Note: Descriptions are shown in the official language in which they were submitted.
CA 02646814 2008-12-16
Attorney Docket 56.0965.CIP
Patent Application
OILFIELD EQUIPMENT COMPOSED OF A BASE MATERIAL
REINFORCED WITH A COMPOSITE MATERIAL
FIELD OF THE INVENTION
[0001] The present invention relates generally to a method of
making oilfield equipment, such as a fluid end for a
reciprocating pump out, of a thin layer of a base material and
reinforcing the base material with a composite material that
supports the stresses incurred by the fluid end during a pump
cycle. Preferably, the base material is less subject to
abrasion, corrosion, erosion and/or wet fatigue than
conventional fluid end materials such as carbon steel.
BACKGROUND
[0002] The fluid end of a reciprocating pump, such as a
triplex pump, is the portion of the pump where a fluid is drawn
in via a suction valve. A plunger then compresses the fluid and
pushes it, with high pressure, through a release valve. These
valves open when the pressure on the bottom side thereof is
higher than the pressure on the top side thereof.
[0003] Fluid ends are often a weak point of reciprocating
pumps, as they break after a certain amount of cycle time due to
wet fatigue pressure cycles. In addition, it is desirable to
limit the weight of fluid ends when they are used, for example,
in applications such as oil well fracturing operations. In such
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Attorney Docket 56.0965.CIP
Patent Application
situations the load capacity for transporting such oil well
fracturing systems is limited. Accordingly, a need exits for an
improved oilfield equipment, such as reciprocating pump fluid
ends, that are reliable and/or light in weight.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Figure 1 is a schematic view of a pump assembly
employing a reciprocating pump according to one embodiment of
the present invention.
[0005] Figure 2 is a cross-sectional view of a fluid end of
the reciprocating pump of Figure 1.
[0006] Figures 3A-3E show one embodiment for manufacturing a
fluid end according to one embodiment o the present invention.
SUMMARY
[0007] In one embodiment, the present invention includes
oilfield equipment composed of a base material which is
reinforced with a composite material. In one embodiment, the
base material is less subject to abrasion, corrosion, erosion
and/or wet fatigue than the material of conventional oilfield
equipment, such as carbon steel. In one embodiment, the base
material is composed of a thin layer, which is reinforced on its
outer surface with a composite material. The use of the
composite material increases the stress that can be withstood by
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Attorney Docket 56.0965.CIP
Patent Application
the base material, while simultaneously reducing the weight of
the oilfield equipment.
[0008] In an embodiment where the oilfield equipment is a
reciprocating pump fluid end, only the base material is in
contact with the fluid pumped by the reciprocating pump.
Although such a fluid end may be used in any appropriate
application, in one embodiment this fluid end is used on a
reciprocating pump in an oil well fracturing operation.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0009] The embodiment of Figure 1, shows a pump assembly 100
that includes a reciprocating pump 102 according to one
embodiment of the present invention. As shown, the
reciprocating pump 102, such as a triplex pump, includes a fluid
end 104 which receives a fluid at a low pressure and discharges
it at a high pressure. The pressurization of the fluid within
the fluid end 104 is created by plungers 114, which reciprocate
toward and away from the fluid end 104 as directed by a
crankshaft, which rotates within a housing 106. The crankshaft,
is driven by a driveline mechanism 108, which in turn is driven
by an engine 110 through a transmission 112.
[0010] Figure 2 shows a cross-sectional view of the fluid end
104 of the reciprocating pump 102 of Figure 1. As shown, the
pump 102 includes a plunger 114 for reciprocating within the
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Attorney Docket 56.0965.CIP
Patent Application
fluid end 104 toward and away from a chamber 116. In this
manner, the plunger 114 effects high and low pressures on the
chamber 116. For example, as the plunger 114 is thrust toward
the chamber 116, the pressure within the chamber 116 is
increased.
[0011] At some point, the pressure increase will be enough to
effect an opening of a discharge valve 118 to allow the release
of fluid from the chamber 116, through a discharge channel 128,
and out of the pump 102. The amount of pressure required to
open the discharge valve 118 as described may be determined by a
discharge mechanism 120 such as valve spring which keeps the
discharge valve 118 in a closed position until the requisite
pressure is achieved in the chamber 116.
