Love-Electronics: April 2011

Contents:--

1) Introduction

2) Function of lubricants

3) Purpose of lubricants

4) Essentialness of lubricants

5) Types of lubricants

6) Properties of lubricants

7) Properties of lubricants that are used in Industries

8) Additives of lubricants

9) References

Let’s talk about industrial lubricants first

· Industrial lubricants are substance that is used in two solid parts or machinery in various industries.

· The main aim of lubricants is to reduce friction occurring between two hard & solid surfaces.

· Lubricants may be solids, semi-solids, and liquid. Solid lubricants are graphite, plastic beads, etc.

· Liquid lubricants are motor oils, synthetic fluids, glycols, modified vegetable oils, etc. Greases are the example of semi-liquid lubricants.

What the function of industrial lubricants is?

· As we know that the basic aim of industrial lubricants are to reduce friction between two surfaces of components and parts of machinery.

· Also we know that friction causes heat. So, lubricant is also helpful in reducing heat generated by moving parts of machinery or engines.

· It cools the machinery and engines.

· That’s why lubricant is sometimes also termed as the coolants and the heat transfer fluids.

· Lubricant provides a protective film between two moving parts that allows two surfaces to be separated.

· In this way it reduces friction and heat form the moving parts of the machinery or engine.

“Lubricants can be mainly categorized in two types”

ü organic and

ü Synthetic.

Ø Most of organic lubricants are prepared from petroleum by the process of refining.

Ø Synthetic oils (lubricants) are prepared through a complex process of chemical compounds using some additives.

Ø Additives are chemical components added to the base oil better performance of lubrication oil.

Ø Typical enhanced properties include oxidation stability, wear protection, and corrosion inhibition. But the basic function of lubricants remains same.

Automotive and automobile industries are the prime consumers of lubricants.

· Motor oils (also known as engine oils) are the single most prime types of lubricants that are used in various types of motor engines, vehicles, industrial engines etc.

· Brake oils, gear oils, etc are also the examples of motor oils.

· Brake oils are special types of lubricants that are used in vehicles brake system.

· Using other lubricants in brake system can damage the components.

· Gear oils are especially designed for the gear boxes and gear system of machinery.

· Tractors oils, Chain saw oils, engine oils, transmission fluids, etc are some useful lubricants for agricultural purpose.

· Metal working industries are also major consumers of lubricants.

· Metalworking fluids include drawing oils, cutting fluids, grinding fluids, forming oils, etc.

· While cutting, grinding or drilling it becomes necessary to use metal working fluids for better performance of tools and better work done.

· Engine coolants, turbine oils, marine oils, hydraulic oils, compressor oils, rock drill oils, greases, rust preventives, forming lubricants, quenching oils, oil compressor, slideway oils, hydraulic fluids, gas engine oils, etc are some popular forms of industrial lubricants used in industries and various equipments for various specific purposes.

· Thus we see that lubricants play a very important role in components of machinery to make them safe and longer life.

· No one think smooth running of machinery without using some lubricants.

· Can we imagine of smooth running of our vehicle without using proper lubricants and motors oils?

Ø If yes, it is also sure that you may suffer sometimes due to break down of your vehicle engine.

Now let us see the purposes for which the lubricants are used:----

Keep moving parts apart:- Lubricants are typically used to separate moving parts in a system. This has the benefit of reducing friction and surface fatigue together with reduced heat generation, operating noise and vibrations. Lubricants achieve this by several ways. The most common is by forming a physical barrier i.e. a thin layer of lubricant separates the moving parts.
Reduce friction:- The lubricant-to-surface friction is much less than surface-to-surface friction in a system without any lubrication. Thus use of a lubricant reduces the overall system friction. Reduced friction has the benefit of reducing heat generation and reduced formation of wear particles as well as improved efficiency.
Transfer heat:- Both gas and liquid lubricants can transfer heat. However, liquid lubricants are much more effective on account of their high specific heat capacity. Typically the liquid lubricant is constantly circulated to and from a cooler part of the system, although lubricants may be used to warm as well as to cool when a regulated temperature is required. This circulating flow also determines the amount of heat that is carried away in any given unit of time. High flow systems can carry away a lot of heat and have the additional benefit of reducing the thermal stress on the lubricant. Thus lower cost liquid lubricants may be used.
Carry away contaminants and debris:- Lubricant circulation systems have the benefit of carrying away internally generated debris and external contaminants that get introduced into the system to a filter where they can be removed.
Transmit power:- Lubricants known as hydraulic fluid are used as the working fluid in hydrostatic power transmission.
Protect against wear:- Lubricants prevent wear by keeping the moving parts apart. Lubricants may also contain anti-wear or extreme pressure additives to enhance their performance against wear and fatigue.
Prevent corrosion:-Lubricants are formulated with additives that form chemical bonds with surfaces to prevent corrosion and rust.

