Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND SYSTEM FOR A THRUST-ABSORBING HORIZONTAL
SURFACE PUMP ASSEMBLY
[001] BACKGROUND OF THE INVENTION
[002] 1. FIELD OF THE INVENTION
[003] Embodiments of the invention described herein pertain to the field of
horizontal surface
pumps.
[004] More particularly, but not by way of limitation, one or more embodiments
of the
invention enable an apparatus and system for a thrust-absorbing horizontal
surface pump
assembly.
[005] 2. DESCRIPTION OF THE RELATED ART
[006] Submersible pump assemblies are typically used to artificially lift
fluid to the surface in
deep wells such as oil, water or gas wells. Additionally, in some instances,
fluids must be
pressurized and moved between surface locations and/or transported through a
supply line to a
tank. For example, it may be desirable to transport produced oil to a
processing facility
located remotely from the well. In such circumstances, submersible pumps may
be used as
surface pumps in horizontal pumping systems. Horizontal surface pump
assemblies are also
used for salt water disposal, water injection and other fluid transfer
applications. Horizontal
pumping assemblies typically include a multistage centrifugal pump
horizontally mounted to a
skid and driven by an electric motor, the pump assembly components are
connected together
by rotating shafts. The electric motor turns the shafts, which operates the
pump. Horizontal
pumps operate at rotational speeds of between 1800 and 3600 RPM, which
requires the pump
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to be capable of bearing high axial loads, for example ranging from about
4,000 to 6,000
pounds in systems making use of roller element bearings.
[007] To handle the thrust of the pump, a standalone thrust chamber is
conventionally placed
in between the motor and the intake of the horizontal pump assembly. Thrust
bearings in the
thrust chamber are submerged in a cavity of clean motor oil, carrying the
thrust of the pump
and maintaining shaft alignment. A conventional horizontal surface pump
assembly including
a standalone, motor-oil cooled thrust chamber is illustrated in FIG. 1. As
shown in FIG. 1,
conventional standalone thrust chamber 1 is between conventional surface motor
2 and
conventional intake 6 of conventional pump 3.
[008] In thrust chambers of horizontal surface pumps, such as conventional
standalone thrust
chamber 1, hydrodynamic bearings and roller element bearings are the most
commonly
implemented thrust bearings. However, roller element bearings are not well
suited for
horizontal surface pump applications because they wear out too quickly due to
the high
rotational speeds and loads to which the horizontal pumps are subjected, and
they generate too
much heat due to oil sheer.
[009] Conventional hydrodynamic bearings also suffer from drawbacks. One
drawback is that
conventional bearings often do not include sufficient surface area to carry
the loads required
of horizontal surface pumps. The rotating disk of a hydrodynamic thrust
bearing is typically a
hard material such as tungsten carbide. The stationary disk typically includes
softer metal
pads made of bronze. However, bronze is only capable of carrying a load of
about 500
pounds per square inch. There is often insufficient space to include large
enough copper pads
on the stationary disk to carry the required loads.
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100101 Another significant drawback to conventional hydrodynamic bearings is
that
conventional hydrodynamic bearings cannot withstand contamination (e.g., by
dirt) of the
motor oil in the thrust chamber. As a result, conventional hydrodynamic
bearings must be
placed in a cavity of clean motor oil, which is located in conventional thrust
chamber 1 of a
horizontal surface pump assembly. However, contamination of the cavity of
clean motor oil
is a common occurrence due to typical oil field or other operating conditions.
Thus, motor oil-
cooled thrust chambers, such as conventional thrust chamber 1, require regular
maintenance
such as oil changes. In addition, if a bearing failure occurs, for example due
to contaminated
motor oil in the chamber, the entire thrust chamber of a conventional
horizontal pump
assembly must be replaced, which is time consuming and expensive.
[0011] A conventional hydrodynamic bearing includes two round disks. One disk
is fixed,
while the other is turned by the shaft in rotation about the central axis of
the fixed disk. A
conventional fixed disk of the prior art is illustrated in FIGs. 2A and 2B. In
some approaches,
as illustrated in FIGs. 2A and 2B, the conventional fixed disk is designed
with conventional
copper pads. The flat, rotating disk pulls motor oil between the conventional
pads. As long as
there is clean motor oil between the surfaces, the thin film of fluid creates
separation between
the disks with hydrodynamic lift. On a conventional rotating disk, a solid
surface is required
on which the conventional pads rotate. Each pad deflects ever so slightly such
that a wedge is
formed at the leading edge. The leading edge is convergent, the trailing edge
is divergent.
The wedge produces a hydrodynamic profile that provides lift. The conventional
pads and
rotating disk must never make contact with each other or a catastrophic
failure will occur. As
a result, extreme pressure additives are added to the motor oil in the
standalone thrust
chamber. Additives provide a boundary layer of protection to prevent direct
face contact until
a wedge is formed. To function properly, the surfaces of hydrodynamic bearings
must be flat
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and smooth. A typical hydrodynamic thrust bearing is usually designed to
operate with a fluid
thickness of between about 0.001 and 0.0004 inches. Any impurities that are
thicker than the
oil film between the disks, such as the common occurrence of dirt in the motor
oil, can cause
surface damage to the bearings. Resulting friction between the disks reduces
or eliminates
their hydrodynamic properties.
[0012] Thus, conventional horizontal surface pumps are not well suited to
carry thrust under
typical operating conditions and are expensive and time consuming to maintain
and repair.
Therefore, there is a need for an apparatus and system for a thrust-absorbing
horizontal
surface pump assembly.
BRIEF SUMMARY OF THE INVENTION
[0013] One or more embodiments of the invention enable an apparatus and system
for a
thrust-absorbing horizontal surface pump assembly.
