Note: Descriptions are shown in the official language in which they were submitted.
~4~ ~ t l~
TEM File No. 145.2
TITT F: EXTERNAL PIPE REINFORCING SLEEVE
FTT~T n OF T~ T~VFNTION
The present invention relates to a reinforcing assembly for a pipe, and in particular
to an external sleeve for reinforcing or sealing pipes used in the oil and gas industry
0 RAcKGRouNn OF T~F ~VFNTION
It is well known that pipes in general, and particularly pipes used in the oil and gas
industry, are subject to defects such as corrosion, mill defects, stress corrosion cracking,
and hydrogen induced cracking. During in~t~ tion and operation of a pipe, pipe wall
defects having the potential to cause failure are identified. The usual methods of
5 preventing such defects from causing a failure are either to remove the defect by cutting
out an entire cylindrical section of the pipe, or by significantly reducing the internal
pressure in the pipe prior to either welding a pressure cont~ining sleeve onto the pipe or
by applying a mechanically tightened or fibre glass sleeve to the pipe.
A disadvantage of these prior methods is that they may require pipe system shut
20 downs and a resultant loss of throughput of product in the pipe. For instance, shut downs
are typically required where sleeves are welded directly to a pipe. Such methods also
involve occupational hazards, potential metallurgical failures, and costly expenditures.
Another disadvantage is that prior art sleeves, if installed while the pipe is under operating
pressures, can loosen and separate from the pipe if the operating pressure later drops for
25 any reason. As a result, prior art sleeves require frequent m~inten~nce, repair and
replacement, which adds significantly to the operating costs of a pipe.
What is desired therefore is a pipe reil~lcil1g sleeve which overcomes the
limitations and disadvantages of these other prior art sleeves. Preferably the sleeve should
not be welded to the pipe, and should be capable of being installed whether the pipe is
30 pressurized (ie. operating) or not. If installed while the pipe is pressurized, the sleeve
should remain firmly secured to the pipe upon depressurization or shut down. Further, the
sleeve should be capable of relatively quick and efricient installation to reduce in~t~ tion
costs.
SU~l~A~Y OF THF. ~VF~TION
s In one aspect the present invention provides a method of reinforcing a lon~itll(1in~1
section of hollow pipe comprising:
providing at least two sleeve segments, each sleeve segment having an inside
surface adapted to fit onto an outer surface of said pipe;
preparing at least one of said outer surface of the pipe and said inside surface of
0 the sleeve segments for receiving an epoxy;
applying said epoxy to at least one of said outer surface of the pipe and said inside
surface ofthe sleeve segments;
mounting said sleeve segments onto said pipe with said epoxy located
therebetween;
applying a clamping force to s~ueeze said sleeve segments onto said epoxy and
said outer surface of the pipe;
heating said sleeve segments to a predetermined temperature above the
temperature of said pipe sufficient for thermal expansion of said sleeve segments;
joining said sleeve segments while expanded to form a continuous sleeve~0 circU,llrel el,lially about said pipe; and
removing said clamping force, and allowing said sleeve to cool to said temperature
of the pipe to form an interference fit therebetween and to seal said section of pipe to
avoid leakage of product therefrom.
In another aspect the invention provides a sleeve assembly for re,l~rorcillg a
longit~ltlin~l section of hollow pipe comprising:
an epoxy m~t~ l; and
first and second sleeve segments adapted to fit onto an outer surface of said pipe
so as to substantially circull~lel"ially encompass said pipe;
said sleeve assembly being formed by:
preparing at least one of said outside surface of the pipe and said sleeve segrnents
for contact with said epoxy material;
- 2 -
coating said outside surface of the pipe with said epoxy material and placing said
sleeve segments over said epoxy material;
applying a radial clamping force to squeeze said sleeve segments onto said outersurface of the pipe;
heating said sleeve segments to thermally expand said sleeve segments;
joining said sleeve segments together about said pipe while said sleeve se~nentsare thermally expanded; and
forming an interference fit between said sleeve assembly and said pipe upon
removal of said clamping force by cooling said sleeve segments.
nF~CRTPTION OF T~ DRAWINGS
Embodiments of the invention will now be described, by way of example only, withreference to the accompanying drawings, wherein:
Figure 1 is a perspective view of an external pipe reinforcing sleeve installed onto a
lS longitudinal section of hollow pipe according to a preferred embodiment of the present
mventlon;
Figure 2 shows the sleeve of fig. 1 prior to installation over a defect in the pipe; and
Figure 3 shows the sleeve of fig. I during installation with a hydraulic jack applying
a clamping force and heating of the sleeve.
nF~CRrPTION OF PRFFFRRFI) FMP~OI~IMENTS
The figures show a sleeve according to a prefelled embodiment of the invention
(generally indicated by reference numeral 10) and a process of mounting the sleeve onto a
hollow pipe 12. The sleeve 10 is mounted over a longihl~lin~l section or portion of pipe
25 12 which requires reinforcement, for instance to prevent rupture or leakage of an defect or
anomaly 14 in the pipe wall 16 The defect may be a stress crack, an area of pipe wall
degradation due to corrosion, a dent, and the like For illustrative purposes, the pipe 12 is
one which transports hydrocarbons under pressure, such as a natural gas or oil pipeline.
