Note: Descriptions are shown in the official language in which they were submitted.
RESTRAINED PIPE COUPLING
Field
This disclosure relates generally to restrained couplings for pipes.
Background
One type of known pipe fitting is a restrained coupling, which is a type of
mechanical coupling
connecting a plain end of a pipe to another pipe. Another type of restrained
fitting is a restrained
flange coupling adaptor for connecting a plain end pipe to a flanged end pipe
or other flanged
component. Such restrained fittings provide flexibility to connections by
allowing some pipe
misalignment, and are useful to connect pipes of certain materials such as
high density
polyethylene (HDPE) and polyvinyl chloride (PVC).
Some restrained couplings are particularly useful to resist axial displacement
caused by
unbalanced hydrostatic thrust forces in a pipe section e.g. from directional
or diameter changes
in the pipeline. The axial hydrostatic force of a pipeline is the product of
the internal pressure of
the pipeline and the cross-sectional area of a pipe section. A change in
direction or diameter in
the pipeline will generate an unbalanced thrust force. When a pipeline is
buried in soil and the
directional or diameter change is gradual, the thrust forces are normally
counterbalanced by the
friction between the pipe and the soil; however, when there are higher
pressures, poor soil
conditions or significant changes of direction in the pipeline, the thrust
forces are typically too
great to resist without mechanical assistance.
Some types of known restrained couplings use radially extending gripping means
to grip the
outside wall of a pipe to provide mechanical restraint against thrust forces.
For example, a typical
restrained flange coupling has multiple circumferentially-spaced gripping
means each comprising
a radially-extending threaded bolt with gripping teeth at a distal end; the
bolt can be radially
extended inwards until the teeth contact the outside wall of the plain end
pipe and apply radial
pressure thereto. The frictional force between the teeth and pipe wall provide
axial resistance to
unbalanced thrust forces. These radially-extending gripping means are
typically unitary bodies,
or comprise multiple components securely fixed together, and are usually set
in place in a fixed
position at the time of installation. Once the pipeline is buried under the
surface, the gripping
means are no longer accessible and their position cannot be changed.
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Date Recue/Date Received 2022-06-27
After installation, a pipeline can be subject to conditions that cause the
pipe wall to shift relative
to the restrained coupling thereby reducing the grip there-between, and
ultimately leading to
leakage and/or pipe failure. WO/2014/106749 proposes a pipe fitting with a
gripping means
having gripping members that can be selectively moved relative to guide means
within a
predetermined range, purportedly to allow for relative movement between the
pipeline and the
fitting after pipeline installation while maintaining the gripping effect of
the gripping means on the
pipeline. However, the pipe fitting disclosed in this patent publication
features a number of
deficiencies including limited thrust load resistance, limited working range
with different pipe
diameters, a tendency to rotate and become misaligned, and can come apart in
use.
It is therefore desirable to provide a solution to at least some of the
existing challenges faced by
prior art devices. In particular, it is desirable to provide a restrained pipe
coupling that has at least
one of improved thrust loading resistance, greater working range and improved
anti-rotation
performance compared to prior art devices.
Brief Description of Figures
FIG. 1 is a perspective view of a restrained flange coupling adapter,
comprising a restraining
gland assembly with multiple gripper units, and a flanged center sleeve
connected to the
restraining gland assembly by tie rods.
FIG. 2 is a perspective view of the restraining gland assembly with multiple
gripper units
extendible radially inwards from an annular main body.
FIGS. 3(a) and 3(b) are two perspective views of a gripper unit comprising a
gripper housing,
gripper body, and gripper bolt (FIG. 3(a) only).
FIGS. 4(a) to (e) are respective top perspective (FIG. 4(a)), bottom
perspective (FIG. 4(b)), top
plan (FIG. 4(c)), rear elevation (FIG. 4(d)) and A-A sectioned view (FIG.
4(e)) of the gripper body.
