Soldering, Brazing , Welding, Lubrication, Bearings, Power Transmission

7/28/2019 Soldering, Brazing , Welding, Lubrication, Bearings, Power Transmission

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CHAPTER 5

Soldering, Brazing , Welding, Lubrication, Bearings, Power transmission

INTRODUCTION

Some products cannot be manufactured as a single piece. The desired shape and size ofsuch products can be obtained by joining two parts of same or different materials. These parts are

manufactured individually and are joined together to obtain the desired product. For example, aircraft and ship bodies, welded machine frames, furniture, computers, bridges and the transmission

or electric towers etc., are all fabricated by joining several different parts.

Based on the type of joint produced joining processes can be classified as1. Temporary Joint.2. Permanent Joint.

If a product is in use for a long time and there is wear and tear, the parts need to bedismantled for maintenance, repair or replacement. A temporary joint can be easily dismantled

by separating the original parts without any damage to them. In case it is a permanent joint, anattempt to separate the parts already joined will result in the damage of the parts. In a permanent

joint, the joint is made such that it has properties similar to the base metal of the two parts. Thejoined parts become one piece. These parts cannot be separated into their original shape, size and

surface finish. Based on the process used for making the joint, the joining processes can befurther classified as

1. Soldering.2. Brazing.3. Welding.4. Mechanical Fasteners like bolts, nuts, rivets, screws etc.5. Adhesive bonding.

Mechanical fasteners are most widely used for temporary joints. Joints obtained by boltsand screws are temporary in nature and can be dismantled easily whenever necessary. Rivets are

semi-permanent fastening devices and the joint can be separated only by destroying the rivetwithout affecting the parent elements.

Adhesive bonding has generally less strength than the mechanical fasteners. But adhesivebonding is used to join odd shaped parts or thin sheets which may not lend themselves to

mechanical fastening.Brazing and soldering are considered to form permanent joints, but for repair or

replacement these joints can be dismantled by heating.Welding is one of the most extensively used fabrication method. The joint strength

obtained in welding is being equal to or some times more than that of the parent metal. Weldingis not only used for making structures, but also for repair work such as the joining of broken

castings. The choice of a particular joining process depends on several factors such asapplication, nature of loads or stresses, joint design, materials involved and size and shape of the

components.


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SOLDERING

Soldering is a method of joining similar or dissimilar metals by the application of heatand using a filler metal having a melting point not exceeding 427

oC and below the solidification

temperature of the base metals. The molten filler metal is made to flow between the two closely

placed adjacent surfaces by the capillary action.

Though soldering obtains a good joint between the two plates, the strength of the joint is

limited by the strength of the filler metal used. Soldering is used for obtaining a leak proof jointor a low resistance electrical joint. The soldered joints are not suitable for high temperature

applications because of the low melting temperatures of the filler metals used.

Fluxes are defined as any solid, liquid or gaseous materials, which, when heatedaccelerate the wetting of metal with the solder. Due to wetting molten solder flow into the joint

and fills the space between the two pieces to be soldered. At elevated temperature flux is highlyreducing in nature preventing the formation of metal oxides. Fluxes that are generally used in

soldering are Rosin, Zinc Chloride and Aluminum Chloride.

The purpose of using the flux is to prevent the formation of oxides on the metal surfacewhen the same is heated. Electric soldering iron is used to supply the heat to melt the solder. The

filler metals used are essentially alloys of lead and tin. The composition of solder used fordifferent purposes are as given below

Soft solder - lead 37% tin 63%

Medium solder - lead 50% tin 50%Plumbers solder - lead 70% tin 30%

Electricians solder - lead 58% tin 42%

Soldering is classified into soft soldering and hard soldering.Soft soldering is used extensively in sheet metal work for joining parts that are not

exposed to the action of high temperatures and are not subjected to excessive loads and forces orvibrations. The melting range of soft solder is 150 to 200

0C. Soft soldering is also employed for

joining wires and small parts. In soft soldering, Zinc chloride and ammonium chloride are themost common soldering fluxes used which are quick acting and produce efficient joints. These

are to be used only for non-electrical soldering work. Rosin and rosin plus alcohol based fluxesare least active type and are generally used for electrical soldering work.

