Note: Descriptions are shown in the official language in which they were submitted.
FLOWLINE RESTRAINT METHOD
This invention is in the field of flowline restraining systems and methods of
installation.
Background
Flowlines are commonly used in several industrial applications. One example
are lines
used in the oil and gas industry to connect a petroleum wellhead to pump truck
or other
such equipment. In some circumstances these flowlines are temporary in nature
and as
such readily assembled by connecting several segments together, the result
being a joint
between each segment. This permits assembly of the temporary flowline to a
custom
length and layout configuration, depending on the location and operational
requirements.
These flowlines are frequently used in operations where the internal pressure
in the
flowline can be several thousand pounds per square inch. Under these
conditions, if a joint
between flowline segments were to fail, the results can be catastrophic. Under
conditions
of high pressure, the energy release resulting from flowline segment
separation can cause
flowline segments to become projectiles that are ejected at high velocity.
This is a
particularly unsafe, and sometimes lethal, situation. Prior art methods have
been developed
to secure flowline segments to reduce the chances of injury or death to nearby
workers in
the case of a fail in a flowline joint. In some cases, these can be clamps
that are secured to
either side of a joint and which have a structure to join each clamp. The
primary drawback
in this type of arrangement is the expense and complexity of the clamping
system, as well
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as the time need to install a clamp at each joint along a run of flowline
segments. Thus,
what is needed a flowline restraint system that is simple, less costly, and
easy to install.
Summary of the Invention
The following discussion provides many example embodiments of the inventive
subject
matter. Although each embodiment represents a single combination of inventive
elements,
the inventive subject matter is considered to include all possible
combinations of the
disclosed elements. Thus, if one embodiment comprises elements A, B, and C,
and a
second embodiment comprises elements B and D, then the inventive subject
matter is also
.. considered to include other remaining combinations of A, B, C, or D, even
if not explicitly
disclosed.
As used herein, the term flowline is understood to refer to any temporary,
semi-
permanent, or permanent fixture assembled to conduct fluids under pressure
from a
source location to an output location. Flowlines may alternatively be referred
to in the art
as pipelines. Flowlines can be constructed from rigid members or flexible
hose. Those of
skill in the art will readily appreciate the various designs and
configurations of flowlines
and pipelines that will be compatible with the invention of the present
disclosure. The
precise nature or means of assembly or construction of the flowline is not
intended to be
limiting to the scope of the invention as defined by the claims.
Unless the context dictates the contrary, all ranges set forth herein should
be interpreted as
being inclusive of their endpoints and open-ended ranges should be interpreted
to include
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only commercially practical values. Similarly, all lists of values should be
considered as
inclusive of intermediate values unless the context indicates the contrary.
The present invention comprises a restraint system for flowlines. In a
preferred
embodiment, a high tensile strength polymeric restraining line is used to
secure adjacent
segments within the flowline. Conveniently, this can be accomplished by
forming a half
hitch knot with the restraining line, around each segment of the flowline. The
restraining
line is further secured at each end to an anchor. When installed, the
restraining system
prevents uncontrolled ejection of a flowline segment should a fail of the
flowline occur,
either along a segment or at a joint between adjacent segments.
10- Thus, in some embodiments there is disclosed a method of restraining a
flowline having
two ends and comprising a plurality of flowline segments connected in in an
end to end
manner with a flowline joint between each adjacent pair of flowline segments,
wherein the
method comprises; coupling a restraining line to a first anchor located in
proximity to an
end of the flowline, said restraining line being a non-sling restraining line;
extending the
restraining line from the first anchor along a restrained portion of the
flowline and
knotting the restraining line around the circumference of each flowline
segment on each
side of each flowline joint within said restrained portion; and securing the
restraining line
to a second anchor at the distal end of the restrained portion from the first
anchor;
whereby upon a failure of a flowline joint within the restrained portion of
the flowline, the
restraining line knotted around the circumference of the flowline segments on
either side
of the failed joint will hold said flowline segments in position in relation
to the remainder
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of the flowline. In some embodiments of the method, the restraining line is
knotted around
each flowline segment in a half hitch knot.
