Quote Originally Posted by Gasbot
Just been looking at the five or six (in service) ally bottles we have here. Test pressure range from 200-212 Bar, with the max service/design pressure of approx 170 Bar - but they vary slightly by manufacturer. If the burst disk is roughly set at 195 Bar, then on the ones I have to hand the margin is pretty slim- although this might be different in other parts of the world. This probably explains why portable extinguishers end up as a PED Cat III as a minimum (via the module H route though I would guess) -
Strange, Except the CO2 oldest bottle I have around, all are actualy pressure tested to 300 bar, have a working pressure of 200 bar, and a 195 bar burst disk.
And the one that doesn't have the 300bar TP/200bar WP stamp is an old UK ali 1.1kg bottle I exchanged for one of the steel ones I got during the Dutch series 2. That one is TP 200bar WP 135bar, and had a 135 bar burst disk. Never could get it refilled over here.

which also possibly explains why there haven't yet been any failures in the extinguisher vessel. After all a notified body isn't going to sign off on any old bit of metal.
It's also perfectly possible that the test pressure doesn't even come close to the burst pressure. If the same safetymargins as for hoses are held, a bottle won't burst untill reaching 600 bar +
I still think its a good idea to get home made components pressure tested though. In my own little world it strikes me as common sense - even more so if the pressure boundry isn't being proved by calculation. In my view I don't see any difference between storage bottles and valve bodies, rams, pipework etc - they are all the same.
Let me rephraze myself then.

Quote Originally Posted by maddox
The thing I agree upon is that storage bottles need to be certified. By the book.
Reasoning behind this. Bottles wil be transported, and not always in the robot. Filled. If something goes wrong during transport, the concequences can be a lot higher than a failing bottle in the arena.

Also, and that is a very valuable point. The only other critical time is during filling.
There was a reason Mentorn had Fireman Pete in his workshop to refill the bottles. Nobody was allowed to enter that. The first Dutch events I took that task upon me.
Maybe food for thought?

Again in my own little world, the only reasons that seem to be on offer for not pressure testing home made pneumatic components is we don't want to do it or we can't do it. Is that a valid reason?
The can't do it is ony for a part correct.
Most of the time it's: we can't afford a test rig and a robot at the same time.
Or we can't afford to pay a firm to do it.
Independents over here did quote prices up to ‚1000 to test a Robots pneumatics. I'm lucky I know people at an independent firm.

The don't want to do is plain stupidity. If anybody working with pneumatics (or any high energy storage) acts like that, we have a potential Darwin Award contender.

There may not have been any failures yet, but who knows what the future will bring?
If you have enough time and changing circumstances, something will go wrong.
I suggest a nice rubber room and soothing music to avoid most of the process called life.