Who doesn’t want a trouble-free operation from its marine diesel engine; especially when a great deal of time, effort and money has been invested into it. The only stress engineers face during the watch keeping duties is to move the ship from Port A to B; without engine breakdown in between. So it becomes essential for officers and trainees to know off common engine troubles; they may face during their watch in the engine room.
Thus an added care is being given on its performance during maneuvering to and from the port or crossing canals. After all, there is nothing more horrible than to know; you got trouble in so and so unit during maneuvering. But the bitter truth is whether its a fishing boat ( less maintenance and care ) or a Merchant ship ( Planed Maintenance & Proper Care ); breakdown do happen thanks to its complexity and number of the engine parts.
On ship, common engine troubles can happen from a number of reason including but not limited to; starting air valve leakage, fuel rack stuck, fuel valve malfunction, defective sensors, overheating, air leakage, breakdown of gauges etc. That is the reason why we are taught just like that to know engine faults and troubles due to above cases. But on ship we usually have to judge and rectify the possible problems based on symptoms; much like a doctor treats you based on your symptoms.
These symptoms and their possible reasons along with remedy are clearly mentioned in engine manuals; provided by the engine manufacturer. Luckily we are all asked to go through it but no one really goes though it nicely; even I skip a lot many things at my time. So here are these most common engine troubles; their symptoms and cure.
Most Common Engine Troubles In Marine Engine
A ) During Starting
You have checked all oil levels, turn the engine on turning gear, Prepare the air starting system, start auxiliary blowers and then; push the button to turn the engine on air. But what you see is that either the engine runs too slowly to start fuel injection or just doesn’t turn at all. You then tried once again, but the result remains the same.
A thousand many questions will arise in your mind; so lets discuss all that possible faults that can happen while the starting operation. The four common engine troubles that you can face are; Engine fails to turn in air, Engine does not reverse, Engine turn too slowly, engine run on air but not on fuel and engine does not pick up rpm.
1 ) Engine Fails To Turn On Air
After giving the start order the engine may fail to start on air if there is low air pressure in the starting air receiver. This situation can arise due to either no pressure in control air system or some valves on the lines shut in between. Many a times you will also find the main starting air valved locked to closed position or malfunctioning.
Other than above common reasons the engine may also fail to turn on air if; the control selectors wrongly set or the air distributor wrongly adjusted. This can also happen due to electrical/pneumatic faults when the electrical signal / control air does not reach to the engine from control room. For Ships with CPP the blades are need to be set to zero pitch setting to start the engine.
- If the starting air presser is low; check whether all the associated valves in the lines are open and start the compressor.
- In case there is a problem with control air pressure; Just changeover the valves to the other side.
- Ensure there is no leak in the starting air line.
- If the starting air valve does not activate; disengage the turning gear and ensure the locking plate is already lifted.
- In case there is a problem with controls; check and rectify the control settings.
- If the distributor itself has a problem, then lubricate the shaft and turn the engine on turning gear to make it work.
- In ships with CPP ensure the pitch is set to zero position during starting.
2 ) Engine Turns Too Slowly And Does Not Reverse
In case you give the signal to turn the engine on air but after sometimes, the engine doesn’t gain rpm and keep turning on slow speed. Then this can happen either if the adjustment of slow turning valve is not correct; or faulty starting air valves. Other than that the above situation can also happen due to; incorrect timing of starting air distributor and if you forget to turn off slow turning manual control switch.
Similarly, if the engine isn’t reversing then there can only be two possible reasons causing it. Either, there is leakage or some problem in the control air line as control air for desired running direction does not reach to the engine. The other issue can be faulty solenoid operated valve that causes change over of the engine running direction.
- Now if the engine turns too slowly, first check whether the slow turning valve setting is correct. If not you need to readjust it to appropriate values.
- Similarly if the starting air distributor have faulty timing; open the distributor housing by pulling out the check pin and the gasket. Once exposed measure the clearance between the interlock and the roller assembly on both sides. If the clearance is more or less than idle value readjust their relative position.
