Leak testing of engineering components comprises use of high pressure test gas, carrier gas, discharge tube detector and laser spectrometer, where both gases are constituents of air

摘要

The objects are located within a flow of a carrier gas and a small amount of a test-gas is internally introduced to the object; alternatively the relative locations of the two gas systems may be reversed. The test-gas is at higher pressure than the carrier gas, into which it will flow if a leakage path exists. The outlet gas from the device is examined for the presence of test-gas by feeding it into an electrical-discharge cell to produce a plasma and analyzing the radiation from the excited gas by laser-absorption or laser-fluorescence spectroscopy. A test object (1) is connected between three-way valves (7,9) , which are set such that carrier gas first flows from a source (3) , via a valve (5), direct to a discharge cell (20) under the influence of a first vacuum pump (14), capable of drawing vacuum down to levels of 1-10 mbar abs.. Simultaneously the test object is evacuated via a valve (9) and a second vacuum pump (15). On reaching a predetermined vacuum level (e.g. 2 mbar), as detected by a gauge/pressure switch (13), the valves are swung to allow the carrier gas to flow through the test object and into the discharge cell. The test object is surrounded by or swept by a jet of test-gas.