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troubleshooting holiday detectors

In Case of Trouble:

  1. Clean battery contacts​

  2. Replace battery with one that has been properly charged

  3. Moderately shake the detector while it is running. If it does not continue to run steadily, remove battery box and slightly bend battery contacts out from detector.

  4. The pipe must have good electrical contact with the earth -- grounded properly.

  5. The ground wire must also have good electrical contact with the earth. It should be about 25 feet long, clean and reasonably free of kinks. Pulling over skids, dried vegetation or dry clods of earth can cause the detector to indicate a holiday where one does not exist or to pass over a known holiday without finding it. In extremely dry conditions it may be necessary to connect ground wire directly to the pipe. Usually a thin weak spark indicates poor grounding.

  6. Correct voltage output for a given thickness of coating has long been a matter of controversy. However, recent formulas have been suggested which may be used as a guide for correct peak voltages on various coating thickness. The calculation is as follows:

  7. These formulas, when applied to a coating of 3/32" thickness and with a constant of 1,250, would indicate applied voltage of 12,500 volts peak or a coating of 16mil. thickness and with a constant of 525 would indicate an applied voltage of 2,100 volts peak. A common practice used in setting inspection voltages in the field is to adjust the output voltage by visual observation. It is the consensus that spark discharge at least twice the thickness of the coating will give adequate inspection voltage and compensate for any irregularity in coating thickness and grounding conditions. If this practice is desired for determining inspection voltage, it should be done while the electrode is in the normal operating position and under actual ground conditions.


Peak voltage in volts

Constant of 1,250 for coatings over 30 mils and 525 for fusion bonded epoxy coatings. 

Thickness of bonded coating in Mils (not including outer wrappers). 

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