[0012] The plunger 114 may also effect a low pressure on the
chamber 116. That is, as the plunger 114 retreats away from its
advanced discharge position near the chamber 116, the pressure
therein will decrease. As the pressure within the chamber 116
decreases, the discharge valve 118 will close, returning the
chamber 116 to a sealed state. As the plunger 114 continues to
move away from the chamber 116, the pressure therein will
continue to drop, and eventually a low or negative pressure will
be achieved within the chamber 116.
[0013] Similar to the action of the discharge valve 118
described above, the pressure decrease will eventually be enough
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Attorney Docket 56.0965.CIP
Patent Application
to effect an opening of an intake valve 122. The opening of the
intake valve 122 allows the uptake of fluid into the chamber 116
from a fluid intake channel 124 adjacent thereto. The amount of
pressure required to open the intake valve 122 may be determined
by an intake mechanism 126, such as spring which keeps the
intake valve 122 in a closed position until the requisite low
pressure is achieved in the chamber 116.
[0014] As described above, a reciprocating or cycling motion
of the plunger 114 toward and away from the chamber 116 within
the pump 102 controls pressure therein. The valves 118,122
respond accordingly in order to dispense fluid from the chamber
116, through the discharge channel 128, and eventually out of
the pump 102 at high pressure. The discharged fluid is then
replaced with fluid from within the fluid intake channel 124.
[0015] Note that although only one plunger 114 is shown in
Figure 2, in embodiments where the reciprocating pump 102 is a
triplex pump each of the three plungers may have the same or a
similar configuration and operation to that of Figure 2. This
is also true of a quintaplex pump, or a reciprocating pump with
any other number of plungers.
[0016] As mentioned above, the continued cycling of the
plungers 114 into and out of the fluid end 104 of the pump 102
and the accompanied fluctuations between positive and negative
CA 02646814 2008-12-16
Attorney Docket 56.0965.CIP
Patent Application
pressure experienced by the inner surfaces of the fluid end 104
makes the fluid end 104 susceptible to failure.
[0017] As such, in one embodiment of the present invention,
the inner surface 130 of the fluid end 104 is manufactured from
a base material 132 that is less subject to abrasion, corrosion,
erosion and/or wet fatigue than typical fluid end materials,
such as carbon steel. Exemplary materials for such a base
material 132 include inconel, incoloy, titanium and stainless
steel, among other appropriate materials.
[0018] However, such base materials 132 are often expensive.
As such, in one embodiment the inner surface 130 of the fluid
end 104 is manufactured from a thin layer of the base material
132, and reinforced by a composite material 134, which forms the
outer surface of the fluid end 104. The composite material 134
enables the fluid end 104 to support all the cyclical stresses
that it will experience during operation of the pump 102 in
which the fluid end 104 is used.
[0019] In one embodiment, the composite material 134 is
composed of fibers and a matrix. The fibers may include, for
example, glass fibers, carbon fibers, Kevlar fibers, metal
fibers or any other product that would provide mechanical
strength to the base material 132 of the fluid end 104, such as
metal wires. The matrix may include epoxy, Peek, or another
similar compound, such as any of those from the same family as
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Patent Application
epoxy or Peek, i.e. a thermoplastic material. Alternatively,
the matrix may include a thermoset material.
[0020] The matrix, or resin holds the fiber of the composite
material 134 in place on the base material 132 of the fluid end
104. In addition, the matrix may add mechanical strength to the
base material 132 of the fluid end 104. However, it is the
fiber itself that is primarily relied upon for improving the
stress resistance of the base material 132 of the fluid end 104.
In one embodiment, fibers that are stronger than metal in one
direction are positioned adequately to support the load cycle of
the fluid end 104.
[0021] This configuration not only improves the fluid end's
104 resistance to abrasion, corrosion, erosion and/or wet
fatigue, but it also has the added benefit of reducing the
overall weight of the fluid end 104, in embodiments where the
composite material 134 weighs less than carbon steel material
and/or the base material.
[0022] In another embodiment, the inner surface 130 of the
fluid end 104 may be composed of a carbon steel material which
is reinforced by the above described composite material 134 to
both increase the overall stress resistance of the fluid end 104
and to decrease the overall weight of the fluid end 104 over
typical fluid ends of the prior art which are composed entirely
of carbon steel. In an alternative embodiment, the inner
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Attorney Docket 56.0965.CIP
Patent Application
surface 130 of the fluid end 104 may be composed of a polymeric
material which is reinforced by the composite material 134.
