james croft
Contributor
Steel cylinders are just as safe as aluminum as long as you keep them dry inside and rinsed with fresh water after each dive. If the valve will keep the pressure in the tank, it will keep water out of the cylinder. I have used steel oxygen cylinders that have 1/2" tapered threads and installed scuba "I" valves with good results. "I" valves can be commonly found on Ebay. Make sure that they have the proper burst disc on the valve. Most were originally sold with the lead filled relief plug that are now illegal to fill. These can be replaced with a burst disc relief. The aluminun oxygen cylinder will have 1/2 " straight threads that are o-ring sealed like a modern scuba cylinder. Occasionally I have stumbled onto 1/2" straight thread, o-ring sealed "j" & "k" scuba valves that will fit these aluminum oxygen cylinders. These are approximately 1970's vintage. I seem to recall White Stag and possibly Sherwood made those size valves a long time ago. They are very scarce and I have only seen a handful in the past 35 years. I have one such 1/2" straight thread o-ring sealed K valve in a Luxfer 3000 psi aluminum cylinder. The cylinder came from a an industrial scba (not scuba) escape "hood". It had a Scott airpac type valve in it. It is a handy size cylinder of approx 19cf and was free.
Overall, the main problem you have is the oxygen bottle pressure is 2015 psi. If you are able to find a vintage 1/2" staight thread o-ring sealed valve and put it in an aluminum oxygen cylinder the burst disc will need to be changed to the reduced pressure to be legal. I can tell you it is probably more trouble than it is worth to have only 2015 psi but I started diving when the only ponies around were DIY and have always tried to dive on the cheap. I still dive my vintage gear but I bit the bullet and bought the proper gear. I mainly use the 2015 psi bottles for argon for drysuit diving or lift bags, etc. If I only had one oxygen cylinder I would keep it for oxygen for diving emergencies. If you ever need oxygen, you will need more than the small cylinder in the DAN kit. I am a PSI certified high pressure cylinder inspector and know the dangers of Do-It-Yourself projects. I would be leery of some one machining down a 3/4" scuba valve to put in a 1/2" valve but I have seen it done. I would not do it myself. Remember, Improvised Cylinders=Improvised Explosives
Overall, the main problem you have is the oxygen bottle pressure is 2015 psi. If you are able to find a vintage 1/2" staight thread o-ring sealed valve and put it in an aluminum oxygen cylinder the burst disc will need to be changed to the reduced pressure to be legal. I can tell you it is probably more trouble than it is worth to have only 2015 psi but I started diving when the only ponies around were DIY and have always tried to dive on the cheap. I still dive my vintage gear but I bit the bullet and bought the proper gear. I mainly use the 2015 psi bottles for argon for drysuit diving or lift bags, etc. If I only had one oxygen cylinder I would keep it for oxygen for diving emergencies. If you ever need oxygen, you will need more than the small cylinder in the DAN kit. I am a PSI certified high pressure cylinder inspector and know the dangers of Do-It-Yourself projects. I would be leery of some one machining down a 3/4" scuba valve to put in a 1/2" valve but I have seen it done. I would not do it myself. Remember, Improvised Cylinders=Improvised Explosives
