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Design for anchor bolt corrosion in refineries, etc

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What is the recommended practice, if any, for accounting for corrosion
acting on anchor bolts for industrial equipment (say, in a refinery,
chemical plant, paper mill, water towers, etc) and the effect this may have
on the bolt ("anchor rod") size?

When selecting connection bolt size for buildings and similar structures the
size is based by determining the tensile stress acting on the shank. But in
this sort of application corrosion seems to be of little concern.

Unlike anchor bolts for most building structures, those for industrial
equipment (and I am thinking specifically of tall pressure vessels and
stacks in refineries) are often subject to large tensile forces. For
industrial equipment subject to large amounts of corrosion the threaded
portions of the rod may also corrode, so it seems reasonable to size the
bolt based on the thread root area in the corroded condition.

I have seen a conflicting opinions in various published references. Maybe
not so conflicting, 'structural' references address sizing anchor bolts by
stress on the shank but do not mention anything about corrosion, texts that
address design of ASME pressure vessels size the bolts based on root area
and generally mention that corrosion is a factor.

So, what is practiced? apply a corrosion allowance to the threads and size
the bolt based on the corroded root area? size the bolt based on the
corroded shank area? Or ???


Thanks!
Tom Barsh, P.E.



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