With the introduction of MARPOL 2020 convention, the focus has once again been on the exhaust gas from the ships that are released into the atmosphere. With ships adopting numerous methods to curb the exhaust pollutants, it is quite imperative to know what are the major exhaust pollutants that a mariner encounters.
One such is the Black smoke.
Causes of Black Smoke
Black smoke coming out of a funnel indicates that there is an imbalance in air fuel ratio.
The scarcity of air or the improper treatment of the fuel being supplied by the injector, are the reason for the occurrence of Black smoke.
This black smoke comprises of large fuel particles that were not properly broken due to the shortage of oxygen during combustion.
Detection of source of black smoke:
On spotting black smoke coming out of funnel, the first order of business is to figure out from where is it originating:
- All the exhaust coming from main engine, generator engine and boiler integrate into a single closure and is released from the same funnel. So, we need to go to the bridge deck and check from which particular exhaust trunk the black smoke is coming from.
- Trace the marked trunk into the funnel room to see whether the smoke is being produced from the generator or the boiler
- If the smoke is coming from the generator, then start the stand-by generator and ensure that the black smoke has stopped, before starting troubleshooting.
If the smoke is coming from the boiler and the causes can’t be detected in running condition, then change all the running machinery to diesel oil, switch off the boiler and start troubleshooting
Checks to be performed on Marine Generators
- Start with checking the overall electrical load of the ship (should be less than sea going load) and make sure that the generators are running at optimum range. If the generators are working for smaller load, then one should stop one generator and shift the load to only one generator to achieve efficient combustion.
- Check your air mesh filter in the turbocharger blower. If the filter is dirty, this might be decreasing the air supply to the combustion blower. If the turbocharger blades and nozzle are dirty or damaged, there needs to be a complete overhauling of the turbocharger
- Check the tappet clearances of the rocker arm as it may not be accurate which may lead to early opening and late closing of the valve leading to loss of inlet air
- There might be insufficient air supply in the generator from the blower which might led to starvation of air. Check the air trunk coming from the engine room blower to confirm that it is working
- Check for abnormality of all units. If the temperature of one unit is greater than the rest, check the fuel injector or fuel pump of that one unit. If the average temperature difference between each unit is beyond 50°C, it might lead to black smoke..
- A thermal and power imbalance may also cause black smoke. Check the performance of the engine
Checks to be performed on the Inert Gas Generator (IGG) and Boiler
- The most common reason for black smoke coming out of Funnel is the air fuel ratio setting. Check that.
- Check for any dripping of burner nozzle by shutting off the boiler and opening the burner door
- If the oil temperature of the heavy fuel is less than what is required then there would be difficulty in burning of complete fuel oil, even if the air available is sufficient. So maintain the fuel oil temperature
- A problem in the atomizer unit of burner can also cause the black smoke.
- If there has been a recent change in the fuel being used, check for the compatible turn down ratio from manual
- Any interruption in air distribution could potentially lead to black smoke, so check the air distribution arrangement.