Hard soldering process is called silver solder brazing. The melting point of the hardsolder is in the range of 350

oC and above. This process gives greater strength and withstands

more heat than soft solder. Hard solder is an alloy of copper and zinc to which silver is addedsome times. German silver, used as a hard solder for steel is an alloy of copper, zinc and nickel.

Sequence of operations:

The following operations are required to be performed sequentially for making soldered joints.

1. Shaping and fitting of metal parts together: The two parts to be joined are shaped to fitclosely so that the space between them is extremely small and filled completely with


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solder by capillary action. If a large gap is present, capillary action will not take place andthe joint will not be strong.

2. Cleaning of surfaces: In order to obtain a sound joint, the surfaces to be soldered arecleaned to remove dirt grease or any other foreign material.

3. Application of flux: The flux is applied when the parts are ready for joining.4.

Application of heat and solder: The parts are held in a vice or with special work holdingdevices so that parts do not move while soldering.

A soldering iron has a copper bit tapered to form an edge at its end. The soldering iron isheated to desired temperature; its surface is cleaned and then dipped in a mass of flux followed

by the application of solder. This enables the solder to melt and spread over the hot surface of thebit to form a coating over it. This operation is known as tinning. After this, the bit is again dipped

in the flux to remove the oxides from its surface, if any, and then in the solder again to pick upits required quantity. It is then ready for application to the work. The solders which have low

percentage of tin have a higher melting point.

Advantages:1. The process is done at low temperatures hence, no metallurgical damage to the basemetal.

2. Simple heating of the solder can dismantle the soldering joint.3. It is cost effective

Disadvantages:1. The strength of the joint is not good compared to welding.2. Flux material has to be cleaned after soldering, as most of the fluxes are corrosive in

nature.

BRAZING

Brazing is a process of joining similar and dissimilar metals where in coalescence is

produced by heating to suitable temperatures above 5000

C and by using a non-ferrous fillermetal having a melting point (up to 900

0C) below that of the base metal. The filler metal is

distributed between the closely fitted surfaces of the joint by capillary action. Brazing gives amuch stronger joint than soldering. The principal difference is the use of a harder filler material

commercially known as spelter. Filler metals used in this process may be divided into copperbase alloys and silver base alloys. The spelter is usually an alloy of copper, zinc and tin. Both

can be joined.

Brazing procedure: The metal to be joined is cleaned for oxides, dust and oil. Fluxes areapplied on the entire surface where the brazing is carried out. The parts are aligned in position

for brazing. The joint is heated using a gas torch with a Carburising flame. Filler metal is addedinto the space where the metal is to be joined. Due to the wetting action of the flux, the molten

filler metal fills the space by capillary action. The joint is allowed to cool and then the fluxes arecleaned from the surface.

Borax is the most widely used flux. Other fluxes used are mixtures of borax, boric acid,fluorides and chlorides. Brazing is a much widely used joining process in various industries


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because dissimilar metals, such as stainless steel to cast iron can be joined by brazing. Almost allmetals can be joined by brazing except aluminium and magnesium. Because of the lower

temperatures used there is less distortion in brazed joints.Silver brazing makes use of a silver based filler metal. Silver brazing is used to give high

strength joints. Though originally used for jewellery applications, silver brazing is now

extensively used in industrial applications. They can be used with a large range of materials, butbecause of its high cost it is used in only special applications requiring high strength and hightemperature service.

Advantages:

1. It can be used to join dissimilar metals.2. It provides good pressure tight joints.3. Different cross sectional thickness material can be brazed.4. Brazing avoids metallurgical damage to the metal.

Disadvantages:

1.

Size limitations of the parts to be brazed - as the outer area has to be elevated to thehigher temperature, in large sections increasing the temperature is difficult.

2. Tight mating parts are necessary for capillary action.3. Fluxes are corrosive in nature, they have to be cleaned properly after brazing.