[0023] In one embodiment the inner surface 130 of the fluid
end 104 is composed of either the base material 132, a polymeric
material, or carbon steel, and has a material thickness of
approximately 1-4" or ~". This layer may be thicker with the
tradeoff being that the weight and expense of the fluid end 104
increase with increasing thickness to the inner surface 130 of
the fluid end 104.
[0024] Autofrettage of the fluid end 104, a process often
performed on reciprocating pump fluid ends, may be performed.
However, even without autofrettage, the implementation of the
fibers of the composite material 134 to the fluid end 104 will
create compressive strength to the interior section of the fluid
end 104.
[0025] It is important to note that although fluid ends of
reciprocating pump are discussed above, the above described base
material 132 with composite material 134 reinforcement may be
used for any pressure containing part, or any part that
experiences a pressure cycle, and also for parts that need to be
light in weight.
[0026] For example, Figure 1 shows a pump assembly 100 having
a drive means, such as an engine 110, which drives a pump 102
through a transmission 112. In additional embodiments of the
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Attorney Docket 56.0965.CIP
Patent Application
invention, any one or all of the pump 102, the transmission 112
and the engine 110 may be composed of any of the material
combinations described above. Such an assembly 100 may be used
for an oilfield operation such as a fracturing operation.
[0027] In addition, in another embodiment of the invention, a
cementing head may be composed of any of the material
combinations described above. Such an cementing head may be
used in an oilfield cementing operation.
[0028] Figures 3A-3E show one embodiment for manufacturing a
fluid end 304 according to the present invention. In this
figure a fluid end 304 is shown in various stages of assembly.
In this embodiment, a thin layer of a base material 332 is used.
For example, a base material thickness of approximately 1--4" or 1-2"
another appropriate thickness may be used. The base material
332 is formed to any appropriate shape for receiving a plunger,
a suction valve, and a discharge valve, necessary for forming
the reciprocating action of the a reciprocating pump.
[0029] For example, in the depicted embodiment, as shown in
Figures 3A-3C, three tubes are welded together, and then
hydroformed to give the overall geometry of Figure 3C. In such
an embodiment, a plunger may be placed in the leftmost arm of
Figure 3C, and suction and discharge valves may be place in the
bottommost and topmost arms, respectively, of Figure 3C to
achieve the appearance of the fluid end 104 of Figure 2.
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Attorney Docket 56.0965.CIP
Patent Application
[0030] As shown in Figure 3D, other parts could be added to
the fluid end 304 of Figures 3A-3C if necessary. For example,
threaded parts 350 could be added as showed in Figure 3D. A
composite material 334 may then be applied to the outer surface
of the fluid end 304 as shown in Figure 3E. For example, the
composite material 334 may be applied by a filament winding
process by using carbon fibers and an epoxy resin, but any
appropriate application process and any appropriate composite
material 334 composition may be used.
[0031] Although, Figures 3A-3E show a fluid end 304 with a
specific geometry, fluid ends made in accordance with
embodiments of the present invention may have any appropriate
shape for holding a plunger, and suction and discharge valves
necessary for forming the reciprocating action of a
reciprocating pump. For example, in one embodiment, the fluid
end is a substantially straight tube. In addition, in some
embodiments, the fluid end is coated by or otherwise receives
the composite without the fluid end being hydroformed or
deformed.
[0032] Also, a fluid end, or any of the other oilfield
equipment described above according to any of the embodiments of
the present invention, may include integrated measurement means
inside the composite material 134,334 to measure temperature
distribution, stress distribution, fluid density, fluid flow
CA 02646814 2008-12-16
Attorney Docket 56.0965.CIP
Patent Application
rate, electrical conductivity, pH and/or acceleration, among
other appropriate properties of the oilfield equipment and/or
the fluid therein. These measurement means could be part of the
fiber itself, or otherwise added inside the composite material
134,334. In exemplary embodiments, the measurement means may
include a sensor, a densitometers, a flow meter, such as an
electromagnetic high pressure flow meter, or any combination
thereof, among other appropriate measurement means.
[0033] The preceding description has been presented with
reference to presently preferred embodiments of the invention.
Persons skilled in the art and technology to which this
invention pertains will appreciate that alterations and changes
in the described structures and methods of operation can be
practiced without meaningfully departing from the principle, and
scope of this invention. Accordingly, the foregoing description
should not be read as pertaining only to the precise structures
described and shown in the accompanying drawings, but rather
should be read as consistent with and as support for the
following claims, which are to have their fullest and fairest
scope.
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