Can anyone help me find a pressure relief valve that can set and maintain the pressure behind it?

[G+_T Nohands]

Can anyone help me find a pressure relief valve that can set and maintain the pressure behind it? I'm trying to prototype a calcium reactor stabilizer for a set it and forget use in saltwater reef aquarium and I'm stuck on finding a valve I can set a specific psi value from 10 psi to 75 psi range. I will have a lift pump or stepper motor constantly on so with saltwater always being pushed into the priming chamber I need to have a way to let saltwater return to the aquarium (or other device) once I set the desired psi and let the valve let water out of the priming chamber while keeping a precise psi in the chamber IE 20 psi and if I set 20 or 22 psi the valve will let water return only after the chamber reach 22 psi then keep that chamber pressure exactly a constant 22 psi or other desired value. I'm working with pvc bulkheads and can work with schedule 40 or schedule 80 so whatever is available and affordable so as long as there's no copper and can handle any corrosive properties of saltwater I'll be gald to find any size connection as long as it works. Can anyone help me find a relief valve that can do what I need it to do? I don't know what words to use to find that type of valve. I get so frustrated when I search online and I get everything but what I'm looking for, I still for the life of me understand how I get led lights and clothing come up in the search results :/

[G+_Damien Wessling]

What's your design flow rate/throughput for the PR valve? (Not being familiar with your process, excuse what may be obvious questions) Why is there a requirement to inject the reactant under pressure? Would be great if you could upload a basic PFD to show your circuit, helps get ones head around the concept.

[G+_Bob Sincick]

plastomatic.com - Plast-O-Matic Valves, Inc. – Valves, pressure & flow controls in PVC, CPVC, Polypro & PVDF

[G+_Golden Retriever]

Ok this is outside the box but pressure cookers use a weighted lid to regulate the pressure would that work?

[G+_Ben Reese]

Bob Sincick recommended something that would work. Expensive solution ($100+) according to the listings on Amazon.

 

I wonder if a pressure sensor could be used in conjunction with a solenoid valve and an Arduino... Cheaper, but more complicated. https://www.amazon.com/150Psi-Pressure-Transducer-Sensor-Diesel/dp/B01N3W21SF/

[G+_Michael Schley]

It's clumsy and would take some space but would be relatively inexpensive. How exact must your settings be? If they have some "wiggle room" and the need to change pressure is not continuous (for example if it is once a day), connect numerous valves in paralell, each with a different pressure (e.g. 20, 25, 30, etc.). Open the one you need and turn off the others as needed from time to time. I'm not familiar with the usage so sorry if I am missing something.

[G+_Damien Wessling]

Are willing to clarify some details on the function of the circuit, to allow us to offer assistance commensurate with your project? Without a reasonable understanding of what you're trying to achieve, pointing you in the right direction is quite difficult. I work in Engineering as a mechanical & piping design draftsman, this may be helpful.