I think some of you are missing the point here.
Mario is right when he says that buffertanks dont need burst disks prds etc.
But the thing Im trying to get across here is as the rules stand an event organiser could ask you to provide written certification or CE type approval for ANY part of your system that opperates above 3.4 bar, and if you could not provide it he would be quite entitled to ban that machine.
Worse still, god forbid there was an accident resulting in someone getting hurt, you can bet your life the H&SE would want to see the paperwork for every inch of that system, Or at least show that EVERY part has the relevent CE type approval for the purpose it was being used for at the time.

Just something to think about.