TWI Developing High Temperature Hydrogen Attack Test Rig

TWI has passed a milestone towards developing a test rig capable of simulating high temperature hydrogen attack (HTHA) in a full scale pipe and monitoring the evolution of damage during the test. HTHA is an insidious form of damage that has severely affected the downstream oil and gas industry in particular, but also other industries.

Following changes to the regulatory framework in the United States, the Health and Safety Executive (HSE) made an assessment of the risks in the UK, with support from TWI, which was published as a Safety Alert by the HSE in December 2018.

Following on from the work done for the HSE, TWI started an R&D work programme to improve understanding of the HTHA mechanism in carbon steels, which are considered to be particularly susceptible. The current regulatory guidance to industry is to remove this material from service at every opportunity and to improve its management as a matter of urgency. Inspection is a key part of any management strategy and the renewed focus on HTHA has spurred on the development of new technologies.

A key challenge for effective management is detecting the emergence of HTHA during the early stages. A working group of industry experts in the subject was assembled as part of the American Petroleum Institute (API) task group for RP 941, which provides guidance for use of steel equipment in hydrogen service at elevated temperatures and pressures. The working group was tasked to revise and update guidance in Annex E of API RP 941, which contains information and recommendations for inspection. TWI took part and monitored activities on this working group and is now preparing the next stages of the R&D programme on HTHA with a view to testing and supporting the revised guidance for industry.

A key output of this work will be validated ultrasonic inspection techniques and procedures whose sensitivity to the early stages of HTHA will be quantified. The large scale test rig is expected to provide well characterised calibration specimens for use in industrial inspection. In addition to inspection capability at ambient condition for use in outages, TWI is aiming to develop the next generation of technology for monitoring critical components during operation at elevated temperatures up to 350°C.

The technology and capability being generated for inspection and monitoring will improve the detection and management of many critical damage types in a number of industries.