Holiday detector

For the examination of paint films or special coatings, e.g. pipe linings, low-voltage holiday detectors with wet sponge electrodes are available. 

The choice of voltage for use with a holiday detector depends on the thickness and type of coating applied to the structure. As a guide, in the case of pipelines, a voltage equivalent to approximately 5 kV/mm thickness is used in testing a coal-tar coating. 

Rasor, J. P., Selecting a Holiday Detector , A Collection of Papers on Underground Corrosion (Ed. George B. McComb, NACE), Vol. 4, 1st edn (1960)... 

Holiday Detector a high-voltage low-current output generator with a built-in spark gap used for detecting pinholes (holidays) in pipeline coatings. 

A special piece of equipment, known as the holiday detector, is a hoop of metal placed around the pipe after it is coated and wrapped. A small electrical current flows through the hoop, If there is a holiday. i.e., a spot where there is no coating, the detector alerts tine operator. This is brought to the attention of a special crew that coats and waps bare spots in tile pipe. 

Holiday detector n. Device for detection of pinholes or voids. 

Holiday detectors must be selected for the thickness and type of coating being tested. Excessive voltage can stress or damage thin coatings if the detector has been set too high. Adherence to the manufacturer s instructions is recommended, including both the manufacturer... 

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