there are still cylinders around with seems although they are being phased out. few and far between. as well, spun cylinders can go also. it's highly unlikely, but it happens. the difference is in how they blow. the spun cylinders consistently fold outward from the failure/impact point retaining most, if not all of their metal intact. this keeps it from becoming a projectile.
either way, my point with the split seem was complete, instant discharge in an unknown direction... which would cause a hazard in a confined space, unlike the idea of a tank becoming a missile in the back seat of a car from a valve blowing.
the tank that blew... we didn't realize it but the valve in the tank itself was faulty. the tank discharged very quickly to say the least. not likely as much of a difference as you'd think. after that tank was re-filled and installed, a couple days later it was empty and being pressure tested. it failed miserably. i knew someone was going to jump on that as soon as i posted it. ahhh, well.