SpudFiles

Would schedule 40 cast iron be good enough for about 500 psi (co2)? or do i need schedule 80 cast iron?

it depends on the pipe diameter, but no matter what you need at least sch80 for 500 psi. even then i recommend sch160.

CO2 is typically held at around 800PSI. It can be higher or lower though, just keep in mind it can be over 1000PSI if it gets too warm.

Cast iron is a brittle metal. It's hard, but if it's hit on something hard it can shatter. Mild steel or aluminum would actually be better. They aren't as hard, but will "give" more when hit since they are more maleable.

Also, that's a very general question you asked. Are you putting it in 1/4 inch pipe, or like 6inch diameter? Like PVC pipe, the wall can be the same size but how much pressure it can hold depends on the diameter. An example: 1/2inch PVC is rated at around 200PSI. And 3 inch is rated at something like 135PSI. Those are probably off, but I think they are in the ballpark.

I would advise against cast iron, for the reasons above. Assuming that your fittings are 2" or smaller it might be okay in Schedule 40 steel, but it would be much safer to use Schedule 80 steel pipe and fittings, which can be bought from Mcmaster.

Schedule 160 steel pipe is overkill, unless you plan on using over 3000 psi. Also, 6000 psi steel fittings and Schedule 160 steel pipe are ridiculously expensive.

I don't know how much pressure a 6x propane/compressed air hybrid mixturte creates, or if DDT (I think it does sometimes, but not all, depending on how lean the mixture is) occurs, but it's still a hell of a lot of pressure. I have Sch 40 2" steel as the chamber, and it holds up just fine. I think the pressure is somewhere in the 500-700 psi range.