CS bolts in DSS body for Valve

[nickypaliwal]

I have seen a piping class of DSS line advising CS bolts.

Where do we use CS bolts with DSS piping ??

Are there other cases like this ?? Lower grade bolts for higher grade metallurgy ?

 

[OGMetEngr]

Wherever corrosion is a concern, which is basically everywhere short of climate control to roughly <60% humidity with constant temperature, this galvanic couple is not advisable. What type of exposure will the bolts see? Are they in direct contact with the pipe?

 

[nickypaliwal]

Yes the bolts are for dual plate type check valve.... However I believe the bolt was a general suggestion for the piping class.... but there was a requirement for PTE coating and Zn -Ni galvanization... still i am surprized ...

 

[OGMetEngr]

If by PTE you mean a thin PTFE filled epoxy, these coatings are for lubrication of threads and offer only very minor short-term corrosion protection. As for galvanizing with Zn, this may help, again depending on exposure. Is this atmospheric exposure, underwater, or other? Sheltered or out in the open if atmospheric?