Whether the pipeline is located above or below ground, it is typically subject to internal
30 pressure fll~ch1~tions, internal and external temperature fluctuations, and to both internal
and external corrosive agents It will be appreciated by those skilled in the art, however,
that the sleeve 10 is not restricted to use on such pipelines but is also suitable for use on
various types of pipes as well, such as those used for transporting drinking water, sewage,
and a host of other liquids and gases, whether pressurized or not.
Referring now to fig.2, the generally cylindrical outer surface 18 of the pipe 12 in
the vicinity ofthe defect 14 (shaded area indicated by 20) should be prepared for receiving
a binding agent, referred to herein as an epoxy, as well as first and second sleeve segm~nts
22a and 22b, respectively. Since the pipe 12 is typically constructed of plate steel and has
been exposed to the elements for some time, the outer surface 18 should be cleaned of rust
and any foreign substances (eg. oil) to allow the epoxy to bind thereto and to provide
good contact with the sleeve segments 22a, 22b. Sand-blasting has provided good results.
o The sleeve segments 22a, 22b are shaped and sized to encircle the section of pipe
to be reinforced. Each sleeve segment 22a, 22b is formed of plate steel with an outside
surface 24a and 24b, respectively, and an inside surface 26a and 26b, respectively, having
a radius of curvature generally matching that of the pipe's outer surface 18 so as to fit
thereon. The sleeve segments together substantially circumferentially encompass the pipe,
leaving a small gap 28, say about .25 to .50 inches, between facing ends of the sleeve
segments on opposed sides of the pipe to accommodate therrnal expansion of the sleeve
segments as described later. In order to fit onto the pipe, each sleeve segment must not
exceed a semi-circular shape in transverse cross-section with an arc of no more than 180
degrees. It will be appreciated that in peculiar circumstances three or more sleeve
20 segments may be provided wherein the segments side-by-side substantially encompass the
pipe, but this is not plerelled because of the added cost and complexity of welding the
segment~ together, as described later. It will also be appreciated that the outside surfaces
24a, 24b form smooth curved surfaces as shown, although this need not be the case. The
sleeve segments may also be formed of material other than plate steel, such a stainless
2s steel which is also easy to weld. It is preferable, however, that the sleeve segments be
formed of material which matches or is complementary to that of the carrier pipe 12 to
avoid promoting corrosion by setting up a cathodic cell or reaction therebetween. Prior to
in~t~ tion, the inside surfaces 26a, 26b should be cleaned of rust and any foreign
substances to allow the epoxy to bind thereto. The preparation may be done on site or in
30 the shop.
A connector plate, or "zipper", 30 is welded to the opposed ends of one of the
sleeve segrnent~ (in the present case to the first sleeve segment 22a) as indicated at 32.
$ ~
Typically such welding is performed prior to installing the sleeve segments onto the pipe,
although such welding could be delayed until the sleeve segments and connector plates are
clamped onto the pipe as discussed below. The latter option is not prefel,ed because of
greater h~nrlling difficulties. Each connector plate 30 must extend beyond the opposed
s circulllfel~e~llial ends of the sleeve segment 24a so as to overlap with the outside surface of
the second sleeve segment 22b as shown in figs.1 & 3. Each connector plate may be
composed of several plates, if desired. The connector plate should be of a comple"~n~aly
or matching material to that of the sleeve segments to minimi7e or avoid cathodic reaction
therebetween. One connector plate 30 could also be joined to each sleeve segrnent, if
0 symmetrical sleeve segments are desired. The connector plates may also be formed
integrally ~,vith the sleeve segment, but production costs may be higher with this option.
Although alternate joining means may be used, such as hinges or bolts, this is not plefe"ed
because of possible interference with the sleeve's fit onto the pipe, greater difficulties in
coating the sleeve once installed, possible corrosion at bolt interfaces, and industry
1S perceptions that such connections are temporary.
The method of forming a sleeve on the pipe 12 according to the present inventionwill now be described. Having prepared the pipe's outer surface 18 and the inside surfaces
26a, 26b of the sleeve segments as described above, the epoxy is applied around the pipe
to the outer surface 18 in the vicinity 20 of the defect. Alternately the epoxy might be
20 applied to the inside surfaces of the sleeve segments, but generally this is not as practical.
