Pumping chemically aggressive wastewater containing solids

Pumping chemically aggressive wastewater containing solids

In industry and commerce, wastewater is produced that combines several requirements: chemical aggressiveness, solids and, in some cases, abrasive components. This calls for a pump that is both corrosion-resistant and capable of handling solids – a combination that neither a general-purpose all-plastic pump nor a grey cast iron pump can fully meet.

Corrosion resistance through the choice of materials

The focus is on the material combination. In the TopLine-C, the pump housing, impeller and motor housing are made of Stainless steel 1.4436 – a molybdenum-alloyed steel with significantly higher resistance to pitting corrosion and chlorides than standard stainless steels. The motor shaft is designed from high-strength duplex steel 1.4462, whilst the screws are designed from 1.4571. The elastomers and the second sealing stage are made of FPM (Viton), which is resistant to a wide range of chemicals; the floating ring seals are designed as an SiC/SiC pairing in a tandem arrangement with an Oil barrier chamber.

Assessing chemical limits realistically

The pump is suitable for a pH range of approximately 5 to 14; in the case of particularly aggressive chemicals, the lists of materials that are compatible with them are decisive. With regard to salinity, the following applies: temperature-dependent limit: at temperatures between 1 and 15 °C, a salt content of around 3.5 per cent is possible; at temperatures between 16 and 20 °C, around 1 per cent is still possible.

This leads to an important distinction: for the highly saline water from Water softening systems This stainless-steel pump is not intended for such applications – the salinity is significantly higher there, and a chemically inert plastic pump is required. It is also unsuitable for sewage, long-fibre components or solids larger than 10 mm, flammable or explosive Media, and for use in ATEX zones.

Hydraulics and Operation

The TopLine-C operates with a multi-channel impeller and conveys solids up to a particle size of 10 mm. In submerged operation, continuous duty (S1) with up to 20 cycles per hour is possible; when the Motor is out of the water, intermittent duty (S3, 40 per cent) applies. The maximum medium temperature is 40 °C (60 °C for short periods), and the immersion depth is up to 20 m. A temperature sensor in the Motor coil (trip temperature 140 °C) monitors the coil.

Typical applications include the disposal of aggressive wastewater in industrial and commercial settings, car parks, and emergency drainage in the event of flooding. The range comprises the 50M and 65M models, with different delivery heads and flow rates.

At a glance

• Materials → Stainless steel 1.4436 (molybdenum-alloyed)

• Solids (ball passage) → 10 mm

• pH range → 5 to 14

• Salt content → temperature-dependent, approx. 1 to 3.5 %

Conclusion

Aggressive industrial fluids containing solids require a Pump that combines corrosion resistance with the ability to handle solids. A stainless steel version made from 1.4436 with FPM seals covers a wide range of pH levels and chemicals – with the clear caveat that very high salt concentrations, such as those found in water softening systems, require a different material solution. The key factors for selection are the pH values, salinity, medium temperature and particle size.