assembling flanges with studbolts

[abbver98]

In appendix 2 of ASME VIII div 1 I see no mention of using studbolts (two side threaded wire + nut at each side); only bolt (screw + 1 nut). But in ASME B16.5 we can use studbolts.
Does ASME VIII div 1 allow using studbolts ? To avoid lossen at high temperature (differential straining) should we use nut and counter nut (in total 4 nuts) ? Should we use also spring washer to maintain adherance ?
Thanks for help

 

[unclesyd]

Comeback with a physical description of your joint and the environmental conditions.

We use studs on all piping flanges up to 1250F. We never use bolts on piping flanges except on some water lines.

 

[abbver98]

flange made with CS (A105N)
316 SS bolting B8M/8M size 7/8"
graphite gasket 2 mm thickness
non standard dimension
temperature depending on application : sometimes 100°C, others till 450°C
some units intended to NACE
media : steam or hydrocarbon

 

[bvi]

Studs are the norm and are of course permited. But why in the world would you use low strength stainless bolting that gauls with a carbon steel flange. It seems to be a recipe for problems.

 

[abbver98]

bvi,
what do you mean by "gauls" ? which problem did you face with such boltings ?
I think it's the standard bolting available in the market ? Do you an idea of other 316 SS bolting ?
Thanks

 

[MJCronin]

abbver98...

Where are you located and where, in the world is this facility ?

-MJC

 

[gr2vessels]

abbver98

ASME VIII allows you to use any stud bolt listed in B16.5, even if Table 2-5.2 in Appendix 2 shows the hex head of a bolt... Those stud bolts don't require double nuts or spring washer in standard piping or vessel applications. Some special cases with vibrations might require double nuts or other locking devices. Also, the softer stainless steel bolting could adhere / seize to the carbon steel flange due to the bolting tensions, makeng it difficult to remove or even to turn a nut on the bolt. It usually ends in damaging the bolts, flange and compromising the joint.
Cheers,
gr2vessels

 

[GenB]

nothing will happen in using the certified ss bolts in this case, but w/ c/s flanges c/s studs bolts/studs are standard.- if the c/s bolt is certified, there is no difference as to certified studs. one uses studs because are better adn easier and cheaper (yes they are cheaper and better) I use x heavy nuts for my aplications, I love'it.
no washers are allowed. double nuts are permitted and used for locking purposes only,
genb

 

[11echo]

Hmmm... I've worked alot of years in the oil fields and have not seen double nutted flange connections! I have seen the use of Hex. Hd. cap screws on tank nozzles where they had a butterfly valve as the block valve, but these require the threaded lug type of butterfly. We would put Hex. Hd. bolts thru on both sides, cautious to insure that they weren't touching in the middle of the body.
And lately I've even seen the use of Bellville(sp?) washers on steam systems, to try cutting down on steam damages connections when the connection loosens up. They are a type of lock washer, but semi-pricey.

 

[deanc]

Is your bolt head marking "plain"? This is common for many of the prepackaged gasket installation kits. It is only a low strength carbon steel bolt.

Do your Appendix 2 calcs. to spec. your bolts. You may be surprised.

11echo:
I like B7 studs for steam service. If the gaskets scream before the line warms up your preload may be to low. You can also go to a sprial wound gasket.

 

[11echo]

deanc ...We always use both B7 studs and spiral wound gaskets. Problem is once they are installed, nobody goes back and re-torques them ...ever! They loosen up and the steam cuts the flange face, and things go to H*LL in a hand basket from there! This Bellville washer thing is something new, will be interesting to see how it plays

 

[jte]

echo-

I wish I could complain about retorquing piping flanges! I usually see exchangers torqued and piping flanges "torqued" to "two arm-grunts". Its amazing we don't deal with more piping flange leaks.

jt

 

[TBP]

11echo - having somebody off the construction or maintenance crew go back the day after a steam line has been in service for a day to check the flange bolts - along with steam trap function, expansion joints, packing nuts, etc. - is all that's needed. Anybody calling themselves a "steamfitter" should have learned that as an apprentice. This problem sounds like a maintenance management issue, as opposed to a technical one.

 

[TBP]

jte - I've spent a lot of years in piping maintenance & construction, and at least in the Class 150 & 300 flanges, I've never used - or seen used - a torque wrench on flanges in these piping systems. Leaks are extremely rare. Of far greater importance than "precise torque" would be proper flange alignment and the correct NEW gasket for the service. If a flanged joint is being disassembled, then a new gasket should be installed.

I think if plants stopped using millwrights and electricians for their piping maintenance (and/or low-bid maintenance contractors), a lot of these problems would never come up for discussion because they wouldn't exist. Steamfitting/pipe fitting is a separate trade for a reason.

 

[11echo]

TBP,
We've none the go thru after start-up to do the snug-up on these flange studs, pretty standard practice. I was working with a company that was trying to generate a yearly procedure to re-torque and document this operation, but I don't think it took root. The bean counters back in the office didn't see a return on the effort. These steam systems are 2500# to 600#, alittle different then your low-pressure steam lines. What’s the old adage ...Never enough time to do it right, but always enough time to do it over!?? *G*

 

[DFGD]

The use of stud bolts is accepted, you have to use only two nuts and two plain washers, but you have to thighten it with a torquimether (In some mechanical handbooks you can find the proper torque). Also for safety you can use thread lockers (for reference see loctite web page) or lock washers, but this is not mandatory.