U.S. patent application number 15/575974 was filed with the patent office on 2018-05-31 for subsea motor-compressor unit.
The applicant listed for this patent is Nuovo Pignone Tecnologie SRL. Invention is credited to Manuele BIGI, Francesco BONGINI, Luciano MEI, Giacomo RAGNI.
Application Number | 20180149159 15/575974 |
Document ID | / |
Family ID | 53765433 |
Filed Date | 2018-05-31 |
United States Patent
Application |
20180149159 |
Kind Code |
A1 |
RAGNI; Giacomo ; et
al. |
May 31, 2018 |
SUBSEA MOTOR-COMPRESSOR UNIT
Abstract
The present invention concerns a motor-compressor unit,
particularly a subsea motor-compressor unit comprising, housed in a
single casing, a compressor and a motor, further comprising, inside
said casing, a washing apparatus connectable to an external source
of a washing agent for selectively washing specific target areas of
said motor-compressor unit.
Inventors: |
RAGNI; Giacomo; (Florence,
IT) ; BIGI; Manuele; (Florence, IT) ; BONGINI;
Francesco; (Florence, IT) ; MEI; Luciano;
(FLorence, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nuovo Pignone Tecnologie SRL |
Florence |
|
IT |
|
|
Family ID: |
53765433 |
Appl. No.: |
15/575974 |
Filed: |
May 18, 2016 |
PCT Filed: |
May 18, 2016 |
PCT NO: |
PCT/EP2016/061122 |
371 Date: |
November 21, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/059 20130101;
F04D 13/086 20130101; F04D 29/703 20130101; F04D 29/5806 20130101;
F04D 25/0686 20130101; F04D 29/705 20130101 |
International
Class: |
F04D 25/06 20060101
F04D025/06; F04D 29/059 20060101 F04D029/059; F04D 29/70 20060101
F04D029/70; F04D 29/58 20060101 F04D029/58 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 2015 |
IT |
102015000016978 |
Claims
1. A motor-compressor unit comprising, housed in a single casing, a
compressor and a motor, further comprising, inside said casing, a
washing apparatus connectable to an external source of a washing
agent for selectively washing specific areas of said
motor-compressor unit; the washing apparatus comprising: at least a
washing device for selectively washing a specific area of said
unit; at least a delivery duct for delivering a washing agent to an
area of said unit to be washed; and at least a spray nozzle
hydraulically connected to the end of a respective delivery duct
facing the area to be washed; the spray nozzle being completely
contained inside the casing.
2. The motor-compressor unit according to claim 1, wherein said
motor compressor unit further comprises a fan to circulate the
process gas through the motor, and wherein said washing apparatus
comprises a first dedicated washing device for washing said fan
comprising a first dedicated delivery duct for delivering a washing
agent to said fan.
3. The motor-compressor unit according to claim 1, wherein said
motor compressor unit further comprises a shaft to which said
compressor and said motor are coupled and one or more auxiliary
bearings for supporting said shaft, and wherein said washing
apparatus comprises one dedicated washing device for washing each
of said auxiliary bearings.
4. The motor-compressor unit according to claim 3, wherein said
motor compressor unit comprises a first auxiliary bearing and
wherein said washing apparatus comprises a second dedicated washing
device comprising a second dedicated delivery duct for delivering a
washing agent to said first auxiliary bearing.
5. The motor-compressor unit according to claim 3, wherein said
motor compressor unit comprises a second auxiliary bearing and
wherein said washing apparatus comprises a third dedicated washing
device comprising a third dedicated delivery duct for delivering a
washing agent to said second auxiliary bearing.
6. The motor-compressor unit according to claim 3, wherein said
motor compressor unit comprises a third auxiliary bearing, and
wherein said washing apparatus comprises a fourth dedicated washing
device comprising a fourth dedicated delivery duct for delivering a
washing agent to said third auxiliary bearing.
7. The motor-compressor unit according to claim 3, wherein each of
said washing devices for washing said auxiliary bearings comprises
a circumferential channel provided in the casing for delivering the
washing agent to said auxiliary bearings along their whole external
circumference.
8. The motor-compressor unit according to claim 7, wherein each of
said circumferential channel further comprises a plurality of spray
nozzles spaced along said circumferential channel.
9. The motor-compressor unit according to claim 1, wherein said
motor compressor unit further comprises at a least a thrust bearing
for supporting axial thrusts acting said shaft, and wherein said
washing apparatus comprises a fifth dedicated washing device
comprising a fifth dedicated delivery duct for delivering a washing
agent to said thrust bearing.
