Lubrication Training - Basics of Lubrication
Types of Lubrication
Hydrodynamic
Boundary
Mixed
Hydrodynamic LubricationOccurs when machine parts are completely separated by a full and continuous film of lubricant
Contact 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.
Hydrodynamic Lubrication
Boundary LubricationUnder certain conditions such as shock loading, heavy loads, high temperature, slow speed and critically low viscosity, the lubricant is no longer hydrodynamic
Frequent 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 essential
Solid additives are mixed into the grease
Mixed 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 boundary
Mixed lubrication is characterized by the likelihood of intermittent surface contact
EP and anti-wear are essential properties in the lubricant
Select a base fluid:
MINERAL OIL or SYNTHETIC FLUID?
How is a lubricant made?
Selecting a base fluid:
MINERAL OIL
Paraffinic or NaphthenicReadily availableComparatively low costLimited performance.
Selecting a base fluid:
SYNTHETIC FLUIDS
PAO, PAG, EsterSynthetically manufacturedComparatively high costImproved performance Longevity Temperature Viscosity Index
Selecting a base fluid:
OTHER SYNTHETIC FLUIDS
SiliconesFluorinatedUltra Performance Ultra Temperature Long Life Lube for Life
Base fluid selected:
Mineral or Synthetic
NOW SELECT THE REQUIRED VISCOSITY.
Selecting the required viscosity:
Generally thinner fluids are used for:
Lighter loads
Faster speeds.
Selecting the required viscosity:
Generally thicker fluids are used for:
Heavier loads
Slower speeds
So how do we measure viscosity?.
Low
Viscosity(Thin)
High
Viscosity(Thick)
mm2 per second
=centistokes (cSt)
400C & 1000C
What 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 15-22-32-46-68-100-150-220-320-460-680-1000 etc
SOLID LUBRICANTSGraphiteMolybdenum disulphide
(MoS2)
PTFE (Teflon)
CHEMICAL SOLUTIONSChlorineSulphurPhosphorous
Product enhancements:
Extreme Pressure (EP) Additives
Product enhancements
OXIDATION INHIBITORSLonger wet life
CORROSION INHIBITORSImproves corrosion protection.
TACKY ADDITIVESImproves adhesion
Lithium soap Calcium soap Aluminium soap
Lithium complex Calcium complexAluminium complex
Improved Performance
-Temperature
-Mechanical stability
General Purpose
Soap Thickeners
Thickener Systems – turn fluids into greases
Thickener Properties
LithiumGood multi-purpose, good mechanical stability,
limited other propertiesLithium ComplexExcellent high temp & mechanical stability
capabilityCalcium ComplexExcellent load carrying and water resistance
Aluminium ComplexExcellent temperature capability & water
resistance
Other grease thickeners:
Bentonite clay
Silica
PTFE.
Other Thickener Systems
NLGI PENETRATION TEST
NATIONAL
LUBRICATING
GREASE
INSTITUE of America.
How is the grease thickness checked ?
SEMI FLUID/
FLUID GREASE
NLGI Numbers - WHAT DO THEY MEAN?
Generally applied by
Automatic Lubricator
NLGI No 6 BLOCK GREASE Old Technology
NLGI No 5 SEMI-SOLID ELASTIC-LIKE GREASE
Very rarely used, but can be found in marine or shipping applications
NLGI No 4 VERY TACKY GREASE Rarely used now, but found sometimes found in heavy open gears or mining equipment
NLGI No 3 HEAVIER GREASE Used mainly for hand applied or caulking guns
NLGI No 2 85% OF MARKET Generally used in grease guns
NLGI No 1 THINNER GREASE Generally used in grease guns, slightly more pump- able for short pipe lines
NLGI No 0 TREACLE LIKE GREASE Used in semi-auto and auto systems with shorts pipelines
NLGI No 00 SEMI FLUID GREASE Used in semi-auto and automatic systems
NLGI No 000
FLUID GREASE Used in some gearboxes and semi & auto lube systems with longer pipe lines
NLGI 6
NLGI 5
NLGI 4
NLGI 3
NLGI 2
NLGI 1
NLGI 0
NLGI 00
NLGI 000
HOW IS GREASE THICKNESS MEASURED?
Premium EP 1Premium EP 2 Premium EP 000
SummaryBase fluid
Mineral or syntheticViscosity
EP additivesChemical and/or solids
Corrosion inhibitorsOxidation inhibitorsThickeners for greases.
TO SUPPORT A ROTATING SHAFT
Outer Race
Inner Race
Balls or Rollers
Lubricant
Shaft
BASIC FUNCTION OF A PRECISION BEARING
BASIC FUNCTION OF A PLAIN BEARINGTO SUPPORT A ROTATING SHAFT
Plain Bush
Lubricant
Shaft
BASIC FUNCTION OF A SLIDE
TO SUPPORT A SLIDING LOAD
FRICTIONAL HEAT
ALL BEARINGS/SLIDES HAVE ONE SURFACE MOVING AGAINST ANOTHER
WHY LUBRICATE?
WHY LUBRICATE?
FRICTIONAL HEAT FRICTIONAL WEAR
Introduction of a lubricant film
REDUCES FRICTIONAL HEAT & WEAR
BASIC FUNCTION OF A LUBRICANT.
Reasons for bearing failure
Material fatigue
9%
Other reasons21%
Improper lubrication
43%
Improper mounting
27%
Breakdown of “improper lubrication” section
Over lubrication
60%
Lack of lubrication
40%
Standard grease gun can develop 3,000 psiHigh pressure grease guns can develop >6,000 psi
Potentially resulting in excessive drag causing: Increased power demand Ball/roller skid Increased friction Excessive heat Excessive race wear Degradation of the lubricant.
Potential failures due to over lubrication
Correct 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 fill
Plain BearingsTypically fill until clean grease shows.
Thank You
Any Questions?
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