Sampling under pressure or negative pressure


City in Italy operates an extensive wastewater treatment plant to which over 100 tanneries are connected. The costs of operating the wastewater treatment plant are shared equally between the city and the tanneries.

The central problem lay in the “fair” distribution of costs, which was no easy task due to the temperamental nature of both parties. The most transparent solution was to automatically record the discharge volumes from each plant and take samples whose quality could be analysed.

We were commissioned to develop automatic sampling equipment. The challenge was to take samples from a closed pipe, which could be depressurised or pressurised depending on the pumping cycle. Our device had to be able to handle both and at the same time ensure that the pressure line would not run empty in the event of a defect or programme error. The system also had to be able to cope with the demanding waste water from a tannery.

Our solution

We have developed a dosing system based on a ceramic slide valve. This gate valve enables sampling under pressure, ensures maximum safety in the event of a malfunction and does not present any problems when handling challenging wastewater. We have combined this system with a downstream vacuum system so that the sample is taken through the ceramic gate valve when the pressure is on and through the vacuum system when the line is depressurised.


In each sampling cycle, the device first endeavours to pressurise the sample. If this does not occur within an adjustable time, the vacuum system is automatically activated to reliably suck in the sample. In the idle state, the system is sealed pressure-tight, ensuring that nothing can escape from the line.

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