We are all aware that there is a high risk of series injury or death from striking a buried utility whilst digging. So naturally we utilise a Cable Avoidance Tool (C.A.T) to search for the presence of buried cables, pipes and other utilities.
Like all safety related equipment, operators should undertake training to understand the correct use of cable avoidance tools. How the equipment is operated will directly affect the performance of the instrument and on occasions cause the C.A.T not to pick up the presence of a buried utility.
The following simple points highlight ways improve the search for buried utilities.
When undertaking a search, we should sweep not only the excavation area but the surrounding terrain to determine the route or path of any utilises that may be present. The sweep should be steady and deliberate, ensuring the whole area is covered by adopting a grid pattern.
How the C.A.T is held can affect the performance of the instrument. If the operator privets their arms and swings the C.A.T, the base of the instrument is lifted into the air and will not be searching for a signal in the ground.
The correct way to hold a C.A.T, is with the instrument vertical and the bottom end just above the ground.
By adopting the correct method of use, will help improve the performance of any instrument. However, there will be occasions where buried cables may not radiate a signal or are too weak.
The perfect example is locating the power cable running to a street light or sign. If the main light is off, the cable may not generate a live signal.
By utilising a Signal Generator (Genny) with the C.A.T, will enhance the search capability. The Genny will apply a tone to a buried cable which can be picked up by the C.A.T locator switched to the Genny mode.
There are two ways the Genny can apply a signal. The first is to directly connect to the service and the second to place the Genny in the area of the utility and ‘induce’ a signal.
The direct connection method is an ideal solution for checking a street light power cable. The connection lead is clipped to the metal cover of the street lamp with the second part clipped to the earth stake. Once plugged in, the Genny will transmit a signal to the metal street light frame which in turn is earth through the power cable.
With the operator standing approximately 10 paces away from the Genny (to avoid any chance of picking it up directly), the operator sweeps the area around the street light.
When the C.A.T is passed over the ‘induced’ utility, the display will indicate a peak signal. By moving slowly backwards and forwards, the operator will reduce the sensitivity to narrow the response.
Once the signal has been identified, the operator can turn the instrument on it’s axis until the signal reduces. This indicates that the C.A.T is above and in line with the target.
This procedure is then replicated until the length of the line has been traced.
When inducing a signal through the Induction method, the Genny is placed over the utility. A signal is applied to the utility, allowing the operator to trace with the C.A.T. But in congested areas, multiple services can be induced with the same signal.
If this is the case, the Genny can be placed on its side over the second utility to screen its signal, allowing the operator to trace the original service without interference.
By utilising a C.A.T and Genny together, you will dramatically improve your search capabilities.
For further details of correct Genny use and how it improves chances of locating services please contact 0800 069 9533.
Many thanks to Radiodetection for their help in compiling this article.
Always refer to the specific Manufactures manual and training guides for use of all cable avoidance tools.
Click for Radiodetection cable avoidance range
Click for more information on the Cable Avoidance Tools (C.A.T)
Click for more information on the Signal Generators (Genny)