PRESSURE BOOSTER WITH INTEGRATED SPEED DRIVE

Abstract

Pressure booster (1) for boosting the pressure of petroleum fluids, produced water or seawater, comprising a pressure booster (2) with a motor (3), a rotatable motor shaft (4) and a rotatable pump or compressor shaft (5) where 5 the pressure booster in the form of a centrifugal pump (2) or compressor is arranged. The pressure booster further comprises: a hydraulic variable speed drive (6) arranged between the motor and the pressure booster, the hydraulic variable speed drive comprising an impeller (7) and a turbine (8), wherein the impeller of the hydraulic variable speed drive is 10 arranged on the motor shaft and the turbine of the hydraulic variable speed drive is arranged on the pump or compressor shaft, a common driver side fluid (10) for cooling, lubricating, flushing and powering of the hydraulic variable speed drive, and cooling, lubricating and flushing of the motor and bearings, circulated by one of an impeller (9) on the 15 motor shaft, a pump and a hydraulic power unit, a control system (11) for controlling the coupling of the motor shaft to the pump or compressor shaft by the hydraulic variable speed drive, wherein the motor shaft drives the pump or compressor shaft via the hydraulic variable speed drive.

Claims

1. An apparatus for boosting the pressure of petroleum fluids, produced water or seawater, the apparatus comprising a pressure booster with a motor; a rotatable motor shaft and a rotatable pump or compressor shaft where the pressure booster in the form of a centrifugal pump or compressor is arranged; a hydraulic variable speed drive arranged between the motor and the pressure booster, the hydraulic variable speed drive comprising an impeller and a turbine, wherein the impeller of the hydraulic variable speed drive is arranged on the motor shaft and the turbine of the hydraulic variable speed drive is arranged on the pump or compressor shaft; a common driver side fluid for cooling, lubricating, flushing and powering of the hydraulic variable speed drive; and cooling, lubricating and flushing of the motor and bearings, circulated by one of an impeller on the motor shaft, a pump and a hydraulic power unit; and a control system for controlling the coupling of the motor shaft to the pump or compressor shaft by the hydraulic variable speed drive, wherein the motor shaft drives the pump or compressor shaft via the hydraulic variable speed drive.

2. The apparatus according to claim 1, comprising a driver side impeller on the rotatable motor shaft.

3. The apparatus according to claim 1, wherein, in addition to a process fluid inlet and a process fluid outlet, the external connections consist of an electric power supply line, and a control link, thereby eliminating both of a variable frequency drive and a continuous supply of barrier fluid at controlled overpressure from a topsides or onshore location.

4. The apparatus according to claim 1, wherein the motor and the hydraulic variable speed drive are arranged in a common driver side compartment isolated from a process fluid to be pressure boosted by the pump or compressor, wherein the hydraulic variable speed drive comprises a separation wall on a side of the hydraulic variable speed drive facing the motor or compressor, the separation wall isolates the common driver side compartment from the process fluid.

5. The apparatus according to claim 1, comprising internal lines, gaps, channels or external pipe sections for circulating the common driver side fluid internally in a motor housing and a hydraulic variable speed drive housing and between the housings, or internally in a common driver side compartment wherein the motor and the hydraulic variable speed drive are arranged, and externally through a cooler.

6. The apparatus according to claim 1, wherein the pressure booster comprises a closed loop control system.

7. The apparatus according to claim 1, comprising a driver side impeller on the rotatable motor shaft that pressurizes the common driver side fluid to at least 5, 10, 15 or 20 bar absolute pressure at normal operation, to power an actuator system of the control system and power the hydraulic variable speed drive while eliminating any risk of cavitation, in one of a separate motor housing and a common driver side compartment containing the motor and the hydraulic variable speed drive.

8. The apparatus according to claim 1, wherein the hydraulic variable speed drive comprises vanes arranged in the common driver side fluid flow path coupling the impeller to the turbine, and an actuator system, coupled to the vanes, wherein the actuator system controls vane angle of the guide wheel, thereby controlling the rotational coupling from motor shaft to pump or compressor shaft.

9. The apparatus according to claim 1, wherein the control system comprises transmitters for at least rotational speed of the pump or compressor shaft and motor shaft, and vane angle of a non-rotating guide wheel with vanes of the hydraulic variable speed drive; and torque on the pump or compressor shaft if the process fluid to be pressure boosted is a multiphase fluid.

