As counterintuitive as it may sound, seemingly expensive Swiss ceramic grease is taking pellet mills to unprecedented runtime performance levels and significant cost savings. Up to a 95 percent reduction of grease consumption, a significant increase in roller bearing lifetime and a notable reduction in power consumption are achievable in comparison to conventional solid lubricants.

It is an incredulously bold claim by producer Switzerland-headed Bathan AG. Founded in 2010 the company is a developer of specialty oils, additives, and lubricants based on industrial ceramics. High load- and temperature tolerances with good sealing properties are critical characteristics of any solid lubricant, which together with an appropriate lubrication schedule, is essential in order to gain the maximum lifespan from whatever is being lubricated.
Roller bearings in pellet mills are no exception. Yet while ceramic oils and lubricants are being used in engines and other industrial applications including wind turbines, cement production, pharmaceuticals, food- and feed industry, accounts of its use in wood pelleting plants has remained almost as secretive as a Swiss bank account.
Perhaps this has been due to perceived cost combined with a healthy dose of scepticism. Especially formulated for the wood pellet industry, Bathan’s KF7/60M ceramic grease came onto the market in 2012. But priced at around EUR 90 per kg, it is in a league of its own being up to 20 times more expensive per unit than the cheapest conventional alternatives. Coupled with the sensational consumption reduction claim along with Bathan being a small and young company in a field dominated by global multi-nationals, it is entirely understandable that initial demand may not have been very forthcoming.
Less grease, longer lifetime
However, for those pellet mills that were brave enough to give the lubricant newcomer a shot, the reported consumption reductions seem nothing short of spectacular.
– At face value, our ceramic grease seems outrageously more expensive per kg. However, you use far less of it per tonne of pellets produced so in fact, we are generally at cost parity when calculating the cost per tonne pellets, said Holger Streetz, International Sales Manager at Bathan.

The real benefit, as Streetz went on to explain, is the combination of increased production runtime and cost avoidance by the reduction of scheduled maintenance downtimes.
– A key factor for smooth continual process operation is the levelling and synchronization of component lifetimes, said Streetz.
According to him, roller bearings in a typical softwood pellet press have a lifetime of approximately 1 000 hours when using conventional greases such as calcium sulphonate, lithium- or aluminium complex, before refurbishment or replacement is necessary. The shell has typically a lifetime 2 000 to 3 000 hours.
– Thus between downtimes for changing the shell, the lifetime of roller bearings causes two additional downtimes. Having synchronous lifetimes of roller bearings and shells would be perfect. This we have proved is possible with a combination of a careful bearing refurbishment and the use of our high-performance ceramic-based lubricant, said Holger Streetz, pointing out that all pellet presses can use the grease without any modification to the equipment.
Bottom-line benefit
Backed by over 100 000 hours of operational experience on a variety of big name pellet press brands from 20 pellet plants in Europe and the US, the results would seem consistent and impressive. Stefan Zimmermann, Operations Manager at Tschopp Holzindustrie, one of Switzerland’s largest pellet producers with an annual capacity of 90 000 tonnes, was one of the first that agreed to trial the product.
– Of course, I was very sceptical but Rüdiger Heller from Bathan was very persistent. So I agreed to set up a test in May 2014 on one of our three presses, said Zimmermann, when Bioenergy International visited the plant in mid-January 2017. It was a full-on test with everything documented and on protocol. The previous auto-lubrication add-on rate for each of the three presses was once every 335 seconds – today it is as high once every 6 720 seconds. In terms of grease consumption, this means a monthly reduction of 171 kg, from 180 kg to 9 kg, per press or over 6.1 tonnes less grease per annum.
At the same time, the service life of the roller bearings have quadrupled from an average of 1 000 hours to 4 000 hours though, as Rüdiger Heller, CEO of Bathan points out, not everyone can expect to achieve such lifetimes.
– It depends on the quality of the bearings you use, how well the refurbishment work has been carried out and other factors, Heller said.
According to Zimmermann the pellet plant clocks up savings in the 5 to 6 digit range per annum when taking into account reduced power consumption, reduced maintenance and repair costs and increased productivity.
–The environmental benefit of using less grease is an important aspect for us too as the grease ends up in the pellets, said Zimmermann.
The beauty of a-BN
So what makes Bathan’s grease such a slick performance enhancer? Rüdiger Heller lets one well known secret slip – an essential component of its KF7/60M ceramic grease is boron nitride (BN). BN is non-toxic, has a high thermal conductivity, low thermal expansion with good thermal shock resistance.

– This translates into a cooling effect on the bearing, stable volume and that the ceramic particles are able to absorb shocks from changing feed mixtures in the press, Heller explained.
BN has a distinct crystalline structure of which a-BN and b-BN are stable compounds.
– While b-BN has a cubic structure and is highly abrasive, a-BN has a hexagonal structure and is instead an excellent lubricant, said Heller.
The plate-like structure of the a-BN particles enables movement against each other with low energy. In addition, the oxidation process of coated surfaces slows.
– Metals coated with a-BN have an excellent sliding and separating effect that reduces friction and wear better than graphite and molybdenum disulphide. This increases the lifetimes of the coated metals accordingly, said Heller.
Moreover on a microscopic level, ductile deforming of the a-BN particles on coated surfaces occurs under pressure, reducing wear point peaks and smoothing scallop heights. This “thermoplastic levelling” forms polished surfaces with minimal substance loss.
– Basically, the ceramic particles fill all the microscopic irregularities of the metal surfaces providing a smoothening effect. Smoother bearing surfaces along with the other properties of a-BN lead to lower bearing temperatures, a radical reduction in lubricant consumption, longer bearing lifetimes and lower energy consumption, ended Rüdiger Heller.
This article was first published in Bioenergy International Pellets Special 2017. Note that as a magazine subscriber you get access to the e-magazine and articles like this before the print edition reaches your desk!