Safety Valves Constant Pressure Valve VARIVENT®, Type DHV

VARIVENT® constant pressure valves are used to adjust the inlet pressure of the valve on a constant level. In case of any process-related pressure fluctuations, the valve opens or closes to compensate them. The needed product pressure will set through the air supply pressure to the actuator. Therefore a constant air control pressure is required.


As soon as the product pressure operating on the ring face of the valve disc is higher than the closing force set through the air supply pressure of the piston, the VARIVENT® constant pressure valve opens. If the product pressure decreases, the valve automatically closes and creates a constant pressure in the inlet nozzle. 

Additionally the lower part of the valve disc is provided with a control cone to optimize the valve characteristics.

The valve disc of the constant pressure valve is made of PTFE, which has a good resistance against aggressive media and only has a low friction during the movement.

Special Features

  • Mechanically stops of the valve disc 
  • PTFE valve disk with low friction
  • Easy maintenance, only two gaskets
  • Good control characteristics 
  • Different Kvs-values depending on the flow rate
  • Hygienic design
  • 3A certified 


Application Examples

In practice VARIVENT® constant pressure valves are used to keep a constant product pressure at the outlet of a separator. At this juncture the self-regulating VARIVENT® constant pressure valve is a lower priced alternative to a modulating control valve. Since the valve operates automatically after setting the demanded product pressure, no additional pressure transmitter is necessary.

The VARIVENT® constant pressure valve is additionally used to keep the demanded product pressure in heat exchangers.

Extra Equipment

The valve can optionally be equipped with a quick-air-exhaust or a precision pressure regulator. Via the supply- or exhaust air quantity a precise setting of the air supply pressure above the piston surface is possible, which allows the regulation of the demanded constant product pressure at the inlet side of the valve.

Picture 1 (left): The PTFE valve disk is raised by the product flow

Picture 2 (right): Quick air exhaust valve with noise dampener 

Technical Data

Contant Pressure Valve

Technical Data of the Standard Version
Recommended flow directionFrom bottom to top
Housing material1.4404 / AISI 316 L
Valve disc materialPTFE (FDA)
Seal material in contact with the productEPDM, FKM , HNBR
Ambient temperature0 to 45°C
Air supply pressureMax. 8 bar (116 psi)
Product pressureMax. 10 bar (145 psi)
Surface in contact with the productRa ≤ 0,8 μm
External housing surfaceMatte blasted
Connection fittingsWelding end
IdentificationAdhesive ID tag