FIG. 5(a) to (d) are respective top perspective (FIG. 5(a)), bottom
perspective (FIG. 5(b)), front
elevation (FIG. 5(c)), and A-A sectioned view (FIG. 5(d)) of the gripper
housing.
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Date Recue/Date Received 2022-06-27
Summary
According to one aspect of the invention, there is provided a restrained pipe
coupling for coupling
a plain pipe end to another pipe component. The restrained pipe coupling
comprises a restraining
gland assembly having an annular main body with circumferentially-spaced and
radially-facing
gripper openings; and multiple gripper units movably connected to the annular
main body. Each
gripper unit comprises a gripper housing having a bottom sliding surface, a
gripper bolt fixedly
secured to the gripper housing and radially movable through one of the gripper
openings and
fixable at different positions relative to the annular main body, and a
gripper body having a top
sliding surface and a bottom gripping surface. The sliding surfaces of the
gripper housing and the
gripper body are in slidable contact and angled between 20 and 30 degrees from
the axial
direction of the annular main body. In particular, the sliding surfaces can be
angled at about 25
degrees from the axial direction of the annular main body.
The restrained pipe coupling can further comprise a flanged center sleeve
connected to the
restraining gland assembly and having an annular flange with circumferentially-
spaced and
axially-facing flange bolt openings. Alternatively, the restrained pipe
coupling can further
comprise a second restraining gland assembly and a center sleeve connected at
either end to
both of the restraining gland assemblies.
The sliding surfaces can have a continuous flat face extending along the
length of the sliding
surfaces. One of the sliding surfaces can comprise a channel and the other of
the sliding surfaces
can comprise an elongated rib that is slidable in the channel such that the
sliding surfaces are
substantially constrained to translate in a sliding direction. One of the
gripper housing and gripper
body can also comprise a pair of grooved side walls, and the other of the
gripper housing and
gripper body comprises a pair of tongues slidable along the grooved side walls
in the sliding
direction, that also serve to substantially constrain the sliding surfaces to
slide in the sliding
direction
One of the gripper housing and the gripper body can comprise at least one side
wall and the other
of the gripper housing and gripper body can comprise a stopper positioned to
contact an edge of
the at least one side wall when the gripper body has reached a selected
sliding limit relative to
the gripper housing.
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Date Recue/Date Received 2022-06-27
The annular main body can have a channel with angled side walls, in which case
the gripper
housing has a chamfered top surface mating with the angled channel side walls
such that the
gripper units are seated in the channel when in a retracted position.
Detailed Description of Embodiments
Embodiments disclosed herein relate generally to a restrained pipe coupling
comprising a
restraining gland assembly having a set of gripper units that are extendible
radially inwardly to
grip a plain pipe end. Each gripper unit has two portions that are angled and
slidable relative to
each other and which allow the gripper units to compensate for relative
movement of two pipeline
components while maintaining sufficient grip to provide unbalanced thrust
force resistance.
The embodiment shown in FIG. 1 is a restrained flange coupling adapter 10 that
is suitable to
connect a plain end of a pipe to a flanged pipe, fitting or other flanged
component, and which
generally comprises a restraining gland assembly 12 and a flanged center
sleeve 14 connected
to the restraining gland assembly 12 by tie rods 16. Other embodiments include
a restrained
coupling (not shown) for coupling two plain pipe ends, and which generally
comprises a center
sleeve flanked by a pair of connected restraining gland assemblies. Such a
restrained coupling is
useful for joining plain end pipes of the same or dissimilar materials, such
as HDPE pipe, ductile
iron pipe, and PVC pipes, or for joining a plain end pipe with a flexible
restrained connection or
other restrained pipe component.
Referring to FIG. 2, the restraining gland assembly 12 comprises an annular
main body 18 and
multiple radially inwardly extendible gripper units 20. The annular main body
18 has a series of
circumferentially-spaced radially-facing gripper openings 21 for receiving a
gripper bolts 28 of the
gripper units 20. In this embodiment, the gripper openings 21 and gripper
bolts 28 are matingly
threaded to allow the gripper units 20 be fixed in different radial positions
relative to the annular
main body 18. Alternatively, other known securing means for securing the
gripper units 20 to the
annular main body 18 in different positions can be substituted.
