Lubrication

Lubrication is the process of introducing a substance between moving surfaces to reduce friction, wear, and heat generation. The goal is to create a lubricating film that separates contacting surfaces, supports loads, dissipates energy, and protects against corrosion. Proper lubrication extends component life, improves efficiency, and reduces downtime.

Friction reduction occurs through various mechanisms. In full-film (hydrodynamic or elastohydrodynamic) lubrication, a continuous fluid film bears the load. In boundary and mixed regimes, additives form protective layers on surfaces when full film is not present, lowering friction and wear.

Lubricants come in several forms: liquids such as mineral, synthetic, and bio-based oils; greases, which are oil-based lubricants thickened with soaps or polymers; gases such as air in air bearings; and solid lubricants like graphite and molybdenum disulfide. Properties such as viscosity, viscosity index, pour point, flash point, and lubricity influence performance.

Lubricant selection depends on operating speeds, loads, temperatures, material compatibility, and environmental conditions. Additives provide anti-wear, anti-oxidation, detergency, and corrosion protection. Correct viscosity is critical: too high can cause energy loss; too low can cause metal contact.

Applications span engines, transmissions, bearings, gears, turbines, and industrial machinery. Maintenance involves regular oil changes or greasing, contamination control, proper storage, and monitoring for signs of degradation, such as sludge, varnish, or unusual wear.

Environmental and safety considerations include handling, disposal, biodegradability, and fire hazards. Many regions require proper reclamation and recycling of used lubricants and adherence to standards.