Variable Speed Pump Torque Control for Dry-Run Detection
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Solution Overview
Problem
Pumping systems in CBM/CSG applications face challenges in managing dry-run or pump-off conditions, particularly due to entrained gases and variable annulus pressure, which can lead to premature pump failure, as existing control methods struggle to accurately determine water levels and suction pressure in deep wells.
Innovation Solution
A pumping system with a variable speed drive and processor that periodically measures fluid parameters, correlates them with motor torque indicators, predicts values, and adjusts pump operation based on comparisons to prevent faults, allowing for real-time control and detection of system changes without relying solely on transducers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transducers are used to determine suction pressure and water level, then measurement capability is improved, but reliability deteriorates due to pump wear, gas content, and debris affecting transducer accuracy
Solution Approach 1:
The patent introduces motor torque as an intermediary parameter to indirectly determine water level and suction pressure. Instead of relying directly on transducers that are affected by pump wear and debris, the system uses motor torque measurements combined with pump performance curves to infer fluid parameters. This intermediary approach bypasses the reliability issues of direct transducer measurement in harsh CBM/CSG environments.
Solution Approach 2:
The patent replaces mechanical/electrical transducer-based measurement systems with a torque-based control system. By substituting the transducer measurement mechanism with motor torque analysis and pump performance modeling, the system achieves more reliable water level and pressure determination that is not susceptible to wear, gas interference, or debris accumulation affecting transducer accuracy.
2Object-affected harmful factors
If pump setting is placed below gas producing zones, then gas entry is reduced, but water level determination complexity increases due to variable annulus pressure
Solution Approach 1:
The patent implements feedback control using motor torque measurements to continuously monitor and determine water level conditions. The system measures motor torque, compares it against expected torque values based on pump performance curves, and uses this feedback to infer water level and detect dry-run conditions. This feedback mechanism works effectively even when the pump is positioned below gas-producing zones where variable annulus pressure complicates direct measurement.
3Productivity
If pump operates at high speed to increase productivity, then output is improved, but risk of dry-run damage increases
Solution Approach 1:
The patent applies preliminary action by continuously monitoring motor torque and predicting water level conditions before dry-run damage can occur. The system uses torque-based water level determination to anticipate potential dry-run conditions and takes preventive action by adjusting pump speed or shutting down the pump before damage occurs. This allows the pump to operate at high speeds for maximum productivity while maintaining reliability through proactive protection.
Data Source
AI summary
A pumping system and method for operating a pumping system including a motor coupled to a variable speed drive to drive a pump. A torque indicator corresponding to the torque presented to the drive is determined. The torque indicator may be used to detect a fault if it exceeds a baseline torque, or to detect a defective transducer, or to detect a system change by perturbing one parameter and comparing another to a predicted value.