10. The motor-compressor unit according to claim 1, wherein said
washing apparatus comprises a sixth dedicated washing device
comprising a sixth dedicated delivery duct for delivering a washing
agent to the motor upper surface of the motor.
11. The motor-compressor unit according to claim 1, wherein said
motor compressor unit further comprises an intermediate diaphragm
and a collection sump for collecting the liquids possibly entered
into the unit, and wherein said washing apparatus comprises a
seventh dedicated washing device comprising a seventh dedicated
delivery duct for delivering a washing agent to said intermediate
diaphragm, to said compressor and to said collection sump.
12. The motor-compressor unit according to claim 1, wherein said
delivery ducts of said washing apparatus are hydraulically
connected to inlet points provided on the casing.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a subsea motor-compressor
unit for processing a working fluid. The subsea motor-compressor
unit according to the present invention comprises, integrated in a
housing, a motor and a compressor.
[0002] In extraction plants for extracting natural gas from a
subsea field, submersible integrated motor-compressor units are
usually placed directly on the seabed.
[0003] Generally a subsea motor-compression unit comprises a
centrifugal compressor pushing the extracted natural gas to the
mainland, the compressor being arranged in a housing together with
a motor, usually consisting of an electric motor.
[0004] The compressor of the motor-compressor unit could be fluidly
connected with an external separator machine placed between the
well and the inlet of the unit.
[0005] The subsea motor-compressor unit usually has a vertical
configuration having a vertical shaft on which are arranged both
the rotor of the electric motor and the centrifugal impellers of
the compressor, the shaft is supported by a plurality of magnetic
bearings, comprising radial bearings and axial thrust bearings. To
each bearing is further associated an auxiliary bearing.
[0006] With the vertical configuration the drainage is due to the
gravity and the footprint is minimized.
[0007] A main drawback of the motor-compressor units of the known
type usually used in subsea installations, is represented by the
fact that due to the wet droplets contained in the gas processed by
the unit it is possible to have fouling formation both at start and
during operation of the motor compressor.
[0008] Fouling formations are dangerous because may cause
performance degradation of the motor-compressor unit and or failure
of the motor. A week point of the motor-compressor unit is
represented by the bearings, both the radial and thrust bearings
and the auxiliary bearings, particularly interested by fouling
formation as it will be explained more in details in the
following.
[0009] As it has been said, motor-compressor units used in subsea
environments in the production or transport of hydrocarbons are
provided with a shared rotating shaft supported by a rotor-bearing
system. The motor drives the compressor in order to generate a flow
of compressed process gas. As the motor drives the compressor, heat
is generated.
[0010] In case of electric motor, heat is also generated by the
electrical systems that are characteristic of electric motor
drivers. Heat is also generated through the windage friction
resulting from the rotating components operating in pressurized
gas.
[0011] If this heat is not properly dissipated, it negatively
affects the performance of the motor and can damage the insulation
of the stator. Increased temperatures can also adversely affect the
rotor-bearing systems of both the compressor and motor, thus
leading to bearing damage and/or failure.
[0012] For cooling the motor and bearings in a subsea
motor-compressor unit, is provided a cooling circuit which may be
an open loop cooling circuit or a quasi-closed-loop cooling circuit
where gas is drawn from the process stream at some point in the
compression process.
[0013] Only a small amount of process gas is fed into the cooling
circuit from the process stream. The quasi-closed-loop cooling
circuit often uses a small blower to circulate the cooling gas
through the cooling circuit. In subsea applications, the cooling
gas is typically cooled in a sea water-cooled heat exchanger.
[0014] This process gas is then passed through the motor and
bearing areas to absorb heat.
[0015] Unfortunately, notwithstanding the small amount of process
gas used, there is a significant drawback with the cooling circuit
approach to subsea motor-compressor cooling: the presence of wet
droplets and/or of heavy hydrocarbons even in the gaseous state in
the process gas leads to fouling formation at start up and during
the operation of the motor-compressor unit, especially but not only
at the areas where the gas flow is slow and/or at stationary
parts.
[0016] The fouling formation, in contact with hot parts of the
unit, became solid or semi-solid, or very viscous, and particles
stick to both static and rotating parts of the compressor flow
path, adversely affecting the aerodynamic form leading to a
decrease in mass flow, efficiency, pressure ratio and surge margin.
