Project Description
In the oil and gas industry corrosion of pipes can lead to serious leaks that can disrupt production as well as have serious safety implications. At large sites, e.g. Woodside’s Karratha Gas Plant, the pipes carrying liquefied natural gas (LNG) need to be insulated to maintain low temperatures of the liquefied gas. Ingress of water into the insulated cryogenic pipelines may cause rusting, which affects the integrity of the pipes. This is known as corrosion under insulation (CUI). Inspection of the pipeline for rust is expensive and time-consuming as the insulation and cladding need to be removed for visual inspection of the pipe.
The project studied sections of pipe insulation (Cetrafoam closed cell foam and Rockwool) using THz and found that the lowest part of the spectrum (around 0.1 THz or 100 GHz) penetrates the material best. There are two attenuation mechanisms, absorption and scattering. With our current system, we cannot characterize scattering. To do this we need to build what is known as a goniometer, where we can measure the THz scattering from the foam sample over an angular range of 180 degrees and when it is reflected from the metallic pipe.
Once the scattering is fully characterised it is expected that pipe corrosion i.e. rust and delamination will cause changes in this scattering signature. 0.1 THz is on the edge of the microwave regime and more powerful sources exist at this frequency and are relatively low cost. The absorption and scattering features at this frequency. A paper titled, “Non-Contact, Non-Destructive Testing in Various Industrial Sectors with Terahertz Technology” was published in January 2020.
If GHz-THz can be shown to be useful in characterizing and fully penetrating insulation and reflections from normal and corroded pipes show a difference; we plan to expand the project to a prototype THz-CUI detector system that could be trialled on site.