The gripper units 20 extend into a channel 22 that circumscribes the interior
surface of the annular
main body 12. In some embodiments the channel can have straight walls and in
some other
embodiments the channel 22 can have angled walls. The gripper units 20 are
seated in the
channel 22 in a retracted position and can be extended radially inwards into
an extended position
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Date Recue/Date Received 2022-06-27
to grip a pipe end (not shown). An annular flange 24 extends radially outwards
from the annular
main body 18 and comprises a set of circumferentially-spaced and axially-
facing tied rod openings
26 for receiving tie rods (not shown) that attach the gland assembly 12 to the
rest of the flange
coupling 10.
Referring now to FIGS. 3(a) and (b), each gripper unit 20 generally comprises
a gripper housing
30, a gripper body 32, and a gripper bolt 28. A distal end of the gripper bolt
28 is fixed to a top
surface of the gripper housing 30. In the illustrated embodiment, the distal
end is inserted into an
opening 31 on the top surface of the gripper housing 30 and secured by an 0-
ring (not shown).
The gripper bolt 28 spigots into the gripper housing 30, wherein a bolt spigot
33 is an 0-ring
groove that houses the 0-ring (see FIG. 5(d)). Alternatively, the gripper bolt
28 can be secured
to the gripper housing by other known means, e.g. welding, retaining clip, or
by threaded
connection. The gripper bolt 28 has a generally cylindrical threaded outer
surface (threads not
shown) that mate with threads in a corresponding gripper opening 21. The
bottom face of the
gripper housing 30 has a sliding surface that slidably mates with a sliding
surface on the top face
of the gripper body 32 at an angle of about 25 from the axial direction
("sliding angle"). As will
be discussed further below, it has been found that increasing the sliding
angle reduces the radial
load and increases the axial load, and the gripper units 20 can be designed
with a sliding angle
that corresponds to the operating conditions in which the restrained pipe
coupling 10 is intended
to be used. In particular, it is expected that providing gripper units 20 with
sliding surfaces with
have a sliding angle between 20 and 30 are suitable to provide mechanical
restraint for plain
pipe ends subject to typical unbalanced axial thrust forces, e.g. between
8,000 to 10,000 pounds
per gripper.
Referring now to FIGS. 4(a)-(e), the gripper body 32 in some embodiments are
investment
castings and composed of stainless steel 316. However, it will be apparent to
those skilled in the
art that the gripper body 32 can be manufactured by other known techniques and
using other
known suitable materials. The gripper body has a bottom face with a plurality
of transversely
extending teeth 34, and a top face with an angled sliding surface 36. The
teeth 34 have a
curvature that is compatible with target pipe having a range of diameters; for
example, in the
illustrated embodiment the teeth curvature has a 12" radius. An elongated rib
38 extends along
the length of the sliding surface 36 in a sliding direction. A pair of side
walls 40 extend upwardly
from each side of the sliding surface 36 and partially along the length of the
gripper body 32; a
groove 42 extends along an inside surface of each side wall 40 at the same
angle as the sliding
surface 36.
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Date Recue/Date Received 2022-06-27
Referring now to FIGS. 5(a)-(d), the gripper housing 30 in some embodiments
are investment
castings and composed of stainless steel 316, and are nitride case-hardened to
prevent galling.
However, it will be apparent to those skilled in the art that the gripper
housing 30 can be
manufactured by other known techniques and using other known suitable
materials. The gripper
housing 30 has a bottom face with an angled sliding surface 44, and a top
surface with a top
surface protrusion with the opening 31 for connecting to the gripper bolt 28.
In this embodiment
the channel 22 of the restrained gland assembly 12 has angled side walls, and
the gripper housing
30 has a top surface with chambered edges 46 which mate with the angled side
walls and enable
the gripper housing 30 to securely seat within the channel 22.
