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Selection of the right gear oil Overview of Klüber gear oils Viscosity selection Oil level, immersion depth and oil quantities

Gear oils made by Klüber Lubrication Increasing demands on the gear and the lubricant Your global specialist! Today, demands for the transmission of ever growing power and torque in gears of all performance grades in combination with reduced size and weight require new gear designs, new materials, improved surface treatment, modern production techniques as well as the application of mineral and synthetic high-performance lubricants. We are where you are. Our specialists are there to support you, wherever you need them. We help you select the right product or develop a solution tailored to your...

Selection of the right gear oil Maximum operational reliability throughout a gearbox’s service life can only be ensured if lubricants are not only considered necessary operating materials but are taken into account during all design phases as integral structural elements. Ideally, the lubricant should be selected in the design phase of the gear. This brochure describes in a few steps how to select the right gear oil. For special applications, however, e.g. where very long service intervals are to be expected, or where operating conditions are very special, you should consult with the experts...

Operating temperature Temperatures typically found in a gear The oil temperature in industrial gears is between 20 and 150 °C, depending on the type of gear and the application. Heating of a gear system, in particular of the gear wheels, bearings and the lubricant, is one of the most important criteria to evaluate the gear’s performance. The existing temperatures are indicative of the power losses. Apart from design-related influences, oil temperatures mainly depend on the operating conditions. Oil temperatures rise with an increasing ambient temperature and when the oil is exposed to thermal...

Selection of the right gear oil Viscosity Viscosity-temperature behaviour of oils 1 Mineral oil 2 Polyalphaolefin 3 Polyglycol Viscosity decreases with increasing temperature and rises with increasing load. If the viscosity is too high, increased churning and squeezing losses can result in excessive heat, especially at elevated peripheral speeds. If the viscosity is too low, mixed friction conditions prevail and will result in increased wear. Viscosity is highly influenced by temperature. The change in viscosity with temperature is usually determined by means of the viscosity index (VI). The...

Ageing behaviour Low-temperature behaviour An oil’s chemical structure continuously changes when it is subjected to high temperatures, mixed with air or in contact with metal catalysts like copper, iron and others, causing it to age. The speed of the ageing process primarily depends on the oil’s structure and the amount and duration of heat to which the oil is subjected. Also, contaminants like water, rust or dust contribute to oil ageing. By adding special additives the lubricant manufacturer can retard the ageing process effectively. Depending on the base oil type, lubricating oils solidify...

Selection of the right gear oil Anti-corrosion properties Anti-corrosion properties of gear oils are assessed individually for: Hint: When using a gear oil for components made of or con taining copper, like brass or bronze, it should pass the copper corrosion test according to ISO 2160 with the rating 1a or 1b. – corrosion protection on steel – orrosion protection on copper c (compatibility with nonferrous metals) All gear oils from Klüber Lubrication which comply with the requirements of DIN 51517 for CLP lubricating oils are not corrosive on copper and prevent corrosion on steel. Corrosion...

Foaming behaviour Gear oils should be able to separate dispersed air rapidly and prevent the formation of stable surface foam. Foam is generated by air bubbles rising to the surface. The bubbles should burst as quickly as possible to keep foam to a minimum. The oil manufacturer can reduce the foaming tendency by adding anti-foam additives. However, too high a concentration may affect the air shedding capacity. The foaming tendency of a lubricating oil is determined according to ISO 6247 or ASTM D 892. Particularly in case of splash-lubricated gears operating at medium to high peripheral speeds,...

Selection of the right gear oil Elastomer compatibility The materials used for radial shaft seals (RSS) or static seals, e.g. O-ring seals, must not become brittle or softer when exposed to gear oil, as otherwise their sealing capacity would be affected. The seals would suffer premature wear, leading to leakage. Cleaning and possibly expensive gear repairs would become necessary. Especially when higher torques lead to higher operating temperatures, or when a gearbox is changed from mineral to synthetic oil lubrication, compatibility with the seals should be considered. The tests used for verifying...

FZG micropitting test (results) Heavily loaded gears are potentially subject to seizure and pitting, as the high loads generate high pressures and temperatures, which in turn can lead to tooth damage resulting in premature gear failure. The risk is particularly high with less than perfect tooth contours and surfaces, impact loads, vibration, a high degree of sliding friction and high surface pressure. Scuffing: The FZG scuffing test according to ISO 14635-1 is generally undertaken to test the capability of gear oils to protect against scuffing damage. Load stage KS 12 of the FZG scuffing test...

Selection of the right gear oil Mineral or synthetic gear oils Today, many enclosed industrial gearboxes are still lubricated with mineral oils. Where these oils come up against their limitations, e.g. in terms of operating temperatures, the use of synthetic gear oils should be considered. Gear lubricants based on the following synthetic oils have proven most effective: With polyglycol oils, very low friction results can be attained, which is why they are preferably used for the lubrication of gears with a high proportion of sliding friction, e.g. worm and hypoid gears. When combined with corresponding...