Applicability of Back Pressure Regulator for Pump ARC valve

[nirlt]

We are engineering a BFW multistage pump (8 stages) being supplied from reputed pump manufacturer alongwith ARC valve (to be supplied by Pump Manufacturer). At the time of pump ordering, Back pressure regulator (to be mounted in Pump min. continuous flow line) was included in Pump Manufacturer's scope of supply. However, after order they are telling it's not required.

What is the criterion for deciding whether Back pressure regulator is required or not?

 

[BigInch]

If,

your pump can be started quickly against the backpressure of your downstream piping and equipment without vibration and overheating,

your system will not be operated below 20% of pump's BEP flowrate,

your system will not be operated below 60% BEP for any condition other than during startup, shutdown or a quick change of pump station operating configuration,

if your equipment and piping can withstand any rapid pressure increase due to pump startup and shutdown at the flowrate at any pump rpm on the way to BEP speed and do so without excessive water hammer,

You don't need the ARC valve.

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[BigInch]

I just now see that you are asking not only about the ARC valve but also about a "backpressure regulator" installed in the recirculation line.

I have used a control valve in the recirculation line to account for the variable flow condition you must sometimes accomodate while starting up or shutting down a pump, as I tried to explain in your other posting.

I have used control valves for that purpose when there is a need for an accurate method to proportion a pressure build up, to go into the downstream pipe and equipment, versus the need to also maintain a minimum flow through the pump while doing so.

The control valve was needed in those cases because the engine usually had to warm up, or wait for upstream pipeline pressure to build (both conditions could take a period of up to 15 minutes) before we could begin doing a ramp up to maximum pressure.

If you do not have a very high pressure to reach before minimum flow into downstream equipment is reached, you probably will not need a "regulator" or control valve to help you build up that pressure. A simple on/off valve in the recirculation line might be more appropriate, but when you turn it off, pressure should build quickly enough to flow downstream without undue delay and without overheating the pump, so you must get to min flow quicky after valve shutoff.

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