Note: Descriptions are shown in the official language in which they were submitted.
93Q08
R J Pond Limited
"PIPE CONNECTION JOINTS"
The invention relates to pipe connection joints,
particularly but by no means exclusively for sea-bed
pipework.
There is frequently a requirement for a non-
weldable but permanent pipe connection joint in both subsea
and surface applications. In addition, for subsea
applications in particular, it is desirable that a pipe
connection joint should also possess the capability of
telescoping to allow disconnection of an adjacent
connector.
In the installation of a subsea template or
manifold system on the sea-bed, sea-bed flowlines have to
be laid from either a platform or a land installation.
With a deep water application it is usual, because of the
complexity of the operation, to pull a line into its final
position and, after retaining it at the junction, to effect
the final connection to the manifold or template pipework
in a separate operation. This final connection can be
effected in a number of ways, but in all cases it is usual
to spread the pipe ends apart in order to interpose seals
or a seal carrier and then to pull them together and
pressure clamp the pipe ends.
Thus provisions have to be made to allow for
spreading apart of the pipe ends when the final connection
~k
-- 2 --
is made. For this purpose telescopic joints have in the
past been proposed, and although such joints are inherently
attractive they have attracted severe criticism on two main
grounds. Firstly, the resilient seals which have been
necessary to prevent leakage could not be guaranteed to
remain effective over long periods and, secondly, the
joints generally had to be restrained to prevent end
pressure parting.
The present state of the art relating to subsea
installations generally avoids the problems with telescopic
joints by utilising either flexible pipe spools or flex
loops within the manifold pipework structure which deflect
appropriately to allow spreading of the pipe ends to be
connected. As will be appreciated this requires large pipe
bends to be incorporated to accommodate the required
deflection without over-s~ressing of the pipe loops. The
desired result can be achieved with outboard sea-bed
flowline deflection, and although this reduces the size of
the template and manifold structure the successful
deflecting back of the flowline to make the final
connection is not predictable, and indeed the success of
this operation cannot be guaranteed.
Accordingly, the present invention has for its
object to provide a metal sealing pipe connection joint
which, for subsea applications, can be designed as a
telescopic pipe connection joint which successfully
overcomes the foregoing criticisms of prior telescopic
joints for such applications.
1293~08
- 3 -
According to the invention a pipe connection
joint comprises two coaxial tubular joint members which are
telescopically engaged one within the other with an
interference fit which provides both a seal against leakage
from the joint and a friction lock precluding relative
axial separation of the joint members under the intended
working pressure conditions, one of the joint members
incorporating an externally connectible duct leading to the
interface of the joint members whereby fluid under pressure
can be introduced to relieve said friction lock and allow
relative telescopic movement of the joint members.
The interference fit of one of the joint members
within the other may be pressure assisted, with an increase
in the internal working pressure tending to expand the
inner joint member at the interface and thus increasing
both the sealing efficiency and the friction lock.
Seals may be fitted at each end of the interface
region which provides the interference fit. These seals
contain the fluid pressure introduced via said duct to
relieve the friction lock, and they may be elastomeric or
metallic seals. In the latter case the seals or sealing
surfaces may be machined from the joint members themselves.
Such seals but not the plain sealing surfaces are
incidental during normal working operation of the joint
when the interference seal is operative.
Preferably the outer joint member is counterbored
with a stepped counterbore which receives the inner member.
With a joint which is not intended to be
lZ93(~08
telescopically extendable for connection and contractible
for disconnection, substantially the entire length of~ the
counterbore preferably provides the interference fit, with
the inner joint member having a complementary fitting outer
surface. In this case the stepped formation facilitates
initial assembly of the joint, as the inner and outer
members may be partly interengaged before interference
occurs, and said seals are preferably respectively provided
at the inner end of the inner joint member and the outer
end of the outer joint member.
When the joint is telescopically variable in
length, when an appropriate fluid pressure is externally
applied via said duct, an outer portion of the counterbore
in the outer joint member may provide the required
interference fit with the inner joint member having a
reduced diameter inner end sleeve portion which is a free
sliding fit in an inner portion of the counterbore. This
enables the parts of the bores of the two joint members
exposed when the joint is fully compressed to be of a
common diameter, and provides in the working extended
condition an almost continuous bore which allows pigs to be
passed through the joint without losing the pig total
motive seal contact with the bore. A wiper and protection
sealing ring is preferably fitted to prevent ingress of
solids between the counterbore and said sleeve portion, and
a secondary wiper and protection sealing ring may be
disposed at the inner end of said interface region.
