RE: [PipingDesign] Bolt Thread Engagement

From: <Christopher>
Date: Tue Mar 19 2002 - 10:51:00 EST

>what if this can not be achieved (say thread just flush to the nut)? is it
>ok to use a307 in lieu of a193 to tightened flange joint?
I've had more requests to assess partial thread engagement than hot meals. It usually goes something like, 'We screwed up a fastener and don't feel like buying the proper part. We may have 3 (or 2 or 4) threads engaged. Is that OK?' The answer is, 'No, it isn't OK and someone is going to gig you for it. It may hold for a while but you can't develop a proper preload and over time the joint will loosen. Save everyone a lot of trouble and do it right.' The actual wording varies with the situation, but that's the format.

For your specific question (end of bolt flush with the outer surface of the nut), you don't really have full engagement because the threads at the end of each part aren't fully formed. That's why the stick-out is required by code rules--to get the imperfect threads out of the picture.

The answer to the material substitution (A-307 for A-193) is and unequivocal 'No, the materials aren't anywhere near the same.'

Christopher Wright P.E.    |"They couldn't hit an elephant from        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864) Received on Tue Mar 19 10:51:00 2002

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