Volume flow controller
VRK-N 232

constant, automatically regulating, for low flow rates

  • For application in complex piping systems for the controlling the amount of air distribution
  • Mechanically automatically regulating without auxiliary energy
  • Laser-welded housing
  • Push-fit ends with double lip seals airtight according to DIN EN 12237 Class D
  • Flow rate pre-set at factory - can be adjusted by customer using scale
  • Especially suitable for visible installation
  • Special execution: ATEX, painted, stainless steel or with insulation shell or two-sided board or flat flange 

For larger volume flows you can use VRK No. 233.

Field of application: The volume flow controllers VRK are used in complex piping systems for automatically controlling the amount of air distribution. Their task is to maintain a predetermined desired value of the air flow for the supply or exhaust air of a room sustainably and independent from fluctuating channel air pressure. VRK-N is designated for lower pressures according to our product data sheet.


  • 25 mm or 50 mm insulation shell for reduction of radiating noise
  • Silencer for reduction of flow noise
  • Connection on both sides with flat flange or board
    (Standard: male coupling with lip sealing)

Function: In constant-volume controllers without auxiliary energy, the flow control is achieved by an easy-moving, asymmetrical angled control panel that ensures a sensitive response and control behaviour even for small amounts of air flow rates.

Response and control accuracy: The controller operates from the minimum pressure difference, which is a function of the volume flow, up to the maximum pressure difference of 500 Pa in a stable control range. Over this entire pressure range, the flow rate deviation is ± 10% (less than 100 m³ / h ± 10 m³/h). For smaller air velocities below 4 m/s, the flow rate deviation can be ± 20%. Unfavourable flow conditions, pollution or minor bracing during installation can also cause larger deviations.

Temperature range: The components of the controller are largely resistant to ageing and temperature resistant from -30 °C to + 100 °C. On request, the controller is also available in a special version with a temperature resistance up to 180 °C. In volume controllers with actuators, the limiting operating temperatures of the actuators apply, which can be different depending on the type and make.

Controller assembly: The control panel is mounted in a smooth and maintenance-free PTFE bushing. The support is not guided through the pipe body shell, which means that no leaks or high-frequency whistling sounds occur. A pneumatic piston damper prevents overshoot and oscillation of the control plate and ensures an accurate response and control behaviour.

Installation location: The exact balancing of the control plate is ensured by a counterweight arranged vertically on the control plate, which ensures an accurate control response in all orientations. The flow profile in front of the flow controller should be cross-section-filling, since unfavourable flow conditions (such as asymmetric flow, necking, deflection around sharp edges) can negatively affect the response and control behaviour.

Setting: The constant-volume flow controllers are shipped with either the volume flow required by the customer or with a reference flow rate set at the factory. The volume flow can be changed at any time by the customer and read on a scale by manual adjustment with an Allen wrench (2 mm). Optionally, the air flow set-point can be varied by an electric or pneumatic actuator.

Dimensioning: In the selection of the controller and the dimensioning of the pipeline system it should be noted that the flow velocity should not be less than 2.7 m / s in the pipe system. The front and downstream piping system to the controller should have the same diameter. As a reference value, a mean air velocity in the pipe of approx. 4.5 m/s is recommended as a median and orientation value.

Insulation: The flow controllers can be implemented with a sound and heat insulation in the thickness 25 or 50 mm with an insulation shell. 

Installation note: According to DIN EN 12097 an accessibility to the piping system and the volume flow controller for operation and maintenance must be observed. For installation in vertical pipes an additional protection against withdrawal is needed, e.g. by pressing a wart. When installing behind redirections or junctions, the free flow section must be at least 2,5 * ND.

Pipe body: The body tubes are made of galvanized sheet steel or optionally of stainless steel. These are laser butt welded without disturbing misalignment of the inner and outer shell surface. The plug ends are dimensionally press calibrated according to DIN 12237 and are hereby dimensionally stable and fit accurately.

Housing: The housing is made of sendzimir galvanised sheet steel or optionally of stainless steel. These are laser butt welded without misalignment of the inner and outer shell surface. Casing leakage according to EN 1751 Class C.

The push-fit ends are dimensionally press-calibrated according to DIN EN 12237, they are dimensionally stable and fit accurately.

Sealing systems of the push-fit ends:

Tightness: The push-fit ends with rubber lip is airtight according to DIN EN 12237 Class D.

Exchange: If the lip sealing is damaged or lost due to an unforeseen event, it is only necessary to put on a new sealing ring.

Removal: Because of the sealing design, the components can be separated from each other again.

Visible installation: Because no additional sealing components, e.g. tape, are required, the sealing design with lip sealing system is especially suitable for visible installation in a contemporary, appealing, architectural design.

Hygiene: The smooth surface of the laser-welded housing prevents the accumulation of dirt and dust particles.

Stability: Non-ageing lip sealing made of EPDM - a material which is resistant to slightly aggressive vapours and chemical products.

ATEX: We manufacture the constant volume flow controller also in explosion-protected execution according to ATEX. Corresponding to the appliance group 2 it is suitable for the gas explosion-protection zones 1 or 2 as well as the dust explosion-protection zones 21 and 22. The controller is marked as follows: II 2GD c IIB80°.

Packaging: For the construction site storage or applications with elevated pure-safety requirements, the controllers can be supplied in a protective film at a small extra charge. Impurities in the interior of the controller, which may adversely affect the control behaviour, are hereby avoided.

VRK-N No. 232

  • Constant self-regulating volume flow controller for low air velocity starting with 1,4 m/s up to 5,0 m/s
  • Ideal for domestic ventilation
  • Controller can operate up to a differential pressure of 500 Pa 

Please see our brochure for additional information (dimensions, volume flow, drawing) about the versions. 

Software for calculation of acoustic
for Windows 7 and 10; standalone programme

Other Languages

Make: AEROTECHNIK E. Siegwart, Type VRK, volume flow controller, constant, circular, compact construction with housing made of sendzimir galvanised sheet steel, no overlapping, laser-welded; easy-moving, airtight and maintenance-free control panel with metallic piston vibration damper; resistant to slightly aggressive vapours and solvent; good response and control behaviour in all orientations. Tightness of pipe joints according to DIN EN 12237 Cl. D Temperature range: -30°C - +100°C