Valve Rangeability Calculation

[oilersfan007]

How do I calculate the valve rangeability from the datasheet?
Do I just take the flow rate at the max flow condition and divide it by the flow rate at the minimum flow condition? Or do I need you calculate the flow rate at full travel first?

 

[LittleInch]

What do you mean by "rangeability"???

This is not a technical definition of anything.

Clearly at 0% open ther eis no flow and 100% open there is a lot of flow limited only by the max valve Cv.

I think what you might mean is what is a control valve reasonable range of flows with which it can accurately control flow??

In this case you often look for a minimum opening of 25 to 30% and a maximum opening of 70 to 75%.

Beyond these ranges, the valve and its actuator finds it difficult to control flow or pressure with small changes in % opening have a big impact on flow or when more than 70% open only having a small impact on flow.

But you tell me what you define as "rangeability"

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

 

[GB67]

Rangeabilty is the ratio between the minimum and the maximum controllable Cv

It's impossible to calculate the rangeability of a valve from valve data sheets or drawings
It must be calculated measuring real Cv max and Cv min

Regards

 

[LittleInch]

Ok, but what is defined as "controllable Cv"

If you don't define it how can you calculate it / find it?


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

 

[MarekLDM]

If you specify operating parameters:
- Medium (type, density, physical state)
- Medium temperature
- Pressure before the control valve
- The pressure control valve or what is to be the pressure drop across the valve
- Maximum flow
- Minimum flow
- The flow of work
I can choose the control valve and give you the card selection. These parameters will select the appropriate valve KVS (Cv) and characteristics, which will be tailored to your needs and operation.