Control Valves - Large sizes - Authorities

[HeshamM]

When trying to install a two-way control valve of 450mm size, we usually end up using motorized butterfly valves (globe type is very expensive). Does valve authority matters when using BF valves for flow control application?

 

[SAK9]

Hesham,

You need to maintain valve authority for any control application otherwise control will not be stable.You can odrer BF valve to suit your application ie equal percentage or linear depending on the characteristics of your sysem.Equal percentage is suitable for cooling coils where as linear charactericks will suit a heating coil.

From the size of the valve, it seems like you are trying to contol the plate heat exchanger on a district cooling/heating system.

 

[HeshamM]

SAK9, you are totally right about the application. Butterfly valves charactaristic is linear! does that mean it will not work efficiently in cooling systems. And regarding the coil, does the cooling coil have the same charactaristic of plate heat exchanger? they don't. Plate heat exchanger have a linear relation between the flow and the cooling capability. In this case, and if this is true, why should I care about the authority?