Basics of Lubrication

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Animal and vegetable origin was used in 450AD to 1450ADAmontons (1699) gave the classical definition of frictionIn 1883 Petrov repoted the coherent film of lubrication between the rough surface

History of Lube base oil **

Base oil was 1st produced in 18th century in USA 2nd was in Russia Base oil is totally overtook of animal and veg origin oilBase oil derived from the source of crud oilHistory of Lube base oil **

World Lube Oil Production **

Variation in Crude Oil Properties **

Friction Friction is the force resisting the relative motion of surfaces or material elements in contact. The ratio of the force of friction between two bodies and the force pressing them together is known as co-efficient of friction ()Ff/ N = constant ()

Ff = N**

Reducing frictional resistanceFriction between moving parts in contact is unavoidable -but it is desirable to keep this to as low as possible Provide a fine or smooth surface finish. Replacing the one of the material having lower coefficient of friction. Introducing a fluid film which separates the parts slightly thus reducing the friction (Lubrication)Installing balls, rollers or needles between the sliding surfaces which replace the sliding movement by rolling action (Bearings)**

Lubrication Lubrication is the process, or technique employed to reduce wear on surfaces in close proximity, and moving relative to each anotherLubrication is effected by introducing a substance called lubricant. The lubricant film can be a solid, (graphite), a liquid, a semi solid (grease) or exceptionally a gas**

Objectives of LubricationTo reduce frictional resistanceTo reduce wear on the bearing surfacesTo protect the bearing surfaces from corrosionTo carry away heat from the bearingTo reduce noise from the moving components of the machine**

Different Lubricating conditions Dry Lubrication- No lubricant present between the surfaces

Boundary lubrication (Thin film) -This condition is found on machine slide ways (Lathe cross slide, milling machine table).

No oil filmThin oil film**

Full film lubrication- The surfaces are separated by thick film of lubricant and there will not be any metal-to-metal contact

Mixed lubrication- Boundary and full lubricating conditions(Hydrodynamic)Thick oil film**

Essential Base Oil Properties**

Base Oil Components**

Backup slide**

Characteristic on the Basis of Lubricant Performance **

PropertiesAlkanesAlicyclic AromaticsDensityLowHighHighVelocityLowHighHighVIGoodLowPoorMelting pointHighLowlowOxidation GoodLowpoor

Selection of Crude Oil **Both are rich in Alkanes Use to produce base oilGood oxidation stability Low in Alkanes contentFree from the waxLow viscosity/temperature

Low Temperature Properties*Cloud Point*Pour Point * Flow by gravitation*Cold Crank Stimulation*Brookfiled ViscosityHigh Temperature Properties *Volatility : Tendency of an oil to be lost * Flash Point : Auto Ignition of Vapors

Physical Properties ***Detection of 1st formation of wax*Haziness or milky white appearance appear *Apparent Viscosity of oil at low tem. And hight share rate*Low Temp. Viscosity of gear and hydraulic fluid under low share stress

Viscosity: ability of an oil to form lubricating film Absolute Viscosity: Kinetmaic ViscosityViscosity Index: measurs the degree of aromatics removal , comparing the different base oil,Other properties Density Demulsification Foam Characteristics Thermal ConductivityElectrical properties Physical Properties **

Oxidation

Corrosion

Carbon Residue

Seal Compatibility Chemical Properties ***Due oxidation change in viscosity *corrosion *formation of acidDiscoloration of metalChange in surface codition

*Deposit at elevated Temp.*ASTM D189 test is required

ATMOSPHERIC DISTILLATION**

**Vacuum Distillation

**Why do we need further refining?Mineral base oils after vacuum distillation still contain some undesirables:Large paraffin molecules (wax type) have a high pour pointAromatics are considered as carcinogenic and form sludgeUnsaturates have poor oxidation stability, and form sludge and varnishNitrogen compounds catalyse oxidationHowever some components are also desirable:Sulphur compounds - some are natural anti-oxidantsLarge paraffin molecules - have a high viscosity index