The sleeve segrnent 22b and sleeve segment 22a, which has the connector plates 30
welded thereto, are then placed onto the outer surface 18 over the epoxy and tightly
clamped to the pipe as shown in fig.3. Good results have been achieved using a hydraulic
jack and chain assembly 34 to provide the necessary radial clamping force for squeezing
2s the sleeve se~T ~nts onto the epoxy and the pipe's outer surface. More jack assemblies 34
may be used depending on the desired clamping force and the length of the sleevesegments, for example. More clamping force may be required where the pipe is
depressurised during in.st~ tion, for example, because certain pipes which are generally
~ round when pressurized sometimes become slightly oval in shape upon depressurization.
30 It is noted that prior to in~t~ tion the inside surfaces 26a, 26b of the sleeve segm~nts
should also be inspected and cleaned, if necessary, as described earlier for the outer
surface 18 of the pipe.
Heat is next applied to the clamped sleeve segments using torches, as at 36, or
other suitable means, to thermally expand the sleeve segments 22a, 22b. While in their
expanded state, both connector plates 30 are welded to the second sleeve segment 22b (as
indicated on one side at 38), thereby joining both sleeve segments together to form a
5 continuous sleeve 10 circumferentially about the pipe 12 as shown in fig.1. The hydraulic
jack 34 and clamping force is then removed and the sleeve is allowed to cool to the same
temperature as the pipe 12. As the sleeve cools, the plate steel contracts to fomm an
interference fit with the pipe, thereby reinforcing and sealing that section of pipe with the
aid of the epoxy. Immediately following installation and cooling of the sleeve, corrosion
o inhibiting material may be wrapped or otherwise applied to the sleeve and surrounding
area followed by backfilling over the sleeve. The type of material used will depend on
clients' requests, and may range from a tar-type material to a spray on inhibitor.
The temperature to which the sleeve is heated depends on the temperature of the
pipe at the time of in~t~ tion and the amount by which the pipe is expanded from its
5 "normal" state with no internal pressure. Such expansion will depend on factors such as
the pipe's wall thickness and its internal pressure at the time. In any event, the
temperature to which the sleeve segments are heated should provide sufficient thermal
expansion so that upon forming the sleeve and subsequent cooling, the sleeve will remain
in tension whether the pipe is intemally pressurized or depressurized (ie. at ambient or
20 normal atmospheric pressure). As a result, the portion of pipe beneath the sleeve should
remain substantially in compression with respect to the tension in the sleeve whether the
pipe is pressurized or not. Good results have been achieved with plate steel sleeves being
heated to between 100 and 300 degrees F above the temperature ofthe pipe.
It is preferable that the sleeve be installed while the pipe's surface telllpe~ re is
25 within the temperature curing range of the epoxy. If not, some heat may continue to be
applied to the sleeve after joining of the sleeve segments to properly cure the epoxy. Such
situations arise more frequently in cold ~ lim~tes or winter conditions. For example,
certain epoxies might require that the sleeve be kept at about 60 degrees F for 24 hours.
Fortunately, some epoxies are now capable of curing below 32 degrees F, which reduces
30 heating costs and inst~ tion delays.
Several advantages and benefits of the present invention may now be better
appreciated. First, it ~.limin~tes the requirement of many prior art sleeves to weld the
sleeve to the pipe, thus avoiding the possibility of creating cracking in the welds on the
pipe. Second, the sleeve 10 can be installed whether the pipe is pressurized or not, thus
avoiding shut down of the pipe and disruption of flow of product for repair work,
resulting in significant cost savings to the pipe operator. Similarly, the present invention
5 çlimin~tes the need to cut away and remove an entire cylindrical section of defective pipe,
consequently avoiding disruption of flow of product, and occupational and environment~l
hazards related to product contained in the pipe. Third, the epoxy and plate steel
complement one another, namely the epoxy acts as a sealing agent to prevent product
leakage from the pipe, while the plate steel prevents cracks in the pipe wall from extçndin~
o and thin locations in the pipe wall from rupturing. Fourth, significant reductions in
operating stress levels in the pipe have been achieved in test inst~ tions of the sleeve.
Fifth, the pipe and the sleeve have been found to act as one unit during pressurizing and
depressurizing of the pipe, namely without any dislocation of the sleeve from the pipe.
The above description is intended in an illustrative rather than a restrictive sense
and variations to the specific configurations described may be apparent to skilled persons
in adapting the present invention to specific applications. Such variations are intended to
form part of the present invention insofar as they are within the spirit and scope of the
claims below. For example, the sleeve segments 22a, 22b might be welded together by
~ omitting the connector plates 30. This is not desireable, however, due to reslllt~nt
20 difficulties in estim~tinp; the exact size of gap 28 required so that both sleeve segments are
thermally expanded on the pipe into an abutting relationship. It will also be appreciated
that if the gap is too small, the sleeve segments will force each other away from the pipe's
outer surface 18; and, if the gap is not closed upon expansion between the sleeve
segments, then a welding f~cilit~tor, such as a thin metal plate, will likely have to be placed
25 in the re~ -g gap in any event to allow welding between the segments.
