One-Time Tightening ≠ Permanent Sealing: Gasket Cold Flow Characteristics and Hot Retorquing Guidelines
Release time:
2025-09-09
PTFE/rubber gaskets have cold flow (stress relaxation) characteristics: after 24 hours of operation, the gasket is compressed thin, and the bolt torque automatically decreases by 20-30%.
Because 'one-time locking' ≠ 'permanent sealing'.
PTFE/rubber gaskets have cold flow (stress relaxation) characteristics: after 24 hours of operation, the gasket is compressed thin, and the bolt torque automatically decreases by 20-30%. If it is not tightened again, the residual stress is lower than the sealing pressure, and the medium seeps out from the micro gap.
The correct approach:
Tighten diagonally and evenly according to the catalog torque;
After 24 hours of system heating or pressurization, perform a "secondary hot tightening" - tighten diagonally again, first restore the reduced 30% torque, and then apply it to 100%;
It is recommended to use "disc spring gasket" or "graphite composite gasket" for high temperature conditions to compensate for relaxation and avoid repeated tightening.
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