Note: Descriptions are shown in the official language in which they were submitted.
CA 02387635 2002-07-12
1 "MULTI-CHAMBER POSITIVE DISPLACEMENT FLUID DEVICE"
2
3 FIELD OF THE INVENTION
4 This invention relates to positive displacement fluid devices such as
fluid-driven motors and pumps which are operable for pumping high temperature,
6 and contaminated fluids. More particularly, such a fluid device is a
7 circumferential piston pump or motor configured for multi-chambered use in
8 stacked and multi-stage operation.
9
BACKGROUND OF THE INVENTION
11 Conventional methods and apparatus for bringing well fluids to the
12 surface involve various pump systems of different designs and methods of
13 operation. Restrictions on existing pump systems sometimes include
dimensional
14 constraints, the ability to handle high temperature and the need to pump
contaminated fluids, e.g. high sand content particularly at high temperature.
16 Conventional pumps are limited by their use at high temperature and with
17 contaminant sensitive polymers.
18 Further, pumps having rotating components must have some form
19 of bearing to separate the moving from the stationary components. It is a
constant challenge to maintain bearing integrity in high temperature or
21 contaminated environments. Such environments include those typical in the
22 recovery of high temperature hydrocarbons from Steam Assisted Gravity
23 Drainage (SAGD) wells in the heavy oil and bitumen recovery of northern
Alberta,
24 Canada.
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1 In downhole operations, such as conventional oil recovery
2 operations, progressive cavity (PCP) pumps have been applied to great
3 effectiveness. However, as the well becomes deeper, as the temperature
4 increases, and as the level of contamination increases, the elastomers used
begin to fail resulting in pump failure and more frequent and expensive
turnovers.
6 As an alternative, one may consider positive displacement pumps
7 which are applied in food and other fluid industries. Among this class of
pumps
8 are circumferential piston pumps which have been known since at least 1935
in
9 US 2,096,490 to Hanson and still in production today by Waukesha Delavan, WI
(Universal II Series) and Tuthill of Alsip, IL (HD Series). Conventional
11 circumferential piston pumps utilize opposing, contra-rotating rotors
having
12 pistons which are alternately swept through a common chamber. Timing gears
13 coordinate the rotor rotation. Traditionally used in surface applications,
14 significant effort has been applied in order to seal the rotation of the
rotors and
the resulting pumps to date have been typically used in single stage
applications.
16 The rotors are each fitted on a shaft rotatably supported on bearings,
either
17 cantilevered or being fit with bearings at each end. The bearings are
lubricated
18 and separated from the process fluids by seals (commonly known as external
19 bearings).
The usual approach for increasing the volume and fluid flow rate
21 from such positive displacement pumps has been to increase the pump's
22 dimensions. However, in the restricted space of a wellbore, such
dimensional
23 scale-up of pumps is not suitable for providing either the necessary
pressure or
24 the flows in the wellbore.
2
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1 In some applications, such as hot, contaminated downhole wellbore
2 operations, there is an objective to increase either the volumetric flow
rate or to
3 increase the output pressure beyond that which can conventionally be
provided
4 using a conventional circumferential piston pump. Conventional pump
technology has not fulfilled these objectives. The design challenges are
further
6 increased where the fluid is hot and contaminated, further affecting the
challenge
7 of sealing the rotors of such pumps. In particular, in the high pressure,
high
8 temperature contaminated environment of oil well downhole operations, there
is
9 little opportunity to provide an optimum environment for the bearings.
The above problems and challenges are equally applicable to the
11 reverse operation in which fluid is forced through such devices so as to
drive a
12 shaft and act as a motor.
13 Accordingly, there is a need for a fluid device which can operate in
14 high temperature, contaminated fluids and which can be further adapted to
operate in high volume and pressure operations, even in such restricted spaces
16 as a wellbore.
17
3
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1 SUMMARY OF THE INVENTION
2 The invention provides an improved positive displacement fluid
3 device, such as a pump, having one or more pump sections, the pump sections
4 being adapted for axial stacking which enables high volume, high pressure
transport of high temperature production fluid which can contain a substantial
6 degree of contamination. The novel pumping system overcomes the high
7 temperature limitation as well as being associated with a high tolerance to
pump
8 contaminated fluids over a wide viscosity range. The capability to pump high
9 temperature, contaminated fluids is achieved using a circumferential piston
pump
utilizing a novel sealing arrangement. Further, pump sections are stacked in
11 parallel to achieve required flow rates. The parallel stacked pump sections
are in
12 turn stacked in series to meet required discharge head or pressure.
Configured
13 as a pump, the fluid device is driven by a drive shaft for pumping fluid.
14 Configured as a motor, fluid is forced through the sections for turning and
driving
the shaft. Herein, the specification concentrates on a description of the
fluid
16 device as a pump although the principle and inventive concepts apply
equally to
17 a motor configuration.
