Why You Need a System for Locating

What’s the difference between having a good system for locating and not having one??Let’s take a look at a real-life example.

One day our friendly RD locator salesperson received a call from one of his largest customers saying they had a difficult problem.?

They described it this way:

“We have a 12” pipe feeding into a gas turbine electricity generation plant.?We can’t locate the pipe because there is a huge ground grid around the plant and it’s killing us.?We keep losing the signal in the ground grid.??Do you think your equipment can locate this pipe??Can you come out and show us how?”

When the salesperson arrived on the scene, the customer had five or six technicians on site.?There was indeed a visible 12” gas pipe about 200 feet in front of the plant that rose out of the ground making an upside down “U” shape with an isolation joint in the middle before going back into the ground and presumably feeding gas into the turbine generator.?The technicians explained that they put a signal on the pipe, followed it a short distance from where the pipe went into the ground, and then lost it completely.?Nothing they tried seemed to work.

The salesperson asked them to show him what they had done with their RD7200, and sure enough, they had a decent ground with a decent signal going where the pipe seemed to be heading, but it quickly faded away.?So what does one do in this situation?

There is one golden rule to follow above all others when locating:??ASSUME NOTHING.?This rule gets bold type, all caps.?The second thing to remember is, “We have a system for locating because it works.”?

Here’s the definition of a system:

“A set of principles or procedures according to which something is done; an organized framework or method.”?

The nice thing about a system is that when it is followed, it usually results in success.?It helps to prevent mistakes.?It is based on knowledge of locating, not beliefs or assumptions.?A checklist is a type of system.?

Here’s the Radiodetection checklist:

1.???????Be safe -- Wear all required personal protective equipment, e.g. approved high visibility vest and hard hat, to comply with your organization’s requirements.?Observe safe practices in high-traffic areas.

2.???????Read all available maps, as-built diagrams, and identify all visible utilities on the street surface.

3.???????Determine the best method to apply the transmitter signal.

4.???????Verify the transmitter signal output.

5.???????Scan the area for lines carrying the signal.

6.???????Identify the target line by evaluating all the information on the receiver.

7.???????Trace the target line to a known end point for verification.

Each step on the checklist is important.?Each one must be completed or the system falls apart.?Let’s take on the problem above using the locating checklist.

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Be safe.??Everyone followed this with safety vests and hard hats.?There was no traffic in the area.

Read all available maps, etc.??Unfortunately the customer did not have any maps, but this would have saved a lot of trouble.?There were no other visible utilities beyond the 12” pipe.

Determine the best method to apply the signal.?Direct connect was the clear choice since the pipe was accessible.?There was good metal-to-metal contact.?It was possible to get a good ground.

Verify the transmitter signal output.??The customer failed to do this in this case.?They assumed it was good because they were able to pick up a signal (remember the golden rule???ASSUME NOTHING).??When the salesperson applied 512Hz with four power bars, he was able to get 350 mA on the Tx.?It’s fair to question if that was too much signal, but since the customer said the ground grid was absorbing the signal, he started high.

Scan the area.?The customer had not done this.?When they picked up a signal where they assumed (there’s that word again) it should be, they went with it.?When asked, the customer said they did not scan the area.?Scanning the area 360 degrees showed that there was a small amount of current on the customer’s line (15mA), but there was a huge amount at a 45 degree angle from where the pipe went into the ground (290 mA).?This showed that the pipe did not go straight the way it was assumed, but it had a quick angle off to the side after it went into the ground.

Identify the target line.?The large mA reading, the signal strength and depth indicated that the line that angled off was the target, not the one the customer suspected.?Normally Current Direction would also be used, but in this case the customer had a 7100.

Trace the line to a known endpoint for verification.??Tracing the line revealed that it went in a half circle around the plant and ended up at a gas intake valve at the rear of the building.?Not what was expected.?There was no interference from the ground grid.?That was another false assumption.?This verified we were tracing the gas pipe.?Just for fun we traced the weaker signal the customer had been picking up…it turned out to be?bleed off on a water pipe that ended up at a water intake at the front of the building.

At the beginning I asked, “What’s the difference between having a good system for locating and not having one?”?This true story shows it’s the difference between success and failure.?

Here are some key learnings from this example:

ASSUME NOTHING.??In this situation the customer made several false assumptions.?They assumed the ground grid was the problem.?They assumed they had identified the correct pipe. They assumed the pipe would go straight into the plant.?They assumed there was no need to scan the area.?These assumptions did nothing to help them and in fact they made the job more difficult for them.

ALWAYS USE THE SYSTEM.??Follow each step on the checklist as if each one was the most important one.?You can get the job done much faster and more accurately by doing this.

REMEMBER THAT NOBODY IS PERFECT.??If you run into a situation where you aren’t sure what to do, doing nothing is better than doing the wrong thing.?Find someone who does know what to do and ask for help.?That’s what the customer did in this case and it saved them from mismarking the line.

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This article was written by Steve Nichols of Radiodetection. Steve has been teaching about Damage Prevention for over 10 years & has been recognized by many organizations including Colorado 811 for his work.