- In case there is any problem with the starting air valve mounted on the cylinder. First, dismantle it, clean, overhaul and pressure test before reassembly.
- Similarly, you may need to overhaul distributor assembly in case the distributor disc sticks.
- On another hand, if the engine does not reverse even after giving the reverse signal; you need to check each air signal pipeline and valves to find the fault and rectify.
3 ) Engine Turn On Air But Doesn’t Start On Fuel
While most of the time engine starts just fine after initially turning on air; but not always as some times it just doesn’t pick up on fuel. You may think it needs a higher kick or more fuel supply; but still, it only stops once fuel injected. Of all the reasons contributing to the situation, the top three reason’s are; Stop signal puncture valves not aerated, faulty governors and sluggish maneuver gears.
Other than these top three reasons other governing factors are; poor or improper adjustment of maneuvering gear, too low governor pressure setting, chocked fuel oil filters, Improper fuel pump timing, fuel rack got stuck and presence of air or water in the fuel line system. Sometimes the engine also refuses to start in first 2-3 attempts if the engine was cold (stopped) for a long time.
- In case the stop signal valve is not properly aerated, follow the manual instruction to de-aerate the valve manually.
- Ensure there is no other cause of stop signal and rectify if any.
- Check and ensure the deflection reading on the deflection scale of the governor is at 6; when starting the engine.
- Ensure there is correct oil pressure to the governor and the timing settings are correct.
- Many times engine can be started with a little trick of manually shortening the normal starting air period.
- Lubricate the maneuvering gear and check all the moving parts are free to move.
- If the engine is cold, allow for some time with jacket water circulating to heat up the unit.
- Check and rectify any possible leak form injector pipeline.
- Purge out any water or air trapped within the system.
4 ) Engine Run-On Fuel But Show Fluctuating RPM
When the engine starts buts its r.p.m keeps fluctuating the phenomenon is called hunting. It is a situation in which your governor is working like crazy; accelerating and de-accelerating the engine to maintain set speed. Such situation are extremely undesirable as they possess negative impact on the engine performance.
Such conditions can arise mainly due to some faults with the governor or its associated systems. Other than that all other possible reasons are; too high or low scavenge air, one or more cylinder does not fire at the start, the engine was started without ensuring sufficient preheat, chocked fuel oil filter, etc.
- Flush the governor oil, clean with light fuel like petrol or kerosene and then refill the oil.
- Many times this happens because of the cold start; so provide adequate time for the engine to preheat.
- Check and rectify scavenge air limiter settings and ensure the auxiliary blowers are working properly.
- Check and clean the fuel oil filters as many times its one of the leading reasons for the hunting of marine engine.
- While it’s not part of the common engine troubles; sometimes one or two units of an engine does not fire. Under such condition, check for the suction and puncture valves for individual fuel valves.
- If the problem persists change the fuel valves in the associated unit.
B ) In between Normal Running Operation
Fortunately on merchant and navy ships we have sufficient trained crew to handle engine failures and their malfunction. Otherwise that would be one of the main cause for emergency calls for rescue; much like in case of fishing boats and other pleasure vessels. While its common to observe and rectify problem during starting.
Small issues gets unnoticed while running unless you observe its effects on the engine performance. To detect possible malfunction during running pay attention to the following symptoms; A rise or decrease in exhaust temperature across all units, exhaust temperature rise or decrees in particular unit, smoky exhaust and gradual decrease in engine r.p.m.
1 ) Rise In Exhaust Temperature Across All Units
Do you know mostly, if anything goes wrong with an engine the first thing on which it effects is the exhaust temperature. That’s why its one of the key aspects of watch keeping duty; to keep an eye on the exhaust temperature. A rise in exhaust temperature across the units is an indication of; high scavenge air temperature and after burning.
While scavenge temperature can rise due to chocked air filters on turbocharger, defective or ill-maintained air coolers and gas passage. On another hand after burning can occur when there is improper fuel oil, combustion characteristics altered and if the position of camshaft is incorrect. This can be due to either defective chain drive or improper adjustment.