18 In a preferred pumping configuration, the invention is a multi-
19 chamber positive displacement fluid device or pump comprising two or more
stacked positive displacement pump sections, each pump section having a rotor
21 chamber for pumping fluid from an intake adapted for communication or
22 connection with a fluid source to a discharge manifold and through a fluid
23 discharge adapted for communication or connection to a fluid destination.
Each
24 rotor chamber contains rotors driven by common timed drive and idler shafts
extending axially through each stacked rotor chamber. Each of the stacked
4
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1 sections has a common discharge manifold which contributes its incremental
flow
2 to the common discharge manifold. The sections can be stacked in any
3 combination of parallel or series arrangements, each of which utilizes a
drive
4 shaft which extends co-axially through the stack of sections.
If the sections are stacked in parallel, the volumetric flow rate is
6 incrementally increased.
7 If the sections are stacked in series, the discharge pressure
8 capability is incremented. For a series arrangement, the discharge of one
section
9 or stack of sections is fluidly connected to the inlet of a successive
stacked
section through a crossover section. Sections stacked in series with a cross-
over
11 form a pumping stage for incrementally increasing the pressure at the fluid
12 destination.
13 Applied as a motor for a given flow rate of fluid, sections stacked in
14 parallel result in a greater torque at the drive shaft and sections stacked
in series
result in a greater rotation speed.
16 In a multi-section pump, the invention comprises: two or more
17 axially stacked pump sections, each section having a rotor chamber and
18 associated rotors for pumping fluid from an inlet to a discharge manifold
and a
19 drive which extends axially through each rotor chamber for rotating the
rotors and
pumping fluid. Each section comprises a pump housing for housing the rotor
21 chamber and rotors which are sandwiched between end plates and seals.
22 In a multi-stage pump, the invention comprises: a suction stage
23 have having one or more axially stacked suction pump sections, each section
24 having a rotor chamber and associated rotors for pumping fluid from an
inlet to a
discharge manifold; and at least one pressure stage, each stage having one or
5
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1 more stacked pressure pump sections, each pressure pump section having a
2 rotor chamber for pumping fluid from a suction manifold to a discharge
manifold;
3 a crossover section for fluidly connecting the discharge manifold of the
suction
4 stage to the suction manifold of the pressure stage; and a drive which
extends
axially through each rotor chamber for rotating the rotors and pumping fluid.
6 More preferably, the drive comprises a drive shaft or a plurality of
7 co-axially connected drive shafts extending axially and rotatably to the
rotor
8 chamber of each section for rotating one of the rotors; an idler shaft or
idler shafts
9 extending rotatably to each rotor chamber for rotating the other rotor; and
timing
means between the drive shaft and idler shaft for contra-rotating the rotors.
11 The entire stack of sections and crossovers between stages can be
12 fit into the bore of a tubular barrel, compressed sealably together and
retained
13 therein, the barrel forming a pump having a fluid intake or inlet ports to
a suction
14 stage and having a fluid discharge from a pressure stage.
Such a pump has great versatility in its designed flow capacity and
16 lift, all of which can be assembled into a small diameter package and which
is
17 driven through a single drive shaft connection; ideal for downhole
operations or
18 other space restrictive areas. Configured as a motor, the fluid device
19 demonstrates similar same space and performance advantages in meeting
desired output torque and rotational speed characteristics.
21
6
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1 BRIEF DESCRIPTION OF THE DRAWINGS
2 Figures 1 a-1 a are schematic views of the sequential operating
3 principles of a circumferential piston pump;
4 Figure 2 is an exploded perspective view of a multi-stage
circumferential piston pump according to one embodiment of the invention;
6 Figure 3 is a perspective view of an alternate suction stage
7 according to another embodiment, in which the inlets ports for all pump
sections
8 draw from a common suction manifold;
9 Figure 4 is an exploded perspective view of a pump section
configured as a fluid suction section;
11 Figure 5 is an exploded perspective view of a four parallel pressure
12 pump fluid suction sections of Fig. 5, detailing main drive shaft and idler
shaft
13 sections;
14 Figure 6 is an exploded perspective view of a pump section
configured as a pressure pump lift section;
16 Figure 7 is an exploded perspective view of four parallel pressure
17 pump lift sections of Fig. 6, detailing main drive shaft and idler shaft
sections;
18 Figure 8 is an exploded perspective view of a center timing gear
19 assembly;
21 ~ Figures 9a-9d are various views of a fluid cross-over unit. More
22 particularly, Fig. 9a is a perspective view with internal passageway
depicted in
23 hidden lines, Fig. 9b is top view of Fig. 9a, Fig. 9c is a cross-sectional
view of Fig.
24 9b along lines A-A, and Fig. 9c is a cross-sectional view of Fig. 9b along
lines B-
B;
7
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1 Figure 10 is an exploded perspective view of a top bearing
2 assembly;
3 Figure 11 is an exploded perspective view of a complete pump
4 assembly with outer retaining barrel omitted; and
Figures 12a-12c are test results depicting the efficiency, power and
6 torque curves for a five section portion of a pump constructed according to
the
7 embodiment of Fig. 2 when pumping water at standard conditions;
8 Figures 13a-13c are test results according to Figures 12a-12c, also
9 depicting the efficiency, power and torque curves when pumping SAE30 oil at
70°C; and
11 Figures 14a-14c are test results according to Figures 12a-12c, also
12 depicting the efficiency, power and torque curves when pumping SAE30 oil at
13 190°C.