Applications of Brazing:

Brazing has been used to manufacture a wide variety of products such as Honey combsandwich panels for aircraft missiles, motor cycle frames, air plane propellers, Hydraulic fitting,

refrigerator evaporators, manufacture of cutting tools etc.,

WELDING

Welding is a metallurgical process of joining two pieces of metals by the application of heat withor without the application of pressure and addition of filler metal. The joint formed is a

permanent joint. Heat may be obtained by chemical reaction, electric arc, electrical resistance,frictional heat, sound and light energy. If no filter metal is used during welding then it is termed

as Autogenous Welding Process'.The welding process can be classified based on the source of energy to heat the metal and the

state of metal at the joint.

1. Pressure Welding2. Fusion Welding

In Pressure welding process the surfaces of the joint to be welded is heated to a plastic

state and forced together with external pressure to finish the joint. Pressure welding depends onthe application of pressures and temperatures, resulting in a plastic state with local deformation

of the pieces to be joined in the weld area so that a bond between both pieces is made. Thisprocedure is used in forge welding, resistance welding, spot welding in which pressure is

required.


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In the fusion welding, the pieces to be joined are heated to molten state and allowed tosolidify to form joint with or without the addition of filler material. The process is carried out

without the application of pressure. This includes gas welding arc welding and Thermit welding.

The most effective classification based on pressure and fusion welding is shown in the figure 5.1

Fig. 5.1

Welding Electrodes

It is a piece of rod or wire, which is made of metal or alloy, with or without flux coated. Theelectrode at one end is connected to the electrode holder and at other end arc is set up. Electrodes


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come in different diameter and length. The diameter and length depends upon the amount ofweld to be deposited and the type of joint to be welded. Generally thin and large diameter

electrodes are of short lengths and medium size electrodes have bigger lengths. The types ofelectrodes that are generally used for welding are:

Consumable Electrode it melts and supplies filler metal to the weld.

Non Consumable Electrode - it does not melt but separate filler metal is to be added to the

weld.

Consumable ElectrodeIt is made of low melting point metal or alloy. When arc is struck electrode starts to melt

and transfer to the work piece in the form of droplets. These droplets fill the space between thetwo metals to be joined. The thermal efficiency of consumable electrode system is about 85%

when compared to non-consumable electrode of 55%. Consumable electrodes can be furtherclassified into bare electrodes and flux covered electrodes.

Bare electrodes are those, which consist of metal or alloy wire without any flux coating.

Flux covered electrodes are those which have flux covering the metal or alloy. The flux acts as

a shield to protect the arc and also to protect the weld pool. Flux when it gets melted during arc,forms a inert gas shield around the arc and the chemical present reacts with the molten metal to

form slag. .

Non Consumable ElectrodesThese electrodes are made up of high melting point metals like carbon, pure tungsten etc.

These electrodes do not melt during welding process. They generate arc, which melts the workpiece. Generally these metals do undergo vaporization and oxidation during welding. In this kind

of welding filler material addition depends upon the thickness of the plate to be welded.

ARC WELDINGArc welding is a method

of joining metals withheat produced by an

electrical arc. Theworkpieces are made

part of an electriccircuit, known as

welding circuit. Atypical arc welding

setup is shown in Figure5.2

1. An arc weldingcircuit consists

of a power supply to furnish electric power. Fig 5.2 Metal Arc Welding Circuit2. An electrode to conduct the electricity to the arc.


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3. Cables which connect the power supply to the electrode and workpiece to complete thewelding circuit.

4. The arc itself provides the heat for welding.5. The workpiece to weld is kept on a metallic table.

In this process the heat necessary to melt the edges of the metal to be joined is obtained from anelectric are struck between a flux covered stick electrode (filler rod) and the workpieces,producing a temperature of 4000

0C, in the welding zone. The heat of the arc melts the base metal

or edges of the parts fusing them together. Figure 5.3 shows the fine molten droplets of metaland molten flux coming from the tip of the coated electrode. The flux melts along with the

metallic core wire and goes to weld pool where it reacts with molten metal forming slag whichfloats on the top of molten weld pool and solidifies after solidification of molten metal and can

be removed by chipping and brushing. The weld metal cools and solidifies to form the weld. Inmost cases, the composition of the filler material, known as welding rod, needed to provide extra

metal to the weld, is same as that of the material being welded. Welding power sources used maybe transformer or rectifier for AC or DC supply. The requirement depends on the type of

electrode coating and sometimes on the material to be welded.

