Pretty sure hydro testing involves submerging the tank and overrunning it, and making sure it doesn't displace ANY amount of water due to change in shape or volume externally.
I've seen plenty of burst discs fail, regs and valves unthread and the tank starts leaking, I've seen pin valves fail in an ASA with no vent hole, so the tank kicks off the gun hard enough to bruise your ribs pretty badly. I've only seen video of the one time a tank failed at the field. It was in the proshop, so a security cam caught most of what happened. Guy was holding the tank and filling it, the the tank just disappeared and was bouncing around the shop so fast the camera couldn't record it, stuff was just getting dented and falling off the walls. When it stopped you could see the tank had failed at the neck and was peeled back like a banana (as others have described). The reg was still connected by the nipple to the fill station. Amazingly the employee was uninjured.
Originally Posted by Trbo323
Part of owning a cocker is problem solving