[0014] An apparatus and system for a thrust-absorbing horizontal surface pump
assembly are
described. An illustrative embodiment of a thrust-absorbing horizontal surface
pump
assembly comprises a horizontally-mounted electric submersible pump, the
electric
submersible pump comprising a fluid inlet, a motor operatively coupled to the
electric
submersible pump so as to turn the pump, an intake section extending between
the electric
submersible pump and the motor, wherein the intake section comprises a fluid
entrance and an
intake shaft, wherein the intake shaft is rotatably coupled to a motor shaft
on a first side and
an electric submersible pump shaft on a second side, the intake section
comprising a thrust
bearing set exposed to a flow of pumped fluid, the thrust bearing set
comprising a stationary
thrust bearing secured to a chamber base of the intake section, the stationary
thrust bearing
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comprising a first diamond-coated pad secured by a first locking plate, and a
thrust runner
paired with the stationary thrust bearing, wherein the thrust runner rotates
with the intake
shaft, the thrust runner comprising a second diamond-coated pad secured by a
second locking
plate. In some embodiments, the flow of pumped fluid flows from the fluid
entrance of the
intake section to the fluid inlet of the electric submersible pump. In some
embodiments, the
stationary thrust bearing comprises a first plurality of first diamond-coated
pads arranged
circumferentially around the first locking plate and the thrust runner
comprises a second
plurality of second diamond-coated pads arranged circumferentially around the
second
locking plate. In certain embodiments, the thrust runner comprises a base
keyed to the intake
shaft, and wherein the locking plate is secured to the base. In some
embodiments, one of the
first diamond-coated pad, the second diamond coated pad or a combination
thereof has a disc-
shaped profile. In certain embodiments, the intake section further comprises a
first rotatable
sleeve keyed to the intake shaft between the thrust bearing set and the motor,
and a first
stationary bushing paired with the first sleeve to form a radial support
bearing set, a second
radial support bearing set positioned between the thrust bearing set and the
electric
submersible pump, the second radial support bearing set comprising a second
rotatable sleeve
keyed to the intake shaft between the thrust bearing set and the electric
submersible pump, a
second stationary bushing paired with the second sleeve, and a spider bearing
fixedly coupled
between a housing of the intake and the second stationary bushing. In some
embodiments, the
thrust bearing set and the first radial support bearing set are fluidly
coupled by bypass fluid
and the bypass fluid is from a mechanical seal flush.
[0015] An illustrative embodiment of a thrust-absorbing horizontal surface
pump system
comprises an intake chamber between a multi-stage centrifugal pump and an
electric motor,
wherein the intake chamber, multi-stage centrifugal pump and electric motor
are horizontally
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aligned on a surface, and wherein the centrifugal pump moves a fluid, the
intake chamber
comprising an intake shaft extending longitudinally through the intake chamber
and coupled
to an electric motor shaft and a multi-stage centrifugal pump shaft, the
intake chamber further
comprising a thrust bearing set comprising a stationary thrust bearing and a
rotatable thrust
runner, wherein a first face of the stationary thrust bearing positioned
towards the rotatable
thrust runner is at least partially diamond-coated, and wherein a second face
of the rotatable
thrust runner positioned towards the stationary thrust bearing is at least
partially diamond-
coated, a fluid entrance that receives the fluid into the intake chamber, and
a pump inlet that
receives the fluid into the multi-stage centrifugal pump, wherein the thrust
bearing set is
arranged about the intake shaft such that during operation of the electric
motor the thrust
bearing set is in a pathway of the fluid as the fluid flows between the fluid
entrance and the
pump inlet. In certain embodiments, the first face has a first plurality of
diamond-coated pads,
and the first plurality of diamond-coated pads are circumferentially dispersed
about the first
face, and wherein the second face has a second plurality of diamond-coated
pads, and the
second plurality of diamond-coated pads are circumferentially dispersed about
the second
face. In some embodiments, one of the rotatable thrust runner, the stationary
thrust bearing, or
a combination thereof comprises a first plurality of diamond-coated pads
arranged in an inner
circumferential row and a second plurality of diamond-coated pads arranged in
an outer
circumferential row, and wherein each of the first diamond-coated pads in the
inner
circumferential row is arranged interstitially between two of the second
diamond-coated pads
in the outer circumferential row. In certain embodiments, each diamond-coated
pad of the first
plurality of diamond-coated pads has a smaller diameter than each diamond-
coated pad of the
second plurality of diamond-coated pads. In some embodiments, the system
further comprises
a radial support sleeve keyed to the intake shaft between the thrust bearing
set and the pump
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inlet.
[0016] In further embodiments, features from specific embodiments may be
combined with
features from other embodiments. For example, features from one embodiment may
be
combined with features from any of the other embodiments. In further
embodiments,
additional features may be added to the specific embodiments described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The above and other aspects, features and advantages of illustrative
embodiments of
the invention will be more apparent from the following more particular
description thereof,
presented in conjunction with the following drawings wherein:
[0018] FIG. 1 is a perspective view of a conventional horizontal surface pump
assembly of
the prior art.
[0019] FIG. 2A is a perspective view of a conventional fixed disk of the prior
art.
[0020] FIG. 2B is a cross-sectional view across line 2B-2B of FIG. 2A of a
conventional
fixed disk of the prior art.
[0021] FIG. 3 is a perspective view of a horizontal surface pump assembly of
an illustrative
embodiment.
[0022] FIG. 4A is a cross sectional view across line 4A-4A of FIG. 3 of a
horizontal surface
pump intake of an illustrative embodiment illustrating an exemplary flow of
pumped fluid.
[0023] FIG. 4B is a cross sectional view of a horizontal surface pump intake
of an illustrative
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embodiment.
[0024] FIG. 4C is a side elevation view of a horizontal surface pump intake of
an illustrative
embodiment.
[0025] FIG. 5A is a perspective view of a thrust bearing set of an
illustrative embodiment.
[0026] FIG. 5B is a cross sectional view across line 5B-5B of FIG. 5A of a
thrust bearing set
of an illustrative embodiment.
[0027] FIG. 5C is a cross sectional view across line 5C-5C of FIG. 5A of a
thrust bearing set
of an illustrative embodiment.
[0028] FIG. 6 is a sectional view of a diamond-coated pad of an illustrative
embodiment.
[0029] FIG. 7A is a plan view of a locking plate of an illustrative
embodiment.
[0030] FIG. 7B is a cross sectional view across line 7B-7B of FIG. 7A of a
locking plate of
an illustrative embodiment.
[0031] FIG. 8A is a plan view of a runner base of an illustrative embodiment.
[0032] FIG. 8B is a cross-sectional view across line 8B-8B of FIG. 8A of a
runner base of an
illustrative embodiment.
[0033] FIG. 9A is a plan view of an illustrative embodiment of a bearing
holder.
[0034] FIG. 9B is a cross sectional view across line 9B-9B of FIG. 9A of a
bearing holder of
an illustrative embodiment.
[0035] FIG. 10A is a perspective view of a thrust runner of an illustrative
embodiment.
