3Hydrodynamic Lubrication Occurs when machine parts are completely separated by a full and continuous film of lubricantContact between the parts does not occur.Full-fluid-film lubrication is hydrodynamic lubrication, the oil adheres to the moving part and is drawn into the area between the rotating surfaces, where it forms a pressure, or hydrodynamic, wedge.A less common form of full-fluid-lubrication is hydrostatic lubrication, where the oil is supplied to the bearing area under pressure to separate the sliding surfaces.
5Boundary LubricationUnder certain conditions such as shock loading, heavy loads, high temperature, slow speed and critically low viscosity, the lubricant is no longer hydrodynamicFrequent contact between the surfaces, resulting in a significant rise in temperature and subsequent destruction of the contacting surfaces.Under these circumstances, the fluid film is no longer capable of adequately protecting the surfaces.EP capabilities in the lubricant are essentialSolid additives are mixed into the grease
6Mixed LubricationAlthough not a true “mode” of lubrication in the sense of hydrodynamic or boundary, mixed lubrication occurs more frequently then is realized.Mixed lubrication is a transitional mode of lubrication between hydrodynamic and boundaryMixed lubrication is characterized by the likelihood of intermittent surface contactEP and anti-wear are essential properties in the lubricant
7How is a lubricant made?Select a base fluid:MINERAL OILorSYNTHETIC FLUID?
8Selecting a base fluid: MINERAL OILParaffinic or NaphthenicReadily availableComparatively low costLimited performance.
9Selecting a base fluid: SYNTHETIC FLUIDSPAO, PAG, EsterSynthetically manufacturedComparatively high costImproved performanceLongevityTemperatureViscosity Index
10OTHER SYNTHETIC FLUIDS Selecting a base fluid:OTHER SYNTHETIC FLUIDSSiliconesFluorinatedUltra PerformanceUltra TemperatureLong LifeLube for Life
11NOW SELECT THE REQUIRED VISCOSITY. Base fluid selected:Mineral or SyntheticNOW SELECT THE REQUIRED VISCOSITY.
12Selecting the required viscosity: Generally thinner fluids are used for:Lighter loadsFaster speeds.
13So how do we measure viscosity?. Selecting the required viscosity:Generally thicker fluids are used for:Heavier loadsSlower speedsSo how do we measure viscosity?.
14Viscosity (Thick) Viscosity (Thin) 400C & 1000Cmm2 per second=centistokes (cSt)HighViscosity(Thick)LowViscosity(Thin)
15What are the units of viscosity? mm2s = centistokes (cSt) = ISO VG (at 400C)32 cSt - typical low viscosity (thin)680 cSt - typical high viscosity (thick)ISO VG etc
18Thickener Systems – turn fluids into greases Improved Performance-Temperature-Mechanical stabilityLithium complexCalcium complexAluminium complexSoapThickenersLithium soap Calcium soap Aluminium soapGeneral Purpose
19Thickener Properties Lithium Lithium Complex Calcium Complex Good multi-purpose, good mechanical stability, limited other propertiesLithium ComplexExcellent high temp & mechanical stability capabilityCalcium ComplexExcellent load carrying and water resistanceAluminium ComplexExcellent temperature capability & water resistance
20Other grease thickeners: Other Thickener SystemsOther grease thickeners:Bentonite claySilicaPTFE.
21NLGI PENETRATION TEST How is the grease thickness checked ? NATIONAL LUBRICATINGGREASEINSTITUE of America.
22NLGI Numbers - WHAT DO THEY MEAN? NLGI No 6BLOCK GREASEOld TechnologyNLGI No 5SEMI-SOLID ELASTIC-LIKE GREASEVery rarely used, but can be found in marine or shipping applicationsNLGI No 4VERY TACKY GREASERarely used now, but found sometimes found in heavy open gears or mining equipmentNLGI No 3HEAVIER GREASEUsed mainly for hand applied or caulking gunsNLGI No 285% OF MARKETGenerally used in grease gunsNLGI No 1THINNER GREASEGenerally used in grease guns, slightly more pump- able for short pipe linesNLGI No 0TREACLE LIKE GREASEUsed in semi-auto and auto systems with shorts pipelinesNLGI No 00SEMI FLUID GREASEUsed in semi-auto and automatic systemsNLGI No 000FLUID GREASEUsed in some gearboxes and semi & auto lube systems with longer pipe linesSEMI FLUID/FLUID GREASEGenerally applied byAutomatic Lubricator
23Premium EP 2 Premium EP 1 Premium EP 000 HOW IS GREASE THICKNESS MEASURED?Premium EP 2Premium EP 1Premium EP 000NLGI 6NLGI 5NLGI 4NLGI 3NLGI 2NLGI 1NLGI 0NLGI 00NLGI 000
24Summary Base fluid EP additives Corrosion inhibitors Mineral or syntheticViscosityEP additivesChemical and/or solidsCorrosion inhibitorsOxidation inhibitorsThickeners for greases.
25TO SUPPORT A ROTATING SHAFT BASIC FUNCTION OF A PRECISION BEARINGTO SUPPORT A ROTATING SHAFTOuter RaceBalls or RollersShaftInner RaceLubricant
26TO SUPPORT A ROTATING SHAFT BASIC FUNCTION OF A PLAIN BEARINGTO SUPPORT A ROTATING SHAFTPlain BushLubricantShaft
27BASIC FUNCTION OF A SLIDE TO SUPPORT A SLIDING LOAD
28ALL BEARINGS/SLIDES HAVE ONE SURFACE MOVING AGAINST ANOTHER FRICTIONAL HEATWHY LUBRICATE?
33Potential failures due to over lubrication Standard grease gun can develop 3,000 psiHigh pressure grease guns can develop >6,000 psiPotentially resulting in excessive drag causing:Increased power demandBall/roller skidIncreased frictionExcessive heatExcessive race wearDegradation of the lubricant.
34Correct Application of a lubricant LITTLE & OFTEN!Precision Bearings:Typically fill 1/3 to 1/2 of vacant area in bearingHigh speed bearings require approx. 1/3 fillPlain BearingsTypically fill until clean grease shows.