Tank Valves Tightness

[gnulab]

Hi,

How tight does a tank valve need to be screwed into the tank?

For 2nd stage screwed into 1st stage, I was taught to screw it in by hand first. Once it can't go any further, use a spanner to give it a final tug. The tug is a slight tug. The principle (again, was told) behind this reasoning is that the o-ring is what that seal the component.

So, for tank valve, could I use the same advice? Or, I have to screw it real tight using a spanner?


Thanks
Henry

 

[Scared Silly]

Not much more than hand tight works as it is the oring that does the sealing. Usually I can get all of the valves on my cylinders off with thump with the palm of my hand.

 

[muddiver]

Never tighten a cylinder valve with anything except your hand, that's one hand. See Scared Silly's post. The pressure in the cylinder will bind the valve tight in the cylinder threads when filled.

 

[Jim Baldwin]

Hi,

How tight does a tank valve need to be screwed into the tank?

For 2nd stage screwed into 1st stage, I was taught to screw it in by hand first. Once it can't go any further, use a spanner to give it a final tug. The tug is a slight tug. The principle (again, was told) behind this reasoning is that the o-ring is what that seal the component.

So, for tank valve, could I use the same advice? Or, I have to screw it real tight using a spanner?


Thanks
Henry

Just O2 cleaned three tanks. A little O2 lube on the threads and on assembly I usually give the valves 2 or 3 good raps with my fist. Never had a problem with taking apart, seizing up, an o-ring coming out or the valve moving. I've seen shops tap the valves with a mallet. I've just never seen the need.

 

[Doc Harry]

Each cylinder manufacturer has a different specification for cylinder valve torque.

Generally, most torque specifications fall between 40 and 75 foot-pounds of torque.

For instance, XS Scuba recommends that the valves on their cylinders be torqued to 50 to 75 foot-pounds.

Luxfer recommends 50 foot-pounds.

Catalina recommends 40-50 foot-pounds.

Some of the larger storage cylinders - like the HC-4500's - are torqued to 180 to 200 foot-pounds.

I found that 50 foot-pounds is just slightly more than I can tighten a valve by hand. Thus, to properly torque valves, you need some sort of cylinder holder and a torque wrench.

I made a jig that holds cylinders tightly, from my little 14-cubic foot pony bottles to my giant HC-4500s. In order to torque a variety of valves, I use a 1/2-inch digital torque wrench and crow's foot wrenches.

 

[Leadking]

Luxfer specs Luxfer: Technical Bulletins: August 1, 2002

XS says Worthington tanks 50-75 ft lbs

I have always just hit them with my palm and never had a problem. Remember an o-ring seal is not a compression seal. Tighter doesn't mean better.

For more light reading on o-rings see O-ring - Wikipedia, the free encyclopedia

 

[Fishpie]

+1 on all the posters that suggest the palm tapping technique.