Controllability

[ing123]

I have a problem with controlling a small flow in a pilot plant and would appreciate any suggestion. System consists of two horizontal drums D-1 and D-3. There is 0.4 gpm flow from D-1 to D-3 under gravity. Bottom of D-1 is 500 mm above top of D-3. There is an orifice meter to measure the flow and a control valve downstream of the meter. Fluid specific gravity is 0.78. Max static head for the meter and control valve together is 350 mm (0.4 psi). What is the minimum pressure drop for the meter to meaasure accurately? Is the pressure drop thru the control valve sufficient to provide a meaningful control? What is the measure to judge if the control valve can provide good control? Thanks.

 

[AggieCHEN04]

The 0.4 psid seems like an awfully low pressure drop for for flow control, but there really isn't enough information to determine if flow control is acheavable for this application. There are a few more things you would need to know:

-What type of fluid is it? You would need to know the viscosity, vapor pressure, temperature etc.

-What is the orifice bore diameter?

-What is the pipe ID?

-What is the control valve style and size?

-What is the application? Are both these vessels at atmospheric pressure? Does D1 need a constant level?

There are various programs available for sizing control valves and flow orifices. For example, Firstview is a control valve sizing program that is available through Fisher and is free of charge. I use use FE-Sizer for flow orifices, but that program is somewhat expnensive if you're only going to need it once.

 

[ing123]

Thanks AggieCHENO4for the info.