ESP Shaft Spring Clutch for Unpowered Motor Decoupling
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Solution Overview
Problem
Electrical submersible well pumps (ESPs) can spin uncontrollably when not powered, generating electrical charges that pose safety risks to technicians due to fluid flow, which existing solutions like helical spring brakes have not effectively addressed in ESP shaft assemblies.
Innovation Solution
A clutch mechanism using a helical spring with a driven hub assembly that couples and decouples the motor and pump shafts, preventing rotation when power is off, ensuring safety by preventing electrical charge generation during fluid flow or shutdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the ESP motor shaft is allowed to rotate freely when not powered, then the pump can be driven by fluid flow during installation and retrieval, but electrical charges are generated that pose safety risks to technicians
Solution Approach 1:
The clutch mechanism dynamically transitions between engaged and disengaged states based on motor rotation direction. During normal operation, the spring clutch engages to transmit power from motor to pump. During installation and retrieval when fluid flow drives the pump in reverse, the clutch disengages to prevent electrical charge generation while allowing free rotation. This dynamic state change resolves the contradiction between enabling fluid-driven operation and preventing harmful electrical charges.
Solution Approach 2:
The spring clutch acts as an intermediary between the motor shaft and pump shaft. It selectively couples or decouples the connection based on operational conditions. When the motor is not powered and fluid flow causes reverse rotation, the clutch intermediary allows the pump shaft to rotate independently without driving the motor shaft, thus preventing electrical charge generation while maintaining pump operation capability.
2Object-affected harmful factors
If a clutch mechanism is added to prevent motor shaft rotation, then safety is improved by preventing electrical charge generation, but device complexity increases
Solution Approach 1:
The spring clutch mechanism is self-regulating and automatically engages or disengages based on the direction of rotation and presence of motor power. The spring's elastic properties cause it to naturally engage during forward rotation (normal operation) and disengage during reverse rotation (installation/retrieval). This self-service characteristic eliminates the need for external control systems, sensors, or complex actuation mechanisms, thereby minimizing added complexity while effectively preventing electrical charge generation.
Solution Approach 2:
The clutch mechanism exploits changes in rotational direction and torque parameters to automatically transition between engaged and disengaged states. The spring clutch is designed with specific elastic properties that cause engagement under normal operating torque and disengagement under reverse rotation conditions. This parameter-based automatic control achieves safety without requiring complex electronic controls or additional actuators.
3Power
If the spring clutch engages during normal operation, then power transmission from motor to pump is ensured, but the mechanism must be designed to withstand operational forces
Solution Approach 1:
The spring clutch dynamically adapts its engagement force based on operational conditions. During normal motor-driven operation, the spring engages firmly to transmit full power from motor to pump. During installation and retrieval when fluid flow drives the pump, the spring naturally disengages to allow free rotation. This dynamic behavior ensures adequate strength and power transmission during operation while reducing stress on the mechanism during non-operational phases.
Solution Approach 2:
The spring element inherently provides cushioning and shock absorption capabilities before excessive forces can damage the mechanism. The elastic properties of the spring allow it to absorb transient loads and shocks during engagement and disengagement, protecting the clutch mechanism and connected components from damage. This beforehand cushioning ensures the mechanism can withstand operational forces while maintaining durability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively prevents motor shaft rotation when the ESP is not powered, eliminating the risk of electrical charges and enhancing safety during installation, retrieval, and shutdowns by using a helical spring clutch mechanism that engages and disengages based on power availability.
Implementation Method 1
a helical spring with a fixed portion and a flex portion that inserts into the driven hub cavity, when the spring is rotationally static an outer surface of the flex portion is spaced radially inward from an inner surface of the hub receptacle and when the spring is rotated in a first direction the flex portion outer surface radially expands into contact with the inner surface of the hub receptacle
Implementation Method 2
The spring is optionally rotated in a second direction that is opposite the first direction, the outer surface of the flex portion is spaced radially inward from the sidewalls of the driven hub receptacle and the driven hub receptacle is freely rotatable with respect to the spring
Data Source
AI summary
An electrical submersible well pump assembly has shaft couplings. One of the couplings has a lower hub that rotates in unison with the motor shaft and an upper hub that rotates in unison with the pump shaft. A helical spring clutch engages both hubs when the motor shaft is being driven by the motor. Ceasing driving rotation of the motor shaft causes the spring clutch to disengage from the upper hub, enabling the pump shaft to rotate the upper hub without rotating the lower hub.