U.S. patent application number 12/433490 was filed with the patent office on 2010-11-04 for method and apparatus for lubricating a screw pump system.
This patent application is currently assigned to General Electric Company. Invention is credited to David Deloyd Anderson, Hrishikesh Vishvas Deo, Michael V. Drexel, Farshad Ghasripoor, Vasanth Kothnur, Thomas Steen.
Application Number | 20100278672 12/433490 |
Document ID | / |
Family ID | 42782035 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100278672 |
Kind Code |
A1 |
Kothnur; Vasanth ; et
al. |
November 4, 2010 |
METHOD AND APPARATUS FOR LUBRICATING A SCREW PUMP SYSTEM
Abstract
A pump system includes inlet chambers, an outlet chamber, and
rotors disposed inside the inlet chambers and the outlet chamber to
pump a process fluid from the inlet chambers to the outlet chamber
and to direct the process fluid to a separator. A gear chamber is
configured to receive a portion of the process fluid from the
separator. First and second sets of pump bearings are coupled to
the rotors and lubricated by the portion of the process fluid
flowing from the gear chamber. A conduit is configured to direct
the portion of the process fluid from the pump bearings back to the
gear chamber. Some of the portion of the process fluid lubricating
the pump bearings is permitted to leak to the inlet chambers.
Additional process fluid is continually added to the portion of the
process fluid to compensate for fluid leaking to the inlet
chambers.
Inventors: |
Kothnur; Vasanth; (Clifton
Park, NY) ; Anderson; David Deloyd; (Glenville,
NY) ; Drexel; Michael V.; (Delanson, NY) ;
Steen; Thomas; (Ballston Spa, NY) ; Ghasripoor;
Farshad; (Glenville, NY) ; Deo; Hrishikesh
Vishvas; (Guilderland, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
ONE RESEARCH CIRCLE, BLDG. K1-3A59
NISKAYUNA
NY
12309
US
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
42782035 |
Appl. No.: |
12/433490 |
Filed: |
April 30, 2009 |
Current U.S.
Class: |
418/1 ;
418/205 |
Current CPC
Class: |
F04C 13/008 20130101;
F04C 13/005 20130101; F04C 2210/24 20130101; F04C 2/16 20130101;
F04C 13/004 20130101; F04C 11/001 20130101; F04C 2210/62 20130101;
F04C 15/0088 20130101; F01C 17/02 20130101 |
Class at
Publication: |
418/1 ;
418/205 |
International
Class: |
F04C 15/00 20060101
F04C015/00; F04C 2/14 20060101 F04C002/14 |
Claims
1. A method for operating a pump system, comprising: directing a
process fluid into an inlet chamber of a pump casing at a first
pressure; rotating a plurality of rotors disposed inside the pump
casing to pump the process fluid from the inlet chamber to an
outlet chamber of the pump casing at a second pressure; directing
the process fluid from the outlet chamber to a separator; directing
a first portion of the process fluid from the separator downstream;
directing a second portion of the process fluid from the separator
to a gear chamber of the pump at a third pressure; directing the
second portion of the process fluid to lubricate a first set of
pump bearings; directing the second portion of the process fluid to
lubricate a second set of pump bearings; and joining a flow from
the second set of pump bearings to a flow of the second portion of
the process fluid prior to directing a combined flow into the gear
chamber.
2. The method of claim 1, wherein a plurality of gears in the gear
chamber are each coupled to an end of each of the plurality of
rotors.
3. The method of claim 1, wherein the second pressure is greater
than the first pressure.
4. The method of claim 3, wherein the third pressure is greater
than the first pressure and the second pressure is greater than the
third pressure.
5. The method of claim 1, comprising leaking a portion of the
process fluid from the first pump bearing to a first inlet chamber
and leaking a portion of the process fluid from the second pump
bearing to a second inlet chamber.
6. The method of claim 5, wherein directing a second portion of the
process fluid from the separator to a gear chamber of the pump at a
third pressure comprises directing about 15% of a total flow of
process fluid from the separator to a pressure reducer prior to
joining the flow from the second set of pump bearings to compensate
for the leaking of process fluid from the first and second pump
bearings.
7. The method of claim 1, wherein directing a first portion of the
process fluid from the separator downstream comprises directing
about 80% to 90% of a total flow of process fluid from the
separator to a downstream unit.
8. The method of claim 1, wherein the separator separates
particulate matter from the process fluid, and wherein process
fluid having reduced particulate matter content comprises the
second portion of process fluid directed to the gear chamber.
