Testing with chemical reactions and dye penetration

Occasionally leaks can also be located or detected by means of chemical reactions which result in a discoloration or by penetration of a dye solution into fine openings. The discoloration of a flame due to halogen gas escaping through leaks was used earlier to locate leaks in solder joints for refrigeration units. 

A less frequently employed example of a chemical effect would be that of escaping ammonia when it makes contact with ozalid paper (blueprint paper) or with other materials suitably prepared and wrapped around the outside of the specimen. Leaks are then detected based on the discoloration of the paper. 

Method Test gas Smallest detectable leak rate Pressure range Quantitative measurement 

Thermal conduct vity leak detector Gases other than air 10 -7 Positive pressure and vacuum No 

Halogen leak detection Substances containing halogens 10- (10- ) 7.10-= (10- ) Positive pressure (vacuum) With limitations 

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