- In case of high scavenge temperature, the first thing you should do is to check full records of air cooler. If the records show sudden deterioration checks for leaks; otherwise clean it for better performance,
- Another thing needs to be done when there is high scavenge temperature is to perform; dry cleaning of the turbines side of main engine turbocharger.
- In case of after burning first ensure you or anyone else had not manually altered the combustion characteristics; by readjusting fuel injection time in the cylinder.
- Then using the pin gauge method check there is no deflection or issue with the cam shaft.
- At last make sure the fuel you get is of appropriate quality and also filtered / purified properly.
2 ) Fall Of Exhaust Temperature Across All Units
Much like the rise in exhaust temperature, reduction in exhaust temperature beyond a limit is a threat to the engine. It is so because, there is enough information on common engine troubles like high exhaust temperature with remedies. But there is only a few article on what to do when exhaust temperature go down beyond a point.
Exhaust temperature decrease in any engine due to two main reasons namely; low scavenge air temperature and presence of non-fuel fluid in the fuel oil system. Many a time fuel oil system trap steam, air or water in the system and show such results. Similarly, if the thermostat or its setting is faulty; then the scavenge air temperature fall below the required value.
- At first, ensure and check whether the thermostat at the air cooler is working properly.
- Then ensure there is no problem with the sea water system itself; i.e the sea water is not a freezing temperature etc.
- Purge out any steam, air or water in the fuel oil system.
- Then ensure there is no sticky fuel valve spindle or broken fuel valve spring; as in the majority of cases that is the cause of air getting into the fuel oil system.
- Replace faulty fuel valves and ensure no fuel oil is present on top of the piston crown.
- On another hand, also check the pressure of the circulating fuel pump, check the function of de-aerator valve and at last ensure there are no steam leaks in fuel oil preheater.
3 ) High Exhaust Temperature In Single Cylinder Or Unit
One of the common engine troubles and most asked questions in interviews for the M.E.O class 4 and campus placements. The high temperature in a single unit can be caused by a number of factors including the ones mentioned in point 1; i.e rise in exhaust temperature across all units.
Other than that, defective fuel injector nozzle, damaged fuel valve, blow by, build up of combustion products like shoot on turbocharger nozzle, fuel cam slippage, ill-adjusted fuel cam settings, etc. Other than that it can also be caused due to leakage of scavenge air somewhere in the system or scavenge fire.
- Check and adjust the fuel pump lead.
- Change the exhaust valve for that unit at the time and repair it afterward.
- Dry clean the turbine side of the turbocharger.
- Reset the fuel cam setting to the recommended value.
- Check and ensure there is no scavenge fire; take necessary steps if any.
4 ) Black Smoke At The Exhaust
On most ports, authorities can put fine on your vessel for black or smoky exhaust. Even when they not as in case of poor local laws or in international waters; its bad for your engine, environment and operational cost. The common cause of black smoke from ship or your boat is the defective fuel injectors, cold start of engine and scavenge fire.
Other than that it can also be caused because of poor fuel quality, overloading, turbocharger out of synchronicity with the engine, chocked air filters, improper fuel heating ( Low Temp ), turbocharger blades damaged, faulty scavenge air valve ( 4 stroke only ) and at last turbocharger running at very low speed due to multiple chocked points.
- If there is some smoke during starting or when a vessel is accelerated its quite normal; so only thing you can do is to accelerate slowly around ports.
- In case the smoke build up is high there can be a fault with the limiting switch with the governor.
- In case of faulty or defective fuel valve; change it with a spare one on affected units.
- Contain and extinguish scavenge fire as it is one of the common cause of smoky exhaust with power drop.
- Clean the turbocharger air filters.
- In some case, you may also require to perform both wet and dry cleaning of the turbocharger on both sides.
Note: This article is produced on request from “Mr. Alexander Shaun“.
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