Why lubricants are essential:---

· When using an LM system, it is necessary to provide effective lubrication. Without lubrication, the rolling elements or the raceway may be worn faster and the service life may be shortened.

· A lubricant has effects such as the following.

Ø Minimizes friction in moving elements to prevent seizure and reduce wear.

Ø Forms an oil film on the raceway to decrease stress acting on the surface and extend rolling fatigue life

Ø Covers the metal surface to prevent rust formation.

· To fully bring out an LM system's functions, it is necessary to provide lubrication according to the conditions.

· Even with an LM system with seals, the internal lubricant gradually seeps out during operation.

· Therefore, the system needs to be lubricated at an appropriate interval according to the conditions.

Types of Lubricants

· LM systems mainly use grease or sliding surface oil for their lubricants.

· The requirements that lubricants need to satisfy generally consist of the following.

(1) High oil film strength

(2) Low friction

(3) High wear resistance

(4) High thermal stability

(5) Non-corrosive

(6) Highly anti-corrosive

(7) Minimal dust/water content

(8) Consistency of grease must not be altered to a significant extent even after it is

Repeatedly stirred.

And the basic types of lubricants are as follows

· There are four basic types of lubricants they are as follows:

1) Hydrodynamic or Full Fluid Film Lubrication

· Although the reduction of friction via the use of a fluid appears to be a simple concept, it is actually far more complex.

· Lubrication by this method can be divided into four basic types or regimes.

· When a fluid lubricant is present between two rolling and/or sliding surfaces, a thicker pressurized film can be generated by the movement of the surfaces (velocities).

· The non-compressible nature of this film separates the surfaces resulting in no metal to metal contact.

· The condition in which surfaces are completely separated by a continuous film of lubricating fluid is commonly referred to as Hydrodynamic or Full Fluid Film Lubrication.

· In this regime, the lubricant immediately adjacent to each surface travels at the same speed and direction of each surface.

· As you travel through the width of the film, differential speed graduates and direction is reversed.

· Hydrodynamic film thickness can be formed by wedging the lubricant through a convergent gap with the tangential surface velocities. Known as wedging film action, this is similar to a car tire hydroplaning on a wet road surface.

· Although hydrodynamic lubrication is the ideal situation, in many instances it cannot be maintained. Factors which affect hydrodynamic lubrication include Lubricant Viscosity, Rotation Speed or RPM, oil supply pressure and Component Loading. An increase in speed or viscosity increases oil film thickness. An increase in load decreases oil film thickness.

2) Boundary Lubrication

· Boundary Lubrication (sometimes referred to as thin film lubrication) is a condition in which the lubricant film becomes too thin to provide total separation.

· This may be due to excessive loading, speeds or a change in the fluid’s characteristics.

· In such a situation, contact between surface asperities (peaks and valleys) occurs.

· Friction reduction and wear protection is then provided via chemical compounds rather than properties of the lubricating fluid.

· Boundary lubrication often occurs during the start up and shut down of equipment or when loading becomes excessive.

3) Mixed Film Lubrication is a combination of both hydrodynamic and boundary lubrication. In such a situation only occasional asperity contact occurs.

4) Elastohydrodynamic Lubrication

· Elastohydrodynamic Lubrication(EHD or EHL)is the last of the types of lubricants discussed here and occurs as pressure or load increases to a level where the viscosity of the lubricant provides a higher shear strength than the metal surface it supports.

· This regime can occur in roller bearings or gears as the lubricant is carried into the convergent zone approaching a contact area or the intersection of two asperities.

· As a result the metal surfaces deform elastically in preference to the highly pressurized lubricant, which increases the contact area and thus increasing the effectiveness of the lubricant.

Properties of Lubricants

1) KINEMATIC VISCOSITY

Test Number & Name: ASTM D-445 Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids.

Significance & Use: The proper operation of equipment depends on the proper kinematic viscosity at operating temperature of the oil used for its lubrication.

