Pump Sizing

I'd consider the whole system. I'd also ask my pump supplier, if you have one. And, since it is impossible to tell where you are and what you are doing, that's all.

In the absence of non-return valves on the lines into the two vessels, the pressures in the two vessels will balance via their common connection. The pump then has to overcome whatever the balanced pressure is. If the inlet to each vessel is above the liquid space, then it is not possible to state exactly which way the flow will go and how much will go to each vessel.

If non-return valves are present, then the two vessel pressures will not balance, so the pump only has to overcome the lower of the two pressures, and until they do balance, that is where all of the flow will go.

There has to be orifice+ pressure relief valve / pressure control valve + bleeder/ pressure relief valve in one of them (the one at the lower pressure).

In that case the pump builds up the pressure corresponding to the higher pressure.

This is assuming that you are just pressurising and there is no flow.

In case the flow is there then simple pressure control valve for the lower pressure chamber will suffice. Still the pressure equals the higher pressure.

The flows will be additive and not the pressures.

These two tanks will act as one. Assuming that there is low and equal resitance in the plumbing (the lines to both tanks are the same length and both are large enough (relative to the galons per minute) to have low resitance and that the two tanks are relatively the same altitude above the pump. You only need one automatic control switch). In the scenario you described both tanks are conected via the point where the line from the pump divides. If these are presure tanks that have air in them and a liquid is pumped in then the Inlet lines might need to be at the bottom of the tank (depending what you are doing).

Your choice of pump depends on what pressure or head and flow rate you are wanting to get out of the system. Two tanks joined together will act as one. If one tank has a higher altitude from the pump then things could not act how you want. The bottom tank will have more pressure than the higher tank (if they are conected).

When you have complex systems in hydrolics and pneumatics you run a higher risk to have some sort of circuit develope that can start humming or vibrating anologus to Elctronic circuits will behave with capacitance, resitance, voltage, and curent.

Its great to have new people on CR4. Your question has gotten great answers considering your serious lack of information. As a field boiler guy I am going to answer this as if you were trying to control the water level in two boilers with one common pump.

Install simple slide wire 135 ohm 24 vac level control float assemblies on each "vessel"

Make certain your pump exceeds your maximum total flow needs by 50%.

Install modulating valves on the inlet of each vessel that will work with the 24 volt system.This is very durable as well as reliable.

Install a small return line from the outlet of your feed pump back to your storage tank. This small line will come into play when both of your vessels are at the desired level and the modulating valves are closed. An alternate to this process would be to install a three way valve in the discharge of the feed pump with a pressure sensor on the the same line. As pressure builds the three way valve will divert water back to the feed tank both vessels will have close to the same pressure during this process. This last method would allow a less capable pump then the one with the small bypass line that will be returning the minimum recommended flow rate that the pump manufacture recommends.

If your only concern is pressure in each of the "vessels" then I would install a "DP" type of pilot controlled valve on the inlet to each vessel. By installing the sensing line in an over the shoulder or feed forward position the valves will close down as you approach your desired pressure in each vessel you can have different pressures in each vessel this way. Your concern with this system will be pump protection. This can be handled by a Clay type pressure relief valve on out going side of your feed pump relieving back to the storage tank.

As you can tell the "fixes" are endless. Please take this rambling as a lesson in giving the group as much information as you have and understand or at least an end goal for your next question.

I don't mean to be harsh but people in my business get killed by trying to solve problems that they don't really understand.

Give us your real problem and we will help you.

From the field

Mike