Valve Stem Coupling Assembly With Shear Pins for Load Isolation
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Solution Overview
Problem
Gate valve stems often suffer damage due to combined thrust and torque loads, leading to the need for replacement and downtime when overtorque conditions occur, as existing systems do not effectively isolate these loads, necessitating a solution to prevent damage and facilitate easy replacement.
Innovation Solution
A coupling assembly that separates thrust and torque loads using two stems, where securing pins are designed to fail in overtorque conditions, allowing for easy replacement without disassembling the valve, and includes an access door for replacing damaged pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single stem is used to connect actuator to gate, then the structure is simple, but the stem bears both thrust load and torque load which can cause damage under overtorque conditions
Solution Approach 1:
The single stem is segmented into two separate stems: a thrust stem that bears only axial thrust load from the gate, and a torque stem that bears only rotational torque load from the actuator. This segmentation allows each stem to be optimized for its specific load type, preventing the combined loading that causes damage in single-stem designs.
Solution Approach 2:
A coupling assembly acts as an intermediary device between the thrust stem and torque stem. This coupler transfers the axial thrust force from the thrust stem to the torque stem while allowing the torque stem to rotate independently, thus separating the thrust and torque load paths and preventing combined loading on a single stem.
2Reliability
If the stem is damaged due to overtorque, then the valve must be taken off-line for stem replacement, but this causes downtime and loss of productivity
Solution Approach 1:
The torque stem is designed as a sacrificial component that can be easily replaced. It includes a shearable section that can be quickly cut and removed, and a replacement torque stem can be pre-manufactured and shipped. This allows rapid replacement of the damaged component without taking the entire valve off-line for extended periods.
Solution Approach 2:
Replacement torque stems are pre-manufactured and shipped in advance so that when a torque stem fails, a replacement is already available. This eliminates waiting time for manufacturing and ensures rapid replacement, minimizing valve downtime and maintaining productivity.
3Stability of the object's composition
If securing pins are used to prevent stem twisting, then the stems are secured against rotation, but the pins can fail under overtorque conditions causing stem damage
Solution Approach 1:
The securing pins are intentionally designed with controlled weakness points that allow them to shear in a predictable manner under overtorque conditions. This controlled failure mode prevents catastrophic damage to the stems and valve, converting the potential harm of pin failure into a beneficial protective mechanism that limits damage and facilitates quick replacement.
Data Source
AI summary
A coupler that separates a unitary valve stem into two separate but coupled sections to isolates the thrust load from the torque load.