9. A method for operating a pump system, comprising: pumping a
fluid from a pump inlet to a pump outlet; separating a lubricating
portion of fluid flow from the pump outlet; and pumping the
lubricating portion of fluid flow through a circulation path that
includes a gear pump coupled to rotors of the pump, a first pump
bearing and a second pump bearing.
10. The method of claim 9, comprising allowing an amount of the
lubricating portion to flow from the first and second pump bearings
into an inlet side of the pump; and adding fluid to the lubricating
portion circulating through the circulation path to compensate for
the amount of the lubricating portion flowing from the pump
bearings into the inlet side of the pump.
11. A pump system, comprising: inlet chambers; an outlet chamber;
rotors disposed inside the inlet chambers and the outlet chamber to
pump a process fluid from the inlet chambers to the outlet chamber
and to direct the process fluid to a separator; a gear chamber
configured to receive a portion of the process fluid from the
separator; first and second sets of pump bearings coupled to the
rotors and lubricated by the portion of the process fluid flowing
from the gear chamber; and a conduit configured to direct the
portion of the process fluid from the pump bearings back to the
gear chamber; wherein some of the portion of the process fluid
lubricating the pump bearings is permitted to leak to the inlet
chambers, and wherein additional process fluid is continually added
to the portion of the process fluid to compensate for fluid leaking
to the inlet chambers.
12. The system of claim 11, wherein an outlet chamber pressure is
greater than an inlet chamber pressure, and wherein pressures in
the pump bearings are greater than the inlet chamber pressure.
13. The system of claim 11, comprising gears in the gear chamber,
wherein each gear is coupled to a respective end of a rotor and the
gears are configured to circulate the process fluid as a lubricant
through the pump bearings.
14. The system of claim 11, wherein a pump bearing is coupled to
each end of each of the rotors.
15. The system of claim 11, wherein the portion of the process
fluid from the separator directed to the gear chamber comprises
about 10% to 20% of a total flow of process fluid from the
separator.
16. The system of claim 11, comprising a pressure reducer that
receives the process fluid from the separator and directs the
process fluid to the gear chamber to compensate for the process
fluid leaking to the inlet chambers.
17. The system of claim 11, wherein the separator separates
particulate matter from the process fluid, and wherein process
fluid having reduced particulate matter content is directed to the
gear chamber.
18. A pump system, comprising: inlet chambers; an outlet chamber;
rotors disposed inside the inlet chambers and the outlet chamber
and configured to mesh with one another to direct a multiphase
process fluid from the inlet chambers to the outlet chamber; and an
inlet disposed adjacent to the inlet chambers and configured to
direct the multiphase process fluid generally tangentially into the
inlet chamber and to swirl the multiphase process fluid to reduce a
settling of particulate matter from the multiphase process fluid in
the inlet chambers.
19. The system of claim 18, comprising a gear chamber configured to
receive a portion of the multiphase process fluid from the outlet
chamber after a separating of the multiphase process fluid by a
separator.
20. The system of claim 19, wherein a separated multiphase process
fluid is received by the gear chamber and is pumped by gears in the
gear chamber to lubricate pump bearings.
21. The system of claim 19, comprising pump bearings configured to
receive a portion of a separated multiphase process fluid from the
gear chamber, wherein some of the portion of the separated
multiphase process fluid from the pump bearings is configured to
leak to the inlet chambers.
Description
BACKGROUND OF THE INVENTION
[0001] The embodiments disclosed herein relate generally to a screw
pump, and more particularly to lubrication and process fluid
management of a multiphase screw pump.
[0002] Screw pumps are rotary, positive displacement pumps that use
two or more screws to transfer high or low viscosity fluids or
fluid mixtures along an axis. A twin screw pump typically has two
intermeshing counter-rotating rotor screws. The volumes or cavities
between the intermeshing screws and a liner or casing transport a
specific volume of fluid in an axial direction around threads of
the screws. As the screws rotate the fluid volumes are transported
from an inlet to an outlet of the pump. In some applications, twin
screw pumps are used to aid in the extraction of oil and gas from
on-shore and sub-sea wells. Twin screw pumps lower the back
pressure on the reservoir and thereby enable greater total recovery
from the reservoir.
[0003] In many cases, a twin screw pump may be used to pump a
multiphase fluid from a sub-sea well which may be processed to
produce the petroleum products. Accordingly, twin screw pumps may
be configured to prevent the flow of process fluids into the
bearings, timing gears, motor, environment, or the like. In
particular, twin screw pumps may utilize a shaft seal on each end
of each rotor, thereby requiring four seals in total. The shaft
seals also typically require the usage of a lubricant flush system
that maintains the rub surfaces of the sealing system clean and
removes heat from the sealing surfaces.