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[0036] FIG. 10B is a perspective view of a thrust runner of an illustrative
embodiment.
[0037] FIG. 11A is a perspective view of a thrust bearing of an illustrative
embodiment.
[0038] FIG. 11B is a perspective view of a thrust bearing of an illustrative
embodiment.
[0039] FIG. 12 is a cross sectional view across line 12-12 of FIG. 4C of an
intake of an
illustrative embodiment.
[0040] FIG. 13 is a cross-sectional view across line 13-13 of FIG. 4C of an
intake of an
illustrative embodiment.
[0041] FIG. 14 is a cross-sectional view across line 14-14 of FIG. 3 of an
intake of an
illustrative embodiment.
[0042] FIG. 15 is a partial cross-sectional view across line 15-15 of FIG. 14
of a radial
support bearing of an illustrative embodiment.
[0043] FIG. 16 is a side elevation view with part cutaway of an intake of an
illustrative
embodiment.
[0044] FIG. 17 is a perspective view of an intake of an illustrative
embodiment.
[0045] FIG. 18 is a cross sectional view across line 18-18 of FIG. 17 of an
intake with dual
radial support bearings of an illustrative embodiment.
[0046] FIG. 19 is a cross sectional view across line 19-19 of FIG. 17 of an
intake of an
illustrative embodiment.
[0047] FIG. 20 is a cross sectional view across line 20-20 of FIG. 16 of an
intake of an
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illustrative embodiment.
[0048] FIG. 21 is a cross sectional view across line 21-21 of FIG. 16 of an
intake of an
illustrative embodiment.
[0049] While the invention is susceptible to various modifications and
alternative forms,
specific embodiments thereof are shown by way of example in the drawings and
may herein
be described in detail. The drawings may not be to scale. It should be
understood, however,
that the embodiments described herein and shown in the drawings are not
intended to limit the
invention to the particular form disclosed, but on the contrary, the intention
is to cover all
modifications, equivalents and alternatives falling within the scope of the
present invention as
defined by the appended claims.
DETAILED DESCRIPTION
[0050] An apparatus and system for a thrust-absorbing horizontal surface pump
assembly will
now be described. In the following exemplary description, numerous specific
details are set
forth in order to provide a more thorough understanding of embodiments of the
invention. It
will be apparent, however, to an artisan of ordinary skill that the present
invention may be
practiced without incorporating all aspects of the specific details described
herein. In other
instances, specific features, quantities, or measurements well known to those
of ordinary skill
in the art have not been described in detail so as not to obscure the
invention. Readers should
note that although examples of the invention are set forth herein, the claims,
and the full scope
of any equivalents, are what define the metes and bounds of the invention.
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[0051] As used in this specification and the appended claims, the singular
forms "a", "an"
and "the" include plural referents unless the context clearly dictates
otherwise. Thus, for
example, reference to a diamond-coated pad includes one or more diamond-coated
pads.
[0052] As used in this specification and the appended claims, the term
"diamond" includes
true diamond as well as other natural or manmade (synthetic) diamond-like
carbon materials,
which may have a crystalline and/or graphite structure. "Diamond coating" and
"diamond-
coated" as used herein is intended to encompass a pure diamond layer, such as
a diamond
table (of synthetic and/or natural diamond) as well as composites of diamond
in combination
with other materials and having at least 5% pure diamond by weight.
[0053] "Coupled" refers to either a direct connection or an indirect
connection (e.g., at least
one intervening connection) between one or more objects or components. The
phrase
"directly attached" means a direct connection between objects or components.
[0054] "Downstream" refers to the direction substantially with the principal
flow of pumped
fluid when the horizontal surface pump is in operation.
[0055] "Upstream" refers to the direction substantially opposite the principal
flow of pumped
fluid when the horizontal surface pump is in operation.
[0056] One or more embodiments of the invention provide an apparatus and
system for a
thrust-absorbing horizontal surface pump assembly. While for illustration
purposes the
invention is described in terms of an electric submersible pump employed in an
above-ground,
horizontal application, nothing herein is intended to limit the invention to
that embodiment.
[0057] The invention disclosed herein includes an apparatus and system for a
thrust-
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absorbing horizontal surface pump assembly. Illustrative embodiments include a
thrust
bearing assembly employed in the intake section of a horizontal surface pump
assembly.
Placing the thrust bearing assembly in the pump intake may entirely eliminate
the need for a
standalone thrust chamber, may eliminate the need to maintain a clean chamber
of motor oil
and/or may reduce the risk of damage to the thrust bearings from abrasives in
pumped fluid.
When the thrust bearing assembly is placed in the pump intake, pumped fluid
making its way
to the pump inlet flows around the bearing set, cooling the bearings and
acting as a
hydrodynamic fluid, rather than the motor oil and additives traditionally used
as cooling fluid
in conventional horizontal surface pump assemblies. Unique features of the
thrust bearing set
of illustrative embodiments may permit placement of the thrust bearing
assembly in the
intake.
[0058] A thrust bearing assembly of illustrative embodiments includes a thrust
bearing and a
thrust runner exposed to the pumped fluid. The thrust bearing and thrust
runner each include
diamond coated pads dispersed around a locking member. The diamond coated
faces of the
thrust bearing and the thrust runner allow initiation of the pump without the
need for any
lubrication or extreme pressure additives between the face of the thrust
bearing and the face of
the thrust runner. Once the pump is operating, a hydrodynamic film of pumped
fluid may
form between the thrust bearing and the thrust runner.
[0059] Illustrative embodiments of the invention utilize the strength of
diamond to carry high
axial loads from the pump in a limited surface area. A thrust bearing set of
illustrative
embodiments may carry about 5,000 pounds down force per square inch of surface
area. In
contrast, a conventional bronze pad bearing typically only handles about 500
pounds load per
square inch of pad area. A thrust bearing of illustrative embodiments may be
about four
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square inches in surface area. In some embodiments, the bearing set of
illustrative
embodiments is capable of carrying about ten times the load of conventional
thrust bearings
made from bronze and/or hardened steel, and operates successfully in
situations where
conventional bearings would fail due to mechanical overload. Illustrative
embodiments may
carry a shaft thrust load of 12,000 pounds, 15,000 pounds or 18,000 pounds
and/or a flow of
25,000 or 30,000 bpd at 75%-80% efficiency, in one example.
