TERM PAPERFLUID MECHANICS

What are essential properties of lubricants and types used in industries.

SUMITTED BY : RAUSHAN SUDHANSHUSECTION : K4901ROLL NO : RK4901B42REGD : 10901326 SUMITTED TO: HIMANSHU KAUSHAL

AKNOWLELDGEMENT

As usual large number of people deserves my thanks for the help they provided me for the preparation for this term paper.

First of all i would like to thanks my teacher Mr. Himanshu Kaushal for his support during the preparation of this topic. I am very thankful for his guidance.

I would also like to thanks my friends for the encouragement and information about the topic they provided to me during to me during my effort to prepare this topic.

Raushan Sudhanshu

RK4901B42

THE TABLE OF CONTENTS

1-INTRODUCTION

2 – TYPES

3 –PURPOSES

4 – PROPERTIES

5 – USES IN INDUSTRIES

6 -REFERENCES

INTRODUCTIONA lubricant (sometimes referred to as "lube") is a substance (often a liquid) introduced

between two moving surfaces to reduce the friction between them, improving efficiency and

reducing wear. It may also have the function of dissolving or transporting foreign particles

and of distributing heat. A lubricant's ability to lubricate moving parts and reduce friction is

the property known as lubricity.

One of the single largest applications for lubricants, in the form of motor oil, is protecting

the internal combustion engines in motor vehicles and powered equipment.

Typically lubricants contain 90% base oil (most often petroleum fractions, called mineral

oils) and less than 10% additives. Vegetable oils or synthetic liquids such as

hydrogenated polyolefins, esters,silicones, fluorocarbons and many others are sometimes

used as base oils. Additives deliver reduced friction and wear, increased viscosity, improved

viscosity index, resistance to corrosion andoxidation, aging or contamination, etc.

Lubricants such as 2-cycle oil are added to fuels like gasoline which has low

lubricity. Sulfur impurities in fuels also provide some lubrication properties, which has to be

taken in account when switching to a low-sulfur diesel; biodiesel is a popular diesel fuel

additive providing additional lubricity.

Non-liquid lubricants include grease, powders (dry graphite, PTFE, Molybdenum

disulfide, tungsten disulfide, etc.), teflon tape used in plumbing, air cushion and others. Dry

lubricants such as graphite, molybdenum disulfide and tungsten disulfide also offer

lubrication at temperatures (up to 350 °C) higher than liquid and oil-based lubricants are able

to operate. Limited interest has been shown in low friction properties of compacted oxide

glaze layers formed at several hundred degrees Celsius in metallic sliding systems, however,

practical use is still many years away due to their physically unstable nature.

Another approach to reducing friction and wear is to use bearings such as ball bearings, roller

bearings or air bearings, which in turn require internal lubrication themselves, or to use

sound, in the case of acoustic lubrication.

In addition to industrial applications, lubricants are used for many other purposes. Other uses

include cooking (oils and fats in use in frying pans, in baking to prevent food sticking), bio-

medicalapplications on humans (e.g. lubricants for artificial joints), ultrasound examination,

internal examinations for males and females, and the use of personal lubricant for sexual

purposes.

Types:-

There are basically two types of lubricants, petroleum-based and synthetic. Each of these lubricants is suited for particular purposes and conditions. Each is also subject to varying levels of oxidation and degradation and is compatible with only certain types of machinery components, demands, and environments.

Everyone who owns an automobile knows that the engine oil has to be changed regularly to provide longer engine life. The motor oil in an automobile’s engine is commonly a petroleum-based lubricant. Though this type of lubricant contains the samehydrocarbon base as the gasoline used to power the automobile, the formulations are quite different. The hydrocarbon- or petroleum-based lubricating motor oil is designed to protect the various moving parts of the engine, while gasoline, which is also a petroleum product, is formulated to produce the explosive heat needed to power the engine.

Lubricants may be liquid, such as motor oil and hydraulic oil; they may be semi-solid or solid, such as grease or Teflon® tape, or they may be dry, or powdered, such as dry graphite or molybdenum disulfide. All lubricating materials for mechanized equipment are designed to form some sort of protective coating between moving parts of machinery to protect these parts from undue wear, contamination and oxidation.

Synthetic lubricants are precisely engineered chemical reactions on particular components. These reactions are created by specifically applying varying amounts of heat and pressure to the components. Synthetic motor oil is gaining popularity for automobile owners who use it in place of petroleum-based motor oil. Synthetic lubricants are also used more extensively in industry, because, though costlier to use originally, they are better suited to the demands of modern engine and machine technology. Because synthetic motor and machinery oils don’t have to be changed as frequently, consumers actually save in the long run.

There are also petroleum-based and synthetic hydraulic lubricants, also known as hydraulic oils, which are formulated to be lighter and more free-flowing. They are used not only for lubrication, but for the actual operation of hydraulic machinery. Hydraulic oils must be able to flow freely through the pumps that compress the oil for the operation of the machinery, and at the same time, must have the film-forming additives to lubricate the moving parts of the pumping equipment.

