A German ceramics manufacturer used a progressing cavity pump for filling and recirculation of the storage tanks for grog and ceramic slip. The wear parts of this pump, however, had to be replaced every three months due to the highly abrasive substance. To enable more economical production this pump was replaced by a special rotary lobe pump called T.Proc. This pump is specially designed for a long service life with minimum wear. It is made possible by the combination of the operating principle and a special material pairing, which is only offered by Netzsch. Instead of conventional elastomer lobes in a metal housing, this pump comprises two steel lobes rotating in a replaceable rubber housing insert. This achieves a higher durability of the moving components. In addition, the interior is designed without dead space so no slip residue can adhere. The service life is extended to 1.5 years.
The heart of the system are two straight bi-lobe rotors which rotate in opposite directions, moving the medium smoothly but continuously from the inlet to the discharge side. A characteristic feature of this type of pump is the special material pairing. The lobes are made from a particularly robust hardened steel and are not affected by the rotating motion, which clearly increases their service life. In addition, the metal is subject to less deformation under changing temperatures, which means smaller tolerances can be used in production. 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. Rubber pads vulcanised onto the faces of the metal lobes ensure a continuous hard-soft contact, which also protects components and increases service life. Overall, this achieves a six times longer service life and therefore substantial cost savings for abrasive media.
The pump can handle substances from 1 mPas to 1 million mPas. The system transports between 15 and 25 m³ of the abrasive slip per hour at 4 to 5 bar. At the same time, pressure fluctuations and shearing forces are excluded. The simple shape of the vanes allows a large free ball passage to prevent blockages.
Furthermore, this design has a positive influence on the efficiency of the pump: Thanks to the long sealing line, only a very low backflow is generated. Additionally, the specially designed internal geometry of the delivery chamber keeps any pulsation at a very low level, ensuring a gentle, continuous product flow without turbulences. This allows the desired properties of the respective slip to be maintained. At the same time, the special housing geometry in connection with the large ball passages additionally minimises wear.
Pump with “Full Service in Place” concept
In addition to the robustness of the T.Proc pump, easy maintenance was an essential aspect for the ceramics manufacturer. The systems are designed so that they can be opened, cleaned and all wearing components can be replaced in situ without the pump having to be disconnected from the supply.
The rotary lobes are attached outside of the housing with quick-release elements. As a result, they are completely smooth and have no surfaces for deposits, and can also be removed and reinstalled conveniently and independently of each other. They can be released or tightened with just a few steps, without special tools. A positioning and installation gauge integrated into the front cover makes correct positioning easier in this process. The shaft seals are also designed so their glide surfaces seal flush against the rear side of the lobes. This prevents dead spaces where abrasive particle residue could adhere. The seals are preconfigured and easily slide onto the shaft with the rotary lobes during assembly. Thanks to the cartridge design, different types of seals fit into the same installation space to suit changing requirements.