2.3
Contamination and fire in the scavenge air spaces
2.3.1
Causes of contamination
The primary cause of contamination is when combustion materials are blown between the piston
and cylinder into the scavenge air spaces (blow-by). The contamination will be more if the fuel is
not fully burned, which causes exhaust smoke.
2.3.1.1
Unsatisfactory combustion
The causes of unsatisfactory combustion are as follows:
•
The injection valves do not operate correctly (the nozzle tip has trumpets or is worn).
•
The fuel is too cold, specially at low load.
•
Operation with a temporarily low air supply during large differences in engine load and the
scavenge air pressure fuel-limiter set too high.
•
Too much load.
•
Low air supply because the ventilation in the engine room is not sufficient.
•
The silencer and diffuser on the air side of the turbocharger has contamination.
•
The wire mesh and nozzle ring upstream of the turbocharger has contamination.
•
The exhaust gas boiler, the air cooler and water separator, the air flaps in the scavenge air
receiver and the scavenge ports have contamination.
2.3.1.2
Blow-by
The causes of blow-by are as follows:
•
Worn piston rings, broken piston rings or piston rings that cannot move.
•
Worn cylinder liner.
•
Incorrect operation of a lubricating quill.
•
The running surface of the cylinder liners have damage.
If there are one or more of these conditions, the remaining particles will collect at the areas that
follow:
•
Between the piston ring and piston ring groove.
•
On the piston skirt.
•
In the scavenge ports.
•
On the bottom of the cylinder block (piston underside).
•
In the scavenge air receiver.
X72-B
AA00-0000-00AAA-012B-A
Operation Manual
Contamination and fire in the scavenge air spaces
Winterthur Gas & Diesel Ltd.
- 50 -
Issue 003 2021-12