**Further refining processesAromatics are extracted with certain solventsWaxes are removed by solvent dewaxingSulphur, nitrogen compounds and unsaturates are reduced by hydrogenationFurther refining is a balance between:Reducing the undesirable compounds - basestock qualityReducing the desirable compounds - additive treatCost

**SOLVENT EXTRACTIONBASE OIL FEEDSTOCKEach of the particular base oil cuts is mixed with a special solventThe solvent is removed, taking most of the aromatics with itImprovesViscosity indexColourOxidation stabilityLowers the carcinogenicityProcess oils are produced as a by-product, used in rubber tyre manufacture

**SOLVENT DEWAXING

**HYDROFINING

**THE COMPLETE PROCESS

**Typical Inspection Data

Process

Vacuum distillation

Solvent extraction

Dewaxing

Hydrofining

Product

Distillate

Raffinate

Dewaxed Oil

Base oil

VI

81

114

92

92

Colour

-

-

16

>26

Pour Point, C

25

30

-12

-12

Sulphur %

0.48

0.13

0.16

0.10

Nitrogen, ppm

520

24

30

26

Aromatics, %

17

8

10

10

Saturates, %

64.9

83.8

80.0

80.0

The properties of a lubricant can be improved by adding certain chemicals Anti oxidantsFoam depressantsCorrosion inhibitorsDetergent DispersersOiliness improvers

Additives**

The selection of lubricant depend on:

Type of mechanism being lubricatedType of lubricating systemRate of heat removalCost

Selection of Lubricant**

Selection of Lubricant -typical examples **

FeatureLubricantLubricating systemHeat removalMaintenancecostCommentsPlainbearingOilHandLowHighLight dutyCirculatingHighLowContinuousPorousLowLowLow speedsGreaseHandNilHighLight dutyRolling bearingOilOil mistlowLowHigh costOil bathlowLowChurningSplashModerateLowUsed in gear boxGreasePackedNilLowLong lifeCentralNilLowConvenientGearsOilBathModerateLowSimple gear boxCirculatingHighLowHi-duty gearsGreaseHandNilHighHi-duty gearsHousing filledNilLowLow speeds

Historic Method Distillation residue use as lubricant.Wax was removed by chilling H2SO4 was used in order to reduce aromaticsClay was use for adsorption of acid and other impurities Production of Base Oil in Modern RefinerySelective solvent is used for the removal of AromaticsSolvent dewaxing method is replaced by cold pressing Finishing of base oil catalytic hydrogeneration process isnomally use now

Conventional Base Oil Manufacturing Methods**

Distillation De-asphasting Solvent extraction Solvent dewaxing Finishing Modern Catalytic ProcessHydrotreamtent Hydrocracking Base Oil Production **

**Distillation columnsClassified according to: Nature of the feed that they are processing:binary column - feed contains only two components;multi-component column - feed contains more than two components.Number of product streams they have:multi-product column - column has more than two product streams.Where extra feed exits when used to help with the separation:extractive distillation - where the extra feed appears in the bottom product stream;azeotropic distillation - where the extra feed appears at the top product stream.Type of column internals:tray column - trays of various designs used to hold up the liquid to provide better contact between vapour and liquid;packed column - packings are used to enhance vapour-liquid contact.

**Main Components of Distillation ColumnsA vertical shell where separation of liquid components is done.Column internals e.g.trays/plates and/or packings which are used to enhance component separations.A reboiler to provide the necessary vaporization for the distillation process.A condenser to cool and condense the vapour leaving the top of the column.A reflux drum to hold the condensed vapour from the top of the column so that liquid (reflux) can be recycled back to the column.

**Trays and plates Bubble cap traysA riser or chimney is fitted over each hole, and a cap covers the riser. The cap is mounted with a space to allow vapour to rise through the chimney and be directed downward by the cap, finally discharging through slots in the cap, and bubbling through the liquid on the tray.

**Trays and plates

Valve traysPerforations are covered by caps lifted by vapour, which creates a flow area and directs the vapour horizontally into the liquid.

Sieve traysSieve trays are simply metal plates with holes in them. Vapour passes straight upward through the liquid on the plate. The arrangement, number and size of the holes are design parameters.