This implies an increase in the required electrical power in order
to maintain a constant production/delivery rate.
[0017] Additionally, the bearings, and especially auxiliary
bearings of the motor-compressor shaft, are affected by fouling
formation. In fact, each auxiliary bearing usually comprises a
rolling bearing or a plain bearing which works in case that the
magnetic bearing stops working.
[0018] One example of known cleaning apparatus for subsea
compressor units is disclosed in EP1907705B1, wherein a system for
cleaning compressors that are situated at a difficulty accessible
location, e.g., on or near the seabed or downhole in a well bore,
comprises a cleaning liquid line extending between a readily
accessible liquid source and the compressor.
[0019] The prior art document fails to teach how to clean the motor
of a motor-compressor unit.
[0020] In EP1907705B1 the liquid source may be a line for supplying
hydrate inhibitor, anti-foam chemicals, barrier liquid, demulsifier
or other types of chemicals to a subsea production or processing
activity.
[0021] Alternatively, the liquid source can be an accumulator tank
situated in the vicinity of the compressor. In this case, the
accumulator tank is in communication with a high pressure line
diverting high pressurized gas from the compressor to boost the
pressure of the cleaning liquid in the accumulator tank and
evacuate the cleaning liquid.
[0022] The compressor often comprises more than one compressor
stage. The liquid is more particularly injected in the intake
flange of the compressor. The washing liquid will flow through the
compressor and knock loose particles that have adhered internally
in the flow path.
[0023] The washing liquid leaves the compressor via the compressed
gas line and can be carried with the gas to a subsequent station
for separating the washing liquid from the gas.
[0024] The injected inhibitor liquid must be injected in the intake
flange of the compressor as well as the washing liquid.
SUMMARY
[0025] Embodiments of the present invention relates to a subsea
motor-compressor unit for processing a working fluid comprising a
washing apparatus.
[0026] According to an embodiment of the present invention, a
motor-compressor unit for processing working fluid comprises,
integrated in a single unit housed in a case, a motor and a
compressor, and a washing apparatus.
[0027] According to a first aspect of the invention, the integrated
motor-compressor unit comprises a washing apparatus for selectively
washing during operation both the motor and the compressor.
[0028] Additionally, according to a further aspect of the present
invention, the integrated motor-compressor unit is provided with a
washing apparatus for selectively washing thrust bearings and
auxiliary bearings of both the motor and the compressor.
[0029] In an embodiment, the washing of the motor-compressor unit
is performed by means of a washing liquid, more particularly MEG
(monoethylene-glycol).
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Further details and specific embodiments will refer to the
attached drawing, in which:
[0031] FIG. 1 is a sectioned side schematic view of a typical
integrated motor-compressor unit for subsea installation;
[0032] FIG. 2 is a section side schematic view of a detail of the
washing apparatus, the detail is referred to the motor area;
[0033] Figures from 3 to 5 are enlarged section side schematic
views of the washing apparatus of FIG. 2.
DETAILED DESCRIPTION
[0034] The following description of an exemplary embodiment refers
to the accompanying drawings. The following detailed description
does not limit the invention. Instead, the scope of the invention
is defined by the appended claims.
[0035] Reference throughout the specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with an embodiment is
included in at least one embodiment of the subject matter
disclosed. Thus, the appearance of the phrases "in one embodiment"
or "in an embodiment" in various point of the specification is not
necessarily referring to the same embodiment. Further, the
particular features, structures or characteristics may be combined
in any suitable manner in one or more embodiments.
[0036] With reference to FIG. 1, it is shown an integrated
motor-compressor unit 10 comprising a compressor 20 and a motor 30,
more particularity an electric motor, directly connected to said
compressor 20, which are integrated in a single unit.
[0037] The motor-compressor unit 10 comprises a box or casing 50 in
which said compressor 20 and said electric motor 30 are housed. The
casing 50 may be realized in a single piece or, alternatively, it
may comprise multiple parts.
[0038] Said compressor 20 and said electric motor 30 are separated
by an intermediate diaphragm 40 thus avoiding that process gas
comprising solid and/or liquid particles could pass from the
compressor into the motor area.
[0039] Said motor 30 and said compressor 20 are both coupled to the
same axial shaft 60. Alternatively, said compressor 20 could be
coupled to a first shaft portion and said motor 30, particularly
the rotor of said motor, could be coupled to a second shaft
portion, the two shaft portions being connected by means of a
joint.