What it means: Kinematic viscosity is a measure of a liquid's flow under the influence of gravity. It's handy to think of lubricant's kinematic viscosity as it's "I.D. card." AMSOIL formulates its synthetic lubricants to tighter viscosity limits than other manufacturers do, so AMSOIL synthetic lubricants' kinematic viscosity's are midrange, close to neither the high or low limit. That helps components work their best and helps the lubricants stay in grade.

VISCOSITY INDEX

Test Number & Name: ASTM D-2270 Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40°C and 100°C.

Significance & Use: Viscosity index indicates how much a lubricant's viscosity will change according to changes in temperature between 40°C (104°F) and 100°C (212°F), which roughly define the normal temperature range of most operations.

What it means: The smaller a lubricant's viscosity change as a result of temperature change, the higher that lubricant's viscosity index. High viscosity index lubricants, such as AMSOIL products, protect better in operations with temperature variations.

COLD CRANK SIMULATOR APPARENT VISCOSITY

Test Number & Name: ASTM D-2602 Standard Test Method for Apparent Viscosity of Engine Oils at Low Temperature Using the Cold-Cranking Simulator.

Significance & Use: Apparent viscosity has been established as a valid predictor of engine-cranking viscosities at specified low temperatures. Apparent viscosity depends on temperature and shear rate.

What it means: Cold cranking viscosity affects the startability of engines and other equipment in cold temperatures. Low cold cranking viscosities, such as those AMSOIL synthetic lubricants, make for easier cold cranking and more dependable cold temperature starting.

BORDERLINE PUMPING TEMPERATURE

Test Number & Name: ASTM D-3829 Standard Test Method for Predicting the Borderline Pumping Temperature of Engine Oil.

Significance & Use: Borderline pumping temperature is a measure of the lowest temperature at which an engine oil can be continuously and adequately supplied to the components of an automotive engine.

What it means: The lower the borderline pumping temperature, the lower the temperature in which the engine is protected by circulating oil. AMSOIL synthetic motor oil's extremely low borderline pumping temperatures assure excellent low temperature protection.

POUR POINT

Test Number & Name: ASTM D-97 Standard Test Method for Pour Point of Petroleum Oils.

Significance & Use: The test determines the lowest temperature at which an oil flows as the jar is tilted for a prescribed period. The pour point of an oil indicates the lowest temperature at which an oil may be used in some applications.

What it means: the lower the pour point, the more useful the lubricant is in cold temperatures. AMSOIL synthetic lubricants offer exceptionally low pour points.

FLASH AND FIRE POINTS

Test Number & Name: ASTM D-92 Standard Test Method for Flash and Fire Points by Cleveland Open Cup.
Significance & Use: Flash point is the lowest temperature at which application of a flame causes specimen vapors to ignite. Flash point is used to asses the overall hazard of a material and is used in shipping and safety regulations to define "flammable" and "combustible" materials.
Fire point is the lowest temperature at which a specimen sustains burning for five seconds.

What it means: Lubricants with high flash and fire points, such as AMSOIL synthetic lubricants, are safer to use and transport than lubricants with lower ones and have a greater high temperature operating ranges.

NOACK VOLATILITY

Test Number & Name: ASTM D-5800 Determining the Evaporation Loss of Lubricating Oils (Noack's Method)

Significance & Use: Test determines the evaporation loss of lubricating oils at high temperature. Evaporation loss is particularly important to motor and cylinder lubrication, due to the high temperature of these operations and the tendency of evaporative loss to increase in high temperatures. Significant evaporative loss of oil leads to excessive oil consumption and destructive changes in oil properties.

What it means: Lubricants with low Noack scores, such as AMSOIL synthetic lubricants, lose less to volatility than lubricants with high scores. Low-loss oils keep their original protective and performance qualities longer than high-loss oils do, which keeps oil consumption low and fuel economy and equipment protection high.

HIGH TEMPERATURE/HIGH SHEAR VISCOSITY

Test Number & Name: ASTM D-4683 Standard Test Method for Measuring Viscosity at High Temperature and High Shear Rate by Tapered Bearing Simulator.

Significance & Use: Viscosity at the shear rate and temperature of this test is considered representative of the condition encountered in the bearings of automotive engines in sever service. Lubricant viscosity in the bearings of automotive engines in severe service is a critical factor in bearing wear.

What it means: Lubricants with high scores, such as AMSOIL synthetic lubricants, maintain their viscosity in high temperatures after exposure to high shear. That means they continue to protect engine bearing even after exposure to sever service conditions.