**PackingsPackings are passive devices designed to increase the interfacial area for vapour-liquid contact.They do not cause excessive pressure-drop across a packed section, which is important because a high pressure drop would mean that more energy is required to drive the vapour up the distillation column.Packed columns are called continuous-contact columns while trayed columns are called staged-contact columns because of the manner in which vapour and liquid are contacted.

**Basic operationThe feed is introduced somewhere near the middle of the column to a tray known as the feed tray.The feed tray divides the column into a top (enriching or rectification) and a bottom (stripping) section.The feed flows down the column where it is collected in the reboiler.Heat (usually as steam) is supplied to the reboiler to generate vapour.The vapour from the reboiler is re-introduced into the unit at the bottom of the column.The liquid removed from the reboiler is known as the bottoms product or simply, bottoms.

**Basic operationVapour moves up the column, exits the top, and is cooled in a condenser. The condensed liquid is stored in a holding vessel known as the reflux drum. Some of this liquid is recycled back to the top of the column and this is called the reflux. The condensed liquid that is removed from the system is known as the distillate or top product. Thus, there are internal flows of vapour and liquid within the column as well as external flows of feeds and product streams, into and out of the column.

**Propane deasphaltingCoke-forming tendencies of heavier distillation products are reduced by removal of asphaltenic materials by solvent extraction.Liquid propane is a good solvent (butane and pentane are also commonly used).Deasphalting is based on solubility of hydrocarbons in propaneVacuum residue is fed to a countercurrent deasphalting tower. Alkanes dissolve in propane whereas asphaltenic materials (______________), coke-precursors do not.Asphalt is sent for thermal processing.

**Propane deasphalting

**SOLVENT DEASPHALTINGA physical separation based residue up-gradation process, separates vacuum residue on the basis of both molecular type & size.Produces extra heavy viscosity lube base stock and / or feedstock for conversion units.Pitch or Asphalt is obtained as bottom product

**Deasphalting SolventsCommercially used solvents are

LIGHTER SOLVENTS : PROPANE & ISOBUTANE

Higher selectivityReject all resins and asphaltenes Suitable for production of lubes oils

HEAVIER SOLVENTS : n-BUTANE, PENTANE (n& i) and LIGHT NAPHTHA -- Less selective than the lighter solvents Produce higher yields of DAO (suitable as conversion feedstocks)

**General Properties Deasphalting Solvents

Solubility of oil decreases with increase in temperature

More selective at higher temperatures

Exhibit lower critical solution temperature

**Processing of DAOPROCESSING FOR

LUBE: Lube production increased by approx 20%

CRACKING : 1/3rd of cat. cracking feed in a refinery can be DAO

HYDROTREATING : Economical, consumes less hydrogen, less investment

**Processing of Asphalt ProcessBLENDING: Tailor made asphalt (bitumen) or fuel oil

VISBREAKING : Minimizes need or cutter stock GASIFICATION: Hydrogen, steam and power production

**DEASPHALTING: PROCESS VARIABLES SOLVENT COMPOSITIONBlends of light hydrocarbon solventsIncreased operating flexibility

SOLVENT-TO-FEED RATIO (S/F)Selectivity improves by increasing S/F at constant DAO yieldEconomically optimum S/F is used

TEMPERATURE / TEMPERATURE GRADIENTOil solubility in solventDecreases with increase in temp. (optimum temps)Temp. gradient improves separation between DAO-Asphalt phases

PRESSURE Maintained above V.P. of solvent at operating temperatures.