Fig 5.3: Molten Metal and Flux Transfer to Weld Pool

Advantages:1. As a manual process it is applicable to an infinite variety of work and can be executed in

any position.2. There is less buckling and warping of the work.3. It produces strong sound and ductile welds.4. Satisfactory welds can be produced in heavy as well as in light sections.5. Low cost process.


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6. Excellent joint properties can be obtained in mild, low alloy and stainless steels, nickeland copper-base alloys.

7. Low accuracy in setting up required.Disadvantages:

1. Basically a manual process requiring adequate operator skill for good results.2.

Electrodes require frequent changing.3. Multi run welds necessary on thick plate-slag chipping necessary after each run.

4. The principal disadvantage has been the high heat of the metal arc which makes itunsuitable for use on materials less than 1.55 mm thick.

5. High initial cost of welding equipment.GAS WELDING

Gas welding is a fusion welding process, in which a flame produced by the combustion ofcombustible gas with oxygen is employed to melt the metal. Required gas

ratio is mixed in the hand held torch. Combustion takes place at the nozzleor the outlet of the torch. The molten metal is allowed to flow together thus

forming a solid continuous joint upon cooling. This process of welding isgenerally known as Oxygen Fuel Gas welding (OFT). A typical

arrangement is shown in Figure 5.4. The equipments for a gas welding aregas cylinders, pressure regulating valves, gas hoses and fittings, flash back

arrestors and blowpipes or welding torch,

Figure 5.4: Gas Welding EquipmentAcetylene produces high heat content in the range of 32000 C than other fuel gases. Acetylene

gas has more available carbon (92.3 %) and hydrogen (7.7 %) by weight. The heat is releasedwhen the carbon breaks away from hydrogen to combine with O2 and burn.

C2H2+O2 = 2CO+H2+HeatThe oxy-acetylene flame is used to pre heat the parts to be welded around the joint and

also to melt the filler metal. A jet of oxy acetylene flame issuing from the nozzle of a burner isplayed on the junction of the two pieces to be welded. At the same time a filler rod is held in the

zone of jet and its melt is deposited on the fused junction. A weld is obtained after the moltenmetal solidifies. The coating on the filler rod acts as a flux to keep the joint clean. The filler

metal or filler rod used must combine with the parts being joined. The melting point of the fillermetal must be the same or lower than the melting point of the metal being joined.


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Fig. 5.5. Blow torch

Types of Flames

The correct adjustment of the flame is very important for reliable works. One volume ofAcetylene gas requires 2.5 times the volume of oxygen for its complete combustion. Depending

upon the ratio of oxygen supplied for combustion we can classify flames into 3 types. This ratiois known as gas ratio. These flame types have a great effect on the melt pool chemically. There

are 3 types of flames and they are-(i) Neutral Flame,

(ii) Carburising flame, and(iii) Oxidizing Flame.

(i) Neutral Flame

Neutral flame is the one that is used the most. This flame is obtained by supplying equal volumesof oxygen and acetylene. Its zones of combustion can distinguish the flame. The innermost zone,

the cone, is white in color and extends a short distance from the tip of the torch. Acetylene burnsin this zone to form carbon monoxide and hydrogen. The approximate temperature of the inner

cone is 32000

C. The outer cone or envelope is faintly luminous and bluish is color. Carbonmonoxide and hydrogen burn with oxygen to form carbon dioxide and water vapour and henceprevents the atmospheric oxygen from coming in contact with the molten metal pool.

Fig. 5.6 Nuetral flame.

