U.S. patent application number 14/239989 was filed with the patent office on 2014-07-24 for dual motor pump for subsea application.
This patent application is currently assigned to FRAMO ENGINEERING AS. The applicant listed for this patent is Helge Dale. Invention is credited to Helge Dale.
Application Number | 20140205475 14/239989 |
Document ID | / |
Family ID | 44800796 |
Filed Date | 2014-07-24 |
United States Patent
Application |
20140205475 |
Kind Code |
A1 |
Dale; Helge |
July 24, 2014 |
DUAL MOTOR PUMP FOR SUBSEA APPLICATION
Abstract
An apparatus includes a pump having a pump drive shaft for
operating the pump, a first motor connected via a first flexible
coupling to drive one end of the shaft and a second motor connected
via a second flexible coupling to drive the opposite end of the
shaft. The apparatus also includes a variable speed drive
connecting each of the first and second motors electrically to
drive the pump drive shaft.
Inventors: |
Dale; Helge; (Bergen,
NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dale; Helge |
Bergen |
|
NO |
|
|
Assignee: |
FRAMO ENGINEERING AS
Bergen
NO
|
Family ID: |
44800796 |
Appl. No.: |
14/239989 |
Filed: |
August 16, 2012 |
PCT Filed: |
August 16, 2012 |
PCT NO: |
PCT/EP2012/066043 |
371 Date: |
April 1, 2014 |
Current U.S.
Class: |
417/351 |
Current CPC
Class: |
H02K 7/14 20130101; H02K
5/132 20130101; H02K 16/00 20130101; F04D 13/086 20130101; F04D
13/08 20130101; H02K 9/19 20130101 |
Class at
Publication: |
417/351 |
International
Class: |
F04D 13/08 20060101
F04D013/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 23, 2011 |
GB |
1114594.3 |
Claims
1. An apparatus comprising: a pump having a pump drive shaft for
operating the pump, a first motor connected via a first flexible
coupling to drive one end of the shaft and a second motor connected
via a second flexible coupling to drive the opposite end of the
shaft; and a variable speed drive connecting each of the first and
second motors electrically to drive the pump drive shaft.
2. The apparatus according to claim 1 wherein the variable speed
drive is common to the first and the second motor.
3. The apparatus according to claim 1 wherein at least the first
motor comprises an induction motor.
4. The apparatus according to claim 1 wherein the first and the
second motors comprise induction motors.
5. The apparatus according to claim 1 wherein at least the first
motor comprises a permanent magnet motor.
6. The apparatus according to claim 1 wherein both the first and
second motors comprise a permanent magnet motor.
7. The apparatus according to claim 1 wherein at least the first
motor is liquid cooled.
8. The apparatus according to claim 7 wherein the first motor is
liquid cooled by a barrier fluid moving in a single circuit.
9. The apparatus according to claim 7 wherein the first motor
comprises a stator canning comprising a mechanical sleeve and a
stator barrier fluid.
10. The apparatus according to claim 9 wherein the motor barrier
fluid moves in a double circuit.
11. The apparatus according to claim 1 wherein the flexible
couplings are adapted to allow axial expansion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a 35 U.S.C. .sctn.371 national stage
application of PCT/EP2012/066043 filed Aug. 16, 2012 and entitled
"Dual Motor Pump for Subsea Application," which claims priority to
GB Application No. 1114594.3 filed Aug. 23, 2011 and entitled
"Apparatus," both of which are incorporated herein by reference in
their entirety for all purposes.
FIELD OF THE INVENTION
[0002] The present disclosure relates to a pump primarily for use
in subsea applications, particularly in the oil and gas
industry.
BACKGROUND
[0003] Exploration for oil and gas reserves below the sea bed is
becoming more important as stocks of more accessible natural
resources dwindle and it becomes necessary to explore deeper and
more difficult areas. Extreme depths and longer distances require
higher capacity pumping apparatus which must also be robust and
able to withstand the high pressures prevalent under the sea, and
the difficult conditions encountered at significant depths of salt
water. In recent years there has been a trend towards using larger
pumps which require larger and stronger electrical motors but there
is a limitation on how far this technology can be extended. In
addition, any new technology in this field must be extensively
tested and must pass qualification regimes which are time consuming
and thus result in delays in putting the technology into effect in
the field. They also take up considerable personnel resources and
are thus expensive.
SUMMARY
[0004] According to the present disclosure there is provided
apparatus comprising a pump having a pump drive shaft for operating
the pump, a first motor connected via a first flexible coupling to
drive one end of the shaft and a second motor connected via a
second flexible coupling to drive the opposite end of the shaft,
and a variable speed drive connecting each of the first and second
motors electrically to drive to the pump drive shaft.
[0005] Preferably the variable speed drive is common to the first
and the second motor. Electrical conductors for the motors can be
cited in an umbilical cord which can be common for both motors.
