Fail-Safe Retaining Plug for Slam-Shut Valve
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Solution Overview
Problem
Existing slam-shut safety valves in gas distribution systems face failures due to the susceptibility of e-rings and similar locking connections to fluid pressure, leading to disengagement of safety disks and retaining plugs, which compromises the safety device's ability to prevent uncontrolled gas leaks.
Innovation Solution
A fail-safe retaining plug assembly with a lengthened retaining plug and reset pin design, featuring a conical portion and extended sections to maintain alignment and secure the safety disk even if e-rings fail, ensuring the safety disk remains engaged with the valve seat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If e-rings or similar locking connections are used to retain the safety disk and retaining plug, then the components can be removed for maintenance and repair, but the locking connections are susceptible to failure under fluid pressure, causing disengagement of safety components
Solution Approach 1:
The retaining plug is segmented into multiple sections with different functions: a first section with an external thread for the safety disk, a second section with a conical external thread for the reset pin, and a third section forming a shoulder. This segmentation allows each section to perform its specific retention function independently, preventing single-point failure while maintaining ease of assembly and disassembly.
Solution Approach 2:
The retaining plug employs asymmetric threading mechanisms: a first external thread for the safety disk and a second conical external thread for the reset pin. These asymmetric thread designs provide different engagement characteristics and retention forces, ensuring reliable retention under pressure while allowing selective removal for maintenance.
2Device complexity
If the retaining plug and reset pin are designed with standard lengths, then the device structure remains simple, but the safety disk may become disengaged from the valve seat under pressure
Solution Approach 1:
The retaining plug is designed with pre-calculated extended lengths and conical portions that automatically maintain proper alignment and engagement of the safety disk with the valve seat before pressure acts on the system. This preliminary geometric configuration ensures that even under pressure, the safety components remain properly positioned without requiring complex active alignment mechanisms.
Solution Approach 2:
The solution introduces a conical portion on the retaining plug that adds a dimensional element (tapered geometry) to the otherwise cylindrical components. This conical dimension provides self-aligning characteristics and ensures proper positioning of the safety disk relative to the valve seat, preventing disengagement while maintaining structural simplicity.
Data Source
Figure 1~3
Figure 2
Figure 4~5
AI summary
A fail safe retaining plug assembly (142) for a slam- shut safety device includes a reset pin (136), a retaining plug (144) attached to the reset pin at a proximal portion (156), and a safety disk (122) attached to the reset pin at a distal portion (154). The retaining plug assembly is sufficiently long to prevent the safety disk from falling off of the distal portion before the safety disk contacts a valve seat (120). The retaining plug assembly is also sufficiently long to prevent the retaining plug from falling off of the reset pin before the safety disk contacts the valve seat.