MAN B&W 18.08
Page 2 of 2
MAN Diesel
MAN B&W ME-GI TII engines 198 50 60-7.3
In the unlikely event of larger gas amounts enter-
ing the exhaust receiver without starting to burn
immediately, a later ignition may result in violent
burning and a corresponding pressure rise. There-
fore, the exhaust receiver is designed for the
maximum pressure (around 15 bars).
However, any of the above-mentioned situations
will be prevented by the detection of defective gas
valves, which is arranged as follows.
Valve leakage monitoring pressure sensor
The valve leakage monitoring pressure sensor,
installed in the gas block between the window/
shutdown valve and the gas injection valves, is
one unit with sensor and amplifier.
The pressure sensor measures pressure increase
or decrease, concluding whether the window/
shutdown valve or the gas injection valves are
leaking, during every cycle from when the window/
shutdown valve closes and until it opens again,
Ignition failure of injected gas
Failing ignition of the injected natural gas, i.e. mis-
firing, can have a number of different causes,
most of which, however, are the result of failure to
inject pilot oil in a cylinder:
• leaky joints or fractured high-pressure pipes,
making the fuel oil booster inoperative
• seized plunger in the fuel oil booster
• other faults on the engine, forcing the fuel oil
booster to ‘0-index’.
Such misfiring causes a small amount of un-
burned gas in the exhaust receiver to burn with
a diffusion type flame as explained above. The
GCSU detecs misfiring and the gas injection is
stopped and a gas shut down initiated.
Compression and combustion pressure
monitoring
The compression pressure as well as the maxi-
mum combustion pressure are monitored. If low
respectively too high, a gas shutdown is initiated.
Test of tightness of gas pipes
During shop test of the engine as well as vessel
commisioning, a tightness test of the gas piping is
conducted by means of valves installed in the gas
return pipe.
Further information on tightness verification tests
and gas leakage detection is available from MAN
Diesel & Turbo, Copenhagen.
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