dsl eng comp

8/12/2019 Dsl Eng Comp

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Self.assessment

INTRODUCTION

This unit contains) in brief) the essential details in respect of design) construction)working principle and maintenance procedure of the Diesel Engine components" The

discussion has been kept confined to standard locomotives of $ndian *ailways that is

/DM0""

The Diesel engines consists of following major components + assemblies: .

-"Engine base 0"Engine

block

1"Crank

shaft

2"Cam shaft

3"Cylinder headand 4alves

5" 'iner 6"(iston) Piston rings andConnecting rods.

ENGINE BASE :-

/hen diesel engines were of low speed and low horse power the engine base and

blocks were made of heavy cast iron casting" $n older types engines one of the main

functions of the base was to take the crank shaft" $n the modern engines the crankshaft is underhung from the engine block"

/ith the development in diesel engines and with the change in design) fabricatedengine blocks and bases are finding favour though in some small horse power engines

cast iron blocks are still in use" The engine 7base of !'C8 'ocos /DM0) /DM2

are made from weldable uality steel to specification $S.0950 with 9"0 of carbon"

The engine bases of !'C8 'ocos have following functions"

$t has to .

a; Support the engine block b; Serve as oil sump

c; !ccommodate lube oil mainheader

d; Take lub oil pump and water pump at the free end

e; !llow openings for crank case inspection f; Take fitment of crank case e


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is machined smooth and a sealing compound is applied before fitting the block to make

the crank case air tight so that crank case vacuum can be maintained"

EDM2 'ocos is same as that of

/DM0 in respect of material and manufacturing techniue"

$n case of /DS2% Engines there is no separate base" The function of oil sump is

performed by fabricated steel sheet fitted at the bottom of the block with gasket in

between"

ENGINE BLOCK

The engine block is the most important and very highly stressed structure on

which are fitted a number of important fittings like crank shaft) cam shaft) cylinder heads,

cylinder liners) pistons, Con" *ods) fuel injection pumps and cross.head) turbo support)

governor etc to form a complete (ower pack"

Manufacturing (rocess

This structure is fabricated from low carbon steel to specification $S.0950" The

saddle) however) is a forging out of steel to specification $S.-?63" The fabrication is done

in a definite seuence to minimi=e distortion and build up of stresses" $n order to ensurethat best uality of fabrication is done in all cases down hand welding is resorted to" #or

this purpose e


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!fter the inspection the bearing caps are assembled and they are tightened to the

specified torue value" Subseuent to fitting of the caps to the block the engine block is

placed on the hori=ontal boring cum milling machine" 8n this machine) end face milling isdone and boring of main bearing housing and camshaft bearing is done in one setting with

the help of a fiDM2B/DS5 engines base and block is almost the same as /DM0 block e


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Measure cam bearing dimension and change bearing) if necessary"

Main %earing $nspection:

-" Check serration of saddle and MB %earing cap by serration gauge"

0" #it main bearing cap and elongate properly upto "929A as per laid

down procedure"

1" Measure each bore at two different planes A away from both sidesand in each plane at 1 different locations) vertical and at 23angular

position at both sides of it"

Difference in readings at a particular plane gives the value of

ovality limit 9"991A;

Difference in vertical readings gives the value of vertical taperlimit 9"99-AF"

GDifference in angular readings gives value of angular taper limit

9"991A;

Concentricity of Main %earing bore should be maintained within

the following limit:

&ori=ontal misalignment: -; between adjacent bores: 9"990A

0; %etween any to any: 9"992A

4ertical misalignment: -;!djacent 9"99-3A

0;%etween any to any 9"991A

Misalignment is checked with the help of Mandrel and filler gauge"

/hile assembling) block and base should be perfectly aligned within thelimit Hen end: 9"999A) side ways: 9)990A ma


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The !'C8 crankshafts are manufactured from chrome.molybdenum steel

euivalent to S!E 2-29" The process of forging is such that continuous grain is

maintained" $n manufacture of crankshaft) following seuence of operation is generallyfollowed: -

a; #orging and forming operation

b; *ough machining

c; Drill of oil holes"

d; Jltrasonic + Mechanical testing

e; /elding of counter weights + their @.ray test"

f; Stress relieving + shot blasting

g; #inal machining + for giving fillet radius at crank journal corners and making oil holes"

h; Kitriding

i; Hrinding 'apping

j; Static + dynamic balancing

k; #inal inspection

There are two processes of surface hardening with details given below:.

