Flow monitoring through a closed pipe

Three years ago, Detectronic replaced an AV doppler sensor for a Basel-based client that had been in place for 10 years, but was susceptible to ragging. The sensor had been successfully used to monitor wastewater leaving the client’s chemical factory and was replaced with an Orakel non contact radar flow monitor. As such, it was a key component for ensuring the factory met specific regulations and achieved compliance.

Fast forward to 2023 and the client now needed to monitor flow in a 900mm pipe that carries cooling water throughout the facility as well as a 300mm wastewater pipeline. The client did not want an open-pipe monitor in either location so approached Detectronic to discuss whether a non-contact (closed pipe) solution could be found for both monitoring requirements.


  • To monitor cooling water in a 900mm pipe
  • To monitor wastewater in a 300mm plastic pipe
  • Non-contact, closed pipe solution

Planning and implementation

A clamp on flow meter was discounted as an option due to neither pipe being pressurised.

Installing an Orakel Radar flow monitor in the 900mm cooling water pipe became the proposed solution the team came up with. All good on paper but the big question was whether the radar could measure velocity through a closed plastic pipe or not. Never having tried this, we didn’t know the answer until we tried.

At the same time, the customer wanted to use a VEGA sensor for level measurement within the pipe as this measurement is also needed to calculate flow.

Since the Detectronic Orakel system can accept up to 16 sensors, the ideal solution was to extend the Orakel that was already in place by implementing additional input/output cards to take the new sensors. Output cards were also needed to connect the Orakel to a SCADA system for ongoing analysis.

Having never used a radar sensor in closed pipes, this was an interesting project from the outset. Having all the individual components required to achieve the desired objectives, it was necessary to think ‘out of the box’ and use selected items of equipment in a different type of application. And that’s exactly what the technical team did.


After exploring various configurations, the VEGA sensor was connected via a 4-20mA with the Orakel. Easy to install and easy to configure, the solution was actually fitted as if it were an open channel.

The wall of the pipe was 17mm and the sensor was positioned over the exact centre of the pipe and held in place with a specially designed bracket and clamp. There was no requirement to change the default setting of the radar sensor or enter a higher gain.

All 4 sensors (2 radar and 2 level) are all connected to a single Orakel control unit, proving a cost effective solution.

This unique non-contact solution is functioning as expected and delivering robust and reliable data for the client.

Radar and level sensors on cooling water pipe
Orakel control unit
Data reading
Bespoke bracket used to hold radar sensor in place. X marks the centre of the pipe
Radar and level sensors installed on wastewater pipe