[0060] Horizontal surface pump applications may require unique thrust handling
capabilities
as compared to downhole electric submersible pump (ESP) assemblies. In
some
embodiments, an electric submersible pump used in horizontal surface pump
systems may
include the same shaft diameter as its downhole counterpart but include
housing of thicker
diameter, and require increased thrust absorbing capabilities as compared to
downhole ESP
assemblies. By way of example but without limitation, a downhole ESP assembly
may include
a housing of a 4.0 inch diameter, whereas a horizontal surface pump may
include a housing of
8.75 inches in diameter. In another example, 675 pumps may have an unmodified
shaft but the
housing may be increased from a 6.75 inch diameter to 7.25 inch diameter. In
another
embodiment, a downhole ESP assembly may include shafts of a 1.0 inch diameter,
whereas a
comparable horizontal surface pump may include shafts of 2.0-3.0 inches in
diameter. In yet
another embodiment, the housing and shaft diameters of the surface pump maybe
unmodified
between surface and downhole applications, but but the surface ESP pump may
include more
stages in the surface application than the downhole application. In some
instances a downhole
ESP pump may be employed on the surface unmodified.
[0061] Illustrative embodiments of the invention may permit fluid with
impurities, such as
the working fluid, to form a hydrodynamic film between the diamond-coated
thrust runner
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and diamond-coated thrust bearing of illustrative embodiments. In some
embodiments, the
hydrodynamic film is formed after a delay from the time that operation of the
pump is
initiated, without damage to the bearings. This feature of illustrative
embodiments eliminates
the need to use extreme pressure additives, locate and maintain the thrust
runner and thrust
bearing in a cavity of clean oil and/or standalone thrust chamber, and may
assist in preventing
the pump from being susceptible to loss of function from contaminants.
[0062] Use of diamond-coated bearings to carry shaft thrust loads in
horizontal surface pump
assemblies provides unexpected results. One of ordinary skill in the art would
expect that the
high temperatures reached within horizontal surface pump assemblies, which are
has high as
150 F or more, would cause the binders for the diamond coating of
illustrative embodiments
to flake away, resulting in the diamond coating to fall off of the bearings.
However, contrary
to expectations, pumped fluid moving about the system and apparatus of
illustrative
embodiments may provide sufficient heat removal from the bearings of
illustrative
embodiments to keep the diamond-coating intact without operation prohibitive
flaking.
[0063] Because illustrative embodiments do not require a conventional thrust
chamber, in the
instance a bearing failure occurs, an assembled shaft and seal may be the only
components
that need replacement in the event of a bearing failure, rather than an entire
thrust chamber as
in conventional assemblies. In such instances, a back pull-out design may be
employed to
remove and replace the assembled intake shaft and seal. In addition, regular
maintenance and
motor oil changes necessary in conventional designs may not be necessary in
illustrative
embodiments.
[0064] Illustrative embodiments may operate without a hydrodynamic film prior
to the film's
formation, and at the same time suffer no damage to the bearings. Pumped fluid
as the basis of
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a hydrodynamic film, carries about ten times the heat of a conventional motor
oil-based
hydrodynamic film (depending on the composition of the working fluid). Thus,
illustrative
embodiments of the invention may increase the lifespan of the bearing set,
improve its
strength and improve the heat handling capabilities.
[0065] Surface Pump Assembly
[0066] Illustrative embodiments include a horizontal surface pump assembly
system. An
exemplary horizontal pumping system is illustrated in FIG 3. As shown in FIG.
3, horizontal
surface pump assembly 100 is oriented substantially horizontally on surface
105, such that the
length of assembly 100 is resting on, parallel and/or about parallel with
surface 105. Pump
assembly 100 may be mounted on one or more skids 110, such as a pump skid
and/or a motor
skid, and secured within saddles 130. Motor 115 may be a surface motor
modified to operate
with a submersible pump on surface 105 (rather than a submersible motor which
operates with
submersible pumps downhole) and/or an electric motor, and capable of causing
rotation of the
shafts that run through the center of the length of pump assembly 100. Motor
115 may be air-
cooled and have minimal friction due to greased lube bearings or oil lube
bearings. Other
types of motors or prime movers having a horsepower range between about 75 and
3000 hp
well known to those of skill in the art may be employed, and as such, are not
described in
further detail herein. In an example, a gas powered engine with a gear
increaser could be used
as motor 115.
[0067] Electric submersible pump 125 may be a multi-stage centrifugal pump
conventionally
used in downhole electric submersible pump (ESP) assemblies, but instead
implemented here
in a horizontal surface pump application. In some embodiments, the shaft and
housing
diameter of pump 125 may be the same when implemented on the surface as when
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implemented downhole. Exemplary ESP pump 125 shaft diameters may be 7/8 inch,
1.0 inch,
1 3/16 inch, 1.5 inch, or 1 7/8 inch. In some embodiments, ESP pump 125 may be
modified to
include a shaft and/or housing of increased diameter as compared to a
comparable downhole
ESP pump. For example, the housing may be increased from a 4 inch diameter
used in a
downhole application to 8.75 inches for the surface pump application. In
another example, a
downhole ESP assembly may include shafts of a 1.0 inch diameter, whereas a
horizontal
surface pump may include shafts of 2.0-3.0 inches in diameter. ESP pump 125
may also be
capable of functioning in downhole and/or submersible environments.
[0068] Intake chamber 505 may extend between motor 115 and pump 125, connected
to
motor 115 by way of a flex or disc coupling, and serving as the intake for ESP
pump 125. In
some embodiments, intake shaft 200 may be directly attached to a drop out
spacer coupling,
which is directly attached to the motor 115. In some embodiments, Intake
chamber 505 may
also include bearings for carrying thrust and providing radial support,
serving in a dual intake
and thrust capacity. Horizontal surface pump assembly 100 does not include a
standalone
thrust chamber, but rather, intake chamber 505 serves as a combined thrust and
intake
chamber. Motor coupling cover 140 may secure motor 115 and intake chamber 505
together,
whilst intake chamber bracket 145 may support intake chamber 505 and assist in
holding
intake chamber 505 in place.
100691 Pumped fluid may enter assembly 100 through fluid entrance 135 of
intake chamber
505. Fluid entrance 135 may be connected to hoses, piping, a container, and/or
a fluid source.