10. The apparatus according to claim 8, wherein the actuator system comprises a valve and a vane actuator, wherein the common driver side fluid is supplied from the valve to and from the vane actuator, wherein a valve differential pressure is at least 5 or 10 bar between a valve inlet and a valve outlet and an actuator differential pressure is at least 3 or 5 bar between an actuator inlet and an actuator outlet, and the absolute inlet pressure to the vane is 20 bar minimum.

11. The apparatus according to claim 1, comprising an electric actuator.

12. The apparatus according to claim 1, wherein the motor is an asynchronous induction motor.

13. The apparatus according to claim 1, wherein the hydraulic variable speed drive controls the speed of the pump, multi-phase pump or compressor to be in a range from 0 to at least 2 times the rotational speed of the motor.

14. A method for boosting the pressure of petroleum fluids, produced water or seawater, without a variable speed drive, the method comprising: arranging the pressure booster according to claim 1, to an inlet for petroleum fluids, produced water or seawater and an outlet for the petroleum fluids, produced water or seawater; connecting an electric power supply line, connecting a control link, and operating the pressure booster.

15. The method according to claim 14, wherein the pressure booster is controlled via an active closed-circuit control system integrated in the pressure booster, controllable via the control link, wherein the control is based on signals from transmitters for at least rotational speed of the pump or compressor shaft and motor shaft, and vane angle of vanes of the hydraulic variable speed drive, and torque on the pump or compressor shaft if the process fluid to be pressure boosted is a multiphase fluid.

16. (canceled)

17. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0053] FIG. 1 illustrates an embodiment of a pressure booster of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0054] Reference is made to FIG. 1, illustrating a pressure booster 1 of the invention. More specifically, the embodiment is a pressure booster 1 for boosting the pressure of petroleum fluids, produced water or seawater, comprising a pressure booster 2 with a motor 3, a rotatable motor shaft 4 and a rotatable pump or compressor shaft 5 where a centrifugal pump 2 or compressor is arranged. An inlet 29 receives process fluid. Pressure boosted process fluid is delivered through an outlet 30. The pressure booster 2 is a pump if the process fluid is liquid or multiphase fluid, and a compressor if the process fluid is gas. A hydraulic variable speed drive 6 arranged between the motor and the pump or compressor, rotatably couples the motor shaft and the pump or compressor shaft 5. The hydraulic variable speed drive comprises an impeller 7 and a turbine 8, wherein the impeller of the hydraulic variable speed drive is arranged on the motor shaft and the turbine of the hydraulic variable speed drive is arranged on the pump or compressor shaft.

[0055] A driver side impeller 9 is arranged on the rotatable motor shaft. The pressure booster contains a common driver side fluid 10 for cooling, lubrication, flushing and powering and control of the hydraulic variable speed drive, and cooling, lubrication and flushing of the motor and bearings, circulated by the driver side impeller 9. A control system 11 controls the coupling of the motor shaft to the pump or compressor shaft by the hydraulic variable speed drive, wherein the motor shaft drives the pump or compressor shaft via the hydraulic variable speed drive. Furthermore, an electric power supply line 12 delivers the required electric power, and a control link 13 allows transmitting control signals to and from the pressure booster.

[0056] The illustrated embodiment comprises a common driver side compartment 14 isolated by a separation wall 15 from a process fluid to be pressure boosted by the pump or compressor, in a single pressure booster unit 1. The walls of the process compartment 31 can be dimensioned for higher pressure than the walls of the common driver side compartment, except for the separation wall 15 that is common between the compartments.

[0057] The separation wall 15 comprises a seal or packer, between the separation wall and pump or compressor shaft. To eliminate continuous common driver side fluid supply, a common driver side fluid accumulator is preferably arranged for common driver side fluid replacement or supply, if or when required. Alternatively, a port for common driver side fluid supply via an ROV-remotely operated vehicle, is arranged. Alternatively, a flow bore in an umbilical can be used to supply common driver side fluid, for example in the electric power supply line 12. Preferably, the pressure booster of the invention comprises coupling to an umbilical flow bore or separate line with supply of fluid for flow assurance, in the form of glycol, glycol and water mixture, or methanol, for use as and supply of common driver side fluid (10). Alternatively, common driver side fluid leakage and supply can be eliminated by arranging a magnetic coupling with a separation wall between magnetic coupling sides, arranged between the driver side compartment and pump or compressor compartment, in the common pressure booster housing, thereby separating the compartments hermetically and eliminating any leakage and thereby any requirement for supply of common driver side fluid.

