The requirements for slurry distribution have grown enormously in the last few years. Whether cattle, pig or biogas slurry is involved, the aim is always to distribute the nutrient fertilizer evenly and economically over the agriculturally used areas without violation of the regulations governing the use of such types of fertilizer. This is where robust slurry tankers prove their worth. In their pendulum axes, lubrication-free polymer bearings withstand all adverse operating and environmental conditions when the aggressive fertilizer is being delivered.
"We produce about 450 tankers per year," reports Sebastian Zunhammer, CEO of the family-owned company Zunhammer GmbH. At the location in Matzing-Biebing near Traunreut, around 100 employees are employed. They manufacture exclusively customer-specific vehicles in one or two-shift operation. "Whether tyres, distribution or docking systems, pumps or working widths - as a rule, these are tailor-made solutions that are completely manufactured in-house. “
All components of a slurry tank are matched to each other. This applies to the tyres, the tank and the pump, as well as to the chassis. The chassis determines the driving behaviour and road safety of the slurry tanker. "We place a very high value on quality and comfort," says Sebastian Zunhammer.
The previously used brass bearings had too much wear. During the transport and spreading of the slurry, the bearings were also exposed to heavy contamination and stress. Therefore a lubricated bearing arrangement was not practical.
With plastic bearings made of the materials iglidur G, Q and J a suitable bearing was found for every position of the slurry tanker. Due to the freedom from maintenance and lubrication, iglidur plain bearings are very insensitive to dirt and dust. In addition, the coefficient of friction has been improved, resulting in a longer service life.
Various axes systems and additional steering support options are available. For some years now, a pendular trapezoidal axle with hydraulic self-steering has been used as standard equipment in the vehicles. Thanks to the increased steering angle and weight-dependent directional stability, driving comfort can be improved. The individual suspension of the axis elements ensures very good off-road mobility. The steering angle is, as in a car, steeper on the inside than on the outside and describes a clean curve geometry. This reduces tyre wear and protects the turfs when cornering. The steering cylinder and the steering rods are located in the middle and protected. In the pendular trapezoidal axle, there are four tribologically enhanced "iglidur® Q" polymer bearings, which have a diameter of 80 mm.
CEO Zunhammer has a degree in wood engineering, but recognised early that plastic is the material of the future. In 1985 the slurry tanks were consequently converted from wood to fibre-glass reinforced polyester tanks. This resulted in a high weight saving with the same stability and very good drainage properties.
Today the container sizes range up to 27,000 litres. The automatic nutrient analysis shows what such a modern slurry tanker can do. Nutrients are registered with an NIR sensor that continuously picks up information about the composition of the slurry from a slurry pipe. The slurry can thus be examined during filling, spreading or even stirring. Not only nitrogen (N), but also potash (K), phosphate (P) or dry matter (TM) are recorded. The registration of further ingredients is also feasible.
The system is as advanced as modern mineral fertilization - which can completely replace it - and is unique in the world in manure fertilization. "Accordingly, our customer base extends far beyond the borders of Germany," says CEO Zunhammer.
At the very beginning, brass bushings were used in the pendulum axles. In the long run, however, these could not prove their worth. This is because a great deal of dirt and grime accumulates from the roads and fields during the transport and spreading of slurry, which settles everywhere.
"The wear on the brass bushes was too large. That's why we were glad when an effective alternative finally emerged with the polymer bearings," recalls Sebastian Zunhammer. "Because the plastic bearings are simply more robust. " The bearings in the axle do not normally come into direct contact with the slurry. But it can splash violently during distribution, so that residues are deposited that cannot be removed immediately.
Tribo-optimised polymer plain bearings made of the material "iglidur® Q" have been proving their strength in the steering arm of the tandem axle since 1996. Thrust washers, also made of "iglidur Q", is used as additional protection.
"The rotation of the steering is low, but the surface pressure is very high," the design engineer explains the technical requirements. Bauer is also responsible for the company's internal business organisation and quality assurance. The plastic bearings are highly abrasion-resistant even with the most extreme loads as well as insensitive to edge loads and dirt accumulation. "After the lubrication-free bearings were installed, there haven't been any failures any more. In addition, the slurry is also extremely aggressive. An ammonia cloud always hovers around the vehicles, which also affects all components. "The plastic components, especially in the axles, have to withstand a lot," says Thomas Bauer. The more so as it also concerns economic aspects. Agriculture is dependent on the weather. You can't drive out into the field in all weathers. The vegetation must also be suitable for spreading the slurry. No wonder, then, that a slurry tanker is only used on a maximum of 100 days a year. "During this time the performance must of course be right," Sebastian Zunhammer points out. Today, slurry spreading is often carried out by contractors. "They are sometimes on duty 24 hours a day, seven days a week in the high season. There must be no technical faults whatsoever. “