SpudFiles

so, i now have some unused fire extinguishers available to me and also a few old air compressors to butcher for parts. So my first question is about using a fire extinguisher safely.

on the side of one for example its says that it has a working pressure of 690kpa and periodic test pressure of 2.5mpa, so does this mean i could pressurize it up to 2.5mpa (361psi) safely or should i stick to the working pressure? Also would be ok to weld a fitting in the top or do i need to find out the correct thrad size and adapt it to the size i want to use?

Next is the compressors, anything useful i should hunt for in the form of 3-way valves or dump valves?

Stick to the working pressure. The test pressure is done in an explosion proof container for testing or other safe test environment.

http://www.compressed-air-cylinders.com ... sting.html

I would not weld on the valve without complete disassembly, not to mention you might comprimise the strength of the valve material. Probably not a good idea overall. What size threads does it have?