Once fluid proceeds through fluid entrance 135 and enters intake chamber 505,
it may then
proceed to pump inlet 510. In the process of passing from fluid entrance 135
to pump inlet
510, the working fluid may flow around, about and/or through thrust bearings
of illustrative
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embodiments. From pump inlet 510, fluid may continue through ESP pump 125 to
pump
discharge 150, after which the fluid is transported to its destination. A
portion of fluid from
discharge 150 may be routed back into intake chamber 505 as part of a
mechanical seal flush.
Fluid exiting the flush may also be employed to cool and/or lubricate radial
support and/or
thrust bearings in intake section 505 of illustrative embodiments. Pumped
fluid may be oil,
injection water, fluid hydrocarbons, bromine, liquefied chicken fat, or any
other liquid desired
to be carried from one surface location to another and/or between the surface
and a downhole
location, and that adequately cools and lubricates the bearings of
illustrative embodiments.
[0070] Embodiments of pump assembly 100 described herein are uniquely suited
to handle
the extreme axial load requirements and ambient conditions experienced by
horizontal surface
assemblies and the applicable benefits obtained from illustrative embodiments
of the
invention.
[0071] Intake Section
[0072] FIGs. 4A-4C illustrate an intake section of a horizontal surface pump
assembly of
illustrative embodiments. As shown in FIG. 4A, stationary thrust bearing 225
and rotatable
thrust runner 220 are located in intake chamber 505, in the pathway of pumped
fluid during
operation of ESP pump 125. In some embodiments, only a single thrust bearing
225 and
single thrust runner 220 may be employed. Shaft 200 is positioned through the
center of
intake 505 and may be connected to the shaft of surface motor 115 (shown in
FIG. 3) such
that shaft 200 is rotated by surface motor 115. Pumped fluid may enter intake
section 505 at
fluid entrance 135, be drawn into ESP pump 125 at pump inlet 510, and be moved
and/or
lifted by pump 125 towards its destination.
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[0073] As illustrated in FIG. 4B, thrust runner 220 may be keyed to intake
shaft 200, or
otherwise coupled (e.g., by friction) to shaft 200, such that thrust runner
220 rotates with shaft
200 during operation of ESP pump 125. Shaft shoulder 250 may prevent axial
movement of
thrust runner 220. In the example shown in FIG 4B, shaft shoulder 250 may
prevent axial
movement of thrust runner 220 towards pump inlet 510, despite suction of the
pump in that
direction. Thrust bearing 225 may be secured to chamber base 240 of intake 505
with socket
head bolts 245 and remain stationary during rotation of shaft 200. Chamber
base 240 may be
secured to intake chamber bracket 145 with chamber bolts 255.
[0074] Locating thrust runner 220 and thrust bearing 225 in intake chamber 505
may improve
the thrust handling capability of thrust runner 200 and thrust bearing 225 and
reduce buckling,
as compared to locating thrust runner 220 and thrust bearing 225 in a cavity
of clean motor oil
in a thrust chamber or seal chamber.
Conventional thrust bearings are ill-equipped for
location outside the conventional motor-oil cavity due to the necessity of
maintaining
conventional thrust bearings within clean motor oil and/or extreme pressure
additives.
Illustrative embodiments are not so limited.
[0075] Intake Section Fluid Flow
[0076] Returning to FIG. 4A, pumped fluid 260 enters intake 505 through fluid
entrance 135,
and proceeds into assembly intake chamber 505. A first portion 265 of the
pumped fluid may
proceed directly into ESP pump 125. A second portion 290 of pumped fluid flows
around,
about and/or through bearing faces 1035, 425 (shown in FIGs. 10A and 11A),
lubricating and
cooling the bearing set 270. After passing through the bearing set 270, the
second portion 290
of pumped fluid may join the first portion 265 of pumped fluid entering ESP
pump 125.
18
CA 02887280 2015-04-02
[0077] As the discharge-bound fluid 275 proceeds through ESP pump 125 and
exits assembly
100 through discharge 150, a small bypass may be plumbed back to mechanical
seal 1400.
The fluid exiting the pump 125 is at a higher pressure than the fluid entering
the pump 125,
and this pressure differential keeps a portion of the discharge-bound fluid
275, illustrated in
FIG. 4A as bypass fluid 280, flowing through the bypass and into mechanical
seal 1400.
Bypass fluid 280 (flush) cools and lubricates mechanical seal 1400. After
passing by
mechanical seal 1400, bypass fluid 280 may also cool and lubricate radial
bearings, sleeve
1405 and bushing 1410. Bypass fluid 280 may then combine with the second
portion 290 of
pumped fluid to cool and lubricate the thrust bearing set 270 before re-
entering the ESP pump
125. Bypass fluid 280 may be directed from discharge 150 to mechanical seal
1400 using a
flush plan well known to those of skill in the art, for example American
Petroleum Institute's
Flush Plan 11. Mechanical seal 1400 may be a shaft seal, type 2 seal, or
cartridge seal.
[0078] FIGs. 4A, 4C and 16 illustrate positioning of thrust bearing 225 and
thrust runner 220
within intake section 505. As shown, thrust runner 220 and thrust bearing 225
may be placed
upstream from the direct path of first portion 265 of pumped fluid making its
way to pump
inlet 510 and still come into contact with sufficient fluid (second portion
290) to benefit from
the lubricating and cooling benefits of the fluid. Bearing 270 may be
positioned such that it is
tangentially in the flow path (i.e., not directly in the path of first portion
265 of pumped fluid).
The location of bearing set 270 may be calculated to ensure the bearings are
cooled
adequately without choking the flow of pump 125.
[0079] Thrust Bearings
[0080] FIGs. 10A and 10B illustrate exemplary thrust runners of illustrative
embodiments. As
shown in FIGs. 10A and 10B, thrust runner 220 includes runner base 305, which
may be
19
CA 02887280 2015-04-02
keyed to intake shaft 200 (shown in FIG. 4B). Runner locking plate 1025 may be
secured to
runner base 305. As illustrated in FIG. 10A, runner locking plate 1025 may be
secured to
runner base 305 with a series of bearing screws 1015 and/or with fasteners. In
some
embodiments, as illustrated in 10B, runner locking plate 1025 may be brazed in
place. Runner
locking plate 1025 may be raised with respect to runner base 305, as
illustrated in FIG. 10A.
In another example, locking plate 1025 may rest on runner base 305, as
illustrated in FIG.