**General Operating Conditions of SDA Units Vs. Type of Solvent

OPERATING CONDITIONS PROPANE BUTANE PENTANEEXTRACTION RANGE (C)50 80100 130170 210 PRESSURE RANGE (MPa)3.5 4.0~ 4.0~ 4.0SOLVENT RATIO (VOL.)6 94 73 - 5

**Solvent Recovery From DAO & Asphalt Phases EVAPORATIVE MODEMultiple effect evaporation (up to 3 stages)Series of progressively lower pressure flashes followed by stripping

SUPERCRITICAL MODE (FOR DAO PHASE)Phase separation at / above critical temperature of solvent85 to 93% solvent recovered as lighter phase for heat exchange and recycle in the processRecovered solvent has very low DAO contentRemaining solvent from DAO recovered by flashing / stripping

**Solvent extraction and dewaxingSolvent treating is a widely used method of refining lubricating oils as well as a host of other refinery stocks.Since distillation (fractionation) separates petroleum products into groups only by their boiling-point ranges, impurities may remain. These include organic compounds containing sulfur, nitrogen, and oxygen; inorganic salts and dissolved metals; and soluble salts that were present in the crude feedstock.In addition, kerosene and distillates may have trace amounts of aromatics and naphthenes, and lubricating oil base-stocks may contain wax.Solvent refining processes including solvent extraction and solvent dewaxing usually remove these undesirables at intermediate refining stages or just before sending the product to storage.

**Solvent extractionThe purpose of solvent extraction is to prevent corrosion, protect catalyst in subsequent processes, and improve finished products by removing unsaturated, aromatic hydrocarbons from lubricant and grease stocks.The solvent extraction process separates aromatics, naphthenes, and impurities from the product stream by dissolving or precipitation. The feedstock is first dried and then treated using a continuous countercurrent solvent treatment operation.In one type of process, the feedstock is washed with a liquid in which the substances to be removed are more soluble than in the desired resultant product. In another process, selected solvents are added to cause impurities to precipitate out of the product. In the adsorption process, highly porous solid materials collect liquid molecules on their surfaces. The solvent is separated from the product stream by heating, evaporation, or fractionation, and residual trace amounts are subsequently removed from the raffinate by steam stripping or vacuum flashing.

**Solvent extractionElectric precipitation may be used for separation of inorganic compounds.The solvent is regenerated for reused in the process.The most widely used extraction solvents are phenol, furfural, and cresylic acid.Other solvents less frequently used are liquid sulfur dioxide, nitrobenzene, and 2,2' dichloroethyl ether.The selection of specific processes and chemical agents depends on the nature of the feedstock being treated, the contaminants present, and the finished product requirements.

**Solvent dewaxingSolvent dewaxing is used to remove wax from either distillate or residual basestock at any stage in the refining process.There are several processes in use for solvent dewaxing, but all have the same general steps, which are::mixing the feedstock with a solvent;precipitating the wax from the mixture by chilling; andrecovering the solvent from the wax and dewaxed oil for recycling by distillation and steam stripping.Usually two solvents are used: toluene, which dissolves the oil and maintains fluidity at low temperatures, and methyl ethyl ketone (MEK), which dissolves little wax at low temperatures and acts as a wax precipitating agent.Other solvents sometimes used include benzene, methyl isobutyl ketone, propane, petroleum naphtha, ethylene dichloride, methylene chloride, and sulfur dioxide.In addition, there is a catalytic process used as an alternate to solvent dewaxing.

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Africtionalforcetangentialtothedirectionofaflowingfluid,theforceofwhichisdirectlyrelatedtothefluidsviscosityshearstress.Inbloodvessels,shearstressactsonendotheliumandisthemechanicalforceresponsiblefortheacutechangesinluminaldiameter. Stressparalleltoagivensurface(e.g.,afaultplane)thatresultsfromforcesappliedparalleltothesurfaceorfromremoteforcestransmitted throughsurroundingrock.

T=F/A**

Detergenets/Disperants**

The function of dispersants is to greatly enhance the transfer of oil from the water surface into the water column to mitigate oil spill impacts.

The use of dispersants for oil spill response is often a trade-off: increased short-term injury to water column resources to minimize injury to surface water and shoreline resourcesWhat are the Function of Dispersants? **

Dispersants, like detergents, are simply surfactants. Surfactants reduce the interfacial tension between water and oil, permitting the oil to break into tiny droplets. The function of the solvent is to reduce the viscosity of the surfactants. The solvent may also aid in surfactant-oil interaction. Dispersants enhance a natural process. The ultimate fate of oil spilled in the marine environment is biodegradation. Dispersion enhances the rate of natural biodegradation by increasing the surface area of the spilled oil.