In some embodiments, the first anchor is located at a source end of the
flowline. In some
embodiments, the first anchor is located at an output end of the flowline.
In some embodiments, a single restraining line is used to secure the entirety
of the
restrained portion of the flowline, while in still others a plurality of
restraining lines are
used to secure the entire length of the restrained portion of the flowline. In
some cases,
each of the plurality of restraining lines are secured to at least one other
restraining line
by at least one of a saddle knot and a shackle.
In one aspect of the invention is to ensure that the restrained portion of the
flowline is the
entire flowline from origin to destination. In another aspect of the invention
the restrained
portion of the flowline is less than the entire flowline.
In some embodiments, the restraining line is a high tensile strength rope.
There is also provided a restraint system for use in restraining a flowline
having two ends
and comprising a plurality of flowline segments connected in in an end to end
manner with
a flowline joint between each adjacent pair of flowline segments, said system
comprising: a
restraining line for attachment between a first anchor and a second anchor,
said first anchor
being located in proximity to a first end of the portion of the flowline to be
restrained, and
said second anchor located in proximity to a second end of the portion of the
flowline to
be restrained, said restraining line being a non-sling restraining line,
wherein: the
restraining line is of sufficient length to be extended along the restrained
portion of the
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flowline and knotted around the circumference of each flowline segment on each
side of
each flowline joint within said restrained portion; and the restraining line
is of sufficient
tensile strength to maintain the flowline segments on either side of a failed
flowline joint
in position upon failure of said joint. In some embodiments, the restraining
line comprises
a rope.
In some embodiments, a single restraining line is used to secure the entirety
of the
restrained portion of the flowline, while in other embodiments a plurality of
restraining
lines are used to secure the entire length of the restrained portion of the
flowline.
Brief Description of the Drawings
While the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numerals, and where:
Fig. 1 depicts an embodiment of a flowline restraint system showing attachment
of one
end of the restraint to a pump truck;
Fig. 2 depicts an embodiment of a flowline restraint system showing attachment
of one
end of the restraint to a wellhead;
Fig. 3 depicts an embodiment of a flowline restraint system showing an
exemplary
installation configuration at flowline junction;
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Fig. 4 depicts an embodiment of a flowline restraint system showing a
configuration
where a knot is formed near each segment in the flowline;
Fig. 5a depicts a first embodiment of a flowline restraint system comprising a
shackle and
saddle eyes for use in connecting multiple restraining lines into a longer
chain;
Fig. 5b depicts a second embodiment of a flowline restraint system comprising
a shackle
and saddle eyes for use in connecting multiple restraining lines into a longer
chain;
Fig. 5c depicts a first embodiment of a flowline restraint system comprising a
shackle and
saddle eyes for use in connecting multiple restraining lines into a longer
chain;
Fig. 6 depicts an embodiment of a flowlines restraint system in which a double
wrap half hitch knot on either side of a flowline joint is used to secure the
flowline; and
Fig. 7 depicts an embodiment of flowline restraint system in which a
combination of
shackles and a knot around the circumference are placed on either side of a
joint in a
flowline.
Detailed Description of the Invention
The present invention comprises a method of restraining segments used to
fashion a
flowline. The method described herein provides a lightweight restraint, that
is simple to
install, in order to contain a catastrophic break in a flowline operating
under pressure.
In one embodiment, the restraint comprises a restraining line 10, or line,
comprising ultra-
high molecular weight polyethylene fiber (HMPE) rope. Those of skill in the
art will
recognize that any flexible high tensile strength restraining line or line
will be compatible
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with the method of providing a flowline restraint system as disclosed herein.
HMPE
provides several advantages over other materials in that it has a high
strength to weight
ratio, low elongation at the break and resistance to a wide range of chemical
agents.
