API 6A - Stud-Bolt thread engagement 1

[blckwtr]

Is there requirements for the stud bolt thread engagement for a flange?

 

[MJCronin]

bick,

It is my understanding that there are several acceptance criteria on this subject.

For acceptance of new construction, I have seen a minumum of three threads and a maximum of five threads "showing above the nut.

For emergency repairs, ourages etc. I would accept anything above "flush with the top of nut"

I do not belive any piping of pressure vessel code has rules about this

-MJC

 

[blckwtr]

Thank's MJCronin...

But I am more intrerested in the engagement for the stud bolts in for example solid goods if a nut is used on just the outside, not the height above the nut showing. How many threads are required? 1*D, 1,5*D ?

 

[pmover]

Source: ASME B31.1

"135.3.4 Bolt Engagement. All bolts shall be engaged so that there is visible evidence of complete threading through the nut or threaded attachment."

hope this helps.

Also, depending upon situation/client, the client may have specific requirements for thread engagement.

good luck!
-pmover

 

[chicopee]

for any threaded engagement,my understanding over the years was that three was only needed. The inference is that if you have let's say seven threads of engagement, only three of them will be taking the load and the rest of them (threads) is superfluous.

 

[blckwtr]

I think you're right, chicopee... But I don't think any specs will allow it...

 

[BlackArcher101]

blckwtr,

I believe what you are looking for is the length of thread engagement in a studded flange connection?

AWHEM (ASSOCIATION OF WELL HEAD EQUIPMENT MANUFACTURERS) has a good TR for specs on studs. It's titled "Specification For Stud Bolts and Tap End Studs", doc# TR9501. Can be found on this page:

http://www.awhem.org/docs.htm

or a direct link:

http://www.awhem.org/PDFs/TR9501A.pdf

Take a look starting at page 7.

 

[Llexlon]

ASME B31.3 allows 1 thread less than full engagement through the nut.

ASME Section VIII Div.1 requires full engagement

Most (if not all) of the API codes will point you back to original design codes for things they do not cover.

Regards,

Chris Sieh