System for pumping a fluid and method for its operation

Patent metadata

Field	Value
Publication number	US-11846290-B2
Application number	US-201917268940-A
Country	US
Kind code	B2
Filing date	Aug 12, 2019
Priority date	Aug 16, 2018
Publication date	Dec 19, 2023
Grant date	Dec 19, 2023

Abstract

A method of operating a system (16) for pumping a fluid, which system comprises a pump (17) comprising a suction side (18) and a discharge side (19); a motor (20) for driving the pump, which motor is drivingly connected to the pump via a shaft; a recirculation conduit (23) providing a fluid path for the fluid from the discharge side to the suction side of the pump; and a control valve controlling the flow of the fluid through the recirculation conduit, which method comprises the steps of: mapping a plurality of minimum torque diagrams for the pump, where each minimum torque diagram identifies the minimum allowable torque of the pump as a function of an operational parameter of the pump, e.g. the differential pressure over the pump; from said plurality of minimum torque diagrams, identifying the minimum torque diagram best representing the current operation of the pump; monitoring said operational parameter of the pump and, from the minimum torque diagram best representing the current operation of the pump, identifying a minimum allowable torque value corresponding to a monitored value of said operational parameter of the pump, e.g. a monitored differential pressure value; monitoring the torque of the pump and comparing a monitored torque value with the identified minimum allowable torque value; and regulating the control valve such that the monitored torque value does not fall below the minimum allowable torque value. A corresponding pumping system is also disclosed.

First claim

The invention claimed is:

1. A method of operating a system for pumping a fluid, the system comprising:
a pump comprising a suction side and a discharge side;
a motor for driving the pump, the motor being drivingly connected to the pump via a shaft;
a recirculation conduit providing a fluid path for the fluid from the discharge side to the suction side of the pump; and
a control valve controlling the flow of the fluid through the recirculation conduit;
wherein the method comprises the steps of:
mapping a plurality of minimum torque curves for the pump, wherein each minimum torque curve identifies a minimum allowable torque of the pump as a function of an operational parameter of the pump;
from said plurality of minimum torque curves, identifying a minimum torque curve best representing the current operation of the pump;
monitoring said operational parameter of the pump and, from the minimum torque curve best representing the current operation of the pump, identifying a minimum allowable torque value (T 0 ) corresponding to a monitored value (DP m ) of said operational parameter of the pump;
monitoring a torque of the pump and comparing the monitored torque value (T m ) with the identified minimum allowable torque value (T 0 ); and
regulating the control valve such that the monitored torque value (T m ) does not fall below the minimum allowable torque value (T 0 ).

2. The method according to claim 1 , wherein said operational parameter of the pump is a differential pressure over the pump and said monitored value of said operational parameter of the pump is a monitored differential pressure value (DP m ) of the pump.

3. The method according to claim 1 , wherein each minimum torque curve represents a unique combination of a suction pressure and a rotational speed of the pump.

4. The method according to claim 3 , wherein each minimum torque curve defines mapping points for a predetermined suction pressure value and a predetermined rotational speed value of the pump.

5. The method according to claim 4 , wherein the step of mapping each minimum torque curve comprises the sub-step of:
for the predetermined suction pressure value and the predetermined rotational speed value, defining said plurality of mapping points by mapping differential pressure over the pump as a function of torque of the pump for different gas-volume fraction (GVF) values.

6. The method according to claim 5 , wherein the step of mapping each minimum torque curve comprises the sub-step of:
establishing a minimum torque curve from said mapping points by interpolating between the mapping points.

7. The method according to claim 5 , wherein said step of identifying the minimum torque curve best representing the current operation of the pump comprises:
monitoring suction pressure and rotational speed of the pump; and
choosing the minimum torque curve to represent the current operation of the pump based on the monitored suction pressure and torque.

8. The method according to claim 7 , wherein said step of choosing the minimum torque curve to represent the current operation of the pump based on the monitored suction pressure and torque comprises:
choosing, for each monitored suction pressure value and rotational speed value, the minimum torque curve having the next lower suction pressure value and the next higher rotational speed value.

9. A system for pumping a fluid, comprising:
a pump comprising a suction side and a discharge side;
a motor for driving the pump, the motor being drivingly connected to the pump via a shaft;
a recirculation conduit providing a fluid path for the fluid from the discharge side to the suction side of the pump;
a control valve controlling the flow of the fluid through the recirculation conduit;
a first sensor device adapted to monitor an operational parameter of the pump;
a second sensor device adapted to monitor or estimate the torque of the pump;
a control unit in which is stored a plurality of minimum torque curves for the pump, wherein each minimum torque curve identifies a minimum allowable torque of the pump as a function of said operational parameter of the pump;
wherein the control unit is configured to:
identify, from said plurality of minimum torque curves, a minimum torque curve best representing the current operation of the pump;
monitor said operational parameter of the pump and, from the minimum torque curve best representing the current operation of the pump, identify a minimum allowable torque value (T 0 ) corresponding to a monitored value (DP m ) of said operational parameter of the pump;
monitor a torque of the pump and compare the monitored torque value (T m ) with the identified minimum allowable torque value (T 0 ); and
regulate the control valve such that the monitored torque value (T m ) does not fall below the minimum allowable torque value (T 0 ).

10. The system according to claim 9 , wherein said operational parameter of the pump is the differential pressure over the pump and said monitored value of said operational parameter of the pump is a monitored differential pressure value (DP m ) of the pump.

11. The system according to claim 9 , wherein the control unit is adapted to:
monitor suction pressure and rotational speed of the pump; and
identify, at predetermined points in time, the minimum torque curve of said plurality of minimum torque curves which best corresponds to the monitored suction pressure and rotational speed values.

Assignees

• Fmc Kongsberg Subsea As

Inventors

• Todal Karen

Classifications

• F04D15/0005 Primary

  by using valves · CPC title

• F04D13/08 Primary

  for submerged use · CPC title

• F04D15/0094

  Indicators of rotational movement · CPC title

• E21B43/128

  Adaptation of pump systems with down-hole electric drives · CPC title

• F04D13/06 Primary

  the pump being electrically driven · CPC title