One of the products that the building materials manufacturer, Knauf of Iphofen, Germany, produces is a concrete primer. What is intended to ensure that plaster evenly bonds onto smooth walls in construction does, however, create problems during conveyance: the plaster primer contains dispersion and has a mineral solid content of around 60 percent, which has an emery paper effect in the rotary lobe pump feeding the filling station. The newly developed Tornado® T2 of NETZSCH has been in use since April 2012—and very successfully.

The concrete primer is filled from a storage tank using frequency control and a rotary lobe pump that fills various large barrels. The operating mode is intermittent; the pump is started up and shut down for each filling process—five seconds of stationary follows twenty seconds of operation. The speed of the pump is raised as the wear increases.

The conventional rotary lobe pump previously been used by Knauf was able to convey approximately 600 tons (544.31 tonnes) of highly abrasive plaster primer containing dispersion before the rotary lobes and wear plates were so badly affected that the required capacity was no longer achieved.

The high annual production capacity on the mixing system resulted in a considerable maintenance effort. “At busy times we were repairing the pump every three to four weeks,” reports maintenance manager, Armin Ryba. Rotary lobes and wear plates had to be replaced at every repair and at every second repair the shaft seal was changed. Clearly this was a reason to search for an alternative which was provided by NETZSCH, the pump manufacturer from Waldkraiburg in Upper Bavaria.

Rotary Lobe Pump

The Tornado® T2 conveys between 3300 and 11,000 pounds (1500 and 5000 kilograms) per hour in Iphofen. In the process, the service life is more than three times as long in comparison to the pump used previously.


A Tornado® T.Proc 08/45 BD-E was installed in April 2012, a rotary lobe pump of NETZSCH’s new Tornado® generation. Engineered for challenges of this kind, the entire materials concept of conventional rotary lobe pumps was reversed when the Tornado® was redesigned: two lobes made of hardened steel that rotate in a geometrically adapted elastomer insert are used instead of the standard elastomer lobes.

This bi-lobe rotor design creates a considerably longer sealing line to the housing providing more wear padding. A specially developed pulsation reduction system ensures that the most minimal pulsation or shear forces are generated, despite this straight, bi-lobe rotor design. Elastomer inserts are vulcanized onto the edges of the lobes to create a permanent hard-soft contact between the lobes throughout the 360-degree rotation cycle. This avoids high-wear contact between elastomer parts. The elastomer insert acts as a stator and is subject to considerably less dynamic load and deformation than in the traditional rotary lobe pump design when the elastomer functioned as a rotor. Ultimately, energy is saved; wear is reduced and the service life of the pump is increased overall.

Tornado T2 Exploded

Reversing the materials means high-wearing contact between rubber parts is avoided with the new rotary lobe pump. At the same time, the tailored geometry of the insert ensures high capacity without pulsation.

Additionally, the drive of this new pump design was radically modified. The complex timing gear was replaced by a robust synchronized gear with belt drive. This means that not only is the danger of transmission damage greatly reduced, but the weight and installation space required are decreased. The drive requires no lubrication, eliminating the chance oil leaks. Typical repairs or maintenance are simplified because the conveying and gear chambers can easily be opened. The cover and attachment of the components are designed for easy access and every component can be replaced with standard, commercial tools in just minutes.

Tornado® T2

The Tornado® T2 is used to fill the viscous matter and transports the plaster primer from the storage tank to the filling station.


The first inspection of the Tornado® T2 at Knauf has already demonstrated the value of these features after double the capacity had been conveyed: cover and elastomer inserts could be easily disassembled and the conveying elements could be easily disassembled and removed.

In comparison to the conventional rotary lobe pump previously used, there was evidence of significantly less wear, even after double the service life. The cover and housing inserts were practically good as new. They showed only minor leaching and were definitely still usable. The lobes showed consistent material removal with grooves in the front end however, the lobe inserts on the edges were hardly worn. The inspection of the belt drive was also impressive.

There was no wear to note on the double-toothed belt or on the belt pulley. The belt tension had only reduced slightly and not in any critical way with respect to the condition on delivery—in spite of demanding, non-continuous operation with around 60,000 load changes since commissioning.

T2 belt drive

The T2’s belt drive is extremely robust and practically maintenance-free. There was no evidence of traces of wear even after 1200 tons (1088.6 tonnes) at Knauf and the tension still had the same setting as on installation.


At the time of the first inspection, the new Tornado T2 pump had already delivered double the volume of the previously used, conventional rotary lobe pump with only 60 percent of the maximum speed having been reached. “So we still have a lot more potential,” says Dirk Schmalz of NETZSCH. “Based on the operating time so far, the T2 can certainly achieve three times the service life.”

This supposition has now been confirmed after six months’ operation: with three to four times the conveyance there has been more than three times the service life.

There is a high level of satisfaction with the investment in the new rotary lobe pump at Knauf Iphofen. Maintenance manager Armin Ryba comments that they are very satisfied with the new purchase: “The long service life means that we now only incur around half the previous costs for spare parts, repairs and downtimes.” 



Cindy Mariani is the marketing coordinator for NETZSCH Pumps North America, LLC. For sixty years, NETZSCH has served markets worldwide with its NEMO® progressing cavity pumps, TORNADO® rotary lobe pumps, grinding machines, dosing systems and accessories, providing customised, sophisticated solutions for applications in every type of industry. For more information, call 610.363.8010 ext. 209, email, or visit


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