pump motor frequency

If you build up a control loop in frequency with respect to pressure then the flow from the pump will automatically be adjusted to the one required to obtain the set pressure.

Thanks Guro,

Could you please go a bit in detail.

I am not sure what you mean by "lead to a fall in required pressure or will it maintain the same?"

But I will offer this:

If you slow down a pump impeller - the amount of pressure and flow produced by the pump will drop.

Secondly - Choking the flow of pumps is quite common, especially through control valves, and if you want to choke the flow of a pump it is recommended that you do so on the discharge side to avoid cavitation in the pump.

In order to get the flow rate thru the RO membrane the temperature of the incomming water will typically need to be between 27DegC and 30DegC (depends on membrane). The membrane can be damaged if the temperature goes too high (probably mid 30's but again depends on membrane). I just mention this because there was the possibility of the water temperature increasing.

For an RO system, the input pressure of the RO system must always be at or above the design pressure calculated in the RO projection, otherwise the osmotic pressure may cause permeate to backflow through the membrane back into the influent chamber.

Quite.

Good answer!

All the comments I noted were good. I am assuming that cost is a factor and the controller and feed back loop mentioned by yourself and others will be costly.

A simpler method is build the control loop into the plumbing. If you place a pressure regulator and waste gate into the output line then the pressure in the system will be maintained and the over capacity of the pump addressed. If the waste gate returns the excess to the intake you will not waste water.

This potential solution will be low cost and fairly reliable, keep the heat of the water down and be no less energy inefficient than simply chocking the pump which should be done on the high side of the pump as others have mentioned.

Adding a reduction gear or pulley set can also reduce the capacity while meeting the pressure requirements without the cost of the motor fancy drive. This has the advantage of minimal energy waste and low cost.

Higher flow rates through the membranes are beneficial to RO filtration. Are you certain you need to limit flow?

Sincerely,

Mr. Gee

Have you not done your homework? None of the RO makers use such complicated control loops. One manufacturer uses a piston "Clarke" pump and this is a very efficient low power and lower volume pump. Don't ask what the "clarke" pump is since this is at the core of their patented process. However most other RO makers imply uses triple stage pump with built in pressure regulation etc.

Output quantity of product is governed by area of membrane not pump volume.