[0004] Further, in the example the system used to lubricate the
various parts of the twin screw pump system, including bearings
coupled to the rotor screws, may require additional components and
maintenance. This separate lubrication system adds costs and
maintenance to the screw pump system.
BRIEF DESCRIPTION OF THE INVENTION
[0005] The invention provides a method for operating a pump system
that includes directing a process fluid into an inlet chamber of a
pump casing at a first pressure, rotating a plurality of rotors
disposed inside the pump casing to pump the process fluid from the
inlet chamber to an outlet chamber of the pump casing at a second
pressure, and directing the process fluid from the outlet chamber
to a separator. A first portion of the process fluid is directed
from the separator downstream, and a second portion of the process
fluid is directed from the separator to a gear chamber of the pump
at a third pressure. The second portion of the process fluid is
directed to lubricate a first set of pump bearings, and then the
second portion of the process fluid to lubricate a second set of
pump bearings. The flow from the second set of pump bearings is
then joined to a flow of the second portion of the process fluid
prior to directing a combined flow into the gear chamber.
[0006] A similar method may include pumping a fluid from a pump
inlet to a pump outlet, separating a lubricating portion of fluid
flow from the pump outlet, and pumping the lubricating portion of
fluid flow through a circulation path that includes a gear pump
coupled to rotors of the pump, a first pump bearing and a second
pump bearing.
[0007] The invention also provides a pump system comprising inlet
chambers, an outlet chamber, and rotors disposed inside the inlet
chambers and the outlet chamber to pump a process fluid from the
inlet chambers to the outlet chamber and to direct the process
fluid to a separator. A gear chamber is configured to receive a
portion of the process fluid from the separator. First and second
sets of pump bearings are coupled to the rotors and lubricated by
the portion of the process fluid flowing from the gear chamber. A
conduit is configured to direct the portion of the process fluid
from the pump bearings back to the gear chamber. Some of the
portion of the process fluid lubricating the pump bearings is
permitted to leak to the inlet chambers. Additional process fluid
is continually added to the portion of the process fluid to
compensate for fluid leaking to the inlet chambers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0009] FIG. 1 is a diagrammatical representation of a screw pump
system and a production platform in accordance with an embodiment
of the present technique;
[0010] FIG. 2 is a perspective view of a screw pump system, as
shown in FIG. 1, including a separator, in accordance with an
embodiment of the present technique;
[0011] FIG. 3 is a schematic diagram of a screw pump system, as
shown in FIG. 2, including a system for separating and directing
process fluid throughout the screw pump assembly, in accordance
with an embodiment of the present technique;
[0012] FIG. 4 is a detailed perspective view of a screw pump
system, as shown in FIG. 1, in accordance with an embodiment of the
present technique;
[0013] FIG. 5 is a detailed exploded view of a screw pump system,
as shown in FIG. 4, in accordance with an embodiment of the present
technique;
[0014] FIG. 6 is a detailed side view of components within a screw
pump system, including rotor screws, gears, and rotor shrouds, in
accordance with an embodiment of the present technique;
[0015] FIG. 7 is a detailed perspective view of certain components
within a screw pump system, as shown in FIG. 6, in accordance with
an embodiment of the present technique;
[0016] FIG. 8 is a detailed end view of rotor shrouds within a
screw pump system, in accordance with an embodiment of the present
technique;
[0017] FIG. 9 is a detailed side view of rotor shrouds within a
screw pump system, as shown in FIG. 8, in accordance with an
embodiment of the present technique; and
[0018] FIGS. 10 and 11 are schematic diagrams of a screw pump
system including a configuration to swirl the multiphase process
fluid as it enters inlet chambers of the screw pump to prevent
settling of particles, in accordance with an embodiment of the
present technique.
DETAILED DESCRIPTION OF THE INVENTION
[0019] FIG. 1 is a schematic diagram of a screw pump system 10 that
may be provided with a production platform 12 to pump a fluid for
processing, storage and/or transport. As depicted, the screw pump
system 10 may be connected to the production platform 12 via a
conduit or riser 14 that may be used to route a process fluid to
the platform. The process fluid may be a multiphase fluid, such as
raw petroleum based fluid from a sub-sea drilling rig. In addition,
the screw pump system 10 may be located on a sea or ocean floor 16,
wherein the screw pump system 10 pumps the process fluid to a
production platform floating on an ocean surface 18, or anchored to
the sea floor. As depicted, the screw pump system 10 may be located
a distance 20 from the production platform 12, wherein the pump is
used to create the pressure and force needed to pump the process
fluid to the surface 18. In another embodiment, the screw pump
system 10 may be located in a factory or chemical plant and may be
configured to direct a multiphase process fluid to holding tanks or
other structures for processing or storage. In the illustrated
example, the screw pump system 10 may be useful during the
extraction of oil and/or gas from sub-sea wells, to reduce back
pressure and assist in the extraction of the oil and/or gas. In the
depicted embodiment, the screw pump system 10 uses two intermeshing
screws to pump the process fluid. In the example, the screw pump
may be referred to as a twin screw pump.