In general, a flowline 20 can be assembled to provide a conduit for materials
from a
source location, such as a wellhead 30, to a receiving location, such as a
pump truck 40 or
tank. In general, the flowline will be assembled by connecting several
segments in an end
to end manner until a complete flowline is fashioned that links the source end
of the
flowline to the output end. Once the flowline is assembled, and before being
placed into
service, a restraint is then added as will be described.
Conveniently rigging the restraint system can begin at either the source end
or output end
of the flowline. As shown in Figure I, the restraint restraining line can be
fashioned with a
closed loop that attaches to a fixed point on a structural element of a
structure located at or
near the output end of the flowline, for example to the superstructure of a
pump truck 40.
Those of skill in the art will also recognize that there will be other methods
for securing a
line to an anchoring structure such as various forms of knots. It will also be
recognized
that a user may prefer to begin assembling the restraint system beginning at
the source end
of the flowline, for example at a wellhead 30, as depicted in the embodiment
presented in
Figure 2. In either case, the end attachment provides a source of resistance
against which
the restraint is secured and which provides for resistance to maintain the
restraint at a
desired tension once in place. Preferably, the connection will be made to a
structural
element with sufficient strength to support the load exerted on the restraint
restraining line
should a flowline joint 50 fail occur.
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As shown in Figure 1-4, the restraining line is played out along the length of
the flowline.
In some embodiments, the restraining line is wrapped around each flowline
segment to
form a half hitch knot 60. In the embodiments depicted in the Figures, one
half hitch knot
is formed per flowline segment. For additional security, a user may choose to
wrap the
restraining line around the flowline in a half hitch knot on either side of
each flowline joint
50. Figure 3 provides an example of the use of the method to security
flowlines at a
junction, where multiple flowlines may emanate from a source location or where
a
junction 25 is formed at any location where multiple flow lines converge to a
common
point.
By forming half hitch knows at each flowline segment, each flowline segment is
secured
by the restraint such that in the event of the fail of a flowline joint, the
segment or
segments that have become disconnected by the fail are constrained by the
restraint and
are prevented from being freely ejected by the force of the fail, and remain
generally in
place, preventing a disconnected flowline segments from becoming lethal
projectile. The
method and system are not limited to the use of only a half hitch knot.
Those of skill in the art will appreciate that others forms of knot may also
be used to
secure a restraining line around the circumference of a flowline to provide
additional
security at joints or junction in the event of a failure of said joint or
junction. For example,
and as depicted in Fig. 6, a user make fashion a double wrap half hitch 55
around the
circumference of a flowline on either side of a joint in the line. Similarly,
and as depicted
in Fig. 7, one may use a combination of shackles and knots place on either
side of a joint
in a flowline to secure the line.
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The method is also adaptable to other methods and apparatus for securing a
flowline
segment with a restraint restraining line as described. As depicted in Figure
5, a restraint
restraining line having a looped end can be secured to a flowline segment by a
saddle knot
70. In way overlapping restraints can be used to secured adjacent flowline
segments.
Similarly, several restraint lines can be connected to each other to form
longer restraint
structures using saddle knots, shackles 80 or a combination of the two, again
as depicted
in Figure 5. Such methods of attachment are useful when connecting several
individual
restraint lines together to make a longer chain. For example, in some cases
the length of
the flowline may be relatively long, making providing a single contiguous
restraint
restraining line impractical. In these cases, restraints can be assembled in a
modular
fashion and additional restraints added to the chain as needed to secure the
entire length of
the flowline.
It will be appreciated that the system and methods described can be used with
a wide
range of different types and sizes of flowlines. The selection of materials
from which to
fashion restraining lines, as well as the caliber of such lines will be
dependent on the
expected forces that may be exerted upon a restraining line in the event of a
flowline
failure. Such factors are considered to lie within the scope of the claims as
set forth.
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