ALTERNATIVE TRACING GAS MIXTURES FOR VALVE FUGITIVE EMISSION MEASUREMENTS

摘要

Helium is commonly used as a tracer gas for leakage measurements across the world. This gas is easy to use without safety issues and enables to measure a very wide magnitude of leakage rates with well proven detectors (Mass Spectrometers). Nevertheless, shortage and price increase of helium in several world areas, encourage industry users to look for alternative tracing gases for leakage measurement. The Valve Commission of CETIM has decided to investigate the use of two alternative tracer gas mixtures in the field of packing fugitive emissions testing according to ISO 15848-1. This standard allows the use of Helium and Methane as tracer gases. The leakage measurements based on Hydrogen tracer gas has been developed in the recent years, with the use of Hydrogen (5%)-Nitrogen (95%) mixture for safety concerns. The test programme involves comparative fugitive emission measurements on graphite packing, following ISO 15848-1 test procedure with Helium, Hydrogen (5%)-Nitrogen (95%) and Methane (10%)-Nitrogen (90%) mix tracer gases. Several measuring methods are investigated as sniffing, accumulation, flushing and global vacuum using the relevant detectors for the different gases and measurement methods. Whereas the measurements did not appear to be sensitive enough with the Methane (10%)-Nitrogen (90%) for some measurements methods, the Hydrogen (5%)-Nitrogen (95%) mixture has shown a good potential for fugitive emission measurements according to ISO 15848-1.