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**Applications in Oil Solubilization

***Ability to bind easily with oil.Solubilize the oil into the water when concentration exceed critical micelle concentration (CMC).Below CMC all surfactant present as a monomer

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Types of LubricationHydrodynamicBoundaryMixed

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Hydrodynamic LubricationOccurs 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.**

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. 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 boundaryMixed lubrication is characterized by the likelihood of intermittent surface contactAnti-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 performanceLongevityTemperatureViscosity Index**

Selecting a base fluid:

OTHER SYNTHETIC FLUIDS

SiliconesFluorinatedUltra PerformanceUltra TemperatureLong LifeLube 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)HighViscosity(Thick)mm2 per second=centistokes (cSt)400C & 1000C**

SOLID LUBRICANTSGraphiteMolybdenum disulphide (MoS2)PTFE (Teflon) CHEMICAL SOLUTIONSChlorineSulphurPhosphorousProduct enhancements:Extreme Pressure (EP) Additives**

Product enhancementsOXIDATION INHIBITORSLonger wet life

CORROSION INHIBITORSImproves corrosion protection.

TACKY ADDITIVESImproves adhesion**

Lithium soap Calcium soap Aluminium soapLithium complex Calcium complexAluminium complex

Improved Performance-Temperature-Mechanical stabilityGeneral PurposeSoap ThickenersThickener Systems turn fluids into greases**

Thickener PropertiesLithiumGood 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

**

Other grease thickeners:Bentonite claySilicaPTFE.Other Thickener Systems**

NLGI PENETRATION TEST

NATIONALLUBRICATING GREASEINSTITUE of America.How is the grease thickness checked ?**

SEMI FLUID/FLUID GREASENLGI Numbers - WHAT DO THEY MEAN?Generally applied by Automatic Lubricator

NLGI No 6BLOCK GREASE Old Technology NLGI No 5SEMI-SOLID ELASTIC-LIKE GREASE Very rarely used, but can be found in marine or shipping applications NLGI 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 lines

NLGI 6NLGI 5NLGI 4NLGI 3NLGI 2NLGI 1NLGI 0NLGI 00NLGI 000HOW IS GREASE THICKNESS MEASURED?Premium EP 1Premium EP 2Premium EP 000**

TO SUPPORT A ROTATING SHAFTOuter RaceInner RaceBalls or Rollers

LubricantBASIC FUNCTION OF A PRECISION BEARING**

BASIC FUNCTION OF A PLAIN BEARINGTO SUPPORT A ROTATING SHAFT Plain BushLubricant**

BASIC FUNCTION OF A SLIDETO SUPPORT A SLIDING LOAD**

FRICTIONAL HEATALL BEARINGS/SLIDES HAVE ONE SURFACE MOVING AGAINST ANOTHER WHY LUBRICATE?**

WHY LUBRICATE?FRICTIONAL HEATFRICTIONAL WEAR**

Introduction of a lubricant filmREDUCES FRICTIONAL HEAT & WEARBASIC FUNCTION OF A LUBRICANT.**

Reasons for bearing failure**

Breakdown of improper lubrication section**

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. Potential failures due to over lubrication **

Thank You**

VISCOMETRICS : adeviceformeasuringviscosityThepour pointof a liquid is the temperature at which it becomes semi solid and loses its flow characteristics. In crude oil a highpour pointis generally associated with a high paraffin content, typically found in crude deriving from a larger proportion of plant material.

VOLATILITY Evaporatingreadilyatnormaltemperaturesandpressures

ANILINE POINT. : the lowest temperature at whichanilineand a solvent (as gasoline) are completely miscible and which serves as an indication of the type of hydrocarbons present in the solvent, the content of aromatics being higher according as the temperature is lower.

Demulsibilityis the ability to release water. This is important when the equipment is operating in humid climates or in a plant atmosphere that is wet or humid. Paper mills, steel mills and food-processing operations have significant exposure to water-based process fluids.

**Supporting slides

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