Sandblasting flange and piping side affected paint on flange nuts and bolts

[amhaz75]

The paint on hex nuts and bolts was affected by sandblastng operation done on flange joint piping. No mechanical damage was noticed on the body, face or thread of nuts and bolts. The bolts are torqued and the line is in service. My question is do we need to replace the affected bolts or just re-paint will be sufficient? See attached picture.

 

[sk10009]

No problem to use becaude bolts were already tightened and it's ok for you to repaint during next shut down time.

 

[amhaz75]

Thank you SK10009 for your input. Thats what I thought would be good.

 

[racookpe1978]

The "strength" of the nuts and exposed stud/bolt threads is not affected - yet! The exposed threads are "past" the engaged threads within the nut, right? And - as poited out above - the nuts were already tightened, and were not "loosened" during the sandblast.

But! You MUST immediately coat them to prevent the "clean metal" from rusting away because their primary rust protection is gone. Expect to replace the bolts next outage because thread damage while unscrewing them is almost certain to occur on more than 1/2 of the bolts.

 

[amhaz75]

Thank you racookpe1978.
The fastener is an A193 Grade B7 Chromium-Molybdenum Alloy Steel stud bolt chosen for its corrosion resistance and high-temperature strength.
The Fluoropolymer coating (bluing), topcoat is intended to reduce friction during tightening.