Method of hardening &ardness Depth of hardness

$nduction hardening C.29 9"-02A

Kitriding C.59 9"9-0 to 9"9-3A

Henerally for low &( engines the first process is preferred) as depth of case is more and

the crank journals and man bearing journals can be ground down to ne


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location) measure the dimension as that of crank pin"

Kominal Dia: ?"3A) 'imit upto ?"2L5A

8vality:990A ma


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-0 9NC'8C,

0 "9913 T$*

1

- 1 8NC'8C,

Crank web delection: Checking of crank web deflection is one of the majorworks while assembling engine"

Main generator is coupled at one end of the crankshaft) whose other end is

supported on a bearing housed at the magnet frame" !s such) due to

mislocation of magnet frame) if a


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c; 4alve Timing

*otate the crankshaft and bring the corresponding cylinder to compression

stroke ensure compression stroke by feeling free rotation of push rods";

Check the gap between the valve stem and yoke" $t should be 9"912A" $f not

adjust it through valve lever adjustment nut and yoke adjustment nut"d; #$( Timing

*otate the engine to bring the injection point against the corresponding

cylinder"

Match the body cut mark of #$( at inspection window with the given line

mark on guide cup "$f not) adjust it through timing allenscrew provided at

the bottom of the #( lifter"

C>'$KDE* &E!D

The cylinder head is held on to the cylinder liner by seven hold down studs or

bolts provided on the cylinder block" $t is subjected to high shock stress and combustion

temperature at the lower face) which forms a part of combustion chamber" $t is acomplicated casting where cooling passages are cored for holding water for cooling the

cylinder head" $n addition to this provision is made for providing passage of inlet air and

e


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Material co!position:

Total carbon 1"99 to 1"29

Silicon -"?9 to 0"09%.

Sulphur 9"-0 to 9"?"

(hosphorous 9"-3 Ma


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leakage at no==le sleeve) ferrule) core plugs and combustion face"

Dimensional checks :

a; #ace seat thickness: within 9"993A to 9"909A

b; $nterference:

$" 4alve seat insert to housing: 9"99-3A to 9"9913A Stellite;

9"991A to 9"993A /eltite;

$$" 4alve Huide: 9"999?A to 9"99-?A

$$$" >oke Huide: 9"99-3A

c; (rojected &eight:

$" 4alve Huide: 0"03A

$$" >oke Huide: 1"0-9A to 1"060A

d; Clearance between valve and guide: 9"992A to 9"996A

e; Thickness of valve disc + $nsert: 3B10A new; 1B10A min;

f; Straightness of valve stem: *unout should not e


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b; Stop running after attaining normal operating temperature"

c; %ring the piston of the corresponding cylinder at TDC in

compression stroke"

d; #it blow.by gadget Consists of compressed air line with the

provision of a pressure gauge and stopcock; removingdecompression plug"

e; Charge the combustion chamber with compressed air"

f; Cut off air supply at 69 psi" through stop cock and record the

time when it comes down to =ero"

g; 6 to -9 secs is 8,") if less check the leakage"

h; To check leakage) charge continuously at 69 psi

.'eakage through TSC indicates head defective"

.'eakage through Sump indicates defect in (iston or 'iner"

g; Tale.tell hole checks: Tale tell hole in cylinder head tells about the condition of

cylinder heads in running condition as per the following:

$" Ko leakage: 8,

$$" #uel droplets: Jpto 0 dropsBmin 8,"

$f more) Ko==le leak off rate is high"

$$$" #uel Mist: Ko==le seat defective"

$4" /ater leakage: Ko==le Sleeve cracked"

4" 'B8il leakage: *ubber ring on Ko==le perished"

'$KE*S

'iner forms the wall of the combustion chamber as well as it also guides the movement of

piston inside it"'iners are mainly of two types i"e" a; Dry liner b; /et liner"

a; Dry liners are those) which does not come in direct contact with coolant but fits in as asleeve inside an already complete cylinder" The temperature of the inside surface of dry

liner is higher than corresponding wet liner" Dry liners are in use in only very small

engines"

b; /et liners are those) which not only form the cylinder wall,but also form a part of the

water jacket" !'C8 'ocomotives are fitted with wet liners) which have slight interferencefit on upper and lower decks" $n addition to this) synthetic rubber seals of suitable ualities

are to be used) one on the upper deck groove and two on middle deck" 'ack ofinterference or defect in gaskets may result in water leakage causing water contamination

of crank case oil" The liner bore has chrome.plated surface and is honey combed by

-1


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electrolytic process" !'C8 liners have no step si=e in the bore" $t has got only one

standard si=e permitting a wear of 9"99L inch"

The Heneral Motor cylinder liners are fabricated type embodying the water jacket" $nHeneral Motor 'ocomotives) instead of liner bore being chrome plated the piston rings are

chrome plated"

The !'C8 cylinder liners are made of high strength close.grained alloy cast iron heat.

treated to relieve stresses" The liner metal composition of a typical !'C8 engine is givenbelow: -

C8M(8S$T$8K

Jnalloyed cast iron grade -6;

Carbon 1"99 .9 1"39

Silicon -"69 to 0"19

Sulphur 9"-0 Ma< mandatory;