14
8
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1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
2 The principles of positive displacement pumps are hereby adapted
3 and modified for operation in environments known to be challenging to
current
4 pumping technologies. Positive displacement pumps include rotary-actuated
gear pumps and circumferential piston pumps. When fluid operated in reverse, a
6 positive displacement device can be used as a motor. Unless the context is
7 specifically otherwise, the description herein applies equally to operation
as a
8 pump or as a motor.
9 In one embodiment a circumferential piston pump is applied to
overcome the pumping challenges identified by the applicant. The principles of
11 circumferential piston pumps are well known and are summarized briefly
herein
12 for reference.
13 Generally, and using illustrations of a circumferential piston pump
14 as an example (Figs. 1 a-1 e), a positive displacement pump comprises at
least a
rotor chamber 10, rotors 11 fitted into the rotor chamber, a fluid inlet 6 and
a fluid
16 discharge 7. In a single stage implementation, the inlet 6 is connected to
a fluid
17 source and its discharge 7 is connected to a fluid destination. In the case
of an
18 elementary gear pump, two rotors 11 such as meshing gears are rotated in
the
19 rotor chamber 10. The rotors 11,11 are contra-rotated for effective fluid
flow -
either being driven by the fluid as is the case for a motor, or driving the
fluid as a
21 pump.
22 Specifically for a circumferential piston pump, two contra-rotating
23 piston rotors 11,11 are rotated in the rotor chamber 10 about cylindrical
machined
24 bosses 12. Annular piston bores 14 are formed between the rotor chamber 10
and the bosses 12. Each rotor 11,11 has one or more arcuate pistons 15 which
9
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1 travel in circular paths in their respective annular piston bores 14. The
piston
2 bores 14,14 meet at a common point of intersection C in the center of the
rotor
3 chamber 10. The center of rotation of each rotor is spaced outside of the
major
4 diameter (sometime known as external) of the opposing rotors. The point of
intersection C of the piston bores 14,14 is connected at one side to the
pump's
6 inlet 6 and at an opposing side to the pump's outlet 7. Each piston 15
alternates
7 passing through the point of intersection C. Each piston 15 has a trailing
edge
8 and a leading edge. As the trailing edge of a rotor's piston 15 leaves the
point of
9 intersection C, the volume of its piston bore is steadily yet temporarily
increased,
causing a suction and a resulting inflow of fluid from the inlet 6 or suction
side.
11 This is the suction portion of the cycle of each rotor 11. The leading edge
of the
12 same piston 15 then seals the piston bore 14 which traps the fluid drawn
from the
13 inlet 6 and positively displaces it to the outlet 7 or discharge side.
While one
14 rotor's piston 15 is displacing fluid out of its piston bore 14, the other
rotor's
piston 15 is drawing fluid into its piston bore 14. The suction inlet 6 and
16 discharge outlet 7 are constantly isolated, despite the common point of
17 intersection C, due to the continual presence of one rotor 11 or the other
rotor 11
18 sealing between its respective piston bore 14 and against the opposing
rotor's
19 cylindrical boss 12.
In example sequential steps of operation, starting at Fig. 1a, an
21 Open-to-Inlet (0T1) volume is defined in a rightmost rotor bore 14 by the
rotor
22 chamber 10 and by the departing the rightmost rotor piston 15. The
rightmost
23 rotor piston 15 fluid seals the OTI volume at the point of intersection C
where the
24 piston meets and seals against the opposing rotor's cylindrical boss 12.
Comparing Fig. 1 a and 1 e, the OTI volume alternates between the piston bores
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1 14,14 as the pistons 15,15 alternately enter or leave the point of
intersection C.
2 Normally, neither the rotors 11,11 nor the pistons 15,15 contact each other
and
3 only close tolerance fluid seals exist between the rotor 11 and the opposing
4 rotor's boss 12. As the rightmost rotor bore 14 forms the OTI volume (Fig. 1
a),
an Open-to-Outlet (0T0) volume is defined in the leftmost rotor bore 14 by the
6 rotor chamber 10 and the surfaces of rotor pistons 15 between their fluid
seal
7 contacts with the opposing boss 12 where they leave the point of
intersection C.
8 Observing the rightmost piston 15, Figs. 1 a and 1 b illustrate the OTI
suction
9 portion of the cycle, while Fig. 1 c illustrates the trapping of the fluid
and its
positive displacement towards the OTO volume. Figs. 1d and 1e illustrate the
11 continuous discharge of the trapped fluid to the outlet 7. As is shown in
Fig. 1 c,
12 the OTI suction cycle for the leftmost rotor 11 begins when the rightmost
rotor 11
13 is completed its OTI cycle.
