Ok, I have a weird situation. I unexpectedly ran out of propane (doesn’t it happen always). Went to Wal-Mart and got a new one (I think I got the last one). The valve doesn’t turn at all, no matter how hard I try. However, I connected it to my grill (because I was hungry) and it worked! Is this tank, that I cannot turn off, safe for my grill?
If your grill is outside, yes its safe. But …
Odds are that your grill’s valves don’t turn off as well as a typical tank’s does,so you’ll lose a bunch of gas to leaks.
If you grill every day, that might not matter much; you’ll burn most of it before it has a chance to leak away. But if you’re a once a week griller you might lose 3/4ths of the gas to leaks & need a new tank in just a month or two. If it’s worth the $15 to you, take it back for a fresh non-defective one.
Which way are you turning it? It sounds like the valve is already open but the OPD valve wasn’t letting any gas flow because it wasn’t hooked up to a fixture - see here. Once you attached it to your grill, it opened the safety valve and let the gas through. I’d try closing the valve.
Is it a new tank you bought, or one of those Blue Rhino exchangeable tanks? Either way, if you can’t close the valve, I’d bring it back - no point losing all your propane or having a safety issue when you should be able to get a new tank for free - one that won’t close is clearly defective.