HTHA inspection course launches in the UK


Over the past three years, Lavender International has been involved in developing advanced and novel NDT techniques to reliably detect the early stages of high-temperature hydrogen attack (HTHA). Research & development (R&D) work conducted by Lavender has led to a better understanding of modes of inspection that can more reliably detect early-stage HTHA. Results from trials have found that colonies of micro-fissures, individually as small as 50 to 100 μm, can be detected in certain circumstances. This is a landmark step to making inroads into more reliable detection of early-stage HTHA.

HTHA generally occurs when pressurised equipment containing high hydrogen partial pressures operate at elevated temperatures (above 204°C). Over time, the hydrogen diffuses through the pressure vessel wall. Diffused hydrogen can then start to form CH4 (methane). The formation of methane occurs when hydrogen depletes some of the carbon from a carbon steel and this is known as decarburisation. Methane bubbles/voids form in solid steel along the grain boundaries. The combination of these accumulating voids and depletion of carbon has the potential to marginalise the material mechanical properties. This alone is an engineering concern. Over time, the number of methane voids increase along grain boundaries to a degree that micro-fissures (tiny cracks) begin to form, connecting lines of weakness. These progressively grow into large fissures, which have the potential to cause major cracks with a progressive impact on structural integrity.

Tim Armitt, who has had over 30 years’ experience within the NDT industry, has developed a unique HTHA inspection training course designed to educate advanced ultrasonic testing (UT) inspectors in the methodologies and techniques employed to detect the early stages of HTHA.  
Tim will be talking about HTHA and inspection techniques at the NDT 2018 Conference taking place in Nottingham from 10 to 12 September. There will also be HTHA demonstrations on the Lavender stand, 27.