Let’s Talk About Gas Pipelines

Let’s talk about gas pipelines, not the wee one that maybe fuels your cooker if you are lucky enough to be on the grid. No, I’m talking about 5 big ones which are each about 36 to 40inches in diameter and snake their way from St Fergus to the rest of the UK. These babies are pressured up to something over 1000psi. Not the sort of pressure you can hold in with your thumb. They continue to transport thousands of Standard Cubic Feet, Or SCUFs in the trade, day in and day out.

They are buried in the fields around us and the only indication is those familiar red and white poles. Wouldn’t it be great if they could transmit electricity like that? Oh wait….

Well, what has this to do with pylons and SSEN? The answer is there is a phenomenon known by several different names like Pipeline Induced Voltage. If you build a line of pylons close to and parallel to a buried steel body, it will pick up voltage. The effect can occur at distances of a kilometer or more.

PIV is bad news on 2 fronts. It can reach high levels and get trapped inside the pipe. The pipelines are covered in a corrosion resistant coating. Some poor worker touching the bare metal of the pipeline, a good distance away can get zapped…fatally.

The second danger is AC induced corrosion. If you get the voltage trapped inside the pipe and there is a tiny defect in the coating, created for example during installation, current will leak through the defect to earth, corroding the steel until it results in a perforation. Bad news for anyone around.

There are several factors which affect PIV, and the corrosion risk, the distance between pylon line and pipeline, the amount of parallelism, the capacity for electric current to travel through the soil (resistivity), the quality of the coating (a good cover with just one or two small defects is bad) and if it is going to happen it is more likely when there are sudden changes in the direction of pipeline or OHL.

To cut a long story short, SSEN haven’t included the risk to pipelines in their planning application, they have designed a route where there is a lot of parallelism and incredibly close proximity and a lot of bends in the pipelines. They have also failed to do proper measurement and monitoring of the soil resistivity so they can’t reliably model the risk.

Oh and to add insult to injury, if there is a leak, the gas will escape in a cloud mixing with air until it is at explosive levels at something like 50m above the ground, just looking for an ignition source. Now where would you find something all crackly and sparky 50m in the air?.......

Photo is of a fatal accident site in Texas caused by installation of power lines near a gas pipeline.

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