The invention will now be further described with
1293~:g08
-- 5 --
reference to the accompanying drawings which illustrate, by
way of example, two preferred embodiments of the invention
in axial section. In the drawings:
Fig. 1 illustrates a telescopically extendable pipe
connection joint, especially suitable for use in a subsea
installation; and
Fig. 2 illustrates a non-extendable pipe connection
joint suitable for use in subsea and surface installations.
The top half of Fig. 1 illustrates the pipe
connection joint shown therein fully compressed, whereas
the bottom half shows the joint in a fully extended working
condition.
The joint of Fig. 1 comprises two coaxial tubular
joint members 1 and 2 which are telescopically engaged, one
within the other. The outer joint member 1 has a bore 3 of
the same diameter as that of the pipeline with which the
joint is to be used, and the inner joint member 2 has a
through bore 4 of the same diameter. A stepped counterbore
of the joint member 1 presents an intermediate diameter
portion 5 and a larger diameter outer end portion 6. This
counterbore formed in the member 1 is relieved over an
intermediate annular groove 7.
The inner joint member 2 has an outer surface of
complementary stepped form. Inwardly of a relief groove 8
the joint member 2 has a sealing portion 9 which is an
interference fit within the outer counterbore section 6,
and this fit provides both a seal against leakage from the
joint and a friction lock which normally precludes relative
lZ5~3(:~0~3
-- 6 --
telescopic movement of the joint members 1 and 2. In
particular, it prevents the internal working pressure from
blowing the joint apart.
At each end of the interface region 10 which
provides the interference fit resilient seals 11 and 12 are
provided between the joint members 1 and 2, the inner seal
11 being let into the joint member 1 and the outer seal 12
being let into joint member 2. The inner joint member 2
has an inner end sleeve portion 13 which is a free sliding
fit in the intermediate diameter portion 5 of the outer
joint member 1. This enables the normally exposed bore
portions - see lower half of Fig. 1 - to present an almost
continuous bore which allows pigs to be passed through
without losing the pig motive seal contact with the bores 3
and 4, as the thin sleeve portion 13 bridges the groove 7.
A wiper and protection seal 14 is provided
between the sleeve portion 13 and outer joint member 1 at
the outer end of the bore portion 5. This seal 14 is let
into the outer joint member 1 and positioned so that it is
disposed close to the inner or free end of the sleeve
portion 13 at the full joint extension, as shown in the
bottom half of Fig. 1. A second wiper and protection seal
15 which is let into the outer joint member 1 close tOr and
on the inner side of, the seal 11 provides secondary
protection for the interface region 10.
A duct 16 in the inner joint member 2 has an
external connection at 17 and leads to a port 18 which
communicates with a peripheral groove 19 in the interface
3~08
-- 7 --
region 10. This duct 16 can thus be supplied with pressure
fluid which forces the joint members 1 and 2 apart at the
interface region 10, thereby relieving the interference fit
and allowing relative telescopic 'stroking' movement of the
joint members 1 and 2, the full extension range or stroke
of the joint being indicated by reference S.
The described pipe connection joint is intended
to be fabricated into a sea-bed pipework arrangement close
to the inboard/outboard sealed connection of a subsea
template or manifold system. On installation one of the
joint members 1 and 2 is welded to the template of manifold
pipework, and the other to the corresponding connecting
flange or hub. It is probable that the inboard pipework
will require to be retracted when pulling in the outboard
side flowline. With the outboard hub locked down a
connection tool can be run to place and locates on both
inboard and outboard hubs, at the same time plugging into a
hydraulic stroking probe receiver. This receiver, which is
not illustrated, can be permanently piped to the joint
pressure strolcing connection 17.
Although this joint is designed primarily for use
in deep-sea locations as a diverless remote connection, it
can also be used in shallower waters in conjunction with
diver assistance.
To allow stroking of the joint a suitable high
pressure is applied to the stroking port 18, causing the
joint members 1 and 2 to be pressured apart thus allowing
free relative telescopic movement out to the extended
~3~08
- 8 -
position. Once the pipe connection is finally coupled up
the pipe joint can be pressure tested by pressuring through
the stroking port 18 to a pressure equal to the working
internal pressure. As the interference fit is maintained
through to the resilient stroking seal 12, the pipe joint
pressure containment is tested on faces adjacent the
stroking inlet port groove 19. Further peripheral grooves
20 are provided in the joint members 1 and 2 at the
interface region 10. These assist distribution of the
pressure fluid in this region and thus act as anti-locking
grooves to equalise pressure when unlocking the joint by
application of external pressure to the connection 17.
It will be appreciated that in an installation it
is likely that both the inboard and the outboard pipework
will be positively locked down. In that case the friction
lock resistance provided by the interference fit between
the joint members 1 and 2 has only to cater for the
difference in pressure area of the pipe bore and sliding
interface diameter, and not the total bore pressure area
plus the inner tube differential area.
