An application in media delivery can often be handled by using different pump types. However, optimum results and material-preserving transport require rather exact matching of the pump to the different parameters such as viscosity, temperature, NPSH value or shear sensitivity.
Netzsch Pumpen & Systeme GmbH therefore supplements its portfolio of progressing cavity pumps and rotary lobe pumps by three model series of compact screw pumps: the NOTOS two, three and four-spindle pumps. Depending on the type, they are suitable for non-lubricating substances at high pressures up to 80 bar and temperatures up to 300 °C. They thereby cover a wide range of application areas – from lubricants to sealants and on to bitumens or resins. Thanks to special materials, hydraulic compensation and geometry – optimised through FEM simulations – all NOTOS pumps are designed for top efficiency and operating life.
The core feature of the screw pumps from Netzsch is their concept following the High Efficiency Unique Design (HEUD) and producing a proven improved force-performance ratio. This is due, on the one hand, to the very hard materials used – the choice ranges from simple grey cast iron to chrome-nickel steel and on to duplex or Hastelloy alloys – depending on the requirement. The stability of these materials ensures very minor sagging of the spindles, even under the high loads typical for screw pumps; this allows working with very narrow tolerances between dynamic and static parts in the manufacturing process. Possible backflow from the higher pressure to the lower pressure side is thus reduced and the delivery efficiency increased at the same time.
On the other hand, the shape of the spindles has also been adapted to minimise interferences and resistances in the material flow. Netzsch state-of-the-art calculation methods in this process, e.g. the Finite Element Method FEM, permitting a realistic simulation of the pump and the pumping process with freely configurable parameters. In this way, the spindle geometry for the desired delivery characteristics could be determined and medium transport largely free from turbulence and pulsation achieved. The special design also prevents foam development and hardly generates any bother-some running noise.
High operating reliability through exact matching and hydraulic compensation
Beyond this, the choice of materials and the design ensure high robustness and service life of the screw pumps, which secures their reliability and reduces both downtime and maintenance tasks. In addition, each pump is designed specifically for the respective application area, especially in terms of size, which concerns rotational speed and the sliding velocity of the parts moving in synch. This exact matching of technology and equipment to the application allows adapting to the specific properties of the medium and also the loads – due to the type of deployment – early on and to largely compensate for influencing factors that could lead to increased wear or damage.
The hydraulic compensation, achieved with all NOTOS pumps through their special design features, plays a decisive role here: The auxiliary spindles are normally pushed toward the intake side by the axial forces caused by the delivery pressure. This results in increased friction and higher energy demand. With the models from Netzsch, however, a duct connects the high-pressure side with the space of the intake side. The prevailing forces negate each other because of this approach and the net axial force is nearly zero. All three model series of the NOTOS pump are hydraulically compensated by this method.
Generally, the NOTOS series encompasses screw pumps with two (2 NS), three (3 NS) or four (4 NS) spindles. Being able to provide high pressures in a very compact space is one aspect they all share.