14 In the conventional mode of operations, radial surfaces and axial-
end surfaces of the rotor pistons 15 run in close-clearance contact with the
walls
16 of the rotor chamber 10, and due to the reality of manufacturing
tolerances, load-
17 bearing contact may occasionally occur in these zones. Annular apertures
18 defined by the running clearances therebetween determine the amount of
fluid
19 leakage from the outlet 7 to the inlet 6, being from the OTO volume to the
OTI
volume, for a given pressure difference and a given effective viscosity. For
each
21 rotor chamber 10, each rotor 11,11 alternately supports the driving torque.
22 This ends a review of the more conventional aspects of the
23 circumferential piston pump, the principles of which are common with
positive
24 displacement pumps generally and with the present invention. Such
conventional
pumps utilize a pump body or housing having a single inlet 6 and an outlet 7.
11
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1 The typical means for increasing a pump's volume (OTI,OTO) and fluid flow
rate
2 has been to increase the pump's dimensions. However, in the restricted space
of
3 a wellbore, such dimensional scale-up of pumps is not suitable for providing
4 either the necessary pressure or the flows in the wellbore.
Therefore, with reference to Figs. 2 for the overall arrangement and
6 Figs. 4 and 5 for details, and turning to a first embodiment of the present
7 invention, a novel pump 20 comprises two or more positive displacement
8 chambers 10,10..., stacked axially one chamber 10 atop another chamber 10.
9 Each chamber 10 is provided with its respective rotors 11,11, bosses 12,12
and
an end plate 13 for forming a section 21. In stacking the sections 21 and thus
11 stacking the chambers 10,10..., the respective rotors 11,11 of each
discrete
12 chamber 10 are aligned along the same axes and can thereby be driven
through
13 a common drive shaft and idler shaft.
14 Two or more stacked sections 21 having their outlets 7 conjoined
into a common discharge are stacked to form a pump stage 22. A pump 20 can
16 merely have a single stage 22 of one or more parallel stacked sections 21.
17 Practically however, for increased head or discharge pressure, a pump 20
18 preferably comprises two or more stages; a suction stage 22s (figs. 4 and
5) and
19 at least one pressure stage 22p (Figs. 6 and 7).
Each stage 22, whether suction or pressure 22s,22p, comprises
21 one or more pump sections 21 arranged or stacked axially in parallel for
obtaining
22 the desired capacity or fluid flow rates. Stages 22 can also be stacked
axially in
23 series 22s,22p,22p,... for obtaining the desired discharge pressure from
the
24 ultimate outlet from the pump 20.
12
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1 As shown in Fig. 2, a complete pump 20 consists of pump sections
2 21 combined in multiples in a stack 23 and preferably having two or more
stages
3 22 operating in series 22s,22p,22p.
4 The stack 23 of pump sections 21 and drive components (described
later) are sandwiched together for fluid tight connections therebetween. While
6 other means such as threading section 21 to section 21 together or joining
by
7 fasteners could be employed, one convenient means for assembling a
multiplicity
8 pump sections 21 and their associated drive components is to fit the stack
23 into
9 an outer cylindrical retaining barrel 24. The length of the outer retaining
barrel 24
is complementary to the overall height of the stack 23 so that when installed
into
11 the outer retaining barrel, end retaining nuts 25 are secured into each end
of the
12 outer retaining barrel 24 for engaging the stack ends 26 and retaining them
13 together.
14 While each section 21 may actually be identical, the section's
location in the stack can define its role as either a suction or a pressure
section
16 21 s,21 p. A suction section 21 s, multiple sections 21 s,21 s..., or a
suction stage
17 22s is located adjacent to and in fluid communication with a fluid source
and
18 draws the design flow rate of fluid into the pump 20. As shown in Fig. 2,
such a
19 suction stage 22s, can draw fluid independently into each section 21 s,21
s...
through a plurality of corresponding inlets 6,6... in the sections 21 and
21 corresponding inlet ports 27 in the outer retaining barrel 24. Alternately,
as
22 shown in Fig. 3, the fluid can be drawn through a combined suction intake
34.
23 With reference to Fig. 4, a section 21 s configured for suction is
24 illustrated. Each section 21 comprises a pump body or pump housing 30
forming
at least two chambers: a pumping or rotor chamber 10 and a discharge chamber
13
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1 31. For ease of manufacture and assembly, the rotor chamber 31 of each
2 section 21 is sandwiched and sealed between end plates 13. A pair of bosses
12
3 extends from one side of the end plate 13 and project into the rotor chamber
10.
4 The end plate 13 blocks one side of the rotor chamber 10, shown in this
configuration as a top end plate for one pump section while also forming a
bottom
6 end plate for the next adjacent pump section. At an extreme bottom end of a
7 stack of pump sections, a termination plate 32 without bosses is provided.
