/pipes operating up to IOO C or higher, causing thermal
shock at the
splash zone, failure of the protective coating; and the resulting accelerated
corrosion.
The purpose of the invention is to provide a cost effective technology to
repair
and/or rehabilitate these pipelines/risers operating at high pressures without
suspending production, and to solve the problems caused by the accelerated
rates of
corrosion.
The advantages of this invention are it does not require de-rating of pipeline
or
suspending production; it does not require expensive heavy duty connectors to
take
the axial loads or to contain leaks via seals normally incorporated within the
connectors; does not require welding on the pipe to be repaired; and it
overcomes the
limitations of epoxy sleeves and fibre reinforced wraps used independently.
The above invention is used for pipelines submerged in water or sea.
Alternatively the same method can be done for pipelines on land except the
CA 02473867 2004-07-13
procedures are modified whereby the two half oversized steel sleeves can be
welded
together and the flushing with fresh water will no longer be required. The
unwanted
matter can be flushed out using compressed air or inert gas.
5
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