Lubricants & Lubrication

8/11/2019 Lubricants & Lubrication

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Engr. Muhammad Sajid

Lecturer

Department of Chemical Engineering, UOG

The Basics of

Lubricants and lubrication


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Meaning of lubrication

Friction - is createdwhen there is relative motion between two

surfaces

Resistance to motionis defined as friction

Lubrication is use of a material between surfaces to reduce

friction

Any material usedis called a lubricant

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LUBRICANTS

The substances which are used to decrease the force of

friction between the moving parts of machine in contact

are known as Lubricants and the process of decreasing

the force of friction between the moving parts of

machine in contact is known as Lubrication.

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Methods of lubrication

Two main methods

Hydrodynamic lubrication

Boundary lubrication


Also called complete or full flow

Occurs when two surfaces are completed separated by a fluid

film

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Methods of lubrication cont..

Two main methods




Occurs when Hydrodynamic lubrication fails.

By adsorption or chemical reaction

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Lubrication System

Manual Lubrication System

Automatic Lubrication System

Built-in Lubrication System

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Types of Lubricant - Physical

Liquid

Solid

Semi solid

Gases

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Types of Lubricant - Physical

Liquid

Typical lubricants are liquid/fluids

Mineral oil or synthetic oils

Solid

Graphite, MoS2

Semi solid

Greases

Gases

Atomised 2 stroke oils

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Typical lubricants - Application

Engine oils

Gear Oils

Turbine Oils

Hydraulic Oils

Metal working oils

Cutting oils

Forming Oils Rust preventives

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Typical lubricants - Application

Heat Transfer Oils

Heat Treatment Oils

Quenching Oils

Tempering Oils

Refrigeration Oils

Rubber Process Oils

Ink process Oils

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Lubricant - Components

Base Oils

Mineral by-products of crude oil refining process.

Base oils are polymerized or synthesized further and called

synthetic

Additives

Natural

Synthetic

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Selection of Lubricants

Type of lubricantsolid, liquid etc

Place of usetemperature considerations

Environmental conditionsopen or sealed

Frequency of application Life of the lubricant

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Function of a lubricant

Lubricate - Reduce friction

Cooling - Heat transfer

Cleaning - Detergency Noise pollution - dampening

Sealingprevent leakage

Protectionprevent wear

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Lubricate reduce friction

The effects of friction

Metal to metal contact

Leads to wear and tear

Generates heat

Results in Power loss

Lubricant reduces friction by forming a film

Reduces ill effect of friction

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Cleaning

Cleans carbon and varnish deposits

Flushes the entire system removing

Soot

Deposits

Acids

Wear products

Moisture

Removes external contaminants dust, moisture (external)

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Noise reduction

Reduce noise

By preventing metal to metal contact

Dampens noise As between camshaft and tappet

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Sealing

Oil film

Between piston ring and liner

Helps in creating a gas tight seal

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Protection

Protection against acids and moisture

Very important to increase life of component and equipment

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Properties of lubricants

Kinematic viscosity

Viscosity index

Pour Point Flash Point

Total Base Number (TBN)

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Kinematic viscosity

Measure of internal resistance to flow

Thickness of fluid (in laymen terms)

Decreases with increase in temperature

Important in lubricant selection

Increase in used oil indicates oxidation

Specified at 40C and 100C

Measured in Centi Stokes (CSt)

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Kinematic Viscosity -

Recommendations

Low Viscosity oils used

High speeds

Low pressure

Low temperature High Viscosity oils used

Low speeds

High pressure

High temperature

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Viscosity index

Measure of fluids change of viscosity with temperature.

Empirical number

Higher the VI lower will be the change of viscosity withtemperature

Indicator of temperature range of operations

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Pour Point

Lowest temperature at which the fluid will flow

Indicates lowest operating temperature

Measured in C

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Flash Point

Lowest temperature at which the vapor above the liquid will ignite

under flame

Indicated safe maximum temperature of operation.

Indicator of volatility

Test method - COC and PMCC

Measured in C

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Total Base Number (TBN)

Measured the acid neutralizing reserve in oil.

Important for deciding discard of oil

Decreases due to Oxidation of oil

Water contamination

Fuel contamination

Measured in Mg KOH/gm of oil

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What are additives

Lubricant additives

classified on their functional capability

Enhance existing property

Suppress undesirable property

Impart new property

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What are additives

What they do in Engine Oils

Protect metal surfaces

- (rings, bearings, gears, etc.)

Extend the range of lubricantapplicability

Extend lubricant life

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Surface Protective additives

Anti wear and EP Agent

Corrosion & Rust inhibitor

Detergent

Dispersant

Friction modifier

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Surface Protective additives

- Automotive Lubricants

Additive type

Purpose

Typical

compounds

Function

Anti wear & EP Agent

Reduce friction & wear.

Prevent scoring & seizure

ZDDP, Organic Phosphates, acid phosphates,

organic sulfur and chlorine compounds etc.

Chemical reaction with metal surface and formsa film.

Prevents metal-to-metal contact

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