ESP Spring Brake and Shear Pin for Reverse Shaft Locking
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Solution Overview
Problem
Electrical submersible well pumps (ESPs) face issues with spinning motor shafts generating electrical charges when not powered, particularly during installation, retrieval, and shutdown, posing safety risks to technicians due to well fluid flow, which existing technologies have not adequately addressed.
Innovation Solution
The integration of a spring brake mechanism and shear member in the ESP assembly that prevents reverse rotation of the drive shaft assembly by using helical turns and a shear pin to allow free rotation during power supply and stop reverse rotation, ensuring safety by preventing electrical charge generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the motor shaft is allowed to rotate freely during non-powered conditions, then the ESP can be easily installed and retrieved, but the shaft may spin in reverse due to well fluid flow, generating dangerous electrical charges
Solution Approach 1:
The shear pin is installed in advance to prevent reverse rotation of the motor shaft during installation and retrieval operations. The shear pin acts as a preliminary protective measure that shears off when torque is applied in the wrong direction, preventing the harmful electrical charge generation before it can occur
Solution Approach 2:
The shear pin is designed as a disposable sacrificial component that is intentionally made weak and inexpensive. It is replaced after each installation or retrieval operation, providing a simple and cost-effective solution to prevent reverse rotation without requiring complex reusable mechanisms
2Object-affected harmful factors
If a shear pin is installed to prevent reverse rotation, then electrical charge generation is prevented, but the shear pin must be replaced after each operation increasing maintenance time
Solution Approach 1:
The shear pin is designed as a disposable component that is intentionally sacrificed to prevent reverse rotation. By making it inexpensive and simple to replace, the system accepts the time loss from replacement as a trade-off for preventing dangerous electrical charge generation and protecting the expensive motor
3Object-affected harmful factors
If the spring brake is positioned to engage the bore sidewall, then reverse rotation is prevented, but the brake must allow free rotation in the driving direction
Solution Approach 1:
The spring brake is designed with asymmetric engagement characteristics - the helical spring geometry and positioning allow it to engage the bore sidewall only during reverse rotation attempts, while permitting free rotation in the normal driving direction. This asymmetric behavior prevents harmful reverse spinning without interfering with normal pump operation
Solution Approach 2:
The spring brake acts as an intermediary mechanism between the motor shaft and the bore sidewall. It selectively engages the sidewall only when reverse rotation is detected, serving as a mediator that allows normal operation while blocking harmful reverse motion
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
The solution effectively prevents reverse spinning of the motor shaft during non-powered conditions, thereby eliminating the risk of electrical charge generation, enhancing safety during ESP operations such as installation, retrieval, and shutdown.
Implementation Method 1
A spring brake has helical turns. Means for configuring and mounting the spring brake between the shaft assembly and a sidewall of the bore allows free rotation of the shaft assembly in a driving direction and stops the shaft assembly from rotating in a reverse direction
Implementation Method 2
The helical turns are arranged such that commencing rotation of the shaft assembly in the reverse direction causes the second portion of the spring brake to move radially outward into frictional engagement with the sidewall of the bore to stop further reverse direction rotation of the shaft assembly
Implementation Method 3
A shear pin may extend between the shaft assembly and the sidewall of the bore. The shear pin prevents rotation of the shaft assembly before power supply to the motor
Data Source
AI summary
An electrical submersible well pump assembly (ESP) has a spring brake having helical turns mounted between the shaft and one of the housings. The spring brake allows free rotation of the shaft in a driving direction and stops the shaft from rotating in a reverse direction. The spring brake may have one end be affixed to the housing to rotate in unison in both directions. Alternately, the spring brake may have one end affixed to the shaft for rotation with the shaft. Further, the spring brake could be free of being connected to either the shaft or the housing. A shear member may be mounted between the shaft and the housing to prevent any rotation of the shaft during run-in.