Apparatus
New
Firstly, don't buy your own compressor. Its THOUSANDS of dollars down, THOUSANDS in maintenance. Filters, valves, intake, bleeds, air samples... don't. The big big big commercial compressors have better fill rates (cubic ft/min). The giant Mako at our shop is 13 cfm, and boss man puts thousands in it for it to pump clean air, and to be up to standards.
Pay your $10-$15 per air fill. You'll spend less than you would on a compressor.
Anyway:
1. Buy aluminum. They don't rust. That in mind, you have to treat your cylinder well or you'll see aluminum oxide where there is water contact - under your cylinder boot, for example. Rinse it with freshwater, remove the boot with a rubber mallet occasionally.
2. Your weighting is different with steel versus aluminum. I don't recommend LP steel, because these days cylinders are more reliable and fill to a higher pressure.
Get a Luxfer or Catalina aluminum 80, serial number that starts with EA for Luxfer or T for Catalina. These are "neutral" cylinders that fill to 3300 and do not end up positively buoyant at the end of your dives. They are lighter than even LP steel (to carry), and they have great buoyancy characteristics for beginners. Full, they start about 5, pounds negative and end neutral (500psi). Comparatively, "standard" non neutral, 3000psi aluminum 80s start about 1 pound positive and end about 6 pounds positive. Get a 63 aluminum for your son.
3. Never assume a cylinder is ready to go. If you buy online, ask about its "hydro" date. Its hydrostatic requalification. It should have a valid RIN (requalifyer identification number) and the month to the left and the year to the right of that stamp. You can look online for a RIN locator to see if they're legit. never trust your hydro facility until you know you can. As for the visual, the valve should be torqued to 50 ft lbs, use proper lube and a proper o-ring, and be inspected to PSI-PCI standards, as they are the only cylinder inspection training agency recognized by DOT, who regulates high pressure cylinders. High pressure is defined as 29psi or higher, per DOT and CGA.
Buying online from retired divers opens you to the risk of obtaining condemned or horribly damaged cylinders, or the 6351-T6 aluminum alloy, which need an eddy current test because they are prone to sustained load neck cracks. The aluminum 80s of the 6351 alloy were manufactured by Luxfer through January 1988, and Walter Kidde, any year. The Luxfer 63 cbfts were the 6351 alloy until June, 1988. During Hydro, these also must receive a VE test AND stamp next to the year on their hydro stamp.
Bottom line, trust where you get your cylinders from, and trust where you get them inspected. Aluminum 80 neutral, 3300psi, from Luxfer or Catalina would be great for you or your son, but if he needs something smaller, get him an aluminum 63. If you get a 6351, be sure your facility knows what they are doing with their eddy current test.
Pay your $10-$15 per air fill. You'll spend less than you would on a compressor.
Anyway:
1. Buy aluminum. They don't rust. That in mind, you have to treat your cylinder well or you'll see aluminum oxide where there is water contact - under your cylinder boot, for example. Rinse it with freshwater, remove the boot with a rubber mallet occasionally.
2. Your weighting is different with steel versus aluminum. I don't recommend LP steel, because these days cylinders are more reliable and fill to a higher pressure.
Get a Luxfer or Catalina aluminum 80, serial number that starts with EA for Luxfer or T for Catalina. These are "neutral" cylinders that fill to 3300 and do not end up positively buoyant at the end of your dives. They are lighter than even LP steel (to carry), and they have great buoyancy characteristics for beginners. Full, they start about 5, pounds negative and end neutral (500psi). Comparatively, "standard" non neutral, 3000psi aluminum 80s start about 1 pound positive and end about 6 pounds positive. Get a 63 aluminum for your son.
3. Never assume a cylinder is ready to go. If you buy online, ask about its "hydro" date. Its hydrostatic requalification. It should have a valid RIN (requalifyer identification number) and the month to the left and the year to the right of that stamp. You can look online for a RIN locator to see if they're legit. never trust your hydro facility until you know you can. As for the visual, the valve should be torqued to 50 ft lbs, use proper lube and a proper o-ring, and be inspected to PSI-PCI standards, as they are the only cylinder inspection training agency recognized by DOT, who regulates high pressure cylinders. High pressure is defined as 29psi or higher, per DOT and CGA.
Buying online from retired divers opens you to the risk of obtaining condemned or horribly damaged cylinders, or the 6351-T6 aluminum alloy, which need an eddy current test because they are prone to sustained load neck cracks. The aluminum 80s of the 6351 alloy were manufactured by Luxfer through January 1988, and Walter Kidde, any year. The Luxfer 63 cbfts were the 6351 alloy until June, 1988. During Hydro, these also must receive a VE test AND stamp next to the year on their hydro stamp.
Bottom line, trust where you get your cylinders from, and trust where you get them inspected. Aluminum 80 neutral, 3300psi, from Luxfer or Catalina would be great for you or your son, but if he needs something smaller, get him an aluminum 63. If you get a 6351, be sure your facility knows what they are doing with their eddy current test.
