Operation
0450−1/A1
Winterthur Gas & Diesel Ltd.
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Procedures to Prevent Contamination and Fire in the
Scavenge Air Spaces
1. General
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, causes exhaust smoke.
2. Causes and Procedures
2.1 Unsatisfactory Combustion
The causes of unsatisfactory combustion are as follows:
D The injection valves do not operate correctly (the nozzle tip has trumpets or is
worn).
D The fuel is too cold, specially at low load.
D Operation with a temporarily low air supply during large differences in engine
load and the scavenge air pressure fuel limiter set too high.
D Too much load
D Low air supply because the ventilation in the engine room is not sufficient.
D The silencer and diffuser on the air side of the turbocharger has contamination.
D The wire mesh and nozzle ring upstream of the turbocharger has contamination.
D The exhaust gas boiler, the air cooler and water separator, the air flaps in the
scavenge air receiver and the scavenge ports have contamination.
2.2 Blow-by
The causes of blow-by are as follows:
D Worn piston rings, broken piston rings or piston rings that cannot move.
D Worn cylinder liner.
D Incorrect operation of a lubricating quill.
D The running surface of the cylinder liners are damaged.
If there are one or more of these conditions, the remaining particles will collect at the
areas that follow:
D Between the piston ring and piston ring groove.
D On the piston skirt.
D In the scavenge ports.
D On the bottom of the cylinder block (piston underside).
D In the scavenge air receiver.
2.3 Fires
The causes of fires are as follows:
D Combustion gases and sparks, that bypass the piston rings between the piston
and cylinder liner running surface, go into the piston underside.
D If sealing rings of the piston rod gland leak and drain pipes from the piston
underside are blocked, system oil and cylinder lubricating oil will collect. This is a
primary fire risk.
Note: You must do periodic checks of the bottom of the cylinder block and
scavenge air receiver. If necessary clean the cylinder block and scavenge
air receiver.
2014
Operation − Special Procedures
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