normal control valve and auto recirculation valve in the pump minimum flow line 3

[Nick47]

Hi All,
What shall be the basis for selection between normal control valve and auto recirculation valve in the pump minimum flow line?
What are the basic requirements and considerations?

 

[LittleInch]

Cost
complexity,
Ease of operation,

An ARC is normally a valve set up with pilots, springs etc with no requirement for external power or instrumentation.

This is a typical

https://www.emerson.com/documents/a...omatic-recirculation-yarway-en-en-5198076.pdf

Control valve needs input from a flow meter, pressure sensors etc and a small PLC to control the control valve leading back to the inlet or tank.

But they are then more adjustable and you can close them if you need to temporarily or reduce the back flow amount whereas the ARV are not so easy to adjust or monitor. So e.g. if the back pressure on the recirc line changes, the min flow might change for the ARV, but the control valve would control on the min flow and adjust itself accordingly.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Nick47]

Thanks, is it any issue with using ARC before flow control valve (in discharge line)?

 

[LittleInch]

Not really. The ARC is protecting the pump with the other control valve regulating flow forward.

As the flow increases the ARV closes once the flow forward gets higher than the min flow.

That's why it is much better than a fixed orifice back flow.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[pierreick]

Hi,
Consider to read doc attached .
Pierre

 

[Nick47]

Thanks @LittleInch & @pierreick

 

[horacio Torres]

In a not supervised installations is better to used ARC valve


Horacio

https://www.linkedin.com/company/lagotuy/

 

[1503-44]

They work great in any situation.
The least complex installation is always the best.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[SB1976]

Hi Nick,

1. From an application perspective, control valves are used for plant based equipment control, while ARV is generally for facilities based equipment control and protection.

2. ARV is used when the fluid flowrate is not well known and/or may be variable (as in boiler feed water application). In such cases, ARV modulates the flow without the operator intervention. Meanwhile, when the flow is generally known and is of stable nature, control valve is used.

3. We cannot use control valve with very high pressure differential across pumps/systems. Accidental closure of control valve will cause high pressure downstream leading to high flow churning inside pumps which will eventually manifest into high heat generation inside pump thereby damaging the pump bearings/seals/internals. In such cases, ARV is used to make sure high pressure do not trigger high heat buildup. Typical application - Multistage Pipeline pumps.

4. Control valve as means of pump flow control works best for steady flow ahead of heat exchangers / pressurized or non-pressurized vessels / columns as typically found in refineries, petrochemical plants with low to medium pressure ranges.

Trust this clarifies.