What is the thread size for top tank valve on my Air Venture 78 ci tank?

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This is my AV 74CF tank label.

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rodjava said:
Can someone tell me, when installing a new tank valve, do I need to apply any thread dope or thread tape for a proper seal?
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You do not. There wil be an O ring on the valve. It doesn’t hurt to put some silicone grease on the O ring. But just enough to make it shiny, not gobs. In the scuba industry we also put a very light coating of silicone grease on threads to prevent galvanic corrosion. Just a very light brushed on, again, not gobbed on. If you elect not to silicone them it would not be a big deal. Screw valve into tank and just turn till you feel it hard stop, that’s it, O ring does the rest of the job. There should not be any gap between the tank and valve. See photo.
Saber Tactical makes a really nice valve, pricey but nice. Joe Brancato (Air Tanks For Sale) has a nice valve with two gauges, one for tank psi, one for line pressure.

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Here’s a video for a scuba tank but SCBA’s are the same. This is actually a pretty good video.
It was very very rare that we ever needed a tool to loosen a tank valve. Our valves always had an area where there were some wrench flats to put an open end wrench on it to loosen.
Also, his video says no silicone on the O ring. There are two schools on that. Just making it shiny assured that as you tighten the valve you won’t wrinkle the O ring as valve and tank lock up. We turned valve till you feel a solid lock up.
If the valve seats totally there is no chance of O ring extrusion. Extrusion is where the O ring can start oozing out of any gap if not tightened completely.

 
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rcs9250 said:
Here’s a video for a scuba tank but SCBA’s are the same. This is actually a pretty good video.
It was very very rare that we ever needed a tool to loosen a tank valve. Our valves always had an area where there were some wrench flats to put an open end wrench on it to loosen.
Also, his video says no silicone on the O ring. There are two schools on that. Just making it shiny assured that as you tighten the valve you won’t wrinkle the O ring as valve and tank lock up. We turned valve till you feel a solid lick up.
If the valve seats totally there is no chance of O ring extrusion. Extrusion is where the O ring can start oozing out of any gap if not tightened completely.

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Great video! Thank you for sharing it.
 
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