What’s Weighing Down Your Pipeline Integrity Program?

So I’m sitting at my desk, trying to figure out how to make Excel do what I want it to, but all I am getting is “#VALUE!.” What does that even mean? Then my phone rings, and I’m truly grateful for a legitimate excuse to leave the problem at hand.

The call is from our construction supervisor who is overseeing the repair digs on a recently completed 200-mile coating survey on a buried pipeline. He says they are doing the digs on the largest reported signals and asks, can our survey method identify anomalies under concrete coating or swamp weights?

“Well…,” I hesitate because I had no idea that they had any concrete coating or weights on the pipe that we surveyed. I answer truthfully: “Yes, the survey methods can identify any bare steel that has an electric path to the soil.” Then I explain that from experience it is more likely that there is uncoated reinforcing wire in the concrete that is very close to, but not touching the pipe, and that this can and does create a response indistinguishable from a coating fault on the survey methodology that we used. I explain that I have seen this happen on concrete-coated pipe at river crossings and also at swamp and river weights.

“Just where was this dig?” I ask, and he replies “under that paved street in that luxury-gated community.”

Ouch…this was surely an expensive dig for what very well may turn out to be an unnecessary excavation, costing thousands of dollars. Worse yet, this surely caused a significant disruption for the retired population of the neighborhood, undoubtedly mostly made up of retired lawyers, judges and senators judging from the size and beauty of the homes!

My associate then asks; “So why didn’t we know this was concrete-coated pipe before now?” Now he knows better - when you ask me a question you need to be prepared for the answer, and I’ve been told that sometimes that can be a little like drinking from a fire hose.

But I start gently, “Well, for starters, the pipe material and route sheet data did not indicate there was a change in coating type, and technically there wasn’t.” You see, the concrete coating and swamp or river weights are typically applied over the standard coating, therefore, when you ask a computer for a list of coating transitions you don’t always get the concrete stuff. I scratch down a note to add this to our GIS query for our pre-coating survey data review.

We didn’t think to check for concrete because this location happens to be in the middle of a flat and dry community, and concrete coatings and weights are normally only put on the pipe to reduce buoyancy in wet areas. Think of how an oil tanker bobs like a cork on the ocean even though it’s made entirely of steel and filled to the top with crude oil. Like the tanker, the pipeline volume displaces water and soil with a greater density than the pipe and its product, making the pipe buoyant, so without the extra weight it could actually float up to the surface in wet soils.