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Yeah, must have been a big guy!
Don't want to picture it, if it was a woman
Don't want to picture it, if it was a woman
Valve to cylinder torque
- Thread starter nikolay_zhelev
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walkonmars
Contributor
+1 with slightly more than hand tight. The extra torque buys you not very much.
You only want enough torque to prevent accidentally loosening it when you grab the tank by the valve and twisting while it is near empty after a dive. Maybe prevent an accidental bump when your rig is strapped on the dive boat waiting to get filled. The additional excessive torque and resulting additional compression from the additional couple degrees of rotation buys you no significant O-ring compressive sealing benefit. The valve flange base already mates with the top of the tank flange, metal-to-metal.
I use a special home made tool that contacts the flats at the valve base and tap (not pound!) the handle of the tool with a wooden block. I don't need to strap or hold the tank when I tighten. The heavy tank has enough inertia to resist when you tap the tool handle. Some adjustable wrenches can reach the flats similarly. You can tap the wrench handle with a wooden block just the same.
Due to tank pressure, I'm guessing even a loose valve cannot be easily be turned when the pressure inside the tank is more than a few hundred psi pressure. (Anyone tried to turn a loose valve with pressure in tank can let us know?) I don't recommending a test since I have been told escaping gas at several thousand psi from small passages can likely cut through flesh like a knife or in larger amounts blow flesh off your bones.
You only want enough torque to prevent accidentally loosening it when you grab the tank by the valve and twisting while it is near empty after a dive. Maybe prevent an accidental bump when your rig is strapped on the dive boat waiting to get filled. The additional excessive torque and resulting additional compression from the additional couple degrees of rotation buys you no significant O-ring compressive sealing benefit. The valve flange base already mates with the top of the tank flange, metal-to-metal.
I use a special home made tool that contacts the flats at the valve base and tap (not pound!) the handle of the tool with a wooden block. I don't need to strap or hold the tank when I tighten. The heavy tank has enough inertia to resist when you tap the tool handle. Some adjustable wrenches can reach the flats similarly. You can tap the wrench handle with a wooden block just the same.
Due to tank pressure, I'm guessing even a loose valve cannot be easily be turned when the pressure inside the tank is more than a few hundred psi pressure. (Anyone tried to turn a loose valve with pressure in tank can let us know?) I don't recommending a test since I have been told escaping gas at several thousand psi from small passages can likely cut through flesh like a knife or in larger amounts blow flesh off your bones.
Bob DBF
Contributor
I would not characterize the factory spec for torque as excessive, and I doubt they are using that spec for anything to do with the o-ring seal. It seems to be more than I find necessary, and I doubt seriously that I would drag out my torque wrench for that any time soon.
Bob
captain
Contributor
100 psi is more than enough to prevent you from removing a valve without a vise and a wrench.
Actually you should try it sometime. A hand tight valve can sometimes be turned with 100psi or more. The 7/8" UNF threads on the old HP steel tanks are the worst. Those threads are so fine you can quite easy turn the valve with 500psi in the tank - if it wasn't hit with a wrench to begin with.
I use a wrench to bump tighten valves, the torques in here seem high but not inherently damaging.
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no wrench marks for me, bump tight the brass against the open end of the soft valve knob with a soft hammer
if the spindle snaps it was going to snap anyway
10pcs/bag Scuba Valve Spindle Valve Stem Rubber O-ring Type # ST09-3BP | eBay
if the spindle snaps it was going to snap anyway
10pcs/bag Scuba Valve Spindle Valve Stem Rubber O-ring Type # ST09-3BP | eBay
OP
nikolay_zhelev
Registered
Hi guys,
It's nice to see there is a good activity on the topic. Thanks for all suggestions and shared experience.
I went one more time trough the ISO 13341 - Gas Cylinders - Fitting of valve to gas cylinders standard and I found that in Section 1 - Scope the standard excludes breathing apparatus, diving gas cylinders and fire extinguishers. A very important text, which I missed.
Secondly, I noticed that Alec Peirce video explains the procedure for Aluminium tanks only. Would it be the same for steel tanks?
In general I believe that the torque value limiting factor is the brass valve, not the threat size.
If you have more manufacturer manuals regarding valve installation feel free to share, I would love to see some details regarding torque values.
It's nice to see there is a good activity on the topic. Thanks for all suggestions and shared experience.
I went one more time trough the ISO 13341 - Gas Cylinders - Fitting of valve to gas cylinders standard and I found that in Section 1 - Scope the standard excludes breathing apparatus, diving gas cylinders and fire extinguishers. A very important text, which I missed.
Secondly, I noticed that Alec Peirce video explains the procedure for Aluminium tanks only. Would it be the same for steel tanks?
In general I believe that the torque value limiting factor is the brass valve, not the threat size.
If you have more manufacturer manuals regarding valve installation feel free to share, I would love to see some details regarding torque values.
For US based specs, so far you have Luxfer saying 50 ft-lbs (+/-10), and Sherwood saying 40-50 ft-lbs. I'll add that Thermo valves say 50-75 ft-lbs. Which all combined is why I re-install at 50 ft-lbs when working on cylinders and don't sweat what brand it is. (My recollection is that 40-50 was also mentioned at some point in a PSI-PCI course in the past, but I might be mistaken.)
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