[0020] The screw pump system 10 includes several components that
may require lubrication and may be susceptible to wear and tear due
to exposure to particulate matter within the process fluid.
Specifically, the screws within the screw pump system 10 may be
coupled to bearings that require lubrication in order to perform
properly and avoid breakdown. Moreover, in some embodiments, the
lubrication system may require a separate set of components and
lubricants in order to properly lubricate the pump. As depicted,
the lubrication of pump bearings may be achieved by routing the
multiphase process fluid through a circuit of conduits and a system
for separating particulates from the process fluid. The process
fluid may lubricate the components within the screw pump system 10
after the process fluid has been treated, routed and directed to
locations within the screw pump system 10 to make it suitable for
lubrication of the pump components. Moreover, the particulates
located in the multiphase process fluid pumped by the screw pump
system 10 may cause damage to components within the screw pump
system 10 if the particulates are allowed to settle in certain
locations. Accordingly, as discussed below, embodiments include
gears that may be used to grind the particulate matter to crush it,
reducing the size of the particulate matter within the process
fluid, thereby making it suitable for lubrication of the components
and rotors within the screw pump system 10.
[0021] FIG. 2 is a detailed perspective view of an embodiment of
the screw pump system 10. As depicted, the screw pump system 10
includes a twin screw pump 22, which includes two screws or rotors
used to direct a process fluid at a high pressure to a downstream
location. In other embodiments, the screw pump 22 may include more
than two screws that intermesh to pump a process fluid. One of the
screws may be coupled to a driving shaft 24, which may be coupled
to a motor 26. The motor 26 and the driving shaft 24 produce a
rotational output used to drive a driving rotor that is coupled,
via a gear, to drive a driven rotor, thereby producing the
necessary pressure and force to direct the process fluid
downstream. The process fluid, such as a petroleum based multiphase
fluid, may enter the twin screw pump 22 via fluid intakes 28. By
rotating the meshing threads of the rotor screws, the process fluid
is driven from the twin screw pump 22 via a fluid outlet 30. The
fluid output may be directed to a conduit and thereby to a
separator 32. The separator 32 may be configured to remove a
portion of particulates from the multiphase process fluid. Further,
the separator 32 may also be configured to reduce a gas content of
the multiphase process fluid, thereby increasing the liquid portion
of the process fluid. Alternatively, the separator 32 may be
configured to remove a liquid portion of the process fluid to
direct a gas portion of the process fluid downstream via a conduit
34. As depicted, the conduit 34 may be routed to a downstream
device or unit, such as the production platform 12 or another
processing unit. The separator 32 may be configured to direct a
portion of the separated process fluid downstream via conduit 34
while directing another portion of the separated process fluid to a
conduit 36 which may be used to re-circulate the separated
multiphase process fluid.
[0022] In the depicted embodiment, the separated multiphase process
fluid directed through conduit 36 may be joined with process fluid
directed via conduit 38 from an end chamber of the screw pump
system 10. As depicted, the joining of flow from conduits 36 and
38, via a joint 39, may be routed to a chamber 40 for processing.
For example, chamber 40 may be used to cool the circulating
lubrication flow to be routed via a conduit 42 to an end chamber of
the twin screw pump 22. As depicted, the re-circulation flow of a
portion of the separated process fluid directed via conduit 36 is
used along with a flow directed via conduit 38 to re-circulate the
process fluid throughout the screw pump system 10 in order to
lubricate components within the system and reduce particulates
within the process fluid. As described in detail below, the
conduits and fluid circuits may be utilized to reduce settling of
particulates within the process fluid, thereby reducing downtime
and wear of the screw pump system 10 components. In addition,
conduit 44 may be used to circulate process fluid between the end
chambers of the twin screw pump 22, wherein the conduit 44 directs
a separated multiphase process fluid to lubricate pump bearings,
thereby insuring smooth operation of the twin screw pump 22.
[0023] FIG. 3 is a schematic diagram of the screw pump system 10
including conduits that are used for fluid communication between
portions of the screw pump system 10. Specifically, the
configuration, flow, pressure, processing and orientation of the
conduits and chambers within the screw pump system 10 enable the
system to be lubricated by the process fluid while reducing
particulates or contaminants within the process fluid to improve
the pumping operation. As illustrated, the twin screw pump 22
includes fluid intakes 28 which direct the process fluid flow 45 to
inlet chambers 46 and 48. The inlet chambers 46 and 48 are
configured to receive process fluid and are encompassed by rigid
structures or walls, such as bulkhead separators 50 and 52.
