Paper machine 6 at the factory produces 650,000 tons of corrugated base paper each year, all of which is handled at various stages by 11 double-girder overhead cranes, all playing their own crucial role in production, and which have been used since the start of production in 2002.
“The cranes are in use day and night,” says electrical engineer Sven Bohrer. “If one should break one day, the production would have to stop, or at least greatly slow down, until the problem is solved. This would cost us time and money.”
For this reason, Konecranes has performed an analysis on the gear oil of the hoisting gears of eight of the eleven double-girder bridge cranes at Palm (oil analysis services are also now available in the UK). The metal fragments and waste substances it contains make it possible to draw conclusions about the state of the entire gear. Nico Zamzow, vice president, industrial service EMEA central at Konecranes, comments on the method: “The oil analysis protects the crane. Any damage can be identified and treated early with its help. Moreover, system operators are able to optimize the maintenance and servicing of the cranes thanks to the detailed analysis report, and thus significantly increase their lifespan.”
He continues: “The samples are analysed by our laboratory, which specializes in industrial drive train analysis. Here, the lab staff compares the current state of the oil with the samples taken in 2016 and against the OEM design limits. This way, we also use trend analysis to provide the best possible picture of any change within the condition of the gearbox.”
In the latest study, seven of the eight cranes were found to be healthy, as in the gear oil contained few to no foreign elements or waste substances indicating contamination or wear. However, the gear oil of the automated number 5 crane, used in the roll warehouse, was found to have a noticeable increase in its wear partial count, triggering the lab to issue a “caution” notification on the analysis report. Zamzow explains: “Iron particles in the oil can be an indication of increased wear, and a deeper look may be required for this particular hoist”.
If the reason for the wear is not clearly identified and removed, the gear may be permanently damaged, which could have a major effect on production. “If the gear is jammed while there is a roll on the hook, it becomes very difficult to recover it and repair the crane,” argues Zamzow.
To determine whether damage has already occurred, Konecranes engineers perform what it calls a crane reliability study. The modular analysis allows them to check safety-relevant components, such as the hoisting gear as well as the steel structure, the motors, and the electrical equipment of the crane. In addition, the maintenance experts pose questions to crane drivers and technicians, and develop a summary report.
In the case of Palm, Konecranes used a high-definition video endoscope to investigate the hoisting gear. “Just like in medicine, we use the endoscope to reach inaccessible places without having to dismantle the entire gear,” states the vice president. “For the CRS, we use a special, oil-resistant model that was developed for industrial use and can be fitted with different lenses.”
Following the endoscopic investigation, the Konecranes inspectors concluded that the unit 5 hoisting gear needed to be replaced, as well as the cable drum, the cable drum support, the slip-ring unit, the cylinder coupling, and the motor coupling. On the plus side, having discovered the wear relatively early, there was no risk to safety and the replacement could be scheduled in such a way as not to affect production, according to Zamzow.