(hosphorus 9"-3 Ma< (mandatory;

Manganese 9"59 to 9"L9

Chromium 9"03 to 9"59

Molybdenum 9"13 to 9"69 mandatory;

Maintenance & Inspection: >early inspection) 1 yearly + (8& renewal

The cylinder liners suffer from the following major defects:

a; /ear in the bore Kominal bore LR"Ma< allowed L"99LR;

Ma< ovality: "991Rma


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The cylinder liners can be reclaimed by re.chrome.plating in case of wear in the bore up

to a certain limit" $n case of cavitation and erosion) if the cavity is more than -B?A deep

then the liner has to be taken out of use"

PISTONS, PISTON RINGS AND CONNECTING ROD($ST8K

The piston is the most important component in the diesel engine as it takes direct part in

transmission of power" $t is) therefore) necessary that the designers and users must know

the essential details about the piston" The combustion of fuel results in large amount ofheat being developed" 8ut of this about -? of the heat is absorbed by piston only"

The functions of the piston are: .

a; $t compresses the air to reuired pressure + temperature"

b; $t receives the thrust of e


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b; &eat conductivity is 1 times better than !luminium"

c; Compression strength is much more than !luminium at high temperature"

d; /ear is less than !luminium"

%ut the two main disadvantages with cast iron piston are: -

a; /eight of !luminium is 9"9L6 -bs" per cubic inch in place of cast from which is 9"0?2

-bs" per cubic inch" Thus cast iron pistons are about 1 times heavier than !luminiumpiston in weight"

b; (ossibilities of cylinder liner being scored are more in case of cast iron piston"

The factor of weight has become more over riding in view of the high speed of the modern

diesel engines and hence !luminium alloy pistons are favoured" !'C8 03- enginespistons are of !luminium alloy with composition given below.

C8M(8S$T$8K

Copper 3"? to 5"?

inc 9"-9 ma


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b; Scraps down e


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Sulphur 9"903 Ma


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b; Twist: 9"990R) bend 9"99-Rma


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materials

rittle ractures:the entire fracture face is crystalline without any origin" Sudden shock or

loading is the main cause of this type of fracture" There is no reduction in area of cross

section at the point of fracture" Henerally occurs in fragile materials" &owever) sometimes

a part made of tough material) can sometime fracture in a brittle manner if that partcontains a large enough flaw or if there is sufficient elastic or plastic constraint"

Fatigue ractures' They result from the application of repeated or cyclic stresses) each of

them may be substantially below the normal yield strength of the material" #atigue

fracture face has two distinct =ones" $t is comparatively smooth and huge concentriccircles or marks originating from a single nucleus are present" They generally show slight

roughness as the crack grows" The remaining portion is crystalline in nature due to the

sudden fracture.

1" (on)destructi$e testing:. These tests include magnetic particle inspection) ultrasonic

testing) liuid penetrant inspection) and radiography" These tests are done to find out

surface and sub.surface defects" The magnetic particle inspection is done on #erro.magnetic components) while penetrant tests) ultrasonic tests) and radiography tests can be

done on all the components"

Mechanical testing:) Mechanical tests include hardness tests) JTS) elongation) bend tests)i=od.charpy tests etc" They help ascertain whether the component conforms to the physical

properties mentioned in the drawing" Kick break test is done on non.ferrous materials to

see segregation and o


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!nalysis of all the evidence) formulation of conclusion on the basis of all the previous

steps"

*ecommendations are made on the basis of findings) and remedial measures are suggested

to minimi=e such failures"

SUMMARY

This unit mainly deals about the Diesel Engine of /DM0 type 'ocomotive) the standardDiesel 'ocomotive, in use,in $ndian *ailways" Diesel Engine is the power unit of the

'ocomotive) hence it is also called power pack assembly" $t is a 4 shaped -5 cylinder

Engine" Engine %lock) made of fabricated steel) forms the structure of the Engine" 4ariouscomponents are housed in it to form the complete Engine assembly" Cylinder 'iner) Cyl

&ead and (iston form the combustion chamber of the engine" Cylinder head forms the lid

of the combustion chamber" $t houses inlet and e


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SELF ASSESSMENT

1. /hat are the main components housed in the Engine %lock to form the complete

Diesel Engine"

/hat is crank web deflection &ow it is adjusted

/hat are the duties of a Camshaft Each section of camshaft serves how many cylinders

Describe briefly the procedure of installation of camshaft in the Engine block"

/hat are the common defects noticed in the liners in course of service

/hat are the guiding factors for selecting the dimensions of the piston

/hat checks and measures should be done during fitment of piston rings

/hat checks and measurements are reuired to be done during overhauling of Cylinderheads

/hat are the various types of fracture &ow do you detect them

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dsl eng comp

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