Look behind the scenes
Used service water from industrial processes is one of the most problematic types of waste water due to its composition, which is often very demanding for conveying systems. In order to enable problem-free treatment of this kind of waste water in spite of this, the T.Envi® is specially designed for a long service life with minimum wear, so that it can also convey extremely abrasive media without any problem.
A large German building materials and concrete parts manufacturer regularly experiences considerable amounts of mineral waste water with pebbles up to 20 mm in size when cleaning the mixing plant. The mixture is collected in a settling tank from where it has to be conveyed to a treatment plant via a 10 m long riser for further de-watering and separation. However, the centrifugal submersible pumps which had been used for this until 2015 did not withstand the stones and sand in the water for long due to the high speed required. Excessive abrasion and wear meant it made no sense to carry on using the pumps after only around six months. The company therefore decided to switch to a rotary lobe pump.
A T.Envi® from NETZSCH was used which is specially designed to be extremely robust and for a long service life with minimum maintenance effort. The reason for this is an innovative mixture of materials: instead of elastomer lobes rotating in a metal housing, this involves two hardened steel lobes rotating in a elastomer housing insert which is easy to replace. Steel is less susceptible to material fatigue due to dynamic forces – of the type that arise when there is repeated stress on the elastomer or plastic rotary lobes which are otherwise common – this means longer durability of the moving components is achieved. In addition, there is less expansion of the metal with changing temperatures, thus allowing to work with lower tolerances in manufacturing which is reflected in higher efficiency. This has the added advantage that the pump can be run at a lower speed, which affords the components greater protection and reduces wear even more. Furthermore a belt drive is fitted which also ensures synchronising of the shafts and lobes. This means the design has a minimum of parts, making it less susceptible to failures, simplifying maintenance and significantly reducing the required spare parts inventory in comparison to complex gear boxes. So far checks have shown hardly any wear, in spite of the mineral components in the waste water.