Lightning expertise helps protect pipeline instrumentation
Abriox has upgraded the lightning protection on its remote corrosion monitoring solutions for pipelines, with the help of the lightning test consultancy services of Cobham Technical Services. The degree of protection of the system against high energy surges has been substantially enhanced by a development exercise incorporating advice on the nature of coupling between lightning power surges and ground-based equipment, and characterization studies including destructive testing.
The protection has been implemented on Abriox's Merlin cathodic protection (CP) monitor. This telemetry-based instrument is one of the most widely used field devices for remotely monitoring the anti-corrosion CP systems that are installed on pipelines, storage tanks and other buried metal infrastructure used in onshore oil and gas networks.
"Pipelines are a significant attractor for lightning, and in some regions of the world strikes can occur frequently. We've always had lightning protection on our corrosion monitor, but the only feedback we ever got on how it performed in the real world tended to be when a burnt-out unit arrived back from the field," said Jason Hanlon, technical director of Abriox. "How much energy was present, what the shape of the energy surge was, whether it arrived directly or indirectly remained a mystery - and we decided that it would be a good idea to better understand the risk by talking with lightning experts."
An initial review considered the particular installation conditions and environments of the Merlin CP monitor, and a typical catastrophic field failure. A destructive test at Cobham's test facility in Abingdon was performed. It became clear that the corrosion monitor was most likely dealing with power surges that arrived following direct strikes on the pipeline itself, or the supply to the electrical rectifiers that provide the impressed-current cathodic protection system. Unlike some of the areas that Cobham works in - particularly aircraft protection - there are no standard lightning test waveforms for this type of nearby strike to ground-based equipment, but that did not prevent Cobham from creating a representative waveform specifically for this testing purpose.
The destructive test exercise also demonstrated to Abriox that some of the external lightning surge protection devices originally selected for use with Merlin did not actually perform in the way the manufacturer’s datasheet indicated. Although other aspects of the Merlin design provided a good degree of protection, the Abriox designers sought further improvement.
After the exercise, Abriox gained a better understanding of the nature and energy levels of lightning-related power surges, and decided to re-engineer the system to increase the protection level. This exercise involved both uprating the surge protection circuitry, using different components and changing the physical layout of parts of the embedded electronics system.
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