Further, an outlet chamber 54 is located between the inlet chambers
46 and 48. The outlet chamber 54 is separated from the inlet
chambers 46 and 48 by the bulkheads 50 and 52, which enable the
management of pressure within and between the respective chambers.
The outlet chamber 54 may be configured to direct the multiphase
process fluid out through the fluid outlet 30 as the process fluid
outflow 55 is directed to the separator 32. In addition, the inlet
chambers 46 and 48 may also surrounded by barriers such as upper
radial bearing flange 56 and lower radial bearing flange 58.
[0024] The barriers, including bearing flanges 56 and 58, as well
as bulkheads 50 and 52, enable the inlet chambers 46 and 48 to be
separated from the adjacent outlet and end chambers, thereby
enabling fluid flow and pressure management. As depicted, an upper
end chamber 60 may be coupled to the upper radial bearing flange
56. Similarly, a lower end chamber 62 is coupled to the lower
radial bearing flange 58. The end chambers 60 and 62 may each
contain pump bearings, to enable smooth rotation of the screws
within the twin screw pump 22. The pump bearings are lubricated by
re-circulated process fluid and conduits of the pump system 10. For
example, the upper end chamber 60 may include a first set of pump
bearings, wherein each bearing is coupled to the upper ends of each
of the rotor screws. Further, the lower end chamber 62 may contain
a second set of pump bearings coupled to the lower ends of the
rotor screws. The bearings may be any suitable bearings to
facilitate shaft rotation, such as journal bearings. For example,
journal bearings may support the rotor shaft where the shaft, also
known as a journal, may turn in a bearing with a layer of oil or
lubricant separating the two parts through fluid dynamic effects.
In an example, the lubricant used for the journal bearing may be
process fluid with reduced particulate matter.
[0025] The lower end chamber 62 may also include a pair of gears,
wherein each gear is coupled to an end of the rotor. The gears
transfer force and power from the driving rotor to the driven rotor
and may be referred to as timing gears. As will be described in
detail below, the gears may be utilized for crushing of
particulates within the process fluid as the process fluid flows
through the gears, thereby enabling the process fluid to be
suitable for lubrication of the pump bearings. After crushing of
the particulates within the process fluid, the process fluid may be
routed to lubricate the pump bearings within the end chambers 60
and 62. Thus, the gears serve not only to transfer mechanical
energy between the rotors, but to pump the lubricating fluid, and
to grind any particulate in the fluid to an acceptable size for
lubrication and wear avoidance. For example, the separated
multiphase process fluid may flow into the joint 39, wherein the
flow in conduit 38 joins the separated multiphase process fluid to
form a combined flow 42 into the lower end chamber 62. Upon flowing
into the lower end chamber 62, the entire portion of process fluid
may flow through the gears which are configured to crush the
particulates, thereby reducing the particulate size within the
process fluid. After crushing of the particulates, the multiphase
process fluid may be routed to lubricate the pump bearings within
the lower end chamber 62. Further, the process fluid, including the
crushed particulates, may also be routed via the conduit 44 to the
upper end chamber 60, wherein the process fluid is directed to the
pump bearings located within the upper end chamber 60. As the fluid
circulates throughout the upper end chamber 60, a portion of the
process fluid may be directed, via conduit 38, to join the
separated multiphase process fluid from conduit 36. Accordingly,
the joining of flows from conduits 36 and 38 may be considered a
makeup or re-circulation flow within the fluid communication
circuit.
[0026] In addition, barriers between the inlet chambers 46 and 48
may be configured to enable leaks 64 and 66, wherein the process
fluid may be configured to leak from the end chambers 60 and 62
into the inlet chambers 46 and 48. Specifically, leaks 64 and 66
are some of the portion of separated multiphase process fluid that
is utilized to lubricate the pump bearings and, therefore, may
include reduced size particulates as compared to the process fluid
flow entering the inlet chamber 45. Accordingly, the leaks 64 and
66 in the barriers may enable the process fluid with reduced
concentrations and size of particulates to improve flow within the
inlet chambers 46 and 48, along the rotor screws, and to the outlet
chamber 54. For example, the process fluid including reduced
particulates, may stir up or reduce a settling of particulates
within the incoming flow of process fluid 45 by mixing with, and
diluting, the increased particulate fluid 45entering the inlet.