- Although the joint of Fig. 1 has been described
as installed in a template or manifold system, it will
further be appreciated that it also provides advantages for
the mid-connection of sea-bed flowlines. In this case the
joint allows tow out of complete lengths of pipeline, which
lengths can be joined remotely on the sea-bed without the
use of large expanding pipe loops.
Apart from its general simplicity the joint
3~0~3
provides considerable flexibility which allows the final
operating position to be within a considerable tolerance
band whilst still working effectively. Any tendency for
the pipe to move under pressure end load will only enhance
the presetting load of the flowline connection. As
compared with the present normal practice in the art, the
joint of the invention takes the place of an equivalent
360 bend having a diameter at least four times the length
of the present joint.
A flexible boot 21 is fitted to protect the
surface of the joint member 2 which enters the member 1
during stroking of the joint and which would otherwise be
exposed. This avoids encrustation deposits on that surface
which would impede stroking after a period in service on
the sea-bed. The boot 21 is clamped at one end around the
joint member 1 by a clamp ring 22, and at the other end
around the joint member 2 by a clamp ring 23.
The embodiment of Fig. 2 is fundamentally similar
to that of Fig. 1 but is simplified by the omission of the
capability of telescopic extension under pressure. Similar
basic parts of this embodiment are identified by the same
reference numerals as those used in Fig. 1 but increased by
'100'. The outer and inner joint members 101 and 102 have
through bores 103 and 104 of common diameter matching that
of the pipeline in which the joint is to be fitted. In the
assembled condition which is illustrated the inner end of
the member 102 abuts a step 130 in the outer member 101 at
the inner end of the stepped counterbore 105,106 in the
i'~93~08
-- 10 --
latter. In this case the intermediate groove 7 of Fig. 1
is omitted, and the members 101 and 102 are an interference
fit over the full length of the counterbore, that is over
both portions lOS and 106 thereof.
Thus the resilient seals 111 and 112 which are
respectively positioned at the ends of the interface region
providing the interference fit are comparatively widely
spaced. The inner seal 111 is now mounted on the inner
member 102 at the inner end thereof, and the outer seal 112
is mounted in the outer member 101 at the outer end
thereof. The counterbore portions 105 and 106 are of
substantially equal effective length and the comparatively
short radial duct 116 and external connection 117 are
formed in the outer member 101 and positioned centrally of
the counterbore portion 106. The peripheral groove in the
interface region, with which the duct 116 communicates, is
accordingly now formed in the outer joint member 101. The
further spaced grooves 120 which assist distribution of
externally applied fluid pressure at the interface region
are now formed some in the counterbore portion 106 and some
on the now-fitting smaller diameter inner end portion 113
of the inner joint member 102.
To assemble the connection joint the inner member
102 is partially inserted into the outer member 101 until
25 the inner seal 111 enters the counterbore portion 105, when
the outer seal 112 also operatively engages the inner
member 102. Fluid pressure is now applied externally,
through the connection 117 and duct 116 between the members
lZ~3~0~
-- 11 --
101 and 102. This pressure is containea by the seals 111
and 112 and spreads the engaged ~ubular portions of the
joint members radially apart, expanding the member 101 and
contracting the ~.ember 102. This allows the members to be
pushed fully together to the normal operative position
illustrated in Fig. 2, and on release of the applied
pressure a permanent metal sealing joint is obtained,
providing a metal seal and friction lock by utilising a
compound tubular arrangement with an interference fit in
accordance with the invention.
The joint once assembled can be pressure tested
through the external connection 117 at a lower pressure
than that required to separate the joint members, that is
at the internal working pressure of the joint. A pressure
assisted seal is obtained, as with the internal working
pressure applied a greater pressure sealing and friction
loc~ is provided by the action of increasing the hoop
stress in the tubular portion of the outer member 101 which
surrounds the inner member 102.
If the joint is subsequently required to be
broken, fluid pressure is applied via the external
connection 117 to force the joint members 101 and 102 apart
radially, thus allowing them to be separated axially.
Apart from simplified construction, this connection joint
possesses the general advantages of speed of connection
(and disconnection), the ability to pressure test the joint
externally, and a dimensionally low profile.
In either of the described embodiments the inner
1~3(~(~8
- 12 -
resilient seal 11 or 111 may if desired be omitted. In
this case application of a test pressure to the external
connection 17 or 117 provides a positive check, if the
joint "holds" this pressure, of the integrity of the
interference seal between the joint members 1 and 2. If
suited to installation procedures, the duct 16 of the first
embodiment may alternatively be provided by a radial bore
through the outer joint member 1, as with the corresponding
duct 116 of the embodiment illustrated in Fig. 2.
