# US 2021/0340985 A1 · System for Pumping a Fluid and Method for its Operation

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- Number: US 2021/0340985 A1
- Document ID: US20210340985A1
- Status: Published application
- Kind: A1
- Application number: 17/268,940
- Filed: 2019-08-12
- Published: 2021-11-04
- Earliest claimed: 2018-08-16
- Assignees: FMC Kongsberg Subsea AS
- Applicants: FMC Kongsberg Subsea AS
- Inventors: Karen Todal
- Web page: https://patentgrep.com/patent/US20210340985A1

## CPC

- F04D 15/0005: {by using valves}
- F04B 49/035: Bypassing
- F04B 49/24: Bypassing
- F04D 13/08: for submerged use
- F04D 15/0011: {by-pass valves}
- F04D 15/0094: {Indicators of rotational movement}
- F04D 27/0223: {Control schemes therefor}
- F04D 31/00: Pumping liquids and elastic fluids at the same time
- E21B 43/128: {Adaptation of pump systems with down-hole electric drives}
- F04B 2201/1202: Torque on the axis
- F04D 15/0066: {by changing the speed, e.g. of the driving engine}
- F05D 2270/3015: differential pressure
- F05D 2270/335: Output power or torque
- F04D: NON-POSITIVE-DISPLACEMENT PUMPS (engine fuel-injection pumps F02M; ion pumps H01J41/12; electrodynamic pumps H02K44/02)
- F04B: POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS (machines for liquids, or pumps, of rotary-piston or oscillating-piston type F04C; non-positive-displacement pumps F04D; pumping of fluid by direct contact of another fluid or by using inertia of fluid to be pumped F04F)
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS

## 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.

## Claims

### Claim 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 diagrams for the pump, wherein each minimum torque diagram identifies a minimum allowable torque of the pump as a function of an operational parameter of the pump;
from said plurality of minimum torque diagrams, identifying a 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 a current operation of the pump, identifying a minimum allowable torque value (T0) corresponding to a monitored value (DPm) of said operational parameter of the pump;
monitoring a torque of the pump and comparing the monitored torque value (Tm) with the identified minimum allowable torque value (T0); and
regulating the control valve such that the monitored torque value (Tm) does not fall below the minimum allowable torque value (T0).

### Claim 2 (depends on 1)

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 (DPm) of the pump.

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 3)

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

### Claim 5 (depends on 4)

The method according to claim 4, wherein the step of mapping each minimum torque diagram 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.

### Claim 6 (depends on 5)

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

### Claim 7 (depends on 5)

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

### Claim 8 (depends on 7)

The method according to claim 7, wherein said step of choosing the minimum torque diagram 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 diagram having the next lower suction pressure value and the next higher rotational speed value.

### Claim 9

A system for pumping a fluid, comprising:
a pump comprising a suction side and a discharge side;
a motor for driving the pump (17), 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 diagrams (112a) for the pump, wherein each minimum torque diagram 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 diagrams, the minimum torque diagram best representing the current operation of the pump;
monitor said operational parameter of the pump and, from the minimum torque diagram best representing the current operation of the pump, identify a minimum allowable torque value (T0) corresponding to a monitored value (DPm) of said operational parameter of the pump;
monitor a torque of the pump and compare the monitored torque value (Tm) with the identified minimum allowable torque value (T0); and
regulate the control valve such that the monitored torque value (Tm) does not fall below the minimum allowable torque value (T0).

### Claim 10 (depends on 9)

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 (DPm) of the pump.

### Claim 11 (depends on 9)

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 diagram of said plurality of minimum torque diagrams which best corresponds to the monitored suction pressure and rotational speed values.