, Gas Starting and control air system
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2.01
0615 BC
STARTING AND CONTROL
AIR SYSTEM
Introduction
Compressed air is used for starting and control of the
Bergen-gas engine. The starting arrangement is
based on air-driven starter motor acting on a
replaceable ring gear on the flywheel.
In the control air system, dry and clean air is required
for problem-free operation of oil mist detector,
I/P-converters and various solenoid valves.
Starting air
The starting air release valve on engine (74SA) is
operated by an electric solenoid. 30 bar starting air is
led to the starter motor assembly. First, the pinion
carries out an approach movement to the flywheel.
Secondly, the main valve is opened and 30 bar enters
the air starter (32SA) for full operation.
Remote start is performed by an electric signal to the
solenoid of the starting air release valve.
See system drawing below.
Maximum starting air pressure is: ................. 30 bar
g
and minimum pressure for safe starting is:
................................................................................18 bar
g
*)
Ref. technical data, part 1.04.
Note: The engine is run on starting air for 5 seconds before fuel
gas is admitted. *) For safety reasons a starting attempt must not
be made when starting air pressure is lower than 20 bar
g.
For ventilation of exhaust gas system before start of
engine, see charge air and exhaust gas system.
Starting air capacity
Starting air volume and compressor capacity are to
be sized according to the classification societies re-
quirements.
Air compressors and capacities
Installed air compressor capacity should be sufficient
to charge the starting air receivers from atmospheric
- to max. pressure in 60 minutes.
Total required compressor capacity Q is:
, Nm
3
/h
where
p
2
= Maximum starting air pressure = 31 bar
a
p
0
= Atmospheric pressure in bar
a
J = Total starting air receiver capacity in m
3
t = Compressor operating time in minutes
s = Safety factor, normally 1,2
Nm
3
/h = cubic meter normal (at 1 bar/0°C)
Due to redundancy requirement, minimum two air
compressors are normally installed, each with a
capacity of 50% of total required capacity.
Be aware of requirement for compressor derating due to
ambient air temperature.
The air compressors are normally electrically driven
and automatically started at a starting air pressure of
16 bar
g
.
Required time t for recharging from 18 bar
g
to
30 bar
g
, with one of two compressors is:
, minutes
where
p
1
= Initial pressure in starting air receiver, 18 bar
g
Q = Compressor capacity in Nm
3
/h
Option:
One diesel engine driven air compressor.
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