[0040] Due to the fact that said compressor 20 and said motor 30
are coupled to the same shaft 60, or to a plurality of shaft
portions joined together, the motor 30 unit and the compressor 20
unit are not separated, and the process gas processed by the
compressor passes through both.
[0041] The process gas is also used for cooling the motor in the
cooling system: for cooling the motor and bearings in the subsea
motor-compressor unit, is provided a closed-loop cooling circuit
where gas is drawn from the process stream.
[0042] Due to the presence of wet droplets in the process gas, both
the compressor 20 and the motor 30 are subject to fouling
formations, both at start up and during operation of the
motor-compressor unit.
[0043] Additionally, the motor-compressor unit 10 comprises three
magnetic radial bearings and a magnetic axial thrust bearing, each
one of said bearings having an auxiliary bearing. More in details,
with reference to FIG. 1, an example of motor-compressor unit 10
may comprise three auxiliary bearings 61, 62, 63 for supporting
both a rotor of the electric motor 30 and a rotor of the compressor
20.
[0044] Each magnetic radial bearing can also support axial thrusts,
depending on the way they are mounted. Therefore, for example, one
or more of said three auxiliary bearing can work also as an axial
bearing contrasting axial thrusts.
[0045] In an embodiment said auxiliary bearings 61, 62, 63 are
rolling bearing or plain bearing which works in case that the
magnetic bearing to which the auxiliary bearing is associated stops
working.
[0046] A first bearing 61 and a second bearing 62 of said three
auxiliary bearings are positioned and support said shaft 60 of said
electric motor 30 close to its ends.
[0047] A third bearing 63 of said three auxiliary bearings supports
and is positioned on a free end of said rotor of said compressor
20.
[0048] In this configuration, the number of auxiliary bearings for
supporting the electric motor 30 and compressor 20 is reduced to
the minimum possible, as three supporting bearings are used.
[0049] Said motor-compressor unit 10 comprises a further thrust
bearing 64, an active magnetic thrust bearing suitable for
supporting axial thrusts, situated on said rotor of said electric
motor 30.
[0050] The cooling of the motor-compressor unit is effected by
means of a quasi-closed circuit, not shown in the figures, equipped
with an external exchanger and a fan 70 situated inside the unit at
the end of the rotor of said electric motor 30, to circulate the
cooling gas through the stator and rotor parts.
[0051] The auxiliary bearings 61, 62 of the motor side and the
thrust bearing 64 are cooled by the same gas which is circulating
in the motor, by means of the system and the fan 70.
[0052] For the third auxiliary bearing 63 of the compressor side,
the cooling is guaranteed by means of a gas discharge from the
compressor sent to the third auxiliary bearing 63 through a
dedicated channel.
[0053] Due to the fact that process gas is used for cooling the
bearings, the same are particularly subject to fouling
formations.
[0054] Each auxiliary bearing 61, 62, 63 usually comprises a
bearing rolling bearing or plain bearing which works in case that
the rolling bearing stops working.
[0055] The auxiliary bearings are stationary during the normal
operation of the motor-compressor unit, and therefore are
particularly subject to fouling formations.
[0056] A collection sump 100 is further provided at the end of the
compressor rotor of the compressor 30, within the casing 50. The
collection sump 100 is suitable to collect completely the liquid
possibly entered inside the motor-compressor unit 10 during the
subsea installation and the liquid still present in the unit during
the operation.
[0057] A drainage system is provided inside the motor-compressor
unit 10 in order to drain liquids from both the motor and the
compressor to the collection sump 100.
[0058] The configuration of said motor-compressor unit 10 can be
either horizontal or vertical depending on the particular
installation demands.
[0059] When the configuration is vertical, with the compressor at
the bottom, the collection sump 100 is provided inside the casing
50 and under the compressor 30.
[0060] According to an embodiment of the present invention shown in
Figures from 2 to 5, said motor-compressor unit 10 further
comprises, provided inside the motor-compressor unit 10, a washing
apparatus, generally indicated with the reference number 80 in the
attached figures, said washing apparatus comprising one or more
washing devices for selectively washing specific areas of said unit
10.
[0061] More in details, each of said washing devices for
selectively washing specific areas of said unit 10, in turn
comprise at least a dedicated delivery duct 81, 82, 83, 84, 85, 86,
87, 88, 89, 90 for delivering a washing agent to a target area of
said unit 10 to be washed.
