Technical Paper
Accelerated Life Testing of Push Fit Couplings for Climate Control and Fuel Line Applications
1998-02-23
981083
Push fit couplings are becoming increasingly popular for vehicle climate control systems due to the simplicity of assembly operations that they allow. An accelerated ageing test has been developed which includes the effect of vehicle vibration and thermal cycles. The couplings include elastomeric seals which after time may age, harden and lose sealing force contact. There can also be some permeation of gas through the seal material although this is usually at a low level which can be calculated provided that the permeation constants for the elastomeric materials have been measured. A novel test rig has been developed which allows 12 couplings to be tested simultaneously. There is continuous monitoring of the amount of gas that leaks past the coupling seals using sensitive transducers on the gas collection cells. A test sequence has been developed which includes a primary period of several days at 120°C followed by a secondary period of a few hours cooling to between -20 or -40°C.