2.2.2. Pressure Relief Dampers for high opening pressures, with switching function KL-EM

In a great variety of different applications within HVAC systems pressure relief dampers manufactured by Krantz are used to limit the pressure and control it, respectively. Typical applications include the protection of ductwork from inadmissible high loading caused by positive pressure or negative pressure, positive pressure ventilation of staircases, or setting a defined pressure drop between adjacent rooms.



Dimensions W x H x D 630 x 400 x 510 mm
Weight 23 kg
Range of air flow 1

Vmin= 1 400 l/s [5 000 m³/h]

Vmax= 125  √Opening pressure [Pa] l/s

[Vmax= 450 √Opening pressure [Pa] m³/h]

Opening pressure, adjustable 700 - 2 400 Pa

1 Higher range flow achivable by parallel Connection of several dampers


  • Airtight according to EN 1751, class 4 in closed position opens fully when opening pressure set is attained (switching function)
  • Closes automatically upon interruption of flow
  • Setting of opening pressure by variation of lever arm
  • Closing of damper after exceeding of opening pressure by hand


The Pressure Relief Damper KL-EM features a switching function. Independent of the range of volume flow of the outlet flow the damper blade gets fully opened when the opening pressure is exceeded. When the pressure in the ductwork falls below the opening pressure after the malfunction has been remedied, the damper normally remains open. In this state of operation the damper KL-EM must be closed manually, whereas it closes automatically when the flow is interrupted, e. g. by disabling of the fan. Despite its smaller outside dimensions type KL-EM is capable of removing flows at higher range of volume flow as compared with KL-E.