Publication in the November issue of -Betriebstechnik & Instandhaltung- (Operating Technology and Maintenance)

• 03 Mar 2006

The following article on ADDINOL Eco Gear, our high-performance gear oil for industry, was published in the current issue of the renowned technical journal "Betriebstechnik & Instandhaltung" (= Operating Technology & Maintenance).

The right lubrication matters. Lubricant re-smoothes damaged tooth flanks in gears

All over the world and in all industries gears are essential. They transmit and translate energy, movements and forces and work under various, often extreme conditions. The choice of the lubricant is essential for a trouble-free operation.

The lubricant is a construction element and decisive for the performance and the lifetime of the gears. It also determines the efficiency and safety of the connected aggregates. Gear oils according to DIN 51517-part 3 (CLP-oils) are normally used in industrial gears. However, they are not always up to the extreme requirements.

The maintenance engineers of a rolling mill had to learn this too. The gear of a duo roll stand was lubricated with industrial gear oil CLP and maintained properly. Still damages like corrosion, scuffing, pittings and a displaced edge in the rolling circle were found during inspection. These were clearly visible and could also be felt as razor-sharp edges and burrs. Everything pointed to a near breakdown of the whole gear because of consequential damages of the rolling bearing.

To avoid a standstill and high repair costs the maintenance company contacted ADDINOL Lube Oil – an expert for high-performance lubricants. After a thorough inspection of the gear the engineers of the lubricant manufacturer considered the further operation possible if the gear was immediately changed to the high-performance gear oil Eco Gear 220 M.

ADDINOL Eco Gear 220 M is based on mineral oils and contains the ADDINOL substance combination Surftec. It adapts to the changing loads and conditions in the toothing and prevents for example micro-pitting of new gears. For used gears the maybe already existing micro-pitting can be changed from a progressive to a degressive progress of the damage.

Micro-pitting and pittings are prevented; sharp edges of nicks are rounded off. The gear runs almost wear-free, friction is reduced.

To support the correctness of the prognosis the lubricant expert gave a warranty for the safe operation of the respective gear. The gear was changed to the new lubricant.

During the next inspection two years later it turned out that the condition of the tooth flanks had not aggravated; the load bearing tooth flanks were smoothed completely and operation was stable.

Already existing strong pittings and scuffings had not changed in size and number since the change. Already existing damages (scuffing/pitting/displaced edge in rolling circle) were visibly and perceptibly smoothed; there were no sharp edges or burrs any more. Before the oil change there were clear signs of corrosion, these had completely disappeared. The condition of the gear remained stable and constant.

Micro-pitting

Micro-pitting occurs with mixed and boundary friction on gear wheels and in rolling bearings. Characteristic for micro-pitting are small surface fissures of a size of about 10 µm.

Micro-pitting can already develop in the early stage of operation because of high loads; it is advanced wear. The wear process is influenced by physical and chemical characteristics of the lubricant, type of gear, surface roughness and operating conditions.

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