For the weld tie-ins to High Pressure Steam Separator, contractor wants an exception for hardness check for qualifying WPS - they want to use old WPS, qualified based on Rockwell B hardness tests.
My view is that to prevent Caustic SCC in HP Steam system, hardness control particularly at fusion line (HAZ) is essential; hence hardness testing shall be carried out using a permitted methods i.e, Vickers 10 scale as per NACE SP0472 for WPS Qualification and cooling rates and temper bead thermal methods for hardness control shall also be applied. Production hardness tests may be avoided based on the exception given in Table 2 (for the right combination of welding process and filler materials) if preproduction hardness test is carried out and filler materials is recorded.
Appreciate your comments about my understanding as above. What is the practice at your plant? Many materials / welding engineers still consider steam service as clean service and relax any special welding precautions/ requirements.
Thanks,
Akshat Agrawal
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