SCHOOL OF MARITIME STUDIES Form no : 08/02
VELS UNIVERSITY Date : 15/02/2012
THALAMBUR Issue no : 02/12
Rev. no : 00
INSPECTION OF MAIN ENGINE COMPONENTS
AIM:
To inspect all main engine components.
PARTS OF ENGINE:
Basic Structure of a Engine consists of :
1. Bedplate
2. Engine Chocks
3. Holding Down bolts – Foundation Bolts
4. Engine Frames – ‘A’ Frames
5. Cylinder Block
6. Tie Rods
7. Cylinder Cover
8. Valve Gear if the engine is fitted with a cam operated exhaust valve.
9. Exhaust Valve – where fitted.
10. Camshaft & Drive (Gear or Chain)
11. Cams
12. Cylinder Liner.
13. Piston
14. Piston cooling arrangements
15. Piston Rod stuffing box.
16. Crankshaft & Main Bearings
17. Connecting Rod & Crankpin bearings
18. Crosshead and upper end bearings
19. Crosshead Guides.
20. Turbocharger
21. Air Cooler.
22. Thrust Block
23. Flywheel
24. Fuel Pumps
BED PLATE:
The bedplate is a substantial, rigid structure which forms the base on which the engine is built. It is supported
by the ship structure through the double bottom arrangement, but this support does not reduce the rigidity
needed & in fact with some modern vessels, the hull is left flexible and the bedplate stiffened so that a simple
four-point attachment to the hull can be used. This reduces the distortions developed in the bedplate when hull
deflection occurs.
ENGINE FRAMES.
These fit between the bedplate and cylinder block beam. They are sometimes referred to as the entablature.
They serve the following functions.
a) Support the cylinder blocks, turbo-chargers, camshaft and driving gear, scavenge belt etc.
b) Provide a facing for the girders & absorb the guide forces.
c) Develop an oil tight easing, for forced lubricating oil system, & support pipes & walkways.
SCHOOL OF MARITIME STUDIES Form no : 08/02
VELS UNIVERSITY Date : 15/02/2012
THALAMBUR Issue no : 02/12
Rev. no : 00
BEDPLATE HOLDING DOWN BOLTS.
Holding down bolts may be fitted or clear. If collision & side chooks are used the bolts are usually clear. If not
the bolts at the flywheel end are fitted, remainder clear, to ensure the coupling to output shaft is not strained.
Bearing faces of bolt heads & nuts must be normal to the bolt shank & parallel to each other to prevent any
bending stresses. If necessary the bedplate & tank top may be machined.
TIE BOLTS:
These are fitted to relieve the frames of tensile stress.
The bolts are mounted between the transverse girder of the bedplate and the upper face of the cylinder
jacket. As this in variably makes the bolt very long it is sometimes fitted in two lengths joined at the
base of the cylinder jacket. Hydraulic tightening tensions the bolt and this pre-tensioning should be
sufficient to keep the frames in compression throughout the engine cycle. This produces a substantial
tensile stress in the bolts requiring them to be checked frequently.
CYLINDER LINERS.
The liner is regarded as a thick cylinder under the action of a fluid pressure. The material is to be strong to with
stand the tensile loop stress. The interior surface forms the wall of the combustion chamber. There is a
considerable temperature stress on the material of the body. The two surfaces tend to expand at differential rates
for being at different temperatures. But the body prevents their free expansion this causes a stress to be set up.
The liner is secured at the top flange by cover studs. A compressive stress is set up on this part of the liner.
Besides, the surface of the liner needs to be resistant to wear and corrosion. The choice of material must also
consider such factor as its amenability to various metalworking and forming processes such as casting,
machining, surface treatment etc.