[0062] In an embodiment, each delivery duct 81, 82, 83, 84, 85, 86,
87, 88, 89, 90 comprises a spray nozzle hydraulically connected to
the end of the delivery duct facing the target area to be washed.
The spray nozzles are not shown in the drawings.
[0063] The washing apparatus 80 is connectable to an external
source of a washing agent.
[0064] Said washing agent is a pressurized washing fluid, more
particularly the washing fluid is MEG (monoethylene glycol).
[0065] In an embodiment, said washing apparatus 80 comprises at
least one of the following dedicated washing devices: a first
dedicated washing device for washing the fan 70 comprising a first
dedicated delivery duct 81 for delivering a washing agent to said
fan 70; a second dedicated washing device for washing the first
auxiliary bearing 61 comprising a second dedicated delivery duct 82
for delivering a washing agent to said first auxiliary bearing 61;
a third dedicated washing device for washing the second auxiliary
bearing 62 comprising a third dedicated delivery duct 85 for
delivering a washing agent to said second auxiliary bearing 62; a
fourth dedicated washing device for washing the third auxiliary
bearing 63 comprising a fourth dedicated delivery duct 86 for
delivering a washing agent to said third auxiliary bearing 63; a
fifth dedicated washing device for washing the thrust bearing 64
comprising a fifth dedicated delivery duct 83 for delivering a
washing agent to said thrust bearing 64; a sixth dedicated washing
device for washing the motor comprising a sixth dedicated delivery
duct 84 for delivering a washing agent to the motor 30, to the
upper motor surface 31; a seventh dedicated washing device for
washing the intermediate diaphragm 40, comprising a seventh
dedicated delivery duct 87 for delivering a washing agent to said
intermediate diaphragm 40; an eight dedicated washing device for
washing the compressor 20 the compressor 20 and the collection sump
100, comprising an eight dedicated delivery duct 88 for delivering
a washing agent to said compressor 20 and to said collection sump
100; said eight dedicated washing device further comprising
additional dedicated ducts 89, 90 for delivering a washing agent to
specific areas of said compressor 20.
[0066] According to an embodiment of the present invention shown in
the attached Figures, the washing apparatus 80 is contained inside
the motor-compressor unit 10. More in details, the washing devices
comprises a duct and a spray nozzle facing the target area to be
washed which are completely contained inside the casing 50.
[0067] The casing 50 has a substantially cylindrical shape.
[0068] When the casing has a substantially cylindrical shape, each
of the ducts for delivering a washing agent to the auxiliary
bearings 61, 62, 63 further comprises a circumferential channel
provided in the casing 50 all around the circumference. Thanks to
the circumferential channel the washing agent could be delivered to
the corresponding auxiliary bearing 61, 62, 63 along their whole
external circumference through a plurality of spray nozzles, spaced
along said circumferential channel.
[0069] The washing agent is a washing liquid.
[0070] More particularly the washing agent comprises MEG
(monoethylene glycol), which is usually available in subsea
boosting stations for other uses.
[0071] Otherwise, the washing agent could be any other washing
agent suitable to remove the fouling formations.
[0072] The washing agent is injected into the washing apparatus 80
through inlet points 91, 92, 93 specially provided on the casing
50. Alternatively, the washing agent is injected into the washing
apparatus 80 though inlet points which coincide with flanged
apertures already provided on the casing 50.
[0073] The delivery ducts of said washing apparatus 80 are
hydraulically connected to said inlet points 91, 92, 93 provided on
the casing 50.
[0074] The washing agent sprayed by the spray nozzles of said ducts
is then drained through the drainage system already provided in the
motor-compressor unit.
[0075] Depending on the injection point of the washing agent, part
of said washing liquid may be processed by the compressor and
therefore evacuated through the compressor outlet.
[0076] When the motor-compressor unit has a vertical configuration,
the drainage is facilitated by gravity.
[0077] Therefore, according to an embodiment of the present
invention dedicated spray nozzles are provided for each critical
component of the motor-compressor unit.
[0078] According to an embodiment of the present invention, the
washing apparatus as described above is provided with controlled
valves for controlling the flow of the washing agent through the
delivery ducts, so that the washing agent can be delivered to a
predetermined area to be washed in a selective manner.
[0079] This written description uses examples to disclose the
invention, including the preferred embodiments, 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.
* * * * *