bolts/nutsin caustic or amine service. 1

[jiang1976]

We use SA193-B7M/SA194-2HM for Bolts and Nuts in H2S service. How about amine or caustic service. Can we use SA193-B7/SA194-2H for amine or caustic service?

Thanks

 

[SJones]

The degradation mechanisms in the bolting resulting from exposure to amine or caustic solutions are different to those from other H2S containing fluids. They will be dependent upon the stress levels in the bolting rather than related to their mechanical properties. If the bolting (it is assumed that the bolting is external and not continuously immersed in the fluid) has been installed with correct torquing, resulting in a stress no more than 75% of SMYS, the risk of failure from exposure ensuing from say, a flange leak, would be negligible. However, you may still wish to use B7M to prevent any bolting mix ups with H2S service on the same plant.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[jiang1976]

continue this issue.

If the bolting is used for vessel internal (vessel in caustic service). Do we really need to use B7M?

Accoding to S Jones comments above, we do not need to worry about the caustic stress cracking for B7 bolting because there is no residual stress in the bolting material.