Studs vs. Bolts 4

[jdogg05]

What is the functional difference between a stud and a bolt? I am not refering to obvious assembleability concerns. I have heard that studs eliminate (or greatly reduce) the torsional load and thus provide a more accurate clamp force... I don't quite understand this mathematically.

Why are studs used for pipe flanges? Why not bolts? Is a stud actually a better fastener? COULD, studs theoretically be used in place of bolts (with arguably better results) if ease of installation and practicality of assembly were not concerns?

 

[jdogg05]

fegenbush,

What is a "red wrench" and what is your point about bolts vs studs in that context?

 

[fegenbush]

jdogg05,

A "red wrench" is a vernacular term for an oxygen-fuel torch. Maintenance work often involves simply using a torch to cut off the existing fasteners therefore, from a maintenance standpoint, it is irrelevant whether studs or bolts are used. The comment was made in reference to the comment made by moltenmetal regarding ease of maintaining a stud versus a bolt.

/Apologies for using American vernacular.

 

[SnTMan]

Also known as a gas axe

 

[ricklts]

In the past, bolts were normally not used for ASME/ANSI flange connections due to the fact that some headed fasteners were weaker under high loads than a stud with two nuts. The heads would break off the shank. With newer manufacturing tolerances and material controls, those problems have declined. One other reason is that if you use torque as your preload procedure, and work from the bolt head end, then all of your torsional effort has to be translated to the internal threads of the nut, resulting in high torsional stresses - back to the beginning.

When you torque a stud with two nuts, torsional movement will take place at either end of the nut-stud-nut assembly, creating a much better retention of clamping force throughout the fastener. When you tension, it really doesn't matter, you are lifting the nut, stretching the shank against the underface of the head, and then running the nut down to capture preload.

Rick