Bitumen pumps or screw pumps from KRAL are suitable for pumping highly viscous liquids such as bitumen. Technical aspects such as the suction behavior or the low-pulsation pumping of the pump play an important role here. With bitumen pumps from KRAL, the efficiency of the pump improves as the viscosity of the medium increases. Screw pumps are particularly suitable as bitumen pumps.

These are best suited for pumping highly viscous media such as bitumen. Screw pumps from KRAL have a linear flow rate characteristic with fine adjustment. This reduces maintenance costs, for example, and therefore also operating costs.

In addition to other aspects such as the compact design, high robustness, high quality and low probability of failure, screw pumps are best suited for pumping bitumen compared to other pumps such as gear pumps or centrifugal pumps.

The challenge of bitumen applications

High-viscosity media such as bitumen must be conveyed in various applications such as tar production or road and asphalt construction. However, this is a challenge from a technical point of view. This will be explained in more detail in the following sections.

What is bitumen?

Bitumen is obtained as a residue from the gentle processing of crude oil. Only special, high-sulphur crude oils are permitted for this purpose. Bitumen consists mainly of hydrocarbons and small amounts of oxygen, nitrogen and sulphur.

The properties of bitumen

Due to its chemical properties, bitumen poses particular challenges for pump manufacturers. Bitumen has the property of only becoming liquid at high temperatures and therefore "pumpable" from a technical point of view. As a result, a high operating temperature from approx. 150 degrees Celsius is usually necessary in order to be able to pump the medium at all.

These temperatures should be taken into account when pumping, as the medium may otherwise falter. In addition, bitumen itself causes contamination and slightly abrasive effects on the pump. This has an effect on the wear of a pump and therefore plays an important role, especially when pumping bitumen.

What does a pump need to be able to do to be suitable for bitumen?

Eine Pumpe, die mit der Aufgabe betraut wird, Bitumen zu fördern, muss vor allem bei einer sehr hohen Betriebstemperatur (z. B. bei bis zu 300 Grad Celsius) fehlerfrei, zuverlässig und ausfallsicher arbeiten können. Zudem muss die Förderung bei extrem hoher Viskosität möglich sein, wenn die Betriebstemperatur wieder etwas niedriger ist.

Eine Bitumenpumpe muss zudem mit einem leicht verschmutzten Medium, das abrasiv auf die Komponenten und Bauteile der Pumpe wirkt, umgehen können. Das Medium Bitumen hat die Eigenschaft, Verschleiß aufgrund von z. B. Verschmutzungen an der Pumpe zu fördern, was sich auf die Lebensdauer und die Einsatzzeit auswirken kann.

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The advantages of our bitumen pumps.

Screw pumps offer several advantages over other pump types.

Compared to gear pumps or centrifugal pumps, screw pumps offer large flow rates with a small construction volume. They are also low-pulsation and quiet. In terms of cooling and lubrication, screw pumps with an application-specific dimensioning of the balancing cylinder provide excellent lubrication and cooling of the sealing surfaces of the mechanical seal.

In addition, there is no accumulation of residue as the leakage from the mechanical seal is discharged immediately after the counter ring via a bore. There is therefore no accumulation of residue that would go unnoticed and could damage the ball bearing. Some fluids form residues that often collect on the mechanical seal and damage the ball bearing. Damage to the coupling, which would cause the pump to fail, is therefore avoided with the screw pump.

Furthermore, the flange of KRAL screw pumps has been designed in accordance with ISO 3019. This allows the pump to be connected to standard bellhousings. This design minimizes the installation volume of an optional magnetic coupling. Another advantage of the screw pumps compared to other pump types is that various highly viscous media such as bitumen can be pumped in consistently high quantities even at high differential pressure.

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Flexible connections

If the outer casing of the screw pump is made of steel, almost any position, direction, size, type and classification of the flange is possible. It can be optimally adapted to any installation situation.

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Housing variants

Depending on the operating requirements, the CG series screw pumps are available with cast iron or steel housings.

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External overflow valve

The overflow valve ensures that the liquid is diverted in the event of overpressure.

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Rotary shaft seal

The CK series screw pump is only available with a radial shaft seal. The CL series screw pump can be equipped with different shaft seals thanks to the longer spindle set. External ball bearings are also possible. This pump line is used as a horizontal or vertical foot pump or flange pump as well as a vertical container pump.

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Seal housing

Depending on the operating requirements, different shaft seals are possible for the CL series. The CL screw pump is the slide-in pump used in the CG series. The different housing options allow enormous flexibility in terms of fluid connections. An optional external overflow valve can be fitted to CG screw pumps.

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Longer spindle set

Thanks to the longer spindle set, external ball bearings are also available as an option.

The advantages of KRAL screw pumps at a glance:

High power density
Low noise (quiet)
compact design
low-pulsation conveying
high efficiency
Continuous conveying without crushing and turbulence
very good NPSH value
low-maintenance operation
long service life

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The use of screw pumps and bitumen pumps from KRAL.

What are the special features of the individual series?

In comparison to other pump designs, the KRAL bitumen pump series conveys highly viscous media such as bitumen consistently in high quantities, even at a high differential pressure, with low pulsation, low noise and quiet operation. They offer a compact installation space and a high degree of flexibility, combined with high efficiency. They have a good NPSH value and a high power density as well as continuous delivery.

The KRAL bitumen pump series are also low-maintenance and have a long service life. The differences lie, for example, in the different specifications for pumping the maximum and minimum viscosity of the medium.

Advantages of KRAL

As a family business based in Austria, KRAL offers quality "Made in Austria".

KRAL has a very fast delivery time, a high degree of flexibility, fast quotation submission and intensive customer support. KRAL is also available to customers on site for technical challenges.

Another advantage: KRAL offers service from a single source. From development to construction and installation at the customer's premises. As one of the leading manufacturers in the field of screw pumps and bitumen pumps, KRAL offers outstanding quality standards and quality certificates, e.g. in accordance with EN ISO 9001.