[0058] The common driver side fluid is circulating internally in the common driver side compartment through internal lines, gaps, channels 16; and externally through external pipe sections 17, through a cooler 32.

[0059] The hydraulic variable speed drive comprises a non-rotating guide wheel 19 with vanes 20 arranged between the impeller and turbine, and an actuator system 18, coupled to the guide vanes. The actuator system 18 controls vane angle of the guide wheel, thereby controlling the rotational coupling from motor shaft to pump or compressor shaft. The actuator system 18 is a part of the control system 11. Alternatively, the vanes are arranged in the common driver side fluid flow path coupling the impeller to the turbine, wherein vane angles are controllable by an electric actuator, a rotating vane actuator or another actuator. Controlling the vane angles control how much of the common driver side fluid shall flow through the flow path acting to couple the impeller to the turbine, and how much of the fluid shall bypass the coupling.

[0060] Alternatively, only static vanes or static guide structure are used. This is preferable if the pressure booster motor is a permanent magnet motor, which require a topsides or subsea VFD/VSD for start of the motor, which topsides or subsea VFD/VSD can readily be used for speed control, whilst the hydraulic variable speed drive of the pressure booster acts like a step up gear. Frictional losses of the common driver side fluid, or any alternative fluid, follows fluid velocity at an exponent of about 2,7, therefore the benefit of reduced motor rpm is substantial.

[0061] The control system comprises transmitters for at least rotational speed 21 of the pump or compressor shaft and the motor shaft, and vane angle 22 of a non-rotating guide wheel with vanes of the hydraulic variable speed drive; and torque 23 on the pump or compressor shaft if the process fluid to be pressure boosted is a multiphase fluid.

[0062] The illustrated actuator system 18 comprises a valve 11 and a vane actuator 24, wherein the common driver side fluid is supplied from the valve to and from the vane actuator, wherein a valve differential pressure is at least 5 bar or 10 bar between a valve inlet 25 and a valve outlet 26 and an actuator differential pressure is at least 3 bar or 5 bar between an actuator inlet 27 and an actuator outlet 28, and the absolute inlet pressure to the vane is 5, 10, 15 or 20 bar minimum.

[0063] The pressure booster, method and use of the invention enables the following features, advantages or technical effects: [0064] Soft start and stop of pump (“motor protection”—reduce mechanical wear/tear) [0065] Variable speed control (with constant speed motor), which is essential in subsea rotating machinery [0066] Operating pump at higher than motor speed (up to at least 2× motor speed)—less viscous losses than if both pump and motor shaft spins at for example 6000 rpm and more stable system (less vibration) [0067] Inherent regulating capability—constant power transmitted provided guide vane position is constant—if gas enters pump then torque drops and rpm increases to keep kW (power) constant—and higher speed removes the gas (and vice versa) [0068] Improved rotodynamic stability in general (by having “non-mechanical contact” between motor and pump shafts) [0069] Closed Loop Electric Control system preferably used to regulate Hydraulic variable speed drive HVSD in a subsea or unmanned Rotating Machine; has not been used subsea before. [0070] Using the inherent differential pressure in the common driver side fluid to actuate the actuator. [0071] Using the same fluid in the HVSD as is in the el. motor (no separating seal or wall—this is normally present, not separate volumes or fluids, in principle not separate pressures either) [0072] Actuator (such as RVA) position measurement—differential measurements instead of “single ended”—as the actuator or RVA moves in many directions due to pressures and exact position is needed —unique [0073] Overpressure of the common driver side fluid—at least 5 bar absolute pressure as opposed to conventional hydraulic couplings. [0074] Driver side arrangement with orifices and gaps and lines to control the fluid flows and pressure throughout the “Motor-HVSD-Pump” system (stabilize, cool and lubricate) [0075] Allow to eliminate barrier fluid supply from topsides or onshore, at least continuous supply or/and continuous connection. [0076] Eliminate a separate barrier fluid and accordingly any separate barrier fluid supply.

[0077] The pressure booster of the invention may include any feature or step here described or illustrated, in any operative combination, wherein each such operative combination is an embodiment of the present invention. The method of the invention may include any feature or step here described or illustrated, in any operative combination, wherein each such operative combination is an embodiment of the present invention.