A marine air compressor provides compressed air for various purposes on a ship. An air compressor is one of the most important equipments on a ship which needs special care and routine maintenance. In this article we will know the basics of the marine air compressor by first getting familiarized with the different parts of the same.
The main parts of the marine air compressor are:
1) Cylinder liner:
It is made of graded cast iron and is accompanied with water jacket around it to absorb heat produced during compression process. It is designed so as to give a streamline passage to the pressurized air resulting in minimum pressure drop.
For a non-lubricating type compressor, light weight aluminum alloy piston are used and for lubricating type graded, cast iron piston are used with piston rings for sealing and scrapping off excess oil.
3) Piston Rod:
In high capacity compressor which is normally big in size, piston is attached to piston rod made up of alloy steel. They are fitted with anti friction packing ring to avoid chances of compressed air leakage.
Connecting rod plays its role to minimize thrust to the bearing surface. It is made up of forged alloy steel.
5) Big end bearing and Main bearing:
They are constructed to give rigidity to the running rotational mechanism. They are made up of copper lead alloy and have a long operational life if proper lube oil and lubrication is provided.
6) Crank shaft:
It is a one piece designed part, using counterweights for dynamic balancing during high speed of rotation to avoid twisting due to torsion forces. Connecting rod big end bearing and main bearing are connected to crank shaft at crank pin and journal pin which are polished to ensure long working life of bearings.
7) Frame and crankcase:
Normally they have rectangular shape and accommodate all the moving parts and that’s why are made up of rigid cast iron. Main bearing housing is fitted on a bore in crank case and is made with highest precision to avoid eccentricity or misalignment.
8 ) Oil pump:
A lubricating oil pump is fitted to supply lube oil to all the bearings, which can be chain or gear driven, through crank shaft. Pressure of oil can be regulated by means of regulating screw provided in the pump. A filter in the inlet of the pump is also attached to supply clean and particle free oil to the bearings.
9) Water pump:
Some compressor may have attached water cooling pump driven by crankshaft through chain or gear. Some system does not use attached pump as they use water supply from main or auxiliary system for cooling.
10) Suction and Discharge valve:
These are multi-plate valves made up of stainless steel and are used to suck and to discharge air from one stage to another and to the air bottle. Proper assembling of valves is very important for efficient operation of the compressor.
11) Suction Filter:
It is a air filter made up of copper or soft steel with a paper material to absorb oil and wire mesh to avoid any metal or dust particle to go inside compression chamber.
Inter-coolers are normally fitted in between two stages to cool down the air temperature and to increase the volumetric efficiency of compressor. Some compressor have inbuilt attached copper tubes for cooling and some have outside assembly of copper tube inter-coolers.
13) Driving Motor:
An Electrical motor is attached to the compressor for making it operational and is connected to the compressor through the flywheel.
There are the main parts of a marine air compressor. The parts may vary according to the requirement of the system or ship.