All about torque...

[potbellied yeti]

Curious as to what is appropriate for torque on the various components of scuba assembly.

1. Tank valve to cylinder - consensus seems to be hand tight + a whack of the palm? Dip tube?
2. DIN to yoke insert for tank valve?
3. 1st stage assembly - see service guide
4. Hose to HP/LP ports - hand tight and light tightening with a wrench so it doesn't back off? Same for the other end to SPG, 2nd stage, etc? Is anything different if there is an air spool inserted?

What are the appropriate tools for assembling things properly? What are the consequences for over- or under-torquing?

I tried searching, found some resources... but still not positive about it all.

TIA

 

[Degenerate]

I tighten my DIN screw pretty lightly, no need to force it that last 1/8 of a turn "to be safe", never had issues.
On the first stage side of the hoses I will hand tight them and then give it a very gentle extra push with a wrench, I do the same with the SPG end of the HP hose.
The LP hose for my 2nd stage just gets hand tightened, nothing more.

 

[tbone1004]

All of the following are o-ring sealed which means they aren't reliant on torque to seal, only to stay put.

1. 40-50 ft-lbs. Some manufacturers call out different numbers but it is extremely rare to see torque wrenches on tank valves. Overtorque, you'll strip threads, undertorque pretty much nothing
2. 40-50 in lbs. Overtorque, you'll strip threads, undertorque pretty much nothing
3. 1st stage assembly to what? hand tight to the valve
4. Check the specific regulator manual, Poseidon is 6lbft to the first stage. Typically 40-50in lbs for the second stage. Overtorque, you'll strip threads, undertorque pretty much nothing

You need the appropriate torque wrenches and a crowsfoot for the valve and hoses, and allen keys for the port plugs and din insert. Again though, these are all o-ring sealed, so "sufficiently snug" is all that you really need.

 

[boulderjohn]

To me, the real devil is the dip tube. If it is not tight enough, it will fall off, and you will have an annoying rattle in the tank until you open it up again to fix it. Get annoyed and decide to get it on there nice and tight, and you will be buying a new dup tube.

 

[tbone1004]

To me, the real devil is the dip tube. If it is not tight enough, it will fall off, and you will have an annoying rattle in the tank until you open it up again to fix it. Get annoyed and decide to get it on there nice and tight, and you will be buying a new dup tube.

drop of blue loctite

 

[yle]

1. 40-50 ft-lbs. Some manufacturers call out different numbers but it is extremely rare to see torque wrenches on tank valves. Overtorque, you'll strip threads, undertorque pretty much nothing
2. 40-50 in lbs. Overtorque, you'll strip threads, undertorque pretty much nothing

I was looking at that for a couple minutes, thinking it was the same as #1. And thinking "are you sure? seems like a lot for a DIN insert..."

Then I finally realized you switched to inch-lbs.

 

[AfterDark]

Thread fasteners all have standard torque specs based on the type, size and thread of the fastener.

As @tbone1004 posted, standard torque won't apply when O rings are in use, "excessive" torque will ruin an O ring.

Bolt Depot - US Recommended Bolt Torque Table

 

[rjack321]

To me, the real devil is the dip tube. If it is not tight enough, it will fall off, and you will have an annoying rattle in the tank until you open it up again to fix it. Get annoyed and decide to get it on there nice and tight, and you will be buying a new dup tube.

or you can just leave it off, they are an anachronism in 2021

 

[Doc Harry]

I always torque to specs using crow's feet wrenches and a torque wrench

In my experience, the tank value torque is a bit tighter than what I can get by hand. This may be the reason some people say to hand torque the valve, and then give it a bump.

 

[grf88]

This may be of interest to those who would like to check the torque but do not have a suitable torque wrench:
Improvised Torque Wrench