Each certified product related to welding procedure
Regarding welding related to pressure equipment and pressure piping, the applicable laws and regulations (standards) require that the welding methods be conducted and performed using the welding procedure specification (WPS) confirmed in advance. Welding procedure includes welding method, base metal type, welding rod type, temperature of preheating, and stress relief method, and the type of shielding gas. WPS may also be required when welding non-pressure-resistant parts such as welding and hooks and lugs of pressure-resistant parts to pressure-resistant parts.