CD42 Pipeline Pig Location & Tracking System
Page 55
Chapter 7 - Locating a Stationary or Stuck Pig
Finding the Pig’s General Vicinity
When trying to find the general location of a pig, the operator should first be sure that the Gain of the
CD42-R is properly set. If the surrounding environment is noisy, turn the gain down so that the
ambient noise shown on the screen is no higher than the second row of “dots” across the lower part of
the screen. If the Gain is turned down too low, the transmitter will not be located by the CD42-R
receiver. If the Gain is turned up too high, the transmitter signal will be “hidden” in the noise. A Gain
setting of 5-7 should prevent the operator from walking past the pig without locating it.
If the operator leapfrogged the pig properly (Chapter 6 - Tracking a Moving Pig) then he should have
an area bounded by the leapfrogging points where the pig is located. Simply walk the pipeline, as close
as possible, and watch the screen of the CD42-R begin to display the pulses of the CD42-T1 transmitter.
While this is being done, it is very important that the CD42-GP antenna be held
parallel
(Figure 81) to
the pipeline.
Figure 81 A Parallel GP Antenna Orientation
While the antenna is being held parallel, the waveform signals will get stronger the closer the operator
is to the pig (Figure 82). This allows the operator to simply walk the area until a signal is present, no
matter how faint, and then walk in the correct direction to make the signal strength rise. If the operator
walks past the pig, the signal strength will begin to fall. Once the operator thinks the pig has been
located, make a positive ID by laying the antenna down on the ground and verifying the pulse of the
transmitter.
