Corrosion under insulation – an unsolved problem
There are many systems that provide “indications” of corrosion under insulation. Reports suggest that between 1998-2017, corrosion was responsible for around 18% of all pipeline incidents. Our initial evaluation of some of the techniques such as Electro Magnetic Acoustic Transducer (EMAT) and our reading of the literature in this area strongly suggests that results from these techniques can be quite misleading. The problem is that no-one wants the cost of taking the insulation off to assess the level of corrosion without knowing where the corrosion is and there are many hundreds of kilometres of pipe in service. Many of these pipes are ageing.
No major oil company wants to see an oil leak and no leak is good for the environment, but they occur quite frequently. A case study which indicates how inadequate some of the screening is has been published about the San Pablo Bay oil spill after three companies inspected a pipeline and even so there were unfortunate oil spills.
An area that we are particularly interested in and which is potentially more difficult to solve than the usual general pipeline corrosion is what is called “touch point corrosion”. This is where the pipe is supported by a structure which then prevents the pipe from being inspected easily and certainly not accurately. We only like to work with techniques which give clear results which can be quantified and checked. Our tag line is “See, Measure, Verify”.
Defect detection
We have started a journey towards providing the industry with a service that will accurately allow a metric assessment of touch point and corrosion under insulation. As we don’t have faith in the ability of many of the external corrosion detection schemes our schemes work on the inside of the pipe. The starting point is to assess the less common internal corrosion as this can needs to be quantified in addition to the external corrosion. The next step is to ensure that the surface to be inspected is clear of any debris, contamination, rust or anything else that would prevent a good inspection. The final step is to use ultrasonic techniques to assess the wall thickness. All of these operations have to take place remotely from the access point within the structure, often around a number of bends and through a variety of constrictions while navigating other obstacles such as T pieces and valves.
A recent project provided our customer with extremely detailed geometric corrosion information which allowed them to make accurate analysis of the pipe in order to keep the pipe within safe working boundaries. We are currently searching for more customers to discuss how this this technology can benefit their pipelines, particularly in refineries and other plants.