CYLINDER COVER:
This, in combination with the cylinder walls and piston crown provides the perimeter of the combustion
chamber. It is therefore exposed to high mechanical and thermal loads. Sufficient penetrations must be made in
the cover to house:
1. Inlet & exhaust valves.
2. Fuel valve or valves.
3. Air Starting Valve.
4. Relief valve.
SCHOOL OF MARITIME STUDIES Form no : 08/02
VELS UNIVERSITY Date : 15/02/2012
THALAMBUR Issue no : 02/12
Rev. no : 00
5. Indicator cock.
This makes the cover complicated and it is therefore usually cast
PISTONS:
Piston forms the lower part of combustion chamber, the piston is either of two or three part construction Cast
steel crown and cast iron skirt are combined in the piston shown below to obtain the strength and heat resistance
of steel in the upper section where these properties are important and the good wearing properties of cast iron in
the lower section, where piston bears against the cylinder. The piston ring grooves in the piston crown are
SCHOOL OF MARITIME STUDIES Form no : 08/02
VELS UNIVERSITY Date : 15/02/2012
THALAMBUR Issue no : 02/12
Rev. no : 00
chromium-plated. Firing pressure rose from some 40 kg/cm2 to 50 kg/cm2 and on towards 60 kg/cm2. This
higher loading led to the use of forged steel piston crowns.
PISTON RINGS:
The piston rings must provide an effective seal of the combustion space. Under ideal condition the piston ring
surfaces are in complete contact over its entire depth and periphery with the liner surface and ring width on
landing area. The initial seal is established between the ring and the liner by a radial pressure exerted by the ring
when pressed on liner. Following combustion the ring is forced down on the grove landing surface by the gas
pressure. The gas pressure is also throttled at the back of the ring through the small clearance space thus
increasing further the radial pressure against the liner.
The sealing of combustion space by a set of rings on reciprocating piston follows the labyrinth principle. The
gas pressure leaked in behind each piston ring is successively throttled down to the pressure prevailing at the
underside of the piston. In this way its natural tendency to leak out is progressively diminished. The number of
rings, the ring section area and the contact areas are determined by consideration of strength, pressure
difference, volume of space to be scaled, etc. From the foregoing it will be clear each ring is different, being the
highest at the top ring and diminishing successively at the bottom ring.
PISTON ROD STUFFING BOX:
The bore for the piston rod in the bottom of the scavenge air box is fitted with a Piston rod stuffing box, which
is designed to prevent lubricating oil in the crankcase from being drawn up into the scavenge air space. The
stuffing box also prevents scavenge air (in the scavenge air space) from leaking into the crankcase.
INLET VALVE/ PORT:
They are used to intake air inside the combustion chamber from the scavenge space. Either a designated valve is
used or else a scavenge ports are drilled around the cylinder liner.
EXHAUST VALVE:
After the combustion process is completed the exhaust gas is expelled from engine to exhaust manifold by
opening of exhaust valve. There is a separate cam designated to operate the exhaust valve opening. The exhaust
valve is closed by spring air, in older engine and auxiliary engine springs are used.
CROSSHEAD:
This provides an articulating, junction between the connecting rod and piston rod. It is constrained in the
transverse direction by Guides, which absorb and transfer the reaction from the connecting rod the engine
frames.
CAMSHAFTS:
In most of the modern engines the cams and shaft are forged or cast in one piece. In some engines the camshaft
is a straight round shaft and the cams are separate pieces, machined and keyed to the shaft. In some larger
engines, the camshafts are made up of two or more sections bolted together by flanges with fitted reamed holes
to assure accurate timing. Most camshafts are made of forged steel, usually of nickel-chromium alloy steel, and
the larger camshafts are often bored hollow. They are heat-treated and cams are usually surface hardened. The
camshafts are carried in plain bearings.
SCHOOL OF MARITIME STUDIES Form no : 08/02
VELS UNIVERSITY Date : 15/02/2012
THALAMBUR Issue no : 02/12
Rev. no : 00
CRANK SHAFT:
The components forming the crankshaft are the main journal, the web and the bottom endpin.
RESULT:
Thus various parts of main engine are studied and understood.
