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Parent Category: Safety Info Posts

Category: Chemical Process Safety (PSM/RMP)

Published: 13 February 2012

NOTE:  Members should also read Process Safety and our pipe flanges (type of bolts, threads showing, etc.)

Some may claim this to be a trick question.  I assure you it is not meant to be, but as I will point out in this article, having too much bolt extending beyond its nut can be an issue, as well as not having the bolt flush with the outer surface of the nut.  

Have you ever encountered a nut and bolt assembly where something did not look right?  How about a pipe flange or a manway on a pressurized process where the nuts are just biting onto the bolt, clearly because either the wrong bolts were used or an incorrect gasket assembly is being used and not allowing the two flanges to meet their tolerances?  And by the way, this article can apply to any bolt and nut assembly, not just pressurized systems or chemical processes.  As a safety professional, I use the principle on my kid's bicycles!!!  The $64,000,000 question is... how far should a bolt pass through a nut in order for that assembly to meet the full ASME design rating?  

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#7 Bryan 2013-08-01 12:55

THANKS Maurice! I thought I had included that as well. I am updating the posting to provide the B31.3 reference as well.

+1 #6 Maurice 2013-08-01 08:31

ASME B31.3, 335.2.3, states:
Bolts should extend completely
through their nuts. Any which fail to do so are
considered acceptably engaged if the lack of complete
engagement is not more than one thread.

So it is also an ASME requirement (which should not be adopted ;))

+1 #5 E. Tate 2012-12-05 21:24

I have been applying anti sieze on steam gaskets for 30 + years and to my knowledge have not had a failure and it sure makes it eaiser to remove during disassembly

#4 Randy Williams 2012-11-24 05:35

NIce read. Will use some of this in our new training manual

#3 Andrea 2012-08-23 13:38

Thanks for this refresh, very duty.
I need a simple imformation: how could a bolt stay below a nut? 'cause I need to deny a work done to a third party, where some bolts are below nut up to two threads. Thanks in advance, best regards

+1 #2 Hevii Guy 2012-05-10 07:18

Darn: Your comment regarding "bolt length beyond the nut" means that on fasteners larger than 1/2", bolt tensioners cannot be used

Of course, this isn't the case but, it clearly shows that everything still hasn't been considered.

J Albrecht
www.heviitech.com

+3 #1 Mark Montgomery 2012-02-20 19:50

Hi Bryan

Thanks for this article, I found it very useful and will be sharing it with some of my major process clients.

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