Q. What is Holiday Detection?

Each length of coated pipe shall be checked for holidays with a high quality, heavy duty, full wave rectified non pulsating direct current detector, with output variables from 0-3000 V (D.C.). The coating shall be holiday checked with the detector set for 127 V (D.C.) for every 1 mil of coating (5000 V/mm). The voltage shall be set and checked twice per 8 h shift using an accurate volt meter. The detector electrode shall be in direct contact with the entire surface of the coating being inspected and shall be wet sponge or conductive rubber.