Rod Pumping Unit Controller Speed Adjustment
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Solution Overview
Problem
Rod pumping units face reduced service life and increased failure rates due to stresses such as fluid pound, which vary over time and affect components like motors, rods, and gearboxes, leading to higher operational costs and downtime.
Innovation Solution
A controller for rod pumping units that adjusts pump speed in real-time based on position and load signals to anticipate and mitigate fluid pound stresses by decelerating the pump piston before contact with the fluid surface and accelerating after contact, maintaining an average pump speed throughout the stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rod pumping unit operates at constant high speed, then productivity is improved, but component stresses increase reducing service life
Solution Approach 1:
The patent implements variable speed operation by dynamically adjusting the pump speed during the stroke cycle. The controller modifies the motor speed based on real-time feedback from position and load sensors, transitioning from constant high speed to a dynamic speed profile that reduces speed during high-stress periods while maintaining higher speeds during low-stress periods, thus resolving the contradiction between productivity and reliability
Solution Approach 2:
The patent changes the operational parameters of the pump system by varying the speed parameter throughout the stroke cycle. The controller adjusts the motor speed parameter in response to changing load conditions, pump fillage levels, and piston position, thereby optimizing both productivity and component service life through parameter modulation rather than maintaining a fixed high speed
2Reliability
If the pump speed is reduced to mitigate fluid pound stresses, then component reliability is improved, but productivity decreases
Solution Approach 1:
The patent applies preliminary action by detecting pump fillage level and anticipating fluid pound conditions before they occur. The controller uses position and load signals to predict when the piston will contact the fluid surface and proactively adjusts the speed profile in advance, reducing the piston speed before the impact occurs. This preliminary speed reduction mitigates fluid pound stresses while minimizing the overall impact on productivity by only slowing down during the critical impact phase
Solution Approach 2:
The patent implements periodic speed modulation throughout each pump stroke cycle. The controller applies speed reductions periodically at specific phases of the stroke (during downstroke when fluid pound is anticipated) while maintaining higher speeds during other phases (upstroke and early downstroke). This periodic action pattern allows the system to protect components from stresses while preserving overall productivity through strategic speed variation
3Reliability
If real-time speed adjustment is implemented, then fluid pound mitigation is improved, but controller complexity increases
Solution Approach 1:
The patent implements feedback control by continuously monitoring pump operation through position sensors and load sensors, then using this real-time feedback to adjust motor speed. The controller receives feedback signals about piston position, rod load, and pump fillage level, and automatically modifies the speed command accordingly. This feedback mechanism enables effective fluid pound mitigation through a closed-loop control system that adapts to changing conditions without requiring overly complex external control infrastructure
Solution Approach 2:
The patent enables the rod pumping unit to self-regulate its operation by using its own operational data (position and load signals from its existing sensors) to control its speed. The controller processes the unit's own feedback signals and automatically adjusts the motor speed without requiring external intervention or complex external control systems. This self-service approach reduces controller complexity by utilizing the unit's inherent sensing capabilities for autonomous speed management
Data Source
AI summary
A controller for operating a rod pumping unit at a pump speed. The controller includes a processor configured to operate a pump piston of the rod pumping unit at a first speed. The processor is further configured to determine a pump fillage level for a pump stroke based on a position signal and a load signal. The processor is further configured to reduce the pump speed to a second speed based on the pump fillage level for the pump stroke.