Originally Posted by stealthypotatoes
Do you know of any that are cheap and worth it?
we are talking about different systems here, yours is the flow control valve, have to let it run 24/7. once the flow rate is set, the output pressure is low but if the flow stop/obstruct, the pressure will rise and eventually hit 800 psi, or parts(fittings, needle valve, air hose) got blow open because of the rising pressure.
This kind of setup is doable, but what I see the problems are the fittings and needle valves for these setups, normally they are 300 psi rating for the water line, not safe.
industrial high pressure, high precision metering valves can be used on these flow control valve design setups, I've already list them in my metering valve selection thread(link in signature), some of them is ok to use, but need to find the part number and google the .pdf to see their pressure rating and flow control capability. be aware there are two kind of pressure rating, one is the structure pressure rating, normally really high(up to 5000psi) for these metering valves, and another is max pressure differential rating, means inlet/outlet pressure difference has to be within the rating.