Scavenging air receiver inspection and cleaning is one of the maintenance for main engine to be in good running condition.
When I was a cadet before, even though it´s not my line of work to clean the scavenging space receiver, it´s just a common for us to help each other in engine room for any work that needs extra manpower. I thought it is easy because just clean the dirt but when I tried and went inside, my thought changed because it felt like claustrophobia as afraid of small spaces. Since our voyage in tropical area in South East Asia, the engine room was hot already and the engine is just stop for a few hours for cooling.
But before entering, it needs time to ventilate to remove the strong odour of fuel and the heat radiation inside. From the entrance door of the scavenging space would start the cleaning of unburned deposit of fuel oil and most of them are sticky to the metal so the scraper is your friend. In every 3-5 small step, you will see the cylinder liner and piston to clean the body for later inspection by the marine engineers.
The other side of the engine, scavenging port is to remove the other carbon deposits around the stuffing box. De-clogged the drain pipe in order to continuously drain the excess oil when the engine in operation.
Inside the space, they need to inspect the following items.
Flaps – this is a non-return air flaps from the auxiliary blower fan and the turbo charger, if it is moving freely and goes back to rest position and any sign of crack line. This is the supply air for the main engine that needed before internal combustion takes place. You already know that a fire won´t start without the air, one of the ingredient to fire triangle.
Cylinder Lubrication – engineers always checked the condition of the piston and the rings around it to justify if the lubrication is enough or lacking. This is to make the right adjustment to prolong the life of cylinder liner, piston and rings.
Piston Crown – to inspect the top of piston how thick the carbon deposit is. If the fuel injector valves are delivering the right amount of fuel or need adjustments due to leakage.
Piston Rings – to ensure that the rings are free to move when you hit with a piece of wood. To verify the piston rings are movable and not sticking to the grooves. Measure the top ring for the depth if it is still in permissible range, this is the one way how thick or thin the rings are before overhauling.
TIP: Next time before you go inside to clean the scavenging space, much better to use your old coverall because you look like a beggar after but it doesn´t matter, think about it like $ sign.
PS: Pardon my grammar, my English is bad.