Investigation into the Temperature Impact on O-Ring’s Sealing Performance Using Advanced Stress Relaxation Test

Abstract

Due to the lack of historical data, sealing performance of O-rings in the fuel system of aircraft engines is particularly difficult to study. As great efforts are being made to develop alternative fuels in aviation industry, their compatibility issue with elastomeric O-ring materials has become a major concern. So far, no data has been published on how O-rings would behave in alternative fuel scenario while taking the temperature factor into consideration. The purpose of this paper is to investigate into O-ring’s sealing performance under various temperature conditions, with comparison between Gas-to-Liquid (GtL) synthetic fuel and Jet A-1. Technique used to stimulate the real service scenario for O-rings is the stress relaxation test. Distinguishing from regular relaxation techniques, an advanced stress relaxation rig (Elastocon EB17) with the capability of temperature cycling was employed for this study. Nitrile and fluorosilicone O-ring materials which are commonly found in the fuel system were tested respectively. Three sets of tests were designed to look at how each O-ring material will behave under different temperature conditions. Results obtained so far indicated under extremely low temperature conditions, the relaxation processes of both O-ring materials seem to be ‘frozen’ as the sealing force stops decreasing and maintains a relatively stable level. No fuel preference has shown during the process as O-rings in both GtL and Jet A-1 behaved similarly. Nitrile O-ring showed better relaxation characteristic in Jet A-1 than that in GtL under the 24-hour temperature cycling test; while fluorosilicone presented little differences in these two fuels.