Safely providing inhabitants with perfect potable water is one of the most challenging tasks facing Stadtwerke Backnang GmbH. Its staff put their trust in regular checks and extremely reliable metering pumps from ProMinent.
Operating reliability essential
The public utility company in Backnang, a small town around 30 km north-east of Stuttgart, has taken over the management of the Allmersbach water administration union in the valley, where it supplies potable water to almost 2,500 homes. To ensure the water quality required by the administration union in the long term, in 2006 a totally new system was installed for treating and softening potable water by means of rapid decarbonisation.
In line with the German Drinking Water Ordinance, special processes must be followed should a system fail as a result of a defect in a critical component, such as the metering technology for sodium hydroxide. This would incur a lot of work and therefore extra cost for the Allmersbach administration union. The managers at Stadtwerke Backnang GmbH therefore focused on longevity, high operational reliability and low maintenance costs when selecting their equipment.
- Annual supply of around 265,000 m3 of potable water to 2,500 homes
- Treatment and softening of spring water and deep groundwater by means of rapid decarbonisation in a fluidised bed reactor
- Smooth operation of the water softening system thanks to reliable metering of sodium hydroxide around the clock with Sigma motor driven metering pumps
Safe metering of sodium hydroxide at all times
Spring water and deep groundwater local to Backnang has been treated and softened by means of rapid decarbonisation in a fluidised bed reactor for more than nine years now. And since the system was commissioned, three Sigma motor driven metering pumps from ProMinent in two stations have been reliably and continuously metering the challenging chemical sodium hydroxide.
Metering station A, equipped with a Sigma/ 3 (500 l/h at max. 7 bar), feeds 50% sodium hydroxide into a thinning unit from a WHG tank roughly once a day. Metering station B, equipped with two Sigma/ 1 (42 l/h at max. 10 bar), feeds 25% sodium hydroxide into the potable water softening system around the clock. One metering pump is also fitted as a standby – for peace of mind. A third station, metering station C, equipped with a solenoid metering pump gamma/ L, is on hand to meter hydrochloric acid should the pH of the potable water exceed the permitted values.
All the Sigma pumps used in Backnang have an injection-moulded PVDF dosing head. Thanks to the compact surface of the parts in contact with media, this has outstanding resistance to chemicals. The larger metering pump was recently replaced by the new model Sigma S3Cb, while the two smaller pumps have run continuously for nine years.
- Universal use of the Sigma motor driven metering pump in industry for metering or transferring difficult chemicals
- High chemical compatibility of the PVDF dosing head, even when used continuously for years to meter sodium hydroxide
- Guarantee of maximum operational reliability thanks to overload shutdown and multi-layer diaphragm with diaphragm rupture warning system
- The fact that no maintenance is needed and the longevity and reliability of the metering pumps cut operating costs significantly
- Totally smooth operation of the water softening system ensures a perfect supply of potable water