ASME B16.5 vs Navco Piping Datalog Stud Lengths 1

[ChEMatt]

I noticed that the stud bolt lengths are different in the Navco book than those of the most recent B16.5. The standard at this company is that 1 1/2 threads are visible after installation. Some people I've spoken to swear by the Navco publication.

What I'm concerned about is studs that are too short and are tossed aside and re-ordered for longer lengths. In other words, wasted money/material/time.

In your experience, is B16.5 merely the minimum length, and longer bolts should be ordered? For example, a 3" bolt for a 150# flange is 3.5" in B15.6, but in the Navco Piping Datalog it's listed as 3.75". Just a few spot checks looks like they added 1/4" to all the B16.5 lengths.

I understand the issue could be you may run into clearance issues during installation if you have cramped conditions and the bolts are too long. That's not really the situation I'm looking at.

Thanks for your help.

-Matt

 

[XL83NL]

For B31,3, refer to para 335.2.3 for Code requirements on bolt protrusion. (Consequently look at para 135.2.3 when youre working to B31.1).

That being said, the Code provides a minimum set of rules. If youre working to the Code, you have to comply with it.
Fortunately it only provides a minimum. It's up to you to set the max. However, there's max to the max.

As you may have noticed, B16.5 bolt lengths may be short at times. As per B16.5 para 6.10.2 the designer is free to use his/her own length; B16.5 lengths are there only for reference. I believe most of our engineered bolt lengths are quite often longer than the B16.5 lengths.

We typically use bolt lengths that, at both ends, have 2-3 threads protruding the nut. Beyond that, the stresses in the bolts are almost zero.
Another thing we found is that specifying a length that corresponds with that criterium, you really have to max. Dont use more.
Standardize on lengths that incementally go up 1 unit that you can visually determine. E.g. we use lengths of 80 mm, 90 mm, 150 mm, 300 mm. That way you can standardize everything, but still increments you can visually separate.
Dont go for lengths with too little increments 85 mm, 90 mm, 95 mm (i.e. increments of 5 mm).

On the other end (literally), it's also not advisable to have too much length, apart from it being a waste of money.
There are some profesionnals that vote for having the threads flush at the end of on nut, and the rest behind the nut at the other end, such that in case of disassembly, corrosion at both threaded ends wont become too much of a time-consumer when the bolts have to be removed (which is a big problem often w/ B7s).

In the end, I think it's a matter of satisfying code calcs and requirements, together with field practice based on feedback of your bolting technicians.

For further reading, the foreword of B16.5 and non-mand. app. C provide some more details on bolt length calcs in B16.5.