(ii) Carburising Flame

In this flame acetylene proportion is increased in the gas ratio of 0.95 to 1.0. The flame has threezones a) inner white zone b) intermediate whitish cone and c) bluish outer envelope. The inner

zone is sharply defined and white in color. In this zone there is insufficient oxygen to burnsurplus acetylene. Cone temperature is approximately about 3100

0C. The remaining acetylene

continues to the second zone known as the intermediate cone of whitish color. This intermediatezone extends in length depending up on the amount of acetylene present in the gas. The inner


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Fig. 5.7 Carburizing flame.(iii) Oxidizing FlameIn this flame there is excess of oxygen. The flame has

a small inner cone and outer envelope. The inner cone is not sharply defined as in neutral flameand carburising flame. The inner cone is purplish is color. The temperature of the inner cone is

approximate of 33500

34000

C.

Fig. 5.8 Oxidizing flame.

Advantages:

1. The equipment is in expensive in complicated and it is easily portable.2. Useful for welding light metals such as automobile bodies and repair works.3. A large variety of material can be welded.4. Welds can be produced at reasonable cost.5. Compared to electric arc welding this provides greater flexibility with respect to heat

impact and cooling rates.

Disadvantages:

1. Gas welding equipment must always be handled carefully as in certain circumstancesacetylene is explosive (when a flame is applied under pressure) as oxygen when used in

an oily atmosphere (such as an olds dirty garage floor pit).2. A high temperature flame from a hand held torch is dangerous when handled carelessly.3. It is much slower than electric arc welding and does not concentrate the heat close to the

weld. Thus, the heat treated area is larger, which causes more distortion.

4. Highly skilled operators are required to produce a good weld.5. If electric arc welding is available gas welding is seldom used for work over 3.2mm

thick.6. The process is not satisfactory for heavy section

Soldering Brazing

ln case of Soldering, the metals are joined with

the help of a filler metal with a low meltingpoint, below 450o C, and below the melting

point of the metals to be joined.

In case of Brazing, the filler metal has

a melting temperature of more than450'C and up to 1000" C

Weaker joints compared to Brazing. Stronger joints compared to Soldering.


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The typical Solder filler metals are alloys of

tin.

The typical filler metals for Brazing are

Aluminium, Silver, Copper, Nickel and Gold.

The flux used is usually Rosin. The flux used is usually Borax.

Economical Process Not as economical as Soldering

Usually suitable process to join metals with

small thicknesses.

Suitable Process even for joining metals of

larger thicknesses.

Brazing Welding

In case of Brazing, the metals to be joined arenot melted and the joint is produced through

the solidification and adhesion of a thin layerof molten filler metal.

In case of Welding, the surfaces joined aremelted.

There is no penetration into the base metal. There is penetration into the base metal.

The molten Brazing filler alloy spreads along

the joint

The molten Brazing filler alloy does not spread

along the joint and soldifies where it melts.

Relatively weaker joints. Relatively stronger joints are produced.

Average operator skill level is required. High Operator Skill and Experience.Not as econornical as Welding Economical compared to Brazing.

Soldering, Brazing Welding

No direct melting of the base metals being

joined

Direct melting of the base metals being joined

Useful for joining similar & dissimilar metals Useful for joining similar metals

Brazing alloy and the solder have low meltingpoints than the metals to be joined

Welding alloy has high melting point than themetals to be joined

Filler materials are solder and brazing alloy(spelter)

Welding rod is used as filler material

LUBRICATION

Friction is the resistance between the two surfaces in contact. Any substance placed between anytwo rubbing surfaces, which reduces friction is called lubricant.

The important functions of lubricant in bearings are:

1. To reduce friction between the sliding surfaces by separating them with thin film of oi1.2. To reduce wear and thereby increasing the life of bearing.

3. To remove the frictional heat from the bearing.4. To provide protection against corrosion.

Types of lubricantsLubricants are classified into the following three groups:(i) Liquid: The liquid lubricants generally used in bearings are mineral oils, synthetic oils or

animal and vegetable oils. The mineral oils are the most commonly used because of their lowercost and stability. Liquid lubricants are usually preferred where they may be retained.

