Tinker & Rasor PD/H - Pearson-Method Short Locator / Holiday Detector

The Tinker & Rasor Pearson type detector was designed to locate discontinuities, flaws or breaks in the coating of buried pipelines. This method makes possible the exact location of coating breaks in buried lines without access to the surface of the coated pipe. Locating electrical discontinuities aids in evaluating the application of a coating and also these discontinuities can be repaired to eliminate corrosion and to reduce the amount of current required for cathodic protection.

Short location

The apparatus is also effective in locating shorts or undesirable electrical contacts to buried coated pipe. Such electrical contacts should be removed prior to placing a pipeline under cathodic protection, as these contacts would drain a large amount of protective potential from the coated pipe.

The method of locating shorts or contacts on a coated pipe is that of applying a relatively large amount (5 to 15 watts) of audio frequency AC between the pipe and a remote ground connection. A traverse is made along the pipeline with a Receiver equipped with a search coil. A short or contact is observed along the traverse where the average AC signal picked up over the line suddenly drops to a very low level. This is assumed to be a point directly above the contact.

Pipe location

The PD can be used very effectively as a pipe locator on coated pipelines that are electrically connected by a screw or welded joints. This application is particularly effective where it is desired to locate and follow one pipeline along a right-of-way where there are a number of buried lines.

To locate pipe, an audio frequency AC signal is placed between the coated pipe and a good ground connection. The Receiver, containing a search coil, is passed over the area where the pipe is assumed to be located. As the Receiver is moved back and forth in a horizontal plane over the pipe, a sharp null will occur in the received signal. The pipe to be located is assumed to be directly under this null. A well-coated pipeline can be followed for a very great distance by this method when audio power of from five to fifteen watts is applied to the coated pipe.