Alternatively, in a configuration without leaks 64 and 66, the
incoming flow 45 of process fluid may include a large amount of
particulates that may settle within inlet chambers 46 and 48,
thereby impairing fluid flow between the inlet chambers 46 and 48
and outlet chamber 54. Further, the settling and/or buildup of
particulates within the inlet chambers may cause breakdowns or
require maintenance within the screw pump system 10. As may be
appreciated, the industrial environments where screw pumps may be
used emphasize a need for minimum downtime and maintenance.
Accordingly, the leaking of reduced particulate and particulate
size process fluid via leaks 64 and 66 improve process fluid flow
throughout the twin screw pump 22 while reducing maintenance.
Further, the makeup or compensation of process fluid via combined
flow 42 into the lower end chamber 62 may enable a steady flow or
compensation of fluid to account for the leaks 64 and 66 within the
fluid circuit.
[0027] The screw pump system 10 may also include a pressure reducer
68 configured to be a part of the fluid flow path from the
separator 32 to the end chamber 62. As illustrated, the pressure
reducer 68 may be coupled separator 32, wherein the pressure
reducer 68 enables a reduction of pressure as the fluid flows along
conduits 36 and 42 into the end chamber 62. Moreover, the pressures
within the twin screw pump 22 are managed to control fluid flow
within the circuit. For example, the pressure within the outlet
chamber 54, P.sub.1, may be significantly greater than the pressure
within the inlet chambers 46 and 48, P.sub.2. This increase in
pressure, from P.sub.2 and P.sub.1, is caused by the pumping action
of the twin screws. In addition, the pressure within the end
chambers 60 and 62, P.sub.3, may be slightly greater than the
pressure within the inlet chambers 46 and 48, P.sub.2. This
pressure difference between P.sub.3 and P.sub.2 may contribute to
leaks 64 and 66. The pressure P.sub.1 may be significantly greater
than the pressure P.sub.3, causing a need for the pressure reducer
68 to be located between the separator 32 and end chambers 60 and
62 within the fluid flow circuit. The pressure reducer 68 may be of
any suitable type, such as a recirculation valve, a fixed geometry
orifice plate, and so forth.
[0028] FIG. 4 is a detailed perspective view of an embodiment of
the twin screw pump 22. In the embodiment, the twin screw pump 22
includes upper end chamber 60 and lower end chamber 62. The driving
rotor shaft 24 is configured to enter the upper end chamber 60 to
drive the screw rotors. In addition, the upper end chamber 60 is
coupled to the upper radial bearing flange 56. Similarly, the lower
end chamber 62 is coupled to the lower radial bearing flange 58.
The bearing flanges 56 and 58 are each coupled to a central pump
casing cover 70 which may contain the inlet chambers 46 and 48, as
well as the outlet chamber 54. The inlet chambers 46 and 48 may be
coupled to fluid inlets 28 which route the multiphase process fluid
from the sub-sea well or other fluid supply unit. As will be
discussed in detail below, the fluid inlets 28 are tangentially
located with respect to the cylindrical central pump casing 70.
Accordingly, the fluid inlets 28 swirl the process fluid intake,
thereby agitating and mixing the particulates within the process
fluid to prevent settling and buildup of particulates in the inlet
chambers 46 and 48. The fluid outlet 30 is coupled to the outlet
chamber 54 and is configured to direct the process fluid to the
separator 32. Further, conduits, including conduits 36, 38, 42 and
44 may be configured to direct the process throughout the twin
screw pump 22 to lubricate the screw pump components and direct the
multiphase process fluid to a downstream unit.
[0029] FIG. 5 is a detailed exploded view of the twin screw pump
22. As depicted, the twin screw pump 22 contains end chambers 58
and 60, as well as a central pump casing cover 70. In addition,
gears 72 may be located inside a gear housing 74, which is located
within the lower end chamber 62. As previously discussed, the gears
72 may be configured to grind particulate matter as process fluid
flows through the gears to reduce the size of the particulates. A
gear plate 76 is located within the lower end chamber 62 and may be
coupled to the gear housing 74 and lower radial bearing flange 58.
Rotor shrouds 78 may be coupled to the lower radial bearing flange
58. The rotor shrouds 78 may be configured to allow rotor shafts to
rotate within the shrouds and enable a leak of process fluid from
the lower end chamber 62 to the inlet chamber. The rotor shrouds 78
may be of certain geometry with clearances to enable a controlled
leak to the inlet chamber 46. As will be discussed in detail below,
the upper chamber 60 may also include rotor shrouds to enable a
controlled leak to inlet chamber 48.