The gripper housing 30 has a channel 48 that extends along the length of the
sliding surface 44
in the sliding direction, and is designed to slidably receive the elongated
rib 38 thereby minimizing
rotation of the gripper body 32 relative to the gripper housing 30.
The side edges of the sliding surface 44 extend beyond the side walls of the
gripper housing 30
to form tongues 50 that are slidable within the grooves 42 of the gripper body
side walls 40. The
sliding engagement of the tongues 50 and grooves 42, along with the sliding
engagement of the
elongated rib 38 and the gripper housing channel 48 substantially constrain
the sliding of the
gripper body 32 and gripper housing 30 to the sliding direction. A stopper 52
extends laterally
across the rear end of the gripper housing 30 and slightly beyond each tongue
50; the stopper 52
engages with the rear edges of the gripper body side walls 40, thereby
providing an outer limit to
the sliding range of the gripper body 32 relative to the gripper housing 30.
In an alternative embodiment, the locations of the tongues 50 and grooves 42
are reversed, i.e.
the tongues are provided on the gripper body and the grooves are provided on
side walls
extending from the gripper housing.
In an another alternative embodiment, the locations of the elongate rib 38 and
gripper channel 48
are reversed, i.e. the elongated rib is provided on the gripper housing and
the gripper channel is
provided on the gripper body.
Example
A prototype restrained pipe coupling was built and tested with increasing
axial loads to simulate
increasing unbalanced thrust forces in a pipeline. The prototype restrained
pipe coupling had the
following specifications:
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Date Recue/Date Received 2022-06-27
= Gripper body: 316 stainless steel investment castings,
= Gripper housing: 316 stainless steel investment castings, housing nitride-
case hardened
= Restrained gland assembly: 20 gripper units per gland
= Gripper sliding surface angle: 25
= Gripper bolt thread: 7/8"
The prototype coupling was connected to a 24.00" HDPE test pipe with a wall
thickness of 1.4".
Gripper units were installed with a radial torque of 100 ft-lbs. Pipe pressure
was progressively
increased, and the prototype coupling was observed to withstand a pressure of
350-psi before
the pipe failed. This finding compared favorably to known restrained pipe
couplings which failed
at 200-psi or less.
The terminology used herein is for the purpose of describing particular
embodiments only and is
not intended to be limiting. Accordingly, as used herein, the singular forms
"a", "an" and "the" are
intended to include the plural forms as well, unless the context clearly
indicates otherwise. It will
be further understood that the terms "comprises" and "comprising," when used
in this
specification, specify the presence of one or more stated features, integers,
steps, operations,
elements, and components, but do not preclude the presence or addition of one
or more other
features, integers, steps, operations, elements, components, and groups.
Directional terms such
as "top", "bottom", "upwards", "downwards", "vertically", and "laterally" are
used in the following
description for the purpose of providing relative reference only, and are not
intended to suggest
any limitations on how any article is to be positioned during use, or to be
mounted in an assembly
or relative to an environment. Additionally, the term "couple" and variants of
it such as "coupled",
"couples", and "coupling" as used in this description are intended to include
indirect and direct
connections unless otherwise indicated. For example, if a first device is
coupled to a second
device, that coupling may be through a direct connection or through an
indirect connection via
other devices and connections. Similarly, if the first device is
communicatively coupled to the
second device, communication may be through a direct connection or through an
indirect
connection via other devices and connections.
As used herein, a reference to "about" or "approximately" a number or to being
"substantially"
equal to a number means being within +/- 10% of that number.
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Date Recue/Date Received 2022-06-27
It is contemplated that any part of any aspect or embodiment discussed in this
specification can
be implemented or combined with any part of any other aspect or embodiment
discussed in this
specification.
The scope of the claims should not be limited by the preferred embodiments set
forth in the
examples, but should be given the broadest interpretation consistent with the
description as a
whole.
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Date Recue/Date Received 2022-06-27