In 1999, an estimated 37,300,000 tons of lubricants were consumed worldwide. The majority

was for automobiles, but other industrial, marine, and metal work applications are also big

consumers of lubricants. Although air and other gas-based lubricants are known, e.g. in fluid

bearings), liquid and solid lubricants dominate the market, especially the former. Although

generally lubricants are based on one type of base oil or another, it is quite possible to use

mixtures of the base oils to meet performance requirements.

Vegetable (natural) oils and other naturally derived lubricants

These are primarily triglyceride esters derived from plants and animals. For lubricant base oil

use the vegetable derived materials are preferred. Common ones include high oleic canola

oil, castor oil,palm oil, sunflower seed oil and rapeseed oil from vegetable, and Tall oil from

animal sources. Many vegetable oils are often hydrolyzed to yield the acids which are

subsequently combined selectively to form specialist synthetic esters. Other naturally derived

lubricants include lanolin (wool grease, a natural water repellent).

Whale oil was an historically important lubricant, with some uses up to the latter part of the

20th century as a friction modifier additive for automatic transmission fluid.[3]

Synthetic oils :-

Polyalpha-olefin (PAO)

Synthetic esters

Polyalkylene glycols (PAG)

Phosphate esters

Alkylated naphthalenes (AN)

Silicate esters

Ionic fluids

Solid lubricants:-

Dry lubricant:-

Teflon or PTFE

Teflon(PTFE) is typically used as a coating layer on, for example, cooking utensils to provide

a non-stick surface. Its usable temperature range up to 350°C and chemical inertness make it

a useful additive in special greases. Under extreme pressures, teflon powder or solids is of

little value as it is soft and flows away from the area of contact. Ceramic or metal or alloy

lubricants must be used then.

Inorganic solids

Graphite, hexagonal boron nitride, molybdenum disulfide and tungsten disulfide are

examples of materials that can be used as solid lubricants, often to very high temperature.

The use of some such materials is sometimes restricted by their poor resistance to oxidation

(e.g., molybdenum disulfide can only be used up to 350°C in air, but 1100°C in reducing

environments).

Metal/alloy

Metal alloys, composites and pure metals can be used as grease additives or the sole

constituents of sliding surfaces and bearings. Cadmium and Gold are used for plating surfaces

which gives them good corrosion resistance and sliding properties, Lead, Tin, Zinc alloys and

various Bronze alloys are used as sliding bearings, or their powder can be used to lubricate

sliding surfaces alone, or as additives to greases.

Additives:-

Oil additive:-

A large number of additives are used to impart performance characteristics to the lubricants.

The main families of additives are:

Antioxidants

Detergents

Anti-wear

Metal deactivators

Corrosion inhibitors, Rust inhibitors

Friction modifiers

Extreme Pressure

Anti-foaming agents

Viscosity index improvers

Demulsifying/Emulsifying

Stickiness improver, provide adhesive property towards tool surface (in metalworking)

Complexing agent (in case of greases)

Many of the basic chemical compounds used as detergents (example: calcium

sulfonate) serve the purpose of the first seven items in the list as well. Usually it is not

economically or technically feasible to use a single do-it-all additive compound. Oils

for hypoid gear lubrication will contain high content of EP additives. Grease lubricants may

contain large amount of solid particle friction modifiers, such as graphite, molybdenum

sulfide, etc.

Application by fluid types:-

Automotive

Engine oils

Petrol (Gasoline) engine oils

Diesel engine oils

Automatic transmission fluid

Gearbox fluids

Brake fluids

Hydraulic fluids

Tractor (one lubricant for all systems)

Universal Tractor Transmission Oil – UTTO

Super Tractor Oil Universal – STOU – includes engine

Other motors

2-stroke engine oils

Industrial

Hydraulic oils

Air compressor oils

Gas Compressor oils

Gear oils

Bearing and circulating system oils

Refrigerator compressor oils

Steam and gas turbine oils

Aviation

Gas turbine engine oils

Piston engine oils

Marine

Crosshead cylinder oils

Crosshead Crankcase oils

Trunk piston engine oils

Stern tube lubricants

Other lubricants:-

Lanolin

A natural water repellent, lanolin is derived from sheep wool grease, and is an alternative to

the more common petro-chemical based lubricants. This lubricant is also a corrosion

inhibitor, protecting against rust, salts, and acids.

Water

Water can be used on its own, or as a major component in combination with one of the other

base oils. Commonly used in engineering processes, such as milling and lathe turning.

Marketing

The global lubricant market is generally competitive with numerous manufacturers and

marketers. Overall the western market may be considered mature with a flat to declining

overall volumes while there is strong growth in the emerging economies. The lubricant

marketers generally pursue one or more of the following strategies when pursuing business.

Purposes:-

Lubricants perform the following key functions:-

Keep moving parts apart

Reduce friction

Transfer heat

Carry away contaminants & debris

Transmit power

Protect against wear

Prevent corrosion

Seal for gases

Stop the risk of smoke and fire of objects

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. This is termed

hydrodynamic lubrication. In cases of high surface pressures or temperatures the fluid film is

much thinner and some of the forces are transmitted between the surfaces through

Reduce friction

Typically 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. Lubricants may contain additives known as friction

modifiers that chemically bind to metal surfaces to reduce surface friction even when there is

insufficient bulk lubricant present for hydrodynamic lubrication, e.g. protecting the valve

train in a car engine at startup.

