Gear lubricants loading

Gear lubricants In addition to the usual oxidation and corrosion inhibitors, lubricants for heavily loaded gears almost always contain EP additives containing sulphur, chlorine or phosphorus. In order to function, these additives must react locally with the metal surfaces, and yet the extent of the reaction should not be such that it could be described as corrosive, or promote fatigue pitting . These EP additives may be quite safe with ferrous metal surfaces, but may cause severe corrosion on copper alloys, e.g. on bronze worm wheels if for any reason excessive temperatures arise. 

These classes of compounds were the first used during the industrial revolution to improve the performance of machinery and were developed to improve the scuffing load of gear lubricants. Examples of typical structures of sulphur/nitrogen compounds which have found application are given in Fig. 3.12. 

For highly loaded spur, helical, worm and bevel gears, lubricants containing tribological additives such as sulphurized and phosphorus-containing additives are used. These provide excellent anti-wear and extreme pressure protection over a wide range of conditions. 

Synthetic shock loading Heavy or shock loading Heavy or use by most OEMs, especially at operating temperatures exceeding 82°C Preferred for shock loading Heavy or must contain extreme pressure additives Gear lubricant... 

Elastohydrodynamic Lubrication (EHL). Lubrication needs in many machines ate minimized by carrying the load on concentrated contacts in ball and toUet beatings, gear teeth, cams, and some friction drives. With the load concentrated on a small elastically deformed area, these EHL contacts ate commonly characterized by a very thin separating hydrodynamic oil film which supports local stresses that tax the fatigue strength of the strongest steels. 

The spur gear is the least expensive of all gears to manufacture and is the most commonly used. It can be manufactured to close tolerances and is used to connect parallel shafts that rotate in opposite directions. It gives excellent results at moderate peripheral speeds and the tooth load produces no axial thrust. Because contact is simultaneous across the entire width of the meshing teeth, it tends to be noisy at high speeds. However, noise and wear can be minimized with proper lubrication. 

The lubrication of gears is not a simple matter, because of their shape and variability of motion. Fundamental factors which affect their lubrication are gear characteristics, materials, temperature, speed, loading, method of applying the lubricant and environment. 

These have an important influence on both lubrication and wear. At the same speed, steel gears require higher viscosity oil than cast iron or bronze, because they can carry higher loads. Where straight oils are concerned, it is usually true to say that the harder the gear steel, the higher the viscosity needed. 

The three most likely types of operational service misuse are overloading, incorrect lubrication and the presence of contaminants. Overloading is primarily due to the use of too small or too weak a gear unit, and this may be the result of false economy (installing an available unit for an application beyond its capacity) or failure to cater for the effects of shock loads in calculations of power rating. 

CC Highly refined mineral oils with 150 Heavily loaded gears and worms Pressure and bath lubrication of May also be used for manual or... 

The lubrication requirements for single-screw type compressors are not severe, but in oil-flooded rotary units, the oxidizing conditions are extremely severe because fine droplets of oil are mixed intimately with hot compressed air. In some screw-type air compressors, the rotors are gear driven and do not make contact. In others, one rotor drives the other. The heaviest contact loads occur where power is transmitted from the female to the male rotor here the lubricant encounters physical conditions similar to those between mating gear teeth. This arduous combination of circumstances places a great demand on the chemical stability, and lubricating power, of the oil. 

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