# Can I increase pressure on the output side of a backstop/security valve?

I'm working on a system with non-deterministic pressure (because it's based on bio mass fermentation) where CO2 is generated and input into the system at maximal pressure x (e.g. 2 bar). If additional CO2 is produced it ought to be stored in a container with pressure > x and released back into the system through a pressure regulator if the pressure in the system falls < x.

I assume that the input side of the container/storage has to be a backstop valve in order to keep the pressure in the storage. Based on technical terms (which I only know superficially) it has to be a security valve, because it has the function of releasing pressure > x. Usually security valves do that into a space with less pressure (in my use case the pressure will be higher at the second occurance of over-production of CO2). Is there a backstop-security value which allows to redirect all pressure y with y > x into a container with pressure > y?

The container/storage has to contain a (different) security valve which releases pressure into the room if it exceed the maximum of the container.

Usually gases only flow from higher to lower pressure. Thus if the container shall contain CO2 at a greater pressure than the generator, you will need a pump.

To put it differently: A container that shall passively "collect" all CO2 above 2 bar needs to operate at a pressure below 2 bar. If it is operating below 2 bar, it cannot passively feed gas into a system operating at 2 bar. Therefore for your idea to work, you need a pump.

Having read your other posts here (especially the first one), your solution is to add a pressure regulator to the outlet of your bio mass fermenter as pointed out by @mart's answer to your second post. You need a tolerable pressure difference between your generator and your consumers to work with.

If one problem is that the pressure in the fermenter rises above its maximum tolerable pressure, one possible solution may be to increase the volume of your fermenter. Pressure energy is usually stored in volume. However, there will be some loss, since you can only use the energy of the pressure difference between the maximum tolerable pressure of the fermenter and the minimum pressure of your output.