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. The primary drawback

is that high flows typically require larger sumps and bigger cooling units. A secondary

drawback is that a high flow system that relies on the flow rate to protect the lubricant from

thermal stress is susceptible to catastrophic failure during sudden system shut downs. An

automotive oil-cooled turbocharger is a typical example. Turbochargers get red hot during

operation and the oil that is cooling them only survives as its residence time in the system is

very short i.e. high flow rate. If the system is shut down suddenly (pulling into a service area

after a high speed drive and stopping the engine) the oil that is in the turbo charger

immediately oxidizes and will clog the oil ways with deposits. Over time these deposits can

completely block the oil ways, reducing the cooling with the result that the turbo charger

experiences total failure typically with seized bearings. Non-flowing lubricants such as

greases & pastes are not effective at heat transfer although they do contribute by reducing the

generation of heat in the first place.

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. Lubricants for machines that regularly generate debris or contaminants such as

automotive engines typically contain detergent and dispersant additives to assist in debris and

contaminant transport to the filter and removal. Over time the filter will get clogged and

require cleaning or replacement, hence the recommendation to change a car's oil filter at the

same time as changing the oil. In closed systems such as gear boxes the filter may be

supplemented by a magnet to attract any iron fines that get created.

It is apparent that in a circulatory system the oil will only be as clean as the filter can make it,

thus it is unfortunate that there are no industry standards by which consumers can readily

assess the filtering ability of various automotive filters. Poor filtration significantly reduces

the life of the machine (engine) as well as making the system inefficient.

Transmit power

Lubricants known as hydraulic fluid are used as the working fluid in hydrostatic power

transmission. Hydraulic fluids comprise a large portion of all lubricants produced in the

world. The automatic transmission's torque converter is another important application for

power transmission with lubricants.

Protect against wear

Lubricants prevent wear by keeping the moving parts apart. Lubricants may also contain anti-

wear or extreme pressure additives to boost their performance against wear and fatigue.

Prevent corrosion

Good quality lubricants are typically formulated with additives that form chemical bonds

with surfaces to prevent corrosion and rust.

Seal for gases

Lubricants will occupy the clearance between moving parts through the capillary force, thus

sealing the clearance. This effect can be used to seal pistons and shafts.

4. Properties of lubricants:

1. Viscosity: Viscosity is the property of a fluid that determines its resistance to flow. It isvan indicator of flow ability of a lubricating oil, the lower the viscosity, greater the flow ability. If temperature increases viscosity of the lubricating oil decreases. And pressurevincreases, viscosity of the lubricating oil increases.2. Viscosity index: The rate at which the viscosity of oil changes with temperature is measured by an empirical number, known as the viscosity-index. A relatively small change in viscosity with temperature is indicated by high viscosity index. Whereas a low viscosity index shows a relatively large change in viscosity with temperature.3. Flash and fire point: The flash point of oil is the lowest temperature at which it gives off vapors that will ignite for a moment when a small flame is brought near it. The fire point of an oil is the lowest temperature at which the vapors of the oil burn continuously for at least 5 seconds when a small flame is brought near it. The flash and fire points are used to indicate the fire hazards of petroleum products and evaporation losses under high temperature operations. Knowledge of flash and fire points in lubricating oil helps to take preventive measures against fire hazards.4. Cloud and pour point: The cloud point of petroleum oil is the temperature at whichsolidifiable compounds, like paraffin wax, present in the oil begin to crystallize or separate from solution. The pour point of petroleum oil is the temperature at which the oil ceases to flow or pour.Cloud and pour points indicate the suitability of lubricants in cold conditions.5.Aniline point: Aniline point is defined as “ the minimum equilibrium solutiontemperature for equal volume of aniline and oil sample”. A lower aniline point of an oilmeans a higher percentage of aromatic hydrocarbons in it. Aromatic hydrocarbons have atendency to –dissolve natural rubber and certain types of synthetic rubbers. Thus goodlubricating oil should have higher aniline point.Aniline point gives an indication of the possible deterioration of oil in contact withrubber sealing, packing, etc. Aromatic hydrocarbons have a tendency to dissolve natural

rubber and certain types of synthetic rubbers. Consequently, low aromatic content in thelubricants is desirable. A higher aniline point means a higher percentage of paraffinhydrocarbons and hence a lower percentage of aromatic hydrocarbons.Aniline point is determined by mixing mechanically equal volumes of the oil sample andaniline is a tube. The mixture is heated, till homogeneous solution is obtained. Then thetube is allowed to cool at a controlled rate. The temperature at which the two phases (oil

and aniline) separate out is recorded at the aniline point.

General composition:-

Lubricants are generally composed of a majority of base oil and a minority of additives to

impart desirable characteristics.

REFERENCES:-

www.wikipedia.org

www.stle.org/assets/document/ Lubricant _Selection

www.leo lubricants .com