Petrochemical Sector Special Services
Pressure Vessels for Wet H₂S Service
MIND delivered pressure vessels for a compression system intended for a Repsol refinery in Spain. Continuous wet hydrogen sulphide (H₂S) service called for stringent material, heat treatment and inspection requirements.
DESIGN CODE
ASME VIII · Division 1
MATS. REQUIREMENTS
HIC Test / NACE 0103 / PMI
RADIOGRAPHIC TESTING
100% RT before and after PWHT
The Challenge
The project required a coordinated manufacturing and inspection programme for vessels intended to operate continuously in a wet H₂S environment. Material qualification, weld inspection and post-weld heat treatment formed central parts of the specified scope.
Manufacturing Requirements
Material selection and verification
The specified materials underwent testing for resistance to hydrogen-induced cracking (HIC), with test specimens exposed for 96 hours to an H₂S-saturated aqueous solution.
Material selection also followed the NACE sour-service requirements specified for the project, addressing resistance to sulphide stress cracking (SSC).
A 100% Positive Material Identification (PMI) programme verified component chemical composition against the corresponding EN 10204 Type 3.1 material certificates.
Heat treatment and weld inspection (NDT)
Post-weld heat treatment (PWHT) was mandatory. Brinell hardness testing was subsequently performed on every pressure-retaining weld to verify compliance with the specified hardness limits.
The inspection programme included two stages of 100% radiographic testing: one before PWHT and a second after the stress-relief treatment.
Mechanical Design and Surface Protection
The vessels were manufactured in accordance with ASME Section VIII Div. 1. The mechanical assessment included nozzle loads within the applicable UG-22 load cases, together with a 6 mm corrosion allowance specified by the end user.
A heavy-duty C5 protective coating system completed the external protection requirements.
Project Gallery
Capability demonstrated
This project demonstrates MIND’s capability to bring together material verification, mandatory heat treatment, extensive weld inspection and external protection in a single manufacturing scope for demanding refinery applications.
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