8 With reference to Fig. 5, four suction pump sections 21 s are shown
9 with the discharges 31 of each of the pump housings 30 and end plates 13
being
aligned for forming a discharge manifold 31 m for contiguous fluid passage
11 therethrough. Inlets 6 are shown extending from the rotor chamber and
through
12 the pump housing 30. The pump housing, may or may not have a suction
13 chamber 33 which mirrors the discharge chamber 31. In this embodiment, a
14 suction chamber 33 would be a mere artifact of the implementation of pump
housings which are interchangeable for either suction or pressure section use.
As
16 shown in Fig. 2, the assembled suction stage 22s draws fluid from a fluid
source
17 outside the pump 20, typically from a wellbore. Fluid enters the suction
stage
18 through a series of inlet ports 27 formed in the outer retaining barrel 24.
The inlet
19 ports 27 align with corresponding inlets 6 in each of the suction stages 21
s;
typically one inlet port 27 per suction pump section 21. While this
arrangement
21 does require some accuracy in matching inlet ports 27 and pump section
inlets 6,
22 use of individual inlet ports 27 does minimize fluid restriction and
ensures a
23 substantially equal supply of fluid to each pump section 21. Each suction
pump
24 section 21 transports substantially an equal amount of fluid from the inlet
6 and
delivers it to the common discharge manifold 31 m which is located 180 degrees
14
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1 opposite to the suction manifold 33m. The discharge manifold 31 m runs along
the
2 full axial length of each pump stage 22s,22p..., through both the pump
housings
3 10 and the end plates 13 for accumulating and delivering the discharge fluid
to
4 the next pump stage 22.
In the alternate embodiment shown in Fig. 3, the multiple-stacked
6 chambers of the suction stage 22s can all draw from suction intake 34. The
7 suction sections 21 s,21 s... have their inlets 6 extending only from the
rotor
8 chamber 10 to a suction chamber 33 as part of an overall common suction
9 manifold 33m. This simplifies the pump assembly and avoids the need to
accurately align individual section inlets 6 with the inlet ports 27 in the
outer
11 retaining barrel 24. Accordingly, a common or combined suction intake 34 is
12 formed at the initial suction section 21 s or the suction stage 22s. The
intake 34 is
13 formed in the termination plate 32. In this embodiment, the suction
manifold 33m
14 is required to pass the entire design fluid flow rate, and thus the
pressure drop
therethrough must be considered in the design such as increasing the manifold
16 33m cross-section accordingly. The suction manifold 33m may have sufficient
17 cross-sectional areas to supply fluid to all of the multi-chambers 10 in
the stage
18 22 without starving the latter sections 21 of fluid flow. The suction
manifold 33m
19 for all pump sections 21 may be increased in size. The inlets 6 for each
section
21 are all joined through the common suction manifold 33m. In the alternate
21 embodiment in Fig. 3, it is clear that the pressure and suction sections 21
p,21 s
22 may be identical for simplification and economy of manufacture.
23 Turning to Fig. 6, a pressure pump section 21 p is shown herein as
24 differing from an independent inlet operating suction pump section 21 s by
the
absence of an inlet 6 extending through the pump housing 30 which forms a
CA 02387635 2002-07-12
1 suction manifold 33. As shown individually in Fig. 6 and stacked in Fig. 7,
the
2 pressure pump sections 21 p correspond in all other respects to the suction
pump
3 sections 21 s set forth in Figs. 4 and 5 except that the suction chamber 33
now
4 forms the inlet to each section 21. The suction chamber 33 is isolated from
the
outer retaining barrel 24 and is enclosed wholly within the pump housing 30. A
6 pressure stage 22p is typically configured to accept fluid from the suction
stage's
7 common discharge, process the fluid through the one or more sections 21 p in
8 parallel and also discharge the fluid through a common discharge 31 or
manifold
9 31 m.
The end plates 13 are also fitted with suction and discharge
11 chambers 33,31 which are complementary to the pump housing's suction and
12 discharge chambers 33,31 for forming respective suction and discharge
13 manifolds 33m,31 m extending continuously along the pump 20 for contiguous
14 fluid communication between stacked pump stages 22s,22p,22p... . As noted
above, end plates 13 throughout a suction stage 22s may or may not include a
16 suction chamber 33 as the suction section's pump housing 30 may be absent
17 such a chamber, being fitted only with an inlet 6.
18 With reference to Fig. 7, four pressure pump sections 21 p,21 p... are
19 shown with each of the respective suction and discharge manifolds 33,31 of
the
pump housings 30 and end plates 13 being aligned for contiguous fluid passage
21 therethrough.
22 Rotors 11 and their pistons 15 are mounted rotatably over the
23 bosses 12 for rotation in the rotor chamber 10. Single lobed rotors 11 are
shown
24 although double lobed or other rotor arrangements are possible. In US
2,642,808
to Thomas, the entirety of which is incorporated herein by reference, double
16
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1 lobed rotors are implemented. Further, the circumferential piston 15 can
extend
2 axially from the rotor 11 to overhang the boss 12, as illustrated herein, or
can be
3 cantilevered, as taught by Thomas.
