Petrochemical welding joins equipment and piping for chemical processing facilities that convert hydrocarbons into chemical products. These applications demand stringent welding quality due to hazardous materials, high temperatures and pressures, corrosive environments, and potential for catastrophic failures.

Material diversity in petrochemical welding includes carbon steel for general service, stainless steels for corrosion resistance, chrome-moly alloys for high-temperature hydrogen service, nickel alloys for severe corrosion, titanium for chloride service, and clad materials combining corrosion resistance with structural strength. Each material requires specific welding procedures and controls.

Petrochemical welding challenges include thick-wall reactors and vessels requiring multiple passes and post-weld heat treatment, dissimilar metal joints between different alloys, temper bead techniques for heat-sensitive materials, overlay welding for corrosion-resistant cladding, and maintaining chemistry controls for sour service resistance.

Quality requirements exceed many industrial applications due to consequence of failure. Procedure qualification demonstrates acceptable properties, welder qualification verifies skills, preheat and interpass controls prevent cracking, post-weld heat treatment relieves residual stress, and comprehensive NDE detects defects. Documentation provides complete traceability.