LDM-based pneumatic discharge control

Flow measurement and discharge control for wastewater, raw wastewater and rainwater in partially and fully filled pipes.

Pneumatic discharge control for precise flow limitation

The fast, almost self-cleaning and remotely controllable pneumatically driven pinch valve is based on the LDM flow measurement integrated in the system for partial filling and limits waste water, raw waste water and rainwater quantities to a value that can be set as required. As long as the throttle value is not reached during dry weather, the pinch valve remains open, while the flow measurement measures precisely even when partially filled. Thus, the partially filled flow measurement LDM can also be used, for example, for the billing of wastewater fees and operating costs. Furthermore, the system is being used as a rainwater discharge throttle, rainwater tank discharge control, discharge throttle for backwater channels and tanks and much more.

High ease of maintenance

Due to the integrated maintenance opening, the interior of the system is extremely easy and conveniently accessible, which makes the entire system extremely maintenance-friendly. The maintenance opening is certified according to ATEX and is therefore suitable as a separation between the explosion-hazardous interior of the throttle section and the system environment.

Pinch valve vents pipe crown

The following figures show some positions of the pinch valve, which shows that the valve can open completely and unblock the entire cross section as well as close completely. In the intermediate positions it can be seen that the pipe crown remains open until shortly before it is completely closed, so that air can escape and no air cushion in the pipe crown is created that could disturb the flow measurement.Positionen Quetschventil

The pinch valve was originally designed for the dosing of stones and gravel, which is why the integrated hard rubber sleeve is extremely robust and resistant to the processing of solids, gravel and aggressive media.

Pneumatic discharge control with pinch valve and LDM flow measurement

Technical information


  • Pinch valve: ATEX Zone I
  • Flow measurement: ATEX Zone I
  • Maintenance opening: ATEX Zone I
  • Piping: ATEX Zone I

Nominal sizes

  • NW150 to NW400
  • The pinch valve is located immediately after the flow measurement, thus it reacts quickly to flow changes and can also maintain the programmed control value with the smallest deviation and delay time.
  • In comparison with a knife gate valve flow control, the 1 to 10 rule of thumb can be used: While a knife gate valve can move to 100 individual positions in stages, the pneumatic discharge control system, thanks to the infinitely variable pressure control, can achieve at least 1000 individual positions – which is the basis for the high control accuracy.

The control of the pneumatic discharge control contains a touch display with zoom and wipe function, as well as a data logger and a local small DCS for use with a web browser, which can be accessed in the local network or, if desired, from the Internet. In addition to the versatile interfaces, the small DCS or the web server can also be integrated and displayed in the customer’s distributed control system.

Included as standard with modem for using all mobile networks up to 4G/LTE, Fixnet Internet connection and VPN technology

  • Signal outputs: 4-20 mA: instantaneous flow rate and set control value
  • Digital (active/passive): Flow counter and 2x fault
  • Signal inputs: 4-20 mA: set-point control value
  • Digital (potential-free): OPEN (remote); CLOSED (remote); AUTOMATIC; MANUAL START CLEANING;
  • Communication: RS485 (Modbus RTU/ASCII), RS232, Ethernet (Modbus TCP) connection via Internet/VPN.
  • VPN connection for remote maintenance with STEBATEC (Internet connection with STEBAmobile possible)

Connection diagram on request.


  • Pinch valves allow venting in the pipe crown, thus avoiding the formation of air bubbles in the control section, which would disturb the flow measurement
  • Controls with high precision, shortest reset times and no running time limit
  • Pneumatic drive in wet ATEX environment better suited than e.g. electric drive
  • The throttle value can be variably parameterized/adjusted over the entire discharge spectrum
  • The control is remotely controllable and compatible with all commercially available distributed control systems
  • Measures and throttles the flow with a maximum deviation of 2% from the measured value
  • Compact flow measurement and control system incl. calming sections with minimum space requirement
  • Detects soiling and discharges it selectively (flush function, attachment discharge)
  • In case of power or device failure throttling continues with an emergency program
  • Enables partial filling operation and prevents deposits
  • Is easy to maintain and can be opened without tools for cleaning
  • Works with a standardized, mature control program


Why pneumatic pinch valve instead of knife gate valve?

  • Air in the pipe apex can escape
  • Speed: Open to closed in 3 seconds
  • Accuracy: Membrane adjusts very finely, while a knive gate valves movements are large in comparison
  • No emergency power generator necessary for emergency position in case of power failure, as the system continues to operate with residual pressure in the compressor
  • No wear of the spindle and sudden jumping behaviour
  • No electric drives in the hazardous area

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