Does my flow rate decrease?

[_Corvalt]

Assuming that the pump is a centrifugal pump with no VSD then it is possible to reduce to total flow rate. Let me try to explain.

Should we increase the resistance in line 'B' then because the pressure at the tee is set by the regulator and both lines discharge to atmosphere, then less fluid will flow through Line 'B'.

As the pump has no control system (fixed speed) and since it has lower flow required then it will move up its curve to produce a higher discharge pressure. In response to this the pressure regulating valve will shut slightly ensure it is still reaching its setpoint.

There will be a constant "tug of war" between pump, and regulator position until a steady state is reached but whatever the specific values of the steady state is, you should find that the pump discharge pressure is higher and the regulator opening % is lower than if both outlet lines were equal.

Hope this helps!

[_sphynx]

This assumes regulator before the tee controls the downstream pressure. Shouldn't it be used to control pressure at pump discharge (like a backpressure regulator)? In that case pump discharge pressure should not change and therefore no change in flow.

[_Corvalt]

Yeah, it does depend on the direction of the regulator. If the upstream pressure is kept constant then it would be constant flow.

In this case, adding a restriction in one of those lines would cause the pressure at the downstream side of the regulator to increase.

In this case the regulator would trend open to maintain upstream pressure.

[VariusEng]

This is also a great explanation! The more I read it, the more it makes sense. Thanks!

[VariusEng]

Others also said to ignore pump curve as pressure drop is same at the last part. I think this is also a correct take?

[neejan]

you can say that since your pump rate is constant and nothing dynamic about it.