10B. Thickness 310 of runner base 305 may be of sufficient thickness to
increase the load
handling capability of the flat diamond surfaces of illustrative embodiments
such that runner
base 305, runner pad 1020 or runner locking plate 1025 will not bend, deflect
or yield under
load. Bearing screws 1015 and/or silver brazing may additionally secure runner
pads 1020
into place or may secure runner pads 1020 in place rather than runner locking
plate 1025. In
one example, runner pads 1020 may be screwed to runner base 305 with screws
1015, and
runner pads 1020 may be secured in place by runner locking plate 1025.
[0081] A plurality of runner pads 1020, which runner pads 1020 may be diamond-
coated,
may be arranged circumferentially about runner locking plate 1025 and/or
runner base 305,
for example as illustrated in FIGs. 10A and 10B. As shown in FIG 10A, nine,
uniformly sized
runner pads 1020 are arranged about runner face 1035. As shown in FIG. 10B,
runner pads
1020 may be arranged in multiple circumferential rows around runner locking
plate 1025
and/or runner base 305. In the exemplary embodiment of FIG. 10B, eight runner
pads 1020 on
the inner circumference may have a smaller diameter than eight runner pads
1020 on the outer
circumference, and the runner pads 1020 on the inner circumference may be
arranged
interstitially between runner pads 1020 on an outer circumference. The
embodiment shown in
10B may allow runner pads to be positioned closer to the center of runner
locking plate 1025
and/or runner face 1035, thereby providing a higher unit load. The embodiment
of FIG. 10B
CA 02887280 2015-04-02
may also maximize diamond-coated runner pad 1020 density and reduce heat. The
surface
velocity of the inner circumferential row of runner pads 1020 may be lower,
reducing heat
buildup and wear relative to the outer circumferential row of runner pads
1020. In other
embodiments, runner pads 1020 may be randomly dispersed about locking plate
1025, runner
base 305 and/or runner face 1035.
[0082] In some embodiments, runner pad 1020 may be a single diamond-coated
disc. In
certain embodiments, at least three runner pads 1020 may be arranged about
runner locking
plate 1025. The size and number of runner pads 1020 may depend upon the
required loads and
size of the surface area of runner face 1035 and/or runner locking plate 1025.
In some
embodiments, runner pads 1020 include a circular surface area and are
distributed uniformly
around runner opening 1030 of base 305, through which shaft 200 may run.
Runner pads 1020
may be circular in surface area and be 9mm, 16mm, 1/2 inch, 5/8 inch, and/or
3/4 inch in
diameter. Other sizes of runner pads 1020 may be used based on required loads,
the outer
diameter of thrust runner 220, and/or shape of runner pad 1020, which in some
embodiments
may not be circular in profile. In some embodiments runner pads 1020 may be
made with
different profiles other than round, for example a sector of a circle, a
modified ellipse, pie
shape or a parallelogram. The number of runner pads 1020 may vary depending on
the
diameter of the overall bearing, the shape and size of runner pads 1020 and/or
required loads.
[0083] Illustrative embodiments of thrust bearing 225 are shown in FIGs. 11A
and 11B.
Thrust bearing 225 may remain stationary during operation of the pump
assembly. Thrust
bearing 225 may be mounted to chamber base 240 (shown in FIG. 4B) of intake
505 with
socket head bolts 245. Thrust bearing 225 may include bearing holder 405, to
which bearing
locking plate 410 may be secured. Bearing locking plate 410 may be raised with
respect to
21
CA 02887280 2015-04-02
bearing holder 405, as illustrated in FIG. 11A. In another example, bearing
locking plate 410
may rest on bearing holder 405, as illustrated in FIG. 11B. As illustrated in
FIG. 11A, bearing
locking plate 410 may be secured to bearing holder 405 with a series of
bearing screws 1015
and/or with fasteners. In some embodiments, as illustrated in 11B, bearing
locking plate 410
may be brazed in place. Bearing screws 1015, fasteners and/or silver brazing
may
additionally secure bearing pads 415 into place, or may secure bearing pads
415 in place
rather than bearing locking plate 410. In one example, bearing pads 415 may be
screwed to
bearing holder 405 with screws 1015, and bearing pads 415 may be secured in
place by
bearing locking plate 410.
[0084] A plurality of bearing pads 415, which may be diamond-coated, may be
arranged
circumferentially about bearing locking plate 410 and/or bearing holder 405,
for example as
illustrated in FIG. 11A and 11B. As shown in FIG. 11A, nine, uniformly sized
bearing pads
415 are arranged about bearing face 425. As shown in FIG. 11B, bearing pads
415 may be
arranged in multiple circumferential rows around bearing locking plate 410
and/or bearing
holder 405. In the exemplary embodiment of FIG. 11B, eight bearing pads 415 on
the inner
circumferential row may have a smaller diameter than eight bearing pads 415 on
the outer
circumferential row, and the bearing pads 415 on the inner circumference may
be arranged
interstitially between bearing pads 415 on an outer circumference. The
embodiment shown in
11B may allow bearing pads 415 to be positioned closer to the center of
locking plate 410,
thereby providing a higher unit load. The embodiment of FIG. 11B may also
maximize
diamond-coated bearing pad 415 density and reduce heat. The surface velocity
of the inner
circumferential row of bearing pads 415 may be lower, reducing heat buildup
and wear
relative to the outer circumferential row of bearing pads 415.
22
CA 02887280 2015-04-02
[0085] In some embodiments, bearing pads 415 may be randomly dispersed about
bearing
locking plate 410. In other embodiments, bearing pad 415 may be a single
diamond-coated
disc. In certain embodiments, at least three bearing pads 415 may be arranged
about bearing
locking plate 410. The size and number of bearing pads 415 may depend upon the
required
loads, size and/or cross-sectional area of bearing face 425 and/or bearing
locking plate 410. In
some embodiments, bearing pads 415 include a circular surface area and are
distributed
uniformly around bearing opening 420 of bearing holder 405. Bearing pads 415
may be
circular in surface area and be 9mm, 16mm, 1/2 inch, 5/8 inch, and/or 3/4 inch
in diameter.
Other sizes of bearing pads 415 may be used, depending on required loads, the
outer diameter
of thrust bearing 225, and the shape of bearing pad 415. In some embodiments
bearing pad
415 may be made with different profiles other than round, for example a sector
of a circle, a
parallelogram, a pie shape or a modified ellipse. The number of bearing pads
415 may vary
depending on the loads, diameter and/or circumference of the overall bearing.