4 Accordingly, and referring to Figs. 2 and 4-7, when assembled into
a typical pump 20 configuration, a suction stage 22s is demonstrated as having
6 fifteen stacked suction pump sections 21 s and fifteen corresponding inlet
ports
7 27. All fifteen suction pump sections 21 s discharge to the common discharge
8 manifold 33m. The fluid in the suction stage's discharge manifold 31 m is
directed
9 to a first pressure stage 22p. The first pressure stage 22p is also
illustrated as
having fifteen stacked pressure pump sections 21 p. All fifteen pressure pump
11 sections 21 p draw from a common suction manifold 33m and discharge to a
12 common discharge manifold 31 m. The fluid in the first pressure stage's
13 discharge manifold 31 m is directed to a second pressure stage 22p. The
second
14 pressure stage 22p is also illustrated with fifteen pressure pump sections
21 p. All
fifteen pressure pump sections 21 p also draw from a common suction manifold
16 33m and discharge to a common discharge manifold 31 m.
17 Turning to Figs. 7 and 8, one rotor 11 is driven by one or more drive
18 shafts 40,40... which extend through each rotor chamber 10 and which are
19 connected end to end for co-rotation. The opposing rotor 11 is driven by
one or
more idler shafts 41,41... which are also connected end to end for co-
rotation.
21 The one or more drive shafts 40 and one or more idler shafts 41 are
hereinafter
22 referred to collectively and simplistically as singular drive shaft 40 and
idler shaft
23 41 respectively.
24 As shown in Figs. 7 and 8, the pump sections 21 are driven using
the drive shaft 40, extending axially through each pump section 21 and
17
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1 connecting driven rotors 11 in each stacked pump stage 22. The rotors 11 in
2 each pump stage 22 rotate in the same contra-rotating directions as they are
3 driven by one common input main drive shaft 40. The opposing rotor 11 in
each
4 pump section 21 is driven by paired sets of timing gears 50, connected to
the
drive shaft 40 and the parallel idler shafts 41. The plurality of
discontinuous, yet
6 co-axial, conjoined idler shafts 41 each being driven through the timing
gears 50.
7 The timing gears 50 have a dual function: to drive the idler shaft 41 and
their
8 associated rotors 11, and to ensure that the rotors' pistons 15 are timed
correctly
9 so that they do not contact or clash.
A person of skill in the art can design one or more shafts 40,40...
11 and 41,41... for assembly into a single co-rotating shaft 40 or 41. As
shown in
12 Fig. 7, an individual shaft 40 or 41 may be conjoined at splined
connections 42 at
13 its respective and common rotor 11. For example, the ends of the shafts
40,41
14 can be fitted with an external involute spline 42 which fits cooperatively
with an
internally splined coupling bushing (or rotor 11 or gear 50) to co-axially
connect
16 the shaft sections of each of the stacked pump stages 22. Further, as shown
in
17 Fig. 8, the shafts may be conjoined with splined connections at the timing
gears
18 50.
19 The timing gears 50 are housed in timing assemblies 51,51... which
are located at regular intervals between multiple stacked pump sections 21,
and
21 thereby provide accurate timing for the piston sections 21,21... .
Typically, a
22 timing assembly 51 is sandwiched between every four of five pump sections
21.
23 The timing gears 50 are contained in separate timing assemblies 51, fully
24 integrated in each pump stage 22.
18
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1 Regardless of the form of connection to a fluid source, the common
2 discharge manifold 31 m of the suction stage 22s delivers pumped fluid to
the
3 next successive pump stage 22, in this case being the first pressure pump
stage
4 22p. The first pressure stage 22p and successive pressure pump stage 22p is
similar in design and construction to the previous suction pump stage 22s,
6 excluding the suction inlets 6 and inlet ports 27.
7 At the discharge of each stage 22, such as between the suction
8 stage 22s and a pressure stage 22p, the discharge manifold 31 m is routed to
the
9 suction manifold 33m of the successive pump stage. In order to maintain
common rotational axes for the drive shaft 40 and idler shaft 41, and to pump
the
11 discharge flow to the common suction manifold 33m of the successive stage
22p,
12 the fluid needs to cross-over 180 degrees to flow into the common suction
13 manifold 22s of the successive stage 22.
14 With reference to Figs. 2 and 9a-9d, a fluid flow cross-over section
60 comprises a cylindrical block forming an end wall 61 for blocking the
16 preceding stage's suction manifold 33m and a fluid inlet 62 for accepting
fluid
17 flow from the preceding stage's discharge manifold 31 m. The fluid from the
18 preceding stage's discharge manifold 31 m is routed through a fluid flow
passage
19 63 to a fluid outlet 65. The fluid outlet 65 is arranged for discharge into
the
suction manifold 33m of the successive stage 22. As shown in Figs. 9b and 9d,
21 the cylindrical block is fitted with a bore 66 for forming a through
passage for the
22 drive shaft 40. The idler shafts 41, being driven by timing assemblies 51
23 positioned periodically along the pump, are able to terminate either side
of the
24 cross-over section 60. Accordingly, the fluid flow passage 63 is neither
obstructed nor interrupted by the drive shaft 40 or idler shafts 41,41.
