[mikegrundvig]

That failure really surprises me, I would have not expected it to shatter. I've seen burst PVC pipe (schd 40) where people used it to make pneumatic air cannons. They charged and then dropped the cylinder and it exploded. This failure looks EXACTLY like that.

My guess is that this cylinder had been dropped at some point on a corner or edge which can stress fracture and weaken it a lot. Never EVER drop a charged cylinder - very bad things happen. Another possibility is that it's been in the sun for a long while at some point in it's life, that can weaken most plastics a lot too. Some weakening combined with over-tightening and stressing the threads == kablowie!

-Mike