[0030] The drive shaft 24 may be coupled to a drive rotor 80 which
is configured to drive a driven rotor 82, wherein the rotors 80 and
82 are disposed within rotor shrouds 78 and are each coupled to the
gears 72. Accordingly, the driven rotor 82 is mechanically driven
by the rotation of the gears 72 which is initiated by the
rotational output from the driving rotor 80 and the shaft 24 that
is coupled to motor 26. The drive rotor 80 and driven rotor 82 may
be referred to as rotors, screws, threads or a combination thereof,
which are meshed together and rotate to drive a fluid through the
pump 22. In addition, the twin screw pump 22 includes a pump liner
84 within the central pump casing cover 70. The pump liner 84 may
be disposed around the rotors 80 and 82 and may flex to prevent
binding of the pump liner 84 to the screws during a pumping
process. In addition, the pump liner 84 is adjacent to and coupled
to the bulkhead 50 which separates the outlet chamber 54 and inlet
chambers 46 and 48. The pump liner 84 may include a slot 86 which
may be located within the inlet chamber 46 and/or 48 to enable the
process fluid to flow into the rotor threads, thereby enabling a
pumping. Further, the rotor liner 84 may also include slot 88 which
enables the pump to process fluid to flow out of the pump liner 84
to the outlet chamber 54 and through the fluid outlet 30. The
rotors 80 and 82 include shafts that pass the upper radial bearing
flange 56, thrust bearing plate 90 and collars 92. An upper thrust
bearing plate 94 may couple to the thrust bearing plate 90, thereby
encompassing the collars 92 and ends of the rotors 80 and 82.
Accordingly, the thrust bearing plate 90, collars 92 and thrust
bearing plate 94 may form an upper bearing set in the end chamber
60, which may be lubricated by the re-circulated process fluid.
[0031] FIG. 6 is a detailed side view of the embodiment of
components included in the twin screw pump 22. As depicted, the
rotors 80 and 82 may be coupled to gears 72 which may be located at
the ends of each of the rotor shafts. The gears 72 may be
configured to intermesh, thereby driving the driven rotor 82 by a
rotational and mechanical output of the drive rotor 80. Further,
the gears 72 are configured to reduce particulate matter and
process fluid and pump the process fluid throughout the twin screw
pump 22. As the process fluid is pumped throughout the twin screw
pump 22, the process fluid may leak through an upper rotor shroud
96 as well as the lower rotor shroud 78. Accordingly, the process
fluid that leaks through rotor shrouds 78 and 96 may include
reduced particulate content and size, thereby enabling the leaked
process fluid to stir up and reduce a settling of particulates
within the inlet chambers 46 and 48. As previously discussed, the
screw pump system 10 may be configured to direct process fluid to
enable a lubrication of components, including pump bearings, and to
enable the process fluid to enhance process fluid flow by reducing
particulate size in re-circulated process fluid. Further, the
re-circulated process fluid, including fluid directed by the
conduit 42 may be utilized to make up or compensate for the leaks
of process fluid into the inlet chambers 46 and 48. Alternatively,
other mechanisms may be used to leak the process fluid from end
chambers 60 and 62 into the central pump casing cover 70. For
example, one-way valves that are opened via pressure differentials
and/or conduits may be utilized to direct or leak process fluid to
chambers within the central pump casing cover 70. As such, the
fluid entering pump casing cover 70 is configured to stir up or
agitate fluid entering the pump, thereby reducing a settling of
particulates.
[0032] FIG. 7 is a detailed perspective view of an embodiment of
components included in the twin screw pump 22. As depicted, drive
rotor 80 and driven rotor 82 are intermeshing, where threads
disposed on rotor shafts interlock to drive a process fluid from
the inlet chambers 46 and 48 near the peripheral portions of the
rotors to an outlet chamber 54, located near the center of the
rotors. In addition, gears 72 are each coupled to an end of rotors
80 and 82 to crush particulates and time the rotation of the
rotors. The gears 72 are configured to crush or grind particulates
within the process fluid, thereby enabling the process fluid to
lubricate bearings that are coupled to each end of the rotors 80
and 82. As depicted, the pump bearings are configured to support
and enable rotation of the rotors 80 and 82, thereby enabling the
process fluid to flow smoothly through the screw pump system 10. In
an embodiment, the gears 72 may be comprised of a suitable durable
material. For example, the gears 72 may be comprised of cemented
carbide, such as a cemented tungsten carbide, wherein the gears 72
are formed and configured to grind particulate matters within the
process fluid without erosion or destruction of the gears 72 during
a grinding process. The teeth of each of the gears 72 may contact
one another where two teeth from each gear are in contact, causing
a high stress contact to crush particulates in the process fluid,
Additionally, the gears 72 may be straight gears or another
suitable geometry.
