Look behind the scenes
The ceramic production process offers a range of forming processes which can be categorised into the basic types of pressing, plastic forming and casting. For ceramic slip casting, for example, a watery suspension is poured into a porous mould which drains liquid from the slip. This produces a solid layer, the so-called cullet. Slip and grog are initially kept in storage tanks. Due to the viscous and abrasive medium, ceramics manufacturer used a NEMO® progressing cavity pump from NETZSCH for filling and recirculating ceramic slip until 2013. This model was initially recommended due to the very positive experiences with mineral suspensions, such as plaster, mortar or concrete primer.
Due to the high level of abrasiveness of the conveyed grog and ceramic slip, however, it turned out that the wear parts – rotor and stator – still had to be replaced every three months and the shaft sealing every six to eight months. This caused very long service periods and accordingly high costs.
To increase the efficiency of the system, NETZSCH therefore suggested the change to a pump from the TORNADO® T2 range: the rotary lobe pump T.Proc® is specially designed for a long service life with minimum wear, so that it can also convey highly abrasive compounds without problems. This is made possible by the combination of the operating principle and a special material pairing, which is only offered by NETZSCH: Whereas other pump manufacturers normally have elastomer lobes rotating in a metal housing and exposed to a high dynamic load, this unit uses steel rotary lobes while the inside of the pump is lined with a changeable rubber insert. This is reflected in accordingly lower wear and higher efficiency. The protective housing liner made from acrylonitrile butadiene rubber (NBR) can easily be removed as a separate part and replaced cost-efficiently. Overall, this achieves a six times longer service life and therefore substantial cost savings for abrasive media. The innovative drive concept of the TORNADO® T2 range is also characterised by a long service life: A belt drive, toothed on both sides, replaces the timing gear which was previously common for rotary lobe pumps. Due to its complex design, this was prone to malfunctions and defects. In contrast to this, the new drive technology can even survive damage or blockages without major damage. The double-sided toothed belt is not only used for transmission of forces from the motor to the shafts, however, it also synchronises the rotating motion of the lobes. This dual function has the great advantage of simplifying the overall drive design considerably, which increases operational reliability while also saving installation space. In conjunction with the motor being flanged onto the top of the pump chamber, this provides one of the most compact pumps on the market.