Leak Detection: General Remarks and Examples

Abstract

Structure defects may be detected by all the non-destructive analysis techniques from radiography, magnetic particles, liquid penetrating, to ultrasounds, to eddy currents, etc. Nevertheless, to evaluate the quantity of liquid or gas that may be lost in the surrounding ambient specific techniques related to leak detection should be considered. Frequently the maximum acceptable leaks must be evaluated to select the method suitable for the specified object and, finally, to compare the solutions on the basis of costs-benefit relationship. Various leak detection methods and related instrumentation are available (bubbles, ultrasound emission, radar, pressure/vacuum variation, thermal conductivity, halogens, radioisotopes, selective ion pumping, mass spectrometry). Before starting any type of leak testing, it is necessary to decide whether leaks have to be located or measured. Checking the tightness of an object or device implies the measurement of gas flow coming out from a defect or entering through it and reference devices should be provided by primary or accredited laboratories. After a short review of methods/instrumentation attention is given to the calibration of any kind of systems and methods to guarantee the validity of the whole test.