A revalidation programme was undertaken on two soviet built gas/condensate process facilities in Kazakhstan, based on a combination of non-destructive evaluation (NDE), site work and paperwork review.
The first plant had been in operation for some 10 years while the second facility was under construction. The annual ambient temperature range is -45 to +45◦C and the field contains relatively high concentrations of acid gases, i.e. up to 4%H 2S and 6%CO 2. Thus for the operating facility, the first task was to identify potential failure mechanisms and their most likely sites in the high pressure vessels and interconnecting pipework, taking into account the steels of construction. These sites were evaluated by a combination of ultrasonic testing, hardness measurements, samples for chemical analysis and microstructure replicas.
The paperwork exercise involved interrogation of the vessel 'passports' to establish whether adequate consideration had been given to the suitability of materials and weldments for the service. This exercise, together with the site data, allowed for conclusions and recommendations to be drawn on the fitness for purpose of the vessels and pipework.