Helium Leak Detector With Improved Sample-Delivery System

The figure schematically depicts a portable helium leak detector that includes an improved sample-delivery system. This instrumentation is designed for detecting leaks in the fuel and oxidizer systems of the space shuttle main engines. In a helium leak test, helium is used as a tracer gas in place of the hazardous fuel or oxidizer: The fuel or oxidizer plumbing of interest is pressurized with helium. The aft section of the space shuttle (which section contains the plumbing) is purged with air, and the portable helium leak detector is used to monitor for any increase in helium content of the purge exhaust at concentrations down to the part-per-million level. The portable helium leak detector can also be used to perform tests to detect very small leaks in systems other than the space shuttle main engines.