Machinery's Handbook, 31st Edition
Oil Additives
2507
Table 5. Additive Package by Oil Type Guide
Bearing Oil
Gear Oil
Turbine Oil
Hydraulic Oil
Compressor Oil
Crankcase Oil
Additive
Grease
Anti-oxidant
d d d d
d
d d
Corrosion Inhibitor
d d d d
d
d d
Demulsifier Anti-foam Anti-wear Detergent Dispersant Pour Point
d d d d
d
d d d d
d
d
Extreme Pressure EP
d
d
d d
d
d
d d
d
d
d
d
d some
d some
d some
d some
Viscosity Improver
d
Anti-oxidants: Oxygen attacks the base oil, especially at higher temperatures, leading to the formation of sludge, tars, varnish, and corrosive acids. Anti-oxidant additives can improve the oxidation stability of the oil by more than 10 times; lubricants designed for higher operating temperatures will contain higher levels of antioxidants. Corrosion Inhibitor or Antirust Agents : Used to form a protective shield against water on ferrous metals, and copper, tin, and lead-based bearing metals. They also act to neutralize any corrosive acids that may attack the bearing materials. Demulsifying Agents: Stop water from emulsifying with the oil. Antifoaming Agents: When oil is moved quickly, these agents, usually silicon-based compounds, act to retard the formation of air bubbles at the lubricant’s surface; air bubbles contain oxygen that will attack the base oil and cause cavitation in pumps. Extreme Pressure (EP) Additives: Additives such as sulphur, phosphorous, and chlorine are employed to “soften” bearing surfaces, allowing them to break away as small asperi - ties without adhesive “tearing” when metal-to-metal contact is unavoidable. These addi - tives can be detrimental to yellow metal bearing material. Anti-wear Agents: Solids such as molybdenum disulphide (moly), graphite, and PTFE, are employed to assist as additional sliding agents when metal-to-metal contact occurs under heavy loads. See Table 6. Detergents are organic metallic soaps of barium, calcium, and magnesium, acting as chemical cleaners to keep surfaces free from deposits and neutralize harmful combus- tion acids. Dispersants work in conjunction with detergents to chemically suspend the dirt par- ticles in the oil and allow them to be extracted by the lubrication system filters. Pour Point Depressants prevent the formation of wax crystals in paraffinic-based min eral oil at low temperatures allowing it to be more fluid at colder temperatures. Viscosity Improvers : Sometimes a base oil of inferior quality will require thickeners to assist in achieving the specified viscosity levels over a varied temperature range. Viscos - ity improvers are also used to prevent the oil from thinning at higher temperatures allow- ing the manufacturer to build multi-grade lubricants that operate over wider temperature ranges. Viscosity improvers use long chain organic molecules such as polymethacrylates and ethylene propylene copolymers to retard the viscosity shearing and improve an oil’s viscosity performance.
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