B16.5 Stud vs Nut Material Selection
B16.5 Stud vs Nut Material Selection
(OP)
For flange bolting B16.5 lists suitable stud and nut materials in Table 1B. Intermediate Strength materials are required to cover our services.
We have selected ASTM 320 B8M Cl 2 studs and ASTM 194 8MA S1 heavy hex nuts. Both are Carbide solution treated and strain hardened as suggested by Notes 6 and 11 below Table 1B.
An enquiry to Australian bolt suppliers has indicated that while the stud material is readily avaiable the nuts will need to be specially imported. Only non strain hardened ASTM A194 8M nuts are readily available. They advise that this mixed combination has been the normal supply in Australia for the last 20 years.
A review of A194 and A320 did not clarify whether the higher grade nuts are required.
I would like to seek advice regarding whether plain 8M nuts are typically used in other places?
Can someone advise if there is a good reason for this mixed material combination (e.g. to avoid galling)?
Can someone advise if this mixed material combination has been subjected to proof tesing to determine if the full strength of the botls can be used without a risk of failure of the nuts?
We have selected ASTM 320 B8M Cl 2 studs and ASTM 194 8MA S1 heavy hex nuts. Both are Carbide solution treated and strain hardened as suggested by Notes 6 and 11 below Table 1B.
An enquiry to Australian bolt suppliers has indicated that while the stud material is readily avaiable the nuts will need to be specially imported. Only non strain hardened ASTM A194 8M nuts are readily available. They advise that this mixed combination has been the normal supply in Australia for the last 20 years.
A review of A194 and A320 did not clarify whether the higher grade nuts are required.
I would like to seek advice regarding whether plain 8M nuts are typically used in other places?
Can someone advise if there is a good reason for this mixed material combination (e.g. to avoid galling)?
Can someone advise if this mixed material combination has been subjected to proof tesing to determine if the full strength of the botls can be used without a risk of failure of the nuts?
Dennis Kirk Engineering
www.ozemail.com.au/~denniskb





RE: B16.5 Stud vs Nut Material Selection
Why did you select the "ASTM 320 B8M Cl 2 studs and ASTM 194 8MA S1 heavy hex nut" combination ?
-MJC
RE: B16.5 Stud vs Nut Material Selection
The nuts were selected based on Note 11 to be "of corresponding material".
I think now that the 8MA S1 nuts may not be available and that I should have refered to either 8MA (Carbide Solution Treated) or 8M S1 (Strain Hardened)
Dennis Kirk Engineering
www.ozemail.com.au/~denniskb
RE: B16.5 Stud vs Nut Material Selection
Situation in the States:
A strain hardened SS nut of any description is going to be hard to procure. Even if you can find someone to make the nut you are talking about time and a lot of money. A colleague in the bolt business told me today that two suppliers that use to make a strain hardened nut are now no quoting.
He routinely sees a lot of orders for strained hardened studs/bolts with threaded nuts. He says that nearly all his customers that use Austenitic fasteners are now calling out Cl 2 or strain hardened studs/bolts with the threaded nut.
I know when we started using Cl 2 studs there was no thought of using a strained hardened nut for the simple reason the nuts weren't available due to the difficulty in manufacturing them. I cannot recall any problem with this approach on our piping system. Any Austenitic SS stud/bolt under 1 1/4" , whether set in, low temperature or high temperature is a Cl 2 with a threaded nut.
RE: B16.5 Stud vs Nut Material Selection
Given that ASTM 320 B8M Cl 2 studs are required what, in your experience, are the required nuts to go with these and what reference points you to this material?
Can you advise whether ASTM 194 8MA S1 (Carbide Solution Treated and Strain Hardened) heavy hex nuts or 8M S1 (Strain Hardened) heavy hex nuts are available in your area?
Dennis Kirk Engineering
www.ozemail.com.au/~denniskb
RE: B16.5 Stud vs Nut Material Selection
These guys list 'em:
http://www.goasf.com/SpecShts/2NutsStk.html
I think we usta get them from these guys:
Robbins Manufacturing Co
1200 Airport Rd, Fall River, MA 02720
Phone: 508-675-2555
or maybe it was:
http://www.fallrivermfg.com/products_nuts.html
RE: B16.5 Stud vs Nut Material Selection
On the basis that a bolt should fail in tension before the threads in a nut begin to shear (otherwise you might not detect a failure) I have just completed a calculation of bolt tensile capacity compared to nut proof load using the data from ASTM A320 and A194.
For 5/8" size bolt from B8 Cl 2 (Strain Hardened) material the minimum failure load is 28,250 lb.
The A194 8 nut has a proof load of only 18,080 lb.
The A194 8 S1 (Strain Hardened) nut has a proof load of 28,250 lb.
It certainly appears that strain hardened nut will be required to go with the strain hardened bolts?
Dennis Kirk Engineering
www.ozemail.com.au/~denniskb