Pump Torque Control for Multi-Phase Flow Stability
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Solution Overview
Problem
Conventional multi-phase fluid pumping systems rely on complex and expensive flowmeters and are not fast enough to prevent pump instability due to rapid changes in gas volume fraction and density, leading to potential failures.
Innovation Solution
A method utilizing a pump limit characteristics diagram mapping differential pressure against torque, with a control system that monitors and regulates the torque to maintain a minimum allowable value, ensuring sufficient flow without the need for flowmeters, by using a second sensor for torque and a control unit to adjust the control valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional flowmeters are used to monitor fluid flow in multi-phase pumping systems, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent uses torque as an intermediary parameter to indirectly measure fluid flow. Instead of directly measuring multi-phase flow with complex flowmeters, the system monitors the torque on the pump shaft, which varies with fluid density and flow conditions. This intermediary measurement approach provides sufficient control information without requiring complex direct flow measurement equipment.
Solution Approach 2:
The patent replaces complex mechanical flowmeters with a torque sensing system. By substituting direct flow measurement mechanics with torque-based indirect measurement, the system achieves adequate monitoring capability with simpler, less expensive equipment that avoids the complexity of multi-phase flowmeter technology.
2Stability of the object's composition
If differential pressure control is used to maintain pump operation, then system stability is improved, but response speed deteriorates due to slow changes in differential pressure compared to rapid changes in gas volume fraction
Solution Approach 1:
The patent implements a feedback control system using torque monitoring. The torque signal provides real-time feedback about fluid density changes and flow conditions, allowing the control system to respond rapidly to changing conditions. This feedback mechanism enables the pump to maintain stable operation even during rapid gas slug transitions, overcoming the slow response inherent in differential pressure-based control.
3Productivity
If the pump operates in the impermissible region of the DP-Q diagram, then productivity is improved, but reliability deteriorates due to pump instability and surge
Solution Approach 1:
The patent uses preliminary action by establishing a torque-based control strategy that proactively prevents the pump from entering the impermissible operating region. By monitoring torque trends and adjusting the control valve in advance, the system maintains operation within stable regions while maximizing productivity, rather than reacting after instability occurs.
Data Source
AI summary
A method for operating a pump includes establishing a pump limit characteristics diagram by mapping a first system parameter (P1) as a function of a second system parameter (P2) to identify a permissible operating region of the pump; for each first system parameter value (P10), identifying a minimum allowable second system parameter value (P20); monitoring the first system parameter (P1) and identifying a minimum allowable second system parameter value (P20) corresponding to the monitored first system parameter value (P1m); monitoring the second system parameter (P2) and comparing the monitored second system parameter value (P2m) with the identified minimum allowable second system parameter value (P20); and regulating a control valve that controls fluid flow through a return line connecting the suction and discharge sides of the pump so that the monitored second system parameter value (P2m) does not fall below the minimum allowable second system parameter value (P20).