Need Fastener Engineer Skill Set

[whydontu]

Again, with almost no piping experience but lots of fastener experience, I think your studs will work just fine.

Whacha using for a torque wrench?

No torque wrench, just years of experience. The butterfly valve seats wraps around the face of the valve, the valve body has a rib on the O.D. that contacts the mating flange when the seat is fully compressed. Adding a zillion foot-pounds of torque has no effect on the sealing of valve to flange. Once the rib hits the flange you're done and the valve is sealed. Factory recommends 35 ft-lbs, so just a good one-arm pull is all that's needed.

 

[Brent H]

Sorry late to the game, but in any ship board install we have no, no threaded flange bolt holes. Has to be through holes and bolt with nut. Corrosion, cross treads, etc. you can also add butterfly valves that seal between flanges and only the flanges are bolted with the valve sandwiched.

 

[PaulL]

The main difference not being the stress, but rather surface friction at the threads associated with a turning bolt vs a stationary stud.

I think the threaded length on the nut will now come into play as well, which isn't an issue with the bolt-head.

 

[Susquatch]

I think the threaded length on the nut will now come into play as well, which isn't an issue with the bolt-head.

Yes, it does. However, most nuts are deliberately designed to meet the equivalent strength of the bolt. For the same materials, an individual female thread is always stronger than the male threads because the shear diameter is bigger. In any threaded connection, there is a length beyond which there is virtually no additional strength. The stronger the material the shorter the optimum length.

The simple rule of thumb to remember for most bolts and threaded holes or nuts is a length of 1/2 the nominal diameter for steel and 1 to 1 for aluminium and brass.

 

[CWret]

I too am late to the party. But this has been a very interesting read with lots of great comments from much more experienced nuts-and-bolts guys than me.

But - 50 years ago - some improperly torqued cable clamps cost a guy his job (at a coal mine as being the cause for a dragline boom to crash down) he was fired and I was his replacement. So using bolting specifications has always been rather important to me.

Once the rib hits the flange you're done and the valve is sealed. Factory recommends 35 ft-lbs, so just a good one-arm pull is all that's needed.

35ft-lb is a spec and not to be taken lightly. I would also assume that there is (or should be) a torquing sequence (20% then 60% then 100% or whatever).
I could be asleep in left field or out to lunch but this is my 2 cents worth:
If you are using 8 through bolts vs 16 bolts (as per the original design) then the torque sequence and values get substantially altered. I believe the designer was concerned about bolt torque and seating of the flange. Also, the original design made it possible to disconnect one side of the flange without disturbing the other side of the flange.

PS - Did you know that cable clamps can only be used once and then must be discarded?

 

[whydontu]

@CWret , I’m simplifying a bit. At least three passes through the bolt sequence, because the rubber seat compresses as the fasteners are tightened. First pass just snugs up the fasteners, then another pass to about half torque, next pass to rated torque, and then another pass to catch any nuts that might still be looser than desired. The rubber seat takes a set, so I usually go around all the flange connections after startup and go through the whole routine again to avoid any leaks.