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This bench allows to study the features of an industrial pneumatic control needle valve with servomotor. The notions of CV and Kvs can be dealed. The valve can be used with or without positioner.


Teaching objectives

  • Determination of the experimental Kvs of the valve with and without positioner.

  • Drawing and study of the curves :

  • Intrinsic features of the valve

Qv = f(control) at constant head loss

  • Feature of the installed valve :

Qv and ΔP = f (control).

  • Function of the positioner and phenomenon of hysteresis.



A pneumatic servomotor valve is supplied by the water network via a needle control valve. The flow is measured by a rotameter. A regulator allows to adjust the pressure of the network.

The difference of pressure between the upstream and downstream of the control valve is measured with the help of a differential pressure transmitter with local display.

The influence of the positioner on the answer of the valve is determined with the help of a current generator (4/20 mA) allowing the control of the control valve servomotor via an I/P converter (0,2 to 1 bar) or via a pneumatic electro-positioner..

The device is mounted on a welded stainless steel frame, equipped of 4 adjustable feet.


Technical specifiations

  • A regulator 0-3 bar of the water supply circuit with manometer.

  • A needle flow adjusting valve made of stainless steel.

  • A pneumatic needle control valve with variable Cv made of stainless steel.

  • An electro-positioner.

  • A regulator, with air oil separator and manometer.

  • A differential pressure transmitter with local display and bleeding manifold.

  • A rotameter (scale 60 to 600 l/h).

  • An electrical cabinet, IP 55, including :

  • A padlocked main switch,

  • A ON light,

  • An emergency stop button with key

  • A current generator (4/20 mA) with potentiometer and indicator,

  • Control signal output by safety plugs.

  • Technical manual in English


Essential requirements

Power supply: 230 V, 50 Hz, 250 W

Compressed air: 6 bar, 3 Nm3/h.

Water: network clean water 3 bar, 20 °C, 1000 l/h.


850 x 425 x 940 mm