Marine Installation Manual
2022-03
4-61
4 Ancillary Systems
4.5 Fuel gas system
X62DF-S2.0
With this arrangement, the ventilation air is taken from both inlets and flows
through the double-wall piping annular space to the ventilation fan’s suction
side. The correct flow distribution between both venting paths must be set by ad
-
justing the orifices as shown in the ‘Fuel Gas System’ of the MIDS,
.
Extraction fan capacity
The extraction fan capacity is calculated for an air flow rate that ensures air ex
-
changes of no less than 30 times per hour. The volume of extraction air depends
on the volume of the annular space of the main engine’s and the FGSS’s
double-wall piping, including the GVU volume, if a GVU is applied. The on-en
-
gine flow resistance in the annular space is provided in the ‘Fuel Gas System’ of
the MIDS,
. The extraction fan must not be connected to any other con
-
sumer’s FGSS.
According to requirements of classification societies, spare parts should be avail
-
able for each type of fan, except if a second fan is mounted as redundancy.
Dry air supply for
annular space ventilation
If the fuel gas temperature is below the dew point of the annular space ventilation
air, then dry air needs to be supplied for the engine’s annular space ventilation to
prevent condensation. This can be achieved by supplying compressed air
(working air at 7-8 bar(g) is sufficient). For further details, please see the system
proposal as shown in the ‘Fuel Gas System’ of the MIDS,
. The com
-
pressed air capacity must be designed such that the volume of the annular space
can be ventilated at a minimum of 30 times per hour. Some design margin must
be included for the layout uncertainties, as well as to account for air loss through
the flow indicator as applied in the MIDS installation proposal.
Hazardous area
According to the IGC/IGF Code a 1.5 metre hazardous area around both the
ventilation air inlet and outlet must be taken into consideration when designing
the ventilation piping.
4.5.9
Purging by inert gas
Purging and flushing of the fuel gas system is performed in case of fuel gas
leakage detection, a fire alarm or any other emergency, and before maintenance
on the main engine, the iGPR or the GVU. The fuel gas piping system must be
depressurised and any remaining fuel gas must be removed by an inert gas (e.g.
nitrogen). For this purpose, the piping of the WinGD main engine and the iGPR
or the GVU are equipped with inert gas connections.