[0086] The arrangement of bearings pads 415 about bearing locking plate 410
may or may
not mirror the arrangement of runner pads 1020 about runner locking plate
1025. Pad
arrangements may be selected such that, at any point in the rotation of thrust
runner 220 with
respect to thrust bearing 225, at least one bearing pad 415 is always opposite
at least a portion
of at least one runner pad 1020.
[0087] FIGs. 5A, 5B and 5C are illustrative embodiments of thrust runner 220
paired with
thrust bearing 225 to form bearing set 270. Faces 1035, 425 face towards each
other, with
space 500 in between them, space 500 sufficient to accommodate a hydrodynamic
film. Space
500 may be between about 0.00001 to 0.005 inches separation due to temperature
and fluid
viscosity. Water and oil are considered incompressible fluids. As the velocity
of thrust runner
23
CA 02887280 2015-04-02
220 increases, a fluid wedge may be created in space 500, which separates
faces 1035, 425
from one another. The wedge may increase in height with the speed of rotating
shaft 220 and
thrust runner 220, providing greater load capacity. However, unlike
conventional bearings,
the diamond-coated faces 1035, 435 of illustrative embodiments can operate
against each
other without a hydrodynamic profile. Unlike conventional bearings, pumped
fluid, rather
than motor-oil, is used to remove heat. Thus, bearing pads 415 operating on
runner pads 1020
of illustrative embodiments may allow more surface area to be exposed for
better heat
transfer. A hydrodynamic wedge may occur in illustrative embodiments, but
unlike
conventional designs, the hydrodynamic wedge is not necessary for performance
of bearing
set 270. Thus, these illustrative embodiments reduce heat and friction in
order to increase
load capacity. In illustrative embodiments, the movement of fluid between
faces 1035, 425
may sufficiently cool bearing set 270 such that the diamond coating on bearing
pads 415 and
runner pads 1020 remains intact and may not flake away.
[0088] FIG. 6 is an illustration of an exemplary diamond-coated pad of
illustrative
embodiments. Bearing pad 415 is illustrated in FIG. 6, but runner pad 1020 may
similarly be
as illustrated. Bearing and/or runner pad(s) 415, 1020 may be diamond coated,
include a
diamond layer, made of diamond, include leached diamond and/or comprise
diamond, for
example diamond coating 600. In some embodiments, bearing and runner pads 415,
1020 may
be a polycrystalline diamond cutter (PDC), such as a micron-sized synthetic
diamond powder
bonded together by sintering at high pressures and temperatures and/or a
polycrystalline
diamond top layer integrally sintered onto a tungsten carbide substrate using
a high-pressure,
high-temperature process. US Synthetic of Orem, Utah, Element Six of
Luxembourg, Logan
Superabrasives of Houston, Texas, Fujian Wanlong Diamond Tool Co., Ltd. of
Fujian, and
China Zhengzhou LD Diamond Products Co., Ltd. of Zhengzhou, China supply
suitable
24
CA 02887280 2015-04-02
polycrystalline diamond cutters that may be employed in illustrative
embodiments. In some
embodiments, bearing and runner pads 415, 1020 may comprise a polycrystalline
matrix of
inter-bonded, hard carbon-based crystals. For example, bearing and/or runner
pads 415, 1020
may comprise a facing table of polycrystalline diamond integrally bonded to a
substrate of
less hard material, such as tungsten carbide and/or pad base 605, which pad
base may be
tungsten carbide. In embodiments including leached diamond, the leached
diamond may
include a polycrystalline matrix whereby the cobalt or other binder-catalyzing
material in the
polycrystalline diamond is leached out from the continuous interstitial matrix
after formation.
[0089] Illustrative embodiments may include a method of aligning the heights
of pads 1020,
415. The height of each runner pad 1020 may be aligned with each of the other
runner pads
1020 within several thousandths of an inch (e.g., within 0.001, 0.002 or 0.004
inches), such
that each runner pad 1020 is close to or on the same horizontal plane. The
surface of each
runner pad may be lapped to finish the surface of diamond coating 600.
Similarly, each
bearing pad 415 may be aligned within a few thousandths of an inch and lapped
to finish.
Diamond coating 600 (e.g., a diamond table) on a PDC may be tens of
thousandths (e.g., fifty,
sixty or eighty thousandths) of an inch thick and aligned within a few
thousandths, such that a
couple thousands may be lapped and still have plenty of table remaining on
diamond coating
600. In some embodiments, pads 1020, 415 may be brazed in place with no
alignment within
a few thousandths by machining a slot to receive the cutter in a fashion
similar to that used on
bits, and then diamond coating 600 may be subsequently lapped if needed to
align the upper
surface of the pads 1020, 415.
[0090] As shown in FIGs. 7A, 10A, 10B, 11A and 11B, bearing pad 415 and/or
runner pad
1020 may have a circular cross-sectional area, or may have an elliptical,
circular,
CA 02887280 2015-04-02
quadrangular, pie-shaped or sector profile. Pad base 605 may be made of
tungsten carbide and
comprises diamond coating 600. In certain embodiments, the diamond coating may
be
between about 0.070 and 0.080 inches thick, or may be between a few
thousandths of an inch
thick and 0.5 inch thick or more. In some embodiments, diamond coating 600 may
be a
diamond wafer that is silver brazed to pad base 605 or diamond coating 600 may
be a
diamond table.
[0091] FIGs. 7A and 7B illustrate an exemplary embodiment of a locking member.
Bearing
locking plate 410 is illustrated in FIGs. 7A and 7B, but runner locking plate
1025 may also be
as illustrated. As shown in FIG. 7A, nine bearing pads 415 are evenly and
circumferentially
placed about openings in locking plate 410. FIGs. 8A and 8B are an
illustrative embodiment
of runner base 305 of thrust runner 220. FIGs. 9A and 9B are an illustrative
embodiment of
bearing holder 405. As demonstrated in FIGs. 8B and 9B, runner base 305 may
have an
increased thickness 310 as compared to the thickness of bearing holder 405.
[0092] FIGs. 4B, 12 and 13 illustrate an exemplary stationary thrust bearing
225 secured
within intake chamber 505 of horizontal surface pump assembly 100. Stationary
thrust bearing
225 may be bolted into chamber base 240 to ensure stationary thrust bearing
225 does not
substantially rotate. Chamber base 240 may be secured to intake chamber
bracket 145 with
chamber bolts 255. Intake chamber housing 1805 may similarly be secured to
thrust chamber
bracket 145 with bolts. In the illustrative embodiment of FIG. 12, twenty-five
diamond-coated
bearing pads 415, having a circular cross-sectional surface area are arranged
circumferentially
about bearing locking plate 425. Also as illustrated in FIG. 12, stationary
thrust bearing 225
along with thrust runner 220 may be placed in the flow of pumped fluid 260 as
the pumped
fluid enters and/or flows through the intake 505 of illustrative embodiments.
