ASME B16.5 Bolts and Nuts - Impact Test

[Mailo]

Hi,

I'm a bit confused about the bolting material acc. to ASME B16.5. I generally use high strength bolting because it can be used in any flange connection.

I use A193 B7 bolts and A194 2H nuts for high and low temperatures. Can anyone say at which temperature an impact test is required? Is it advisable to use A320 L7 instead of A193 B7 at low temperatures? And which material should be chosen if you have low and high temperatures?

Thanks in advance!

 

[trottiey]

B16.5 just gives recommendations about bolts. You need to look at your code of construction for that kind of thing. (E.g. Section VIII, ASME B31.3 or other.) But yeah, A320 L7 should be tougher at low temperatures than A193 B7.

 

[rmw]

A193 B7 can only be used down to -20F in ASME B31.1, but can be use down to -55 in small sizes and down -40 from 2.5" up to 7" without impact testing in ASME Sec V111. ASME B31.3 just refers you to the BPV code. B31.1 dictates A320 (choice of grades) below -20F.

There is a strange mismatch in the codes where you can have a vessel at -40F OK with A193 B7 bolting (if it had bolts) but to attach a B31.1 pipe to it, you would have to use A320. Go figure.

The material seems to degrade in the presence of piping. (see tongue in cheek.) I wish the code committees would synchronize their stuff and all sing from the same song sheet. After all, the title of the song book is ASME.

Gee.... I spent most of my day today reading through those 3 codes trying to find some wiggle room somewhere to live like a BPV person in a B31.1 world and get rid of the need to use A320 bolting below -20F.

rmw

 

[QAFitz]

There are very few alloying elements in A/SA-194 Gr. 2H so expecting repeating Ft.Lbs or worse yet Mil Lat.Exp. at any temp below ambient is a crap shoot.
SA.A-194 Gr. 7 give much more predictable results.