(ii) Semi-liquid: Grease is a semi-liquid lubricant having higher viscosity than oils. Grease isemployed where slow speed and heavy pressure exists and where oil drip from the bearings is

undesirable. They are used because of their good adhering and higher fluidity characteristics.


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They are used in high speed machineries and transmission systems where good recirculation ofthe lubricant is an essential. They can be compounded with a variety of additives to impart

properties such as viscosity, surface tension, heat carrying capacity, ability to withstand highertemperatures, etc.

(iii) Solid: Solid lubricants are useful in reducing friction where oil films cannot be maintained

because of pressure or temperature. It is used in powder form in liquid carriers. They should besofter than materials being lubricated. Graphite is the most common solid lubricant. Other solidlubricants are soapstone, talc, wax, mica, French chalk, etc.

Properties of lubricants

The following are the important properties of a lubricant1. Viscosity: Viscosity is a measure of internal resistance of fluid to shear and indicates its

relative resistance to flow. When the oil is used as a lubricant, its viscosity is important becausethe load carrying capacity is proportional to the viscosity. High viscosity oil can support heavier

loads and has more internal friction. Viscosity decreases with an increase in oil temperature. It isdesirable that the change of viscosity with temperature kept to a minimum.

2. Flash point: Flash point is the minimum temperature at which an oil gives off sufficientvapour to ignite momentarily on introduction of a flame. A good lubricant should have the flash

point above the operating temperature.3.Fire point: Fire point is the lowest temperature at which oil gives off sufficient vapour to burn

continuously for at least five seconds on the introduction of a flame.4.Pour point: Pour point is the lowest temperature at which oil ceases to flow when cooled.

5.Cloud point: Cloud point is the temperature at which oil becomes cloudy in appearance whencooled.

6.Oiliness: Oiliness is the ability of oil to maintain an unbroken lubricating film between therubbing surfaces.

7.Volatility: When working temperatures are high, some oils vaporize leaving behind a thickresidual oil having different lubricating properties like increased viscosity. A good lubricant

should have low volatility.8.Carbon Residue: Lubricating oils combined higher percentages of carbon in the combined

form. At higher temperatures they decompose depositing a certain amount of carbon. Thedeposition of carbon deposits on the bearing surfaces is highly objectionable, hence a good

lubricant should not deposit carbon when used at high temperatures.

Requirements of a good lubricant1. It must have sufficient viscosity to buildup the necessary pressure to keep the solid surfaces

apart.2. Minimum film strength.

3. High flashpoint and fire point.4. Non-volatile.

5. Free from the corrosive acids.6. It should have physical stability with regard to temperature and pressure.

7. Chemical stability against oxidation.8. Proper fluidity at low temperatures.

9. Resistance to emulsion.


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Lubricator: A lubricator is a device used to supplylubricant continuously and at a regulated rate. Some

of the important types of lubricators are discussedbelow:

1. Screw-Cap Lubricator: The screw cap lubricatorconsists of a lubricator body containing grease whichis covered by a cap over it. The lubricator is attached

to the bearing or a machine part to be lubricated bythe help of a threaded nipple. The turning of the cap

forces the grease to flow through the hole onto thesurfaces to the lubricated. This type of lubricator is

used for applying heavy grease where it is notpossible to maintain an oil film between the surfaces

to be lubricated or when the load on them is veryhigh.

2. Tell-Tale Lubricator: A tell-tale lubricator is the

improved form of a screw cap lubricator. The greaseis taken in a container and is then screwed down on

the body of the lubricator. An adjusting screw, witha vertical slot cut in it from the bottom to three-

quarter of its length, is screwed into the hole. Thehole itself is slightly countersunk. The turning of the

container causes the grease to move towards the topportion of the container. This causes the spring

loaded piston to move up in the cylinder. Thepressure on the grease due to spring force, forces out

the grease to the surface to be lubricated. Themovement of the piston rod end indicates whether

the lubrication is in progress or not. This lubricator iscalled 'tell-tale' because, the position of the knob

tells whether the lubrication is in progress or not.This is best suited in cases which require a regulated

and continuous supply of grease flow is to be alwaysmaintained.

