Valve to cylinder torque

[Jack Hammer]

I've never used a torque wrench to check how tight the valve actually is. I use a large wrench at the base and go as tight as I can by hand then whack the end of the wrench once with a rubber mallet. Removal just requires tapping the wrench by hand a few times.

Due to the size of the threads, I wouldn't be surprised if the torque using this common method was a lot higher than most of us suspect. I've seen several bent valves from people using the face or knob instead of the base to install or remove the valves.

 

[sh1513]

100 Nm (74 ft lbs) is sufficient for either steel or ali cylinders.

S.

 

[divad]

I use a large wrench at the base. I've seen several bent valves from people using the face or knob instead of the base to install or remove the valves.

I guess it's easy to forget that they're made of soft brass.

 

[BRT]

I spin them in and give them a tap on the handle with the heel of my hand. I've seen a guy at a hydro/fill shop do the same in Mexico. Never had one leak yet and when I need to remove them I empty the tank and hive them a tap with my hand the other direction.

 

[captain]

Once the valve face and the tank face are in metal to metal contact the O ring is compressed and there is no gap for it extrude into it will not leak. Any tighter is of no benefit. Once there is 100 psi in the tank it will be almost impossible to unscrew the valve without a wrench and vice.

 

[stepfen]

Hi,
I just got a new 7lt al stage bottle made by Polaris. Here is the relevant portion of the manual (translated by Google from German):

Valve installation: ... The valve is first screwed in by hand with a new sealing ring, then tightened with a suitable tool and a torque of 110 Nm.

So 110Nm are suggested here too. It does sound too much and definitely much more than "a tap on the handle with the heel of my hand" which (just by guess) sounds more like 10-20Nm.

I'm interested because I am about to service (lubricate) another valve I have. I think I will go with the common practice and maybe add a second harder tap with my hand since anyway I don't have such torque wrench.

Cheers

 

[almostDIR]

I was taught to insert a small wrench to the correct flat surfaces on valve body and then give the wrench a little knock with a rubber mallet when installing or removing a valve. NO excessive force used, the tank pressure will keep the valve in place after its pressurised and impossible to remove it until the pressure is released.

Some of my tanks were at hydro last year and the nice persons there over tightened one of the valves so that it was not possible to take it out anymore without breaking it completely. I ended up securing the tank down and jumping on a 3ft wrench to get it out, no amount of hammering could do the trick. Of course I threw the old valve away and installed a brand new valve with the wrench and knock method...

 

[taimen]

I recently checked this from a valve manufacturer (Nautec) and they recommend 100-120 Nm torque. It indeed sounds like a lot, but valve and cylinder manufacturers very consistently cite this value.

 

[happy-diver]

Who

for removal only

 

[scubafanatic]

Who

View attachment 521539

View attachment 521540

for removal only

I don't think he wants to unscrew the whole top part of the cylinder though.