Water Systems - Valves and Kv diagram

Kv diagram for sizing control valves

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

Water valves - Kv diagram

  • 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.

Water valves - Kv diagram example

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 Valves - Control Valve terminology, bodies, trim, flow characteristics, Cv and Kv sizing, noise, actuators and positioners
  • Fluid Mechanics - The study of fluids - liquids and gases. Involves velocity, pressure, density and temperature as functions of space and time

Related Documents

Tag Search

  • en: kv diagram pressure drop flow water control valve modulating
  • es: diagrama kv válvula de control de flujo de agua caída de presión modulante
  • de: kv Diagramm Druckabfall Flusswasser Regelventil moduliert

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