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?