FOUR BALL WEAR TEST

Test Number and Name: ASTM D-4172B Standard Test Method for Wear Preventive Characteristics of Lubricating Fluid (Four-Ball Method).

Significance & Use: Test method determines the relative wear preventive properties of lubricants in sliding contact under the test conditions. Lubricant comparisons are made by comparing the average wear scars on three fixed balls made by one ball in rotating contact with them in baths of the test lubricants.
What it means: The smaller the average wear scar, the better the protection. AMSOIL synthetic lubricants deliver much smaller wear scars - and much better protection - than other lubricants do. The Four Ball Wear Test may be conducted at various levels of severity. Independent laboratory testing shows that AMSOIL Series 2000 and Series 3000 motor oils' wear scars are significantly smaller than those of popular competitor oils in extremely severe test conditions, making these oils ideal for extreme service engine operations.

The essential properties of lubricants and types used in industries:-

Oil Viscosity:

· Technically, the viscosity of an oil is a measure of the oil’s resistance to shear.

· Viscosity is more commonly known as resistance to flow.

· If a lubricating oil is considered as a series of fluid layers superimposed on each other, the viscosity of the oil is a measure of the resistance to flow between the individual layers.

· A high viscosity implies a high resistance to flow while a low viscosity indicates a low resistance to flow.

· Viscosity varies inversely with temperature.

· Viscosity is also affected by pressure; higher pressure causes the viscosity to increase, and subsequently the load-carrying capacity of the oil also increases.

· This property enables use of thin oils to lubricate heavy machinery.

· The loadcarrying capacity also increases as operating speed of the lubricated machinery is increased.

Viscosity index:

· The viscosity index, commonly designated VI, is an arbitrary numbering scale that indicates the changes in oil viscosity with changes in temperature.

· Viscosity index can be classified as follows: low VI - below 35; medium VI - 35 to 80; high VI - 80 to 110; very high VI - above 110.

· A high viscosity index indicates small oil viscosity changes with temperature.

· A low viscosity index indicates high viscosity changes with temperature.

· Therefore, a fluid that has a high viscosity index can be expected to undergo very little change in viscosity with temperature extremes and is considered to have a stable viscosity.

· A fluid with a low viscosity index can be expected to undergo a significant change in viscosity as the temperature fluctuates.

· For a given temperature range, say -18 to 370°C ( 0 - 100°F), the viscosity of one oil may change considerably more than another.

· An oil with a VI of 95 to 100 would change less than one with a VI of 80.

· Knowing the viscosity index of an oil is crucial when selecting a lubricant for an application, and is especially critical in extremely hot or cold climates.

· Failure to use an oil with the proper viscosity index when temperature extremes are expected may result in poor lubrication and equipment failure.

· Typically, paraffinic oils are rated at 38°C ( 100°F) and naphthenic oils are rated at -18°C (0°F).

· Proper selection of petroleum stocks and additives can produce oils with a very good VI.

Pour point:

· The pour point is the lowest temperature at which an oil will flow.

· This property is crucial for oils that must flow at low temperatures. A commonly used rule of thumb when selecting oils is to ensure that the pour point is at least 10°C (20°F) lower than the lowest anticipated ambient temperature.

Cloud point:

· The cloud point is the temperature at which dissolved solids in the oil, such as paraffin wax, begin to form and separate from the oil.

· As the temperature drops, wax crystallizes and becomes visible. Certain oils must be maintained at temperatures above the cloud point to prevent clogging of filters.

ADDITIVES FOR LUBRICANTS :

· The lubricating oil should posses all the above properities for the saticfactory engine
performance.

· The modern lubricants for heavy duty engines are highly refinedwhich
otherwise may produce sludge or suffer a progressive incrase in viscosity.

· For these reasons ,the lubricants are seasoned by the addition of certain oil soluble organic compounds containing inorganic elements such as phosphorus sulphur, AMINE derivatives.

· METALS are added to the minearl baesd lubricating iol to exhibt the desired properties.

· The oil soluble organic compounds added to the present day lubricating to impart one or more of the following characteristics.

Ø Anti-oxidant and anti-corrosive agents

Ø Detergent-dispersent

Ø Extreme pressure addition

Ø Powre point depression

Ø viscosity idex improver

Ø antifoam agent

Ø oilness and film-strength agents.

References:--

http://www.weareoil.com/technical_properties_of_lubricant.htm

http://www.scribd.com/doc/11620108/Properties-of-Lubricants