[0033] The twin screw pump 22 also includes the rotor shroud 96
which may be coupled to an end of the rotors 80 and 82 and may be
configured to enable a leak of reduced particulate process fluid
into the inlet chambers 46 and 48. After the gears 72 have crushed
particulates within the process fluid, the gears may be configured
to pump the process fluid to lubricate pump bearings, wherein the
process fluid is then leaked via rotor shrouds 78 and 96 into the
inlet chambers 46 and 48, thereby reducing a settling of
particulates to improve a flow of process fluid.
[0034] FIG. 8 is a detailed end view of an example of the rotor
shrouds 72 and 96. Rotor shrouds 72 and 96 are identical in
structure and design and may each be placed on an end of rotors 80
and 82. Further, rotor shrouds 72 and 96 may be composed of two
separate components joining at a joint 98, or may be composed of a
single component wherein the two circular structures are part of a
single overall member which may be cast or formed by any suitable
means. Further the rotor shrouds 72 and 96 may be composed of any
durable material, such as stainless steel. The rotor shrouds 72 and
96 including a pair of cylindrical openings 100, which are
configured to enable each of the rotor shafts to pass through the
shrouds. Accordingly, the openings 100 are configured to enable
fluid communication between end chambers 60 and 62 and the chambers
within central pump casing cover 70. The leaking of process fluid
from end chambers 60 and 62 may be controlled by tolerances and
spacing between components, as well as managing the pressures
within the system. The rotor shrouds 72 and 96 may also include
flanges 102 which are used to attach the rotor shrouds to the
bearing flanges 56 and 58. The rotor shrouds 72 and 96 may be
coupled via screws, welds, or other suitable coupling mechanisms to
the radial bearing flanges 56 and 58.
[0035] FIG. 9 is a side view of the rotor shrouds 72 and 96. The
rotor shrouds 72 and 96 include protruding portions 104 that
protrude into inlet chambers 46 and 48 of the twin screw pump 22.
In addition, the rotor shrouds 72 and 96 also include protruding
portions 106 which protrude into the radial bearing flanges 56 and
58, thereby enabling the flanges 102 to be coupled to an interior
surface of the radial bearing flanges. The protruding portions 104
may have a diameter 108 of approximately 14.5 inches (36.8 cm).
Further, the protruding portions 106 may have a diameter distance
110 of approximately 14.25 inches (36.2 cm). The shroud openings
may have an inner diameter distance of 112 of approximately 11
inches (27.9 cm). It should be understood, however, that other
dimensions and dimensional relationships may be used. As depicted,
the rotor shrouds 72 and 96 may be configured to enable a leaking
of process fluid, with a reduced particulate size and content, into
chambers within the pump casing 70 to dilute particulates from
incoming process fluid and reduce a settling of particulates within
the inlet chambers 46 and 48.
[0036] FIG. 10 is a schematic diagram of an example of the twin
screw pump 22, including inlets located on inlet chambers 46 and
48. The inlets 28 (also shown in FIG. 4) are configured to direct a
process fluid inlet flow 45 that is tangential in relation to inlet
chambers 46 and 48. Accordingly, a tangential location 114 within
the cylindrical inlet chambers 46 and 48 enables the process fluid
to swirl about the chambers, as shown by flow patterns 116. As
depicted, the flow patterns 116 swirl around a central axis 118 and
the inlet chambers 46 and 48, thereby agitating particulates within
the process fluid to improve fluid flow and reduce a settling of
particulates within the pump chambers. By improving the process
fluid flow and reducing particulate settling, the tangential inlet
locations 114 reduce wear and tear and improve efficiency in
pumping performance of the twin screw pump 22. Accordingly, the
process fluid flows through rotors 80 and 82 as the rotors turn,
thereby pumping the process fluid from inlet chambers 46 and 48 to
outlet chamber 54 and out of the chambers as shown by outlet flow
30.
[0037] FIG. 11 is a top view of the schematic diagram shown in FIG.
10. As depicted, the tangential location 114 of the process fluid
inlet flow 45 enables a swirling flow 116 about axis 118. The
improved flow characteristics and reduce settling provided by the
tangential inlet of the inlet flow 45 enables an improved flow of
process fluid throughout the screw pump system 10.
[0038] Technical effects of the invention include reduced wear and
maintenance of screw pump components. Further, the embodiments also
lead to simplified assembly and maintenance of screw pump systems
by eliminating dedicated lubrication systems and components.
Moreover, the disclosed embodiments may improve system performance
by managing the pressures through the system to control fluid
flow.
[0039] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
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