Compressed CO2 is a liquid below about 88 degrees F, when you draw from the cylinder the pressure drops and it goes gaseous.
Oxygen, Argon and C25 are gaseous in the cylinder. Acetylene's already been covered, but I've always been told that if it gets transported horizontal you just need to leave it vertical for a few hours to allow the acetone to settle out (I prefer 24
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I've had my O/A cart since 1973, always just take the whole cart in with bottles secured in the cart, laid horizontal and secured in the truck bed so it's totally cinched down - never had an LWS ***** about it. NEVER, as in NEVER, transported without caps in place REGARDLESS of which gas.
Had questions asked once or twice, when they find out I know more about it than they do, the questions stop. (Just under 35 years in industrial instrumentation, produced/created multiple safety videos, + working foreman/instrument tech in a 12 man maintenance crew for the last 10.
Here's my setup, the acetylene's the biggest single cylinder you can get (420 CF), and is BARELY big enough for the rosebud shown (safe withdrawal rate).
Pics aren't clear, but both tanks are held in by a heavy "2 hump" steel strap, I added the chains - the orange straps are just 'cause I hate rattles.
I recently added the twin hose reel, hoses needed replaced anyway and NOT moving that heavy SOB sounds better the older I get... Steve