Need some steer from any experts on HP gas line installations.

Basically what we have is a very botched job from a contractor who installed a gas pipework system for a workshop.

I need to know any standards or requirements that would be required on the soldering/welding of fittings. The standard of valves the would be required as a minimum and any additional safety features, such as HP release valves, that would be required.

Could do with a fairly quick response.

Before I also get a barrage of questions the system has been shutdown and will be refitted correctly. The installation contractor appears to have installed something that would suit domestic water, no not even domestic mains gas. Enough said.

No HP gas from welding operations. The system the contrcator put in was 'scary' and better suited for domestic plumbing. He actually used water valves.

Argon and Oxygen lines within facility being fed from tanks and quads. Lines run around the shops

Current installation has used soft solder connections, water valves, domestic copper pipe and no sign of any PRV's. I almost wonder if the contractor thought he was plumbing in water.

Yes we did start again, it was all ripped out. I still believe he thought he was plumbing in water

What I need is the justification why we had to do it. Where can I find the standards, regulations for installations? I know soldered connections are a no go area, PRV's are a must and you don't use water valves on gas lines but I need to back this with factual reference to standards.