# Pressure regulator question - Concerning flow rates

1. Aug 26, 2014

### thereisnospoo

I see that pressure regulator curves show different flow rates, but I am confused by this because I was under the impression that the flow rate would be an "output" of the force/pressure balance across the pressure regulator.

For example, assuming the inlet to a regulator is 500 kPa, and the outlet is 25 kPa. The flow rate through the regulator is 25 m3/hr.

Say we want to increase that flow rate. Wouldn't we then have to increase the inlet gas pressure? If we increase the inlet gas pressure to 700 kPa, then wouldn't the poppet close a little more to maintain the 25 kPa outlet, and then this would decrease the gas flow rate? So then isn't the flow rate just an "output" of the pressure relationship across the regulator?

I think I'm getting a bit mixed up with the relationship between flow and pressure. If anyone can shed some more light on this it would be greatly appreciated.

2. Aug 28, 2014

### Baluncore

How about posting a link to the regulator and the curves you are considering.

The performance curves will be sensitive to all parameters. A regulator has feedback with a finite loop gain.
How sensitive or insensitive a regulator is to any parameter will depend on the design.

3. Aug 29, 2014

### Q_Goest

I assume what they are showing there is a maximum flow rate.

As you say, the flow rate for a regulator is a function of how much the valve poppet is opening and what the inlet and outlet pressure is. The regulator opens/closes to maintain the downstream pressure. That's done by having a force balance between downstream pressure and a spring or some other means.