19
CA 02387635 2002-07-12
1 Sockets 67 and bearings (not shown) are provided for the
2 termination of a preceding idler shaft and for the termination of a
successive idler
3 shaft. Such sockets 67 can be machined into the cross-over section 60 or
into
4 specialized end plates (not shown) which can be provided as matter of
economics so as to avoid further machining of the cross-over section 60.
6 As known by those of skill in the art of positive displacement
7 pumps, each rotor 11,11 is rotated in close non-contacting tolerance to
their
8 respective bosses 12,12 and to the rotor chamber 20 and the opposing rotor
11
9 so as to effect a positive displacement motoring or pumping action. To
maintain
such operational tolerances, the rotors 11,11 are mounted securely to their
11 respective shafts 40,41 and the shafts themselves are supported
concentrically in
12 the bosses 12,12 using bearings 70. Unlike the conventional wisdom applied
to
13 such circumferential piston pumps, the bearings 70 employed herein are not
14 supported external to the rotor chamber in a protected environment.
Recognizing
the oft times harsh conditions experienced by pumps in hot, or contaminated
16 environments, face-to-face hard bearing surfaces, including tungsten
carbide,
17 silicon carbide, and ceramics are provided inside each boss 12,12 and on
the
18 corresponding locations on the main drive shaft 40 and idler shaft 41. Best
19 shown in Figs. 6 and 8, bearings 70 are fit into each boss 12. Mating
bearings 70
are also ~t to the shafts 40,41 (obscured in Figs. 6 and 8 - an example shown
in
21 Fig. 8). Similar complementary bearings 70 are employed in each timing
22 assembly 51.
23 Best seen in Figs. 4 and 6, sealing between the individual
24 components of the pump housings 30, end plates 13, timing assemblies 51,
and
fluid cross-over sections 60 is accomplished using specially molded high
CA 02387635 2002-07-12
1 temperature O-ring seals 90. The seals 90 are fitted in corresponding shaped
2 grooves 91 formed in each pump housing 30, providing full sealing around the
3 perimeter of each chamber 30, each stacking interface and each individual
4 lubricant and instrumentation port hole 80, running through the full length
of the
pump stage 22.
6 As discussed earlier, each complete assembled pump stage 22 is
7 mounted inside an outer retaining barrel 24 for supporting the complete
8 assembly. Accordingly, each complete stacked pump stage 22 is free of any
9 internal mechanical fasteners.
The outside pump retaining barrel 24 is precision ground and
11 polished on its inside diameter, and provides close tolerance support for
each
12 internally mounted section 21,21 and stage 22. The extreme ends 29 of the
outer
13 retaining barrel 24 are internally threaded, and each match with the
externally
14 threaded retaining nut. The retaining nut 25 can also be provided by a
threaded
1 S fluid cross-over 60. Once the retaining nuts 25 are threaded into each end
of the
16 outer retaining barrel, they sandwiches the stacked pump sections 21 and
stages
17 23 together, compressing the O-ring seals 90 and thereby providing full
internal
18 sealing of the internal pump stage components 21,51,60.
19 The assembly is aided by compressing the stack of pump
components 21,51,60 using opposing mandrels. The end retaining nuts 25 are
21 then threaded into each end of the outer retaining ban-el to retain the
compressed
22 stack in the outer retaining barrel 24. Depending upon the number of
sections 21
23 for the particular pump configuration, and as an example, for three stages
of
24 fifteen sections/stage about 10,000 to 20,000 pounds force is applied.
21
CA 02387635 2002-07-12
1 In operation, each stage of a circumferential piston pump produces
2 a characteristic pulsing at each discharge. Accordingly, and in a preferred
3 aspect, such pulsing is minimized by slightly rotationally incrementing each
pair
4 of rotors 11,11 for each successive section 21,21. One approach is to mount
the
rotors 11,11 on the drive shafts 40 and idler shafts 41 such that the pump
6 OTI/OTO timing for a complete pump stage 22 is incremented, at equal angular
7 intervals throughout the entire 360° shaft circumference, so as to
equally divide
8 the pulsing throughout each 360 degrees revolution. The resulting fluid flow
has
9 an overall reduced variation in pulsation at the discharge manifold 31 m and
provides continuous low pulsation fluid intake and fluid flow discharge
11 characteristics. For example, for a stage 22 having fifteen pump sections
21,
12 each rotor 11 of a rotor pair would be incrementally rotated about 24
degrees on
13 the main drive shaft (360/15). The rotors 11 are connected to the drive and
idler
14 shafts 40,41 by means of splines 42 and shaft keys (not shown). As is the
convention in rotating machines, shaft keyways are rounded with radius ends,
to
16 reduce stresses on the shafts 40,41.
