Fasteners(studs and nuts) in NACE service piping joints

[abhishekagrawal87]

Since fasteners (in any service whatsoever) are not in direct contact with the fluid itself, what supports the argument(for a NACE/sour service application) that NACE/ISO15156 compliant studs to be only used for making flange joints?

If the answer to above is 'No you still need NACE studs for NACE service' then - "As ISO 15156 requires hardness of material to be limited to certain maximum value (22HRC for carbon steels), if the hardness can be limited for studs normally not listed as NACE compatible (for eg: A193B7), can compliance to NACE for that joint be adequately demonstrated?"

 

[auzie5]

Flanges can leak. Furthermore, many flanges have insulation blankets around them (above ground piping) or are taped up tight (below ground pipelines). So a small leak of sour fluids can be traped in the flange "casing" and engulf the bolting materials. We use B7M/2HM studs/nuts for most sour applications.