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# Water Control Valves - Flow Factor Kv Diagram

The flow factor Kv for control valves in water systems can be estimated from the diagram below:

• 1 bar = 1x105 Pa (N/m2)
.

### Example - a Water Valve and Kv value

The maximum pressure drop through a modulating control valve in a water flow system is designed to be 100 kPa. The flow through the valve is 5 liter/s. The required kv value for the valve can be estimated as indicated in the diagram below to approximately 20.

Note - larger valves (with larger Kv) reduces the maximum pressure modulating spans - limiting the ability to provide a stable process control. As a consequence - control valves are often one to two dimensions below the dimensions of the connecting pipes.

Example - with a water flow of 5 liter/s the pipe size would be in the range 3 - 4 inches (80 - 100 mm nominal). A control valve would be in the size kv ~ 20 - or in the range 2 - 3 inches (50 - 80 mm nominal).

## Related Topics

### • Control Valve Sizing

Control Valve terminology, bodies, trim, flow characteristics, Cv and Kv sizing, noise, actuators, positioners and more.

### • Fluid Mechanics

The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.

## Related Documents

### Ball Valves - Flow Coefficients Cv

Flow coefficients - Cv - for typical ball valves - reduced and full bore.

### Control Valves - Adding Flow Coefficients for Valves in Series or Parallel

How to add flow coefficients for control valves in series or parallel.

### Flow Coefficient Cv vs. Flow Factor Kv

Comparing flow coefficients Cv to flow factors Kv.

### Liquid, Steam and Gas - Flow Coefficients Cv

Calculate flow coefficients for the design of control valves - Imperial units.

### Liquid, Steam and Gas - Flow Factor Kv

Calculate flow factor Kv for liquids, steam and gases - metric units.

### Straight Through Diaphragm Valves - Flow Coefficients

Flow coefficients - Cv - and flow factors - Kv - for straight through diaphragm valves.

### Valve Authority

The valve authority expresses the ratio between pressure drop across the control valve compared to total pressure drop across the whole system.

### Valves Types - Operating Size Ranges

Types of valves and their typical operating sizes.

### Water Control Valves - Flow Coefficient Cv Diagram

Sizing of water control valves - Imperial units.

### Water Control Valves - Kv Calculation

Designing water process control valves and their Kv values.

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