Successful retrofit of a wastewater treatment plant with a clamp-on ultrasonic flow meter
Without altering the existing pipework, the Aken Wastewater Association was able to make significant cost savings in optimising the inflow measurements at its sewage treatment works, thanks to the successful installation of the KATflow150 dual-channel flow measurement system
AZV Aken saves a five-figure sum through non-invasive flow measurement
Since 2021, all sewage treatment works in Saxony-Anhalt above a certain size have been required to provide evidence of continuous inflow measurements. However, the Aken Wastewater Association had previously lacked a metrological system for monitoring the main inflow from the north-western part and the secondary inflow from the southern part of its catchment area. With the aim of installing fixed flow meters at two points on the plant without having to “modify the old cast iron pipework with a pipe diameter of DN 500 or the manhole structure”, Mr Thomas Heppner, the plant manager and person in charge, approached Katronic.
Following an initial clarification of technical details, a quotation was submitted to the association for the KATflow 150 dual-channel flow measurement system. This system, designed for permanent installation with two analogue current outputs (4 … 20 mA) and two digital relay outputs, is a non-invasive ultrasonic flow meter particularly suited to the retrofitting of existing plants.
Once Mr Heppner had received approval for the project’s funding, a trial measurement was to be carried out at the sewage treatment works. This would allow for a more accurate assessment of the subsequent technical feasibility of the measurements and the scope of the commissioning process.
As the conditions for a test measurement on the two DN 500 cast-iron pipes located in a shaft structure proved to be inadequate for acoustic sensor coupling due to rust, a number of measures had to be taken in advance to ensure a functional measurement. In addition to tension straps for securing the sensors to the large-diameter pipes, this involved the use of a cordless angle grinder and a ‘K0’ transducer with a higher signal strength.
Once the ‘main inlet’ measurement point had been suitably prepared, a signal was immediately established and measurement values demonstrated. Nothing stood in the way of installing the KATflow 150 evaluation unit.
At the second point, the ‘secondary inlet’, no signal was initially detectable. As it later transpired, during earthworks near the sewage treatment plant, a DN 200 PE supply pipe had been encountered, which appeared to merge a few metres further on into the DN 500 cast iron pipe, where the test measurements had failed. Using a portable clamp-on flow meter, a good measurement signal was then generated and flow rates were confirmed.
The Katronic staff commissioned to complete the work checked the new measuring point on site at the start of their assignment using the portable KATflow 200 clamp-on flow meter. A measurement signal was present, and flow rates could be detected. A K1L transducer, compatible with the KATflow 150, was then clamped onto the 200-mm pipe and wired to the data acquisition unit, located approximately 35 metres away, via an extension cable. The successfully retrofitted KATflow 150 two-channel flow measurement system has since been fully operational and is used for simultaneous flow monitoring on two inlet pipes at the sewage treatment plant.
The AZV Aken was able to save a mid-five-figure sum on the retrofit of the system, a cost that would otherwise have been incurred in the construction of a second shaft and the fitting of expensive measuring equipment therein.
