Used service water from industrial processes is one of the most problematic types of wastewater, owing to its composition, as it is often very demanding for conveying systems, says building materials and concrete manufacturer NETZSCH Pumpen & Systeme.

In order to enable problem-free treatment of this kind of wastewater in spite of this, NETZSCH has developed special models of its Tornado T2 rotary lobe pump which, the company adds, withstands a variety of media.

NETZSCH further points out that the T.Envi is specially designed for a long service life with minimum wear for extremely abrasive media to be conveyed without any problems.

“A large German concrete works has been using this solution since April 2015 to transport its mineral wastewater and has not recorded any relevant signs of wear to date. In contrast, the centrifugal submersible pump which had been used previously, lasted scarcely half a year.”

NETZSCH regularly experiences considerable amounts of mineral wastewater with pebbles up to 20 mm in size when cleaning the mixing plant. Therefore, the mixture is collected in a settling tank from where it has to be conveyed to a treatment plant through a 10-m-long riser for further dewatering and separation.

However, the company explains that the centrifugal submersible pumps, which had been used for this until 2015, did not withstand the stones and sand in the water for long, owing to the high speed required. Excessive abrasion and wear meant that it made ‘no sense’ to continue using the pumps after only six months.

The company therefore decided to switch to a rotary lobe pump.

A T.Envi from NETZSCH was used and was specially designed to be extremely robust over 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, two hardened steel lobes rotate in a rubber housing insert, which is easy to replace,” the company explains, adding that steel is less susceptible to material fatigue, owing to dynamic forces.

This, NETZSCH adds, means longer durability of the moving components is achieved.

In addition, there is less deformation of the metal with changing temperatures, thereby allowing 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.”

If maintenance work should still be required, NETZSCH explains that the complete front can be removed in “next to no time”, which provides access to the whole interior.

Likewise, the rotary lobes can easily be removed or refitted separately from one another as a result of the quick-release system.

“An integrated installation gauge helps with this. In combination with the smooth bi-lobe rotors and the flush-sitting seals, the unusual fastening concept onto the outside of the housing also ensures an interior which has no dead spaces where abrasive particle residues can be deposited.”

Resilient, Space-Saving Drive

A belt drive, which ensures the synchronising of the shafts, is fitted.

“This means the design has minimum parts, making it less susceptible to failures by simplifying maintenance and significantly reducing the required spare parts inventory, compared with complex gearboxes,” NETZSCH explains.

If the pump gets blocked and damages the toothed belt, NETZSCH adds that this can be replaced “without any problem”, just by undoing two screws.

“In contrast, if a conventional gearbox gets blocked, this generally leads to the pump being completely written off.”

A positive side effect of the slim, short design with a belt drive is the small amount of space required by the pump. The fact that the motor can be flange-mounted above the conveying chamber enables an extremely compact machine.

To compensate for future wear, NETZSCH notes that the speed of the T.Envi was increased for the concrete manufacturer and slippage was offset by a wear plate. In addition, the customer installed automatic back-washing with a bypass line and valve control when the pump is shut down.

The design also ensures that the suction hose cannot adhere and a section of the hose is shaped like a siphon and guarantees the fluid supply in the pump, so that the suction head of 3 mWS can be reliably managed.

“This adaptation and its design, which is very tough overall, means the pump has been working without any problems since it was commissioned in April 2015 and has been conveying 18 m³/h at 3 bar.”

So far, NETZSCH enthuses that checks have shown hardly any wear, despite the mineral components in the wastewater.

The company further adds that these examples and experiences show that entirely reliable and sufficiently robust conveying solutions do now exist for efficient treatment of industrial wastewater and sludge.

“This not only opens up the opportunity for companies to improve their ecofriendliness, but also allows appropriate systems to recycle raw materials that are sometimes valuable and reduce the outlay for storage and disposal of wastewater,” the company mentions, noting that, in this connection, customised pumping concepts can make an important contribution to operational reliability and, ultimately, to efficiency.