Every year, the almost inconceivable amount of 1,000,000 tonnes of scrap paper is processed at the Leipa Georg Leinfelder GmbH factories - more than 100 lorry loads per day. At the Schrobenhausen / Bavaria and Schwedt / Brandenburg sites, offset paper for catalogues and magazines, as well as paper packaging, are made from cardboard and corrugated base paper (so-called test liners). Around the world, Leipa operates from the first paper factory which makes scrap paper into high-quality paper for colour print magazines to a quality, which is equal in all relevant characteristics to paper made of primary fibres.
In the Leipa factory in Schwedt, three paper machines are in use. In this case, the large Voith paper machine PM 4 alone produces approximately 360,000 tonnes of high quality magazine paper a year. Unforeseen machine stoppages and the resultant production losses need to be avoided at all costs. Therefore, a proven system of preventative maintenance and regular machine monitoring is permanently integrated into all operations.
Special attention is paid to the lubricants, their maintenance and monitoring. At the end of the day, they represent a high cost factor with the large amount of several thousand litres in the rotational motion systems. Therefore, the longest possible oil change intervals are to be implemented. At the same time, the secure operation of the paper machines depends on the lubricants. Regular oil analyses provide the corresponding information for proactive maintenance.
The hydraulics and circulating oil system of the wet part of the PM 4 require 6,000 litres. The largest tank is the "Nipco Kalander Hydraulik" on the PM 4 with 16,000 litres. The tank for the centralised chassis lubrication for the drying cylinder takes 9,000 litres of synthesis oil. More than 600 bearings are supplied with it. The rotational motion oil is exposed to extreme loads, especially in the drying cylinder. The steam-heated paper machines work operationally in principle under a "hood" in an up to 80°C environment with up to 90°C humidity. Permanent temperatures of up to 95°C occur at the bearings. In addition, vapour or moist air can penetrate directly into the lubricating rotational motion system at the sealed labyrinths of the drying cylinder stocks. Whilst cooling, water from condensation can then displace itself in the bearings and the oil tank. The water content on the bottom of the tank must be assessed on a daily basis without fail. Too much water is driven out with a thin film evaporator in which the boiling point of water is decreased by vacuum so it vapourises at approximately 60°C. Fine lint can also affect the oils. Oxidation products of oil, along with paper particles, can block the allotting valves of the central lubrication system, and therefore inhibit the distribution of oil, for instance. The maintenance workers in Schwedt have equipped all hydraulic systems and central lubrication systems with quick-couplings in order to connect additional mobile filter systems and a vacuum evaporator in the secondary current for the removal of dirt particles or water. The water content of the oil cannot exceed 100 ppm. Thanks to the strict observation of these limits, the amount of downtime essentially sank and the lifetimes of the overall components were doubled.
Should paper machine oil achieve a long service life, function reliably and show a positive effect regarding energy efficiency, it is not done with generic "off-the-peg" oil. After repeated filter blockages and the formation of deposits in the tank and housing cases of the central lubricant system of the wet part of the PM 4, a well-known petroleum company developed an innovative product with a novel additive specifically for this application. It was tested at Leipa in a large-scale field test that was set up. After many promising results, the PM 4 was converted to the new rotational motion oil in 2010. The change was a great success. Amongst other things, gear temperatures were lowered by up to 10°C. A clear indication of reduced friction and therefore a longer service life for the components. The energy consumption of the gears demonstrably reduced by around 3%. Because of the decrease in oil temperature by 10°C, the service life of the oil doubled. Even at the formation of deposits, the new oil had positive effects. The filters now achieve an endurance of nine months instead of two months which was the case before.
Much of the success within the scope of maintenance at Leipa could only be achieved by the application of the OELCHECK lubricants analyses. The analyses provide the deciding factors for almost all maintenance measures to do with lubricants and hydraulic fluids. Overall hydraulic and central lubrication systems are recorded in the maintenance plan. Oil samples are then taken regularly and examined by OELCHECK.
The maintenance workers no longer change the oil in a time-controlled manner rather in accordance with the lubrication state as per the laboratory report. They recognise trends early on and act accordingly. In addition, the use of mobile cleaning equipment is controlled optimally also on the basis of the laboratory results. The necessary knowledge related to the oil is kept up-to-date by regular visits to OilDoc seminars and symposiums.