[0006] The flexible couplings are preferably adapted to allow axial
thermal expansion without affecting the operation of the pump.
[0007] The disclosure can provide a higher capacity pump unit using
proven technology. This makes the pump more acceptable in the
industry and more cost effective to implement because it can be put
into use without the delay and cost of undergoing complex
regulatory qualification processes. In addition the reliability of
the pump is likely to be higher compared to a revolutionary new
pump because tried and tested components are used. It also has the
advantage of that, if one motor should fail, the other will still
drive the pump albeit at reduced capacity.
BRIEF DESCRIPTION OF DRAWING
[0008] For a better understanding of the present disclosure, and to
show how the same may be carried into effect, reference will now be
made to the accompanying drawing, in which:
[0009] FIG. 1 is a schematic cross section of a pump according to
the present disclosure.
DETAILED DESCRIPTION
[0010] A pump 1 comprises a pump shaft 2 which drives impellers 3.
Fluid to be pumped enters the impeller section 3 via inlet 17 and
exits via outlet 18. The pump 1 is contained within a pump housing
4. The pump shaft 2 is mounted for axial rotation on bearing
assemblies 5 and 6 located at opposed ends of the pump shaft 2.
[0011] A first electric motor 7 drives a first motor shaft 27 which
is connected to one end of the pump shaft 2 via a first subsea
motor coupling 8. The coupling is flexible and protected by a seal
9. A second electric motor 10 drives a second motor shaft 28 which
is connected to the other end of the pump shaft 2 by a second
flexible coupling 11 protected by a seal 12. The flexible couplings
8, 11 transfer torque from the respective shafts to the pump shaft
2 but allow longitudinal movement to allow for thermal expansion.
Suitable flexible couplings may be achieved in many known ways. One
example is to use an outer collar connected to one shaft by lock
rings and to the other shaft by gear teeth which allow an axial
sliding movement.
[0012] The motors 7 and 10 each comprise a stator 31 and a rotor 32
attached to the respective shaft 27 and 28.
[0013] The electric motors 7 and 10 may be induction motors or
permanent magnet motors. They are preferably liquid cooled by a
barrier fluid moving in either a single circuit or a double circuit
(canned). The barrier fluid protects the motors both from the
pumped process fluid and the hostile surrounding environment which
will typically be high pressure sea water. The barrier fluid
isolates the motors preventing intrusion of sea water and
preventing contamination from the pumping fluid. It also provides
lubrication for the motors and provides cooling by transporting
heat away from the moving motor parts, e.g. the bearings. To
achieve this, the barrier fluid circulates in a closed circuit
around the moving parts of the motor and the bearings and then the
barrier fluid itself is cooled as it passes through pipes 30 around
which sea water can circulate. The barrier fluid then passes back
around the moving motor parts again. The circulation of the barrier
fluid is achieved using an internal circulation (impeller) pump.
The barrier fluid also helps seal the dynamic seals in the motors
and pump. These dynamic seals have one stationary part and one
rotating part and the barrier fluid is kept at a pressure slightly
higher than the pressure of the process fluid being pumped so that
a small amount of leakage of barrier fluid occurs into the process
fluid. This prevents damage to the motors or pump by ingression of
process fluid. It requires a constant supply of barrier fluid to
the pump which is usually supplied via an umbilical from the
surface.
[0014] The barrier fluid may be circulated in a double circuit if
the motor contains a stator canning. Although not shown, this is a
mechanical sleeve between the stator and the rotor which allows a
separate stator fluid to be used and isolates the stator from the
barrier fluid. The magnetic flux passes through the stator canning
but the stator fluid will not pass through. A typical double
circuit solution is described in WO 2008/127119. It allows the
motor-pump arrangement to be more environmentally friendly since it
allows more flexibility in the choice of barrier fluid and a
specific stator fluid can be chosen to provide more dielectric
properties for the stator, i.e. provide insulation for the stator.
The stator fluid will also be cooled in a separate cooling circuit.
A separate stator fluid circuit also isolates the motor better
since it prevents any contamination through the umbilical.
[0015] The shaft 27 of the first motor 7 rotates in the opposite
direction to the shaft 28 of the second motor 10.
[0016] Power is supplied to the first motor 7 by power conductor
line 13 via electrical connector 14, and to the second motor 10 by
power conductor line 15 via electrical connector 16. A common power
supply (not shown) may be used to supply power to both motors 7 and
10 and the power cables are preferably contained in an
umbilical.
[0017] A variable speed drive may be used to control and change the
frequency of the power supply so as to manage the speed of the
pump, i.e. the number of revolutions of the pump shaft per minute.
The variable speed drive may be situated topside or subsea and may
be separate for each motor or common.
[0018] The first and second motor couplings 8 and 11 transfer
torque from the respective motors to the pump shaft 2. Their
flexibility is such as to allow axial expansion and contraction due
to thermal changes and to accommodate different running
characteristics of the two motors.
* * * * *