3. Drop Feed Lubricator:

A drop feed lubricator is used for oil lubrication. Itconsists of a glass cylinder containing lubricating oil.

The oil is renewed through a filler hole which isclosed by the sliding cover. The glass cylinder is

mounted a lower cover which is screwed on ascrewed plug. The screwed plug has a conical hole

and is normally closed by a needle which is held inposition by the spring. When the snap lever is raised


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to the vertical position as shown by dashed lines in thefigure, the needle will be lifted and the oil flows

through the two oil entry holes provided immediatelyabove the conical hole and then down through the

conical hole and the noz.zle. The flow of oil is seen

through the sight glass. The lubricator is mountedover the part to be lubricated with its threaded endscrewed in place.

4. Glass-Bottle Needle Type lubricator:

A glass-bottle needle type lubricator consists of aninverted spherical glass bottle containing the oil with

a wooden stopper inserted into its neck. A hole isdrilled through the stopper and a needle of uniform

diameter passes through this hole with its lower endresting on the curved surface of the rotating shaft. The

needle is fitted loose in the hole in the stopper. Thelower end of the needle will be resting on the

periphery of the shaft. When the shaft is running, theneedle, due to vibration moves vertically up and down

which enables the oil to flow down through thenarrow annular space between the needle and the

stopper. When the shaft stops rotating, the oil flow also ceases.The oil is retained by the capillary action. The oil flow can be

increased by filing the needle.

5. Syphon Wick Lubricator:A syphon wick lubricator consists of a reservoir having a

central tube. The lubricating oil is filled to a level slightlybelow the tip of the central tube. A wick runs from the oil

reservoir to a considerable depth down in the central tube. Thewick gets soaked in the oil by the capillary action till it is

saturated. Gravity and vibration cause the oil to drip off fromthe lower end of the wick within the tube. The part of the wick

within the tube is carried on a piece of twisted wire. Theamount of oil flow can be adjusted by altering the length of the

wick dipped in the oil or by tightening the twisted wire whichis wound on it. When the machine is stationary the wick is

withdrawn and left in the oil reservoir until required again. Thismethod of lubrication has two main advantages. One is that the oil is filtered and consequently

no dirt is transmitted by the wick; the other, in some cases the feed can be procured from a wellor a gear-box not necessarily situated close to the bearing shaft.

6. Ring Oil Lubricator:

Ring oil lubricator consists of an oil well maintained just below the shaft to be lubricated. Ametallic ring is placed encircling the shaft so as to dip partly in the oil sump. When the shaft


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rotates the ring also rotates and carries the oil with it andlubricates the shaft. This type of lubricator is generally

used in the main bearings supporting the crankshaft ofengines.

7. Splash Lubrication:This method of lubrication is generally employed in I.C.engines to lubricate the cylinder, piston, etc. The splash

method of lubrication may also be used for gears, chains,bearings and other moving parts that can be partly

submerged in an oil reservoir. The crank partly dipsinto the oil sump in the crankcase. As the crankshaft

rotates, it continuously splashes the surfaces of thecylinder, piston, etc. This method of splashing is

employed to lubricate the gear wheels in gearbox.

8. Full Pressure Lubrication SystemAll Car engines have the full-pressure Lubrication

System. This system uses a gear pump to draw the oilfrom an oil sump through a strainer (which is used to

filter unwanted particles). This pumped oil passesthrough a filter and then encounters a relief valve. The

relief valve "relieves" extra oil pressure, if any andreturns the oil to the oil sump. The oil now flows

through the drilled passages to the main bearings.From here, some amount of oil falls back to the sump,

while the rest of the amount passes to the crankpinsthrough a hole which is then led to the piston pins

through a hole drilled inside the connecting rod asshown in the figure. After lubrication, oil falls back to

the sump and the cycle repeats. The full pressurelubrication system is a better method of lubrication

compared to the splash type as lubrication isdistributed uniformly to all required parts. Thus,

through this system, the engine life extends.


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Documents

Soldering, Brazing , Welding, Lubrication, Bearings, Power Transmission