Pump Torque Control via Dynamic Minimum Torque Diagrams
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Solution Overview
Problem
Conventional multi-phase fluid pumping systems, such as those in hydrocarbon production facilities, often require costly flowmeters to monitor fluid flow, and using minimum torque protection can unduly reduce the pump's operating envelope, leading to unnecessary recirculation.
Innovation Solution
The system maps multiple minimum torque diagrams for different operational parameters, identifying the most relevant one for current conditions and regulating the pump to maintain a minimum allowable torque, avoiding the need for costly flowmeters and reducing unnecessary recirculation by using 'local' torque curves specific to combinations of suction pressure and rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional multi-phase flowmeters are used to monitor fluid flow, then reliable flow monitoring is achieved, but system cost increases significantly
Solution Approach 1:
The invention extracts the flow monitoring function from the expensive multi-phase flowmeter and replaces it with a torque-based protection system. The torque monitoring device and control unit work together to provide pump protection without requiring direct flow measurement, thereby eliminating the need for costly flowmeters while maintaining reliable operation through torque-based surge detection
Solution Approach 2:
The invention uses torque as a proxy indicator for flow conditions. Instead of directly measuring flow with complex multi-phase flowmeters, the system monitors torque as a substitute parameter that correlates with flow conditions and pump surge state, providing indirect but reliable monitoring capability at lower cost
2Reliability
If minimum torque protection is used to protect the pump, then pump surge is prevented, but the pump's operating envelope is unduly reduced leading to unnecessary recirculation
Solution Approach 1:
The invention dynamically adjusts the minimum torque threshold based on real-time operating conditions such as suction pressure and discharge pressure. The control unit continuously monitors these parameters and adapts the torque threshold accordingly, allowing the pump to operate closer to its true surge limit under varying conditions while still preventing surge, thereby maximizing the operating envelope without sacrificing reliability
Solution Approach 2:
The system changes the torque threshold parameter dynamically based on operating conditions. Instead of using a fixed minimum torque value that overly conservatively limits operation, the control unit adjusts the threshold parameter in response to changing suction pressure, discharge pressure, and other operational parameters, enabling more efficient operation while maintaining surge protection
3Reliability
If recirculation is activated to maintain minimum flow, then pump surge is avoided, but energy efficiency decreases due to unnecessary recirculation
Solution Approach 1:
The control unit continuously monitors torque, suction pressure, and discharge pressure, using this feedback to dynamically adjust the minimum torque threshold and control recirculation valve operation. This closed-loop feedback system ensures recirculation is activated only when truly necessary to prevent surge, rather than operating continuously based on fixed conservative thresholds, thereby minimizing energy waste while maintaining reliability
Data Source
AI summary
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.