FIG. 13
26
CA 02887280 2015-04-02
illustrates a thrust bearing 225 of an illustrative embodiment braced within
intake 505. FIGs.
20 and 21 illustrate thrust runner 220 keyed to shaft 200 within intake 505 of
an illustrative
embodiment.
[0093] Radial Support Bearings
[0094] One or more sets of radial support bearings may be included on intake
shaft 200 of
illustrative embodiments. Radial support bearings may, in addition to
providing radial
support, also provide upthrust support for assembly 100. FIGs. 4A, 4B and 14
illustrate an
exemplary radial support bearing set located in intake 505. As shown in FIG.
14, radial
support bearings may be placed about shaft 200 in between stationary thrust
bearing 225 and
motor 115 and/or between thrust bearing set 270 and motor 115. Sleeve 1405 may
be keyed to
shaft 200 and rotate with shaft 200 and/or may be held in place by a snap
ring. Bushing 1410
maybe secured to the wall of chamber base 240 with an interference fit and
remain stationary
during rotation of shaft 200.
[0095] FIG. 15 is a partial cross sectional view across line 15-15 of FIG. 14.
As illustrated in
FIG. 15, bushing 1410 may secured to chamber base 240 with an interference
fit. In some
embodiments, bushing 1410 may be a compliant bushing. Sleeve 1405 may be keyed
to shaft
200 at keyway 1500. Bushing 1410 may include grooves 1505 on an inner
circumference to
assist in guiding cooling and/or lubricating bypass fluid 280 between bushing
1410 and sleeve
1405. Grooves 1505 may extend longitudinally along the inner circumference of
bushing 1410
and/or the outer circumference of sleeve 1405 to assist in guiding the flow of
fluid around
bushing 1410 and sleeve 1405.
[0096] To provide additional radial support, for example to counteract
vibrations, in certain
27
CA 02887280 2015-04-02
embodiments a second set of sleeve 1405 and bushing 1410 may also be included
on the
pump side of intake chamber 505 as illustrated in FIGs. 17, 18 and 19. As
shown in FIG. 18
and FIG. 19, in addition to a first sleeve 1405 and a first bushing 1410 in
between bearing set
270 and motor 115, a second radial bearing set of a second sleeve 1405 and a
second bushing
1410 may also be placed in between bearing set 270 and pump inlet 510. Spider
bearing 1800
may be employed to brace bushing 1410 in a stationary fashion within housing
1805 of intake
505, and include fluid thruways 1810 to permit well fluid to pass through
spider bearing 1800
and into pump inlet 510. As illustrated, spider bearing 1800 braces bushing
1410 in place
within housing 1805. In some embodiments sleeve 1405 and bushing 1410 may be
placed on
the pump side of intake 115 rather than on the motor side, as an alternative
to being additional
to a bushing 1410 and sleeve 1405 of the motor side of intake 505.
[0097] Operation of the Pump
[0098] Illustrative embodiments include a method for absorbing the thrust of a
horizontal
surface pump assembly. Once pump assembly 100 has been positioned at the
desired location,
operation of the pump may be initiated. Unlike motor oil with extreme pressure
additives, the
pumped fluid may not provide boundary layer separation between faces 425, 1035
when ESP
pump 125 is first started. This is predominantly due to the pumped fluid's
relatively lower
viscosity, the lack of additives in pumped fluid that would otherwise provide
boundary layer
lubrication and/or due to contaminants in the pumped fluid. Thus, pumped fluid
would not
typically be used as a hydrodynamic film in conventional pump assemblies. As a
result of the
lack of lubrication, thrust runner 220 and thrust bearing 225 must endure
contact of the faces
during start-up. Illustrative embodiments of thrust runner 220 and thrust
bearing 225 are
uniquely suited for this purpose. Diamond coat 600 may endure face to face
contact of the
28
CA 02887280 2015-04-02
thrust bearing 225 and thrust runner 220 of illustrative embodiments and
prevent damage to
thrust runner 220 and thrust bearing 225 prior to formation of the
hydrodynamic film, due to
the extreme hardness of diamond as employed in illustrative embodiments. Upon
continued
operation of ESP pump 125, a hydrodynamic film may form from pumped fluid
between faces
425, 1035. Pumped fluid passing by the bearing set 270 during operation of the
pump 125
may assist in keeping the bearings cool and preventing flaking of diamond coat
600 off of
pads 415, 1020 and/or pad base 605. Thrust runner 220 and thrust bearing 225
may handle
increased axial loads due to the pumped fluid's improved heat transfer rate
over motor oil. In
some embodiments, bearing runner 220 and thrust bearing 225 may handle loads
of up to
about 15,000 pounds, 18,000 pounds, 20,000 pounds, or 25, 000 pounds.
[0099] The inventions described herein improve the thrust absorbing
capabilities of
horizontal surface pumps. The diamond coated faces of the bearings of
illustrative
embodiments allow the thrust bearings of illustrative embodiments to be placed
closer to the
pump, further from the hot motor, eliminate the need for the bearings to be
placed in a cavity
of clean oil and/or eliminate the need for a standalone thrust chamber. Use of
pumped fluid to
act as a hydrodynamic film between the bearings improves the heat and thrust
handling
capabilities of the bearings, improving the function of the pump assembly and
increasing its
lifespan. Illustrative embodiments may eliminate the need for a standalone
thrust chamber and
regular motor-oil changes. Other types of pump assemblies, such as vertical or
horizontal
downhole pumps or other pumps requiring improved thrust absorbing capabilities
may benefit
from the apparatus, system and method of illustrative embodiments.
[00100] While the invention herein disclosed has been described by means of
specific
embodiments and applications thereof, numerous modifications and variations
could be made
29
CA 02887280 2015-04-02
thereto by those skilled in the art without departing from the scope of the
invention set forth in
the claims. The embodiments described above are therefore considered in all
respects to be
illustrative and not restrictive. The scope of the invention is indicated by
the appended
claims, and all changes that come within the scope thereof are intended to be
embraced
therein.
