Marine Auxiliary Diesel Engines are used for the generation of electricity on board merchant ships worldwide. This article discusses the various running hours based maintenance like 250 hours routines, 1000 hours, 8000 hours routines, as well as the daily checks to be made by a marine engineer.
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Maintenance of Marine Diesel Engines
A marine diesel engine has to be maintained in conformity with the various international rules and regulations as per the ISM code. The advice of the manufacturer, as well that of the class and the Administration has to be followed. Thus all marine diesel engines have a maintenance schedule which is normally integrated into the preventive planned maintenance program of the company. It is kept on a dedicated computer with specialized software, which when fed the daily running hours gives you the work to be done, the work becoming due, and the work which is overdue. The ship’s data is synchronized with the head office data by the ways of data exporting twice a month. This allows a superintendent engineer to monitor the ship from the shore office and instruct the chief engineer accordingly. A maintenance schedule has been discussed in this article to give a rough guide line to the marine engineers. However the specific maintenance schedule given by the manufacturer should be followed and the local conditions, the load on the engines, would make it necessary to have a shorter maintenance interval. Engines running on light loads would require more frequent cleaning of the exhaust spaces and the pistons due to higher likelihood of fouling. In addition to the above, any unusual operating conditions, increase in sound, exhaust temperature, etc. must be investigated promptly and corrective actions taken.
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DAILY CHECKS ON THE ENGINE
The following are the daily checks on the engines that should be made by all the watch keeping engineers in their duty hours.
Check the fuel level in the service tank and drain the service and settling tank of any water.
Check the lube oil level in the sump of the engine.
Check the governor lube oil levels.
Check the lubrication of the rocker arms (if running)
Check lube oil pressure, water pressure, exhaust temperatures, cooling water temperature, lube oil inlet temperature, etc. (if running).
Drain the condensate from the scavenge manifold and the air coolers.
Lubricate the fuel racks, linkages, and fuel pump rack operating gear.
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250 HOURS ROUTINE
After an engine has run for 250 hours the generators must be changed over and the engine stopped and the following must be cleaned.
Clean the lube oil filters.
Clean the fuel oil filters.
Clean turbocharger air filters.
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1000 HOURS ROUTINE
A thousand hours routine is little more exhaustive, and we have to check that the injection system and the running gears are all OK and nothing is amiss. The following is done by marine engineers at a thousand running hours of the engines.
Crankcase inspection to be done.
Remove the fuel injectors and pressure tests them. Adjust the pressure and put back.
Change the turbocharger blower and turbine side oil.
Check the tappet clearances.
Take the performance of the engine.
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2000 HOURS ROUTINE
The crankshaft alignment must be checked and the graph plotted. It must be cross checked with the original figures. Once the diesel engines have been set up on the ship, it is very important that the engines be maintained within limits of the initial alignment to obtain a satisfactory performance of the engine and the alternator bearings. Though during the construction phase of the ship a very stiff seating is provided to the engines as foundation, the ship will either hog or sag during the operational life of the ship due to loading and discharging cycles. It is the duty of the operational engineers to take crank shaft deflection at regular intervals and monitor the alignment of the engines.
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4000 HOURS ROUTINE
The four thousand routines are very important and is known as half decarbonization. Basically all the cylinder heads have to be reconditioned and the carbon removed. The liner and the piston top are inspected for any abnormal combustion tell tales. In addition the following are done.
All cylinder heads to be removed, overhauled and carbon removed.
The exhaust and inlet valves inspected, lapped, and tested.
The starting air valves overhauled.
All gaskets, o rings to be renewed.
The cooling water spaces of the cylinder heads to be cleaned.
The top of the piston and the cylinder liner top part cleaned.
Renew the lube oil if required as per the analysis reports.
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8000 HOURS ROUTINES
The 8000 hours routine is called decarbonization by marine engineers. During this all the pistons are pulled out, cleaned, and inspected. The piston rings changed depending on the wear down, the shell bearings inspected, and also the cylinder heads overhauled. In addition the following is also done.
Remove cylinder heads and overhaul.
Withdraw pistons and clean. Change piston rings.
Clean exhaust piping and silencer.
Inspect big end bearings.
Overhaul turbocharger and renew the ball bearings.
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25000 HOURS ROUTINE
Renew the connecting rod bolts.
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The marine auxiliary diesel engines are used for generation of electricity, and hence must be maintained in good condition. The marine engineer has to be on his toes taking care of the engines. The above is just a guide line, but the management in consultation with the engine manufacturers may change the schedule of maintenance. Today’s new engines have a running period of 16,000 hours before taking out the piston. However the old ships still follow the 8000 hours routine. Sometimes the management company likes to over maintain the engine so that it reduces the interval between the overhauls.