17 Referring to both Figs. 2 and 10, the drive shaft 40, running through
18 the full length of the complete pump 20, is supported at the discharge end
of the
19 pump 20 by a thrust/radial bearing assembly 100 . The thrust bearing
assembly
comprises a bearing housing 101 located on top of the uppermost pump stage
21 22p, and forms an integral part of the pump 20 when installed into the
outer
22 retaining barrel 24 . The thrust bearing assembly 100 contains double
thrust
23 bearings 102,102 and double radial bearings 103,103 fit with bearing
housings
24 104 to prevent axial and radial driveshaft movement. The bearing assembly
100
is a sealed unit, with high temperature mechanical seals 105,105 located at
the
22
CA 02387635 2002-07-12
1 upper and lower end of the drive shaft bearing assembly 100. The bearing
2 assembly 100 is filled with high temperature lubricant oil to lubricate the
bearings
3 102,103. The bore of the bearing housing 101 contains the combined stack of
4 bearings 102,103 and has an additional lubricant oil reservoir 106
surrounding
the bearing assembly 100. The reservoir 106 can be refreshed or topped up
6 through a lube oil connection (not shown) at the top of the pump 20 adjacent
the
7 production line connection 110.
8 Alignment of the stacked components 21,51 is accomplished by
9 hollow alignment dowels 80, located in integral lubricant / instrumentation
galleries 81 running through the full length of the complete pump 20. Each
pump
11 housing 30, end plate 13, timing assembly 51 and fluid cross-over section
60
12 have such galleries 81 into which are fit hollow dowels 81 for alignment as
well as
13 for lubricant/ instrumentation purposes. Each pump section 21 is located
and
14 rotationally locked to the adjacent section 21 using the dowels 80.
Further,
through the use of hollow dowels 81, one through four galleries 80 can be
formed
16 along the length of the pump 20. For example, the oil reservoir 106
surrounds
17 the bearing assembly 100 and is also supplied with lubricant externally
through
18 one of the galleries 80 running through the full length of the pump 20.
19 As shown in Fig. 11, assembly of the pump sections 21 comprises
first stacking each of two or more pump housings 30 and rotors 11,11 between
21 end plates 13,13. The end plate's bosses 12,12 center and locate the rotors
22 11,11 in the pump housing 30, and also rotatably support the main drive
shaft 40
23 and idler shaft 41 bearings 70. Pump housings 30 and end plates 13,13 are
24 stacked back to back, with timing assemblies 51 at regular intervals, to
form one
or more stages 22. As shown in Fig. 2, the entire stack 30,13,51... is
23
CA 02387635 2002-07-12
1 compressed and installed in the outer retainer barrel 24 for form the
complete
2 pump 20.
3 The discharge fluid is delivered from the uppermost pump stage
4 22p via the common discharge manifold 31 m to a last cross-over section 60,
connecting to the production pipe line 110 for directing the fluid to the
fluid
6 destination. In a pump 20 flt to a wellbore, the fluid destination would be
the
7 earth's surface.
8
9 Exa ale
Operations for a pump 20 capable of operation in a 9-5/8" wellbore
11 casing include a plurality of 8" diameter pump housings 30 comprises a
suction
12 stage 22s and two pressure stages 22p,22p. Each pump section 20 has a rotor
13 chamber 10 and rotor 11,11 combination having a displacement of 0.833
liters
14 per rotor revolution. Timing gears 50 are provided every five pump sections
21,
or three assemblies 51 per stage 22. Rotational speed of the pump sections 21
16 can vary between about zero to over 600 rpm, limited only by mechanical
17 constraints such as the means for driving the drive shaft and depending on
the
18 characteristics of the fluid. Operating with drive means such as
conventional top
19 drives rotating at 400 rpm, such a pump 20 can produce flow rates of about
1000
liters/minute at 4500 kPa on fluid such as oil having gravity and viscosity
21 equivalent to fluid similar to a SAE30 oil.
22 Having reference to Figs. 12a-12c, a single stage 22 having five
23 sections 21 of the above pump 20 was manufactured, assembled and operated
24 on water at 30°C. The water had a viscosity of less than about 1
mPa~s. The
figures are graphs of pump performance versus fluid discharge flow rates and
24
CA 02387635 2002-07-12
1 discharge pressure. Fig. 12a demonstrates test results for pump efficiency
2 pumping water at 30°C. Figs. 12b and 12c illustrate the pump power
and torque.
3 Figs. 13a-13c illustrate the same parameters of efficiency, power and torque
4 curves when pumping SAE30 oil at 70°C and Figs. 14a-14c illustrated
efficiency,
power and torque curves when pumping SAE30 oil at 190°C.
6 With oil at 70°C, the 5 stages produced flow rates in the order of
7 340 - 300 I/min at between 350 - 1400 kPa respectively. Through
extrapolation
8 to 15 sections 21 per stage 22, one would expect to get about three times
the
9 flow rate or upwards of 1000 liters/min, and when pumped through two
additional
pressure stages, each having 15 sections for maintaining the flow rates, one
11 could expect discharge pressures of up to about 4200 kPa.
