WinGD X72DF, Installation Manual

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Marine Installation Manual 2021-08 4-58
4 Ancillary Systems
4.4 Fuel gas system
X72DF
Purging gas properties For purging, WinGD requires an inert gas (typically nitrogen) with the following
properties:
Table 4 - 8 Purity of inert gas (engines with iGPR)
Table 4 - 9 Purity of inert gas (engines with GVU)
Purging gas pressure The purging gas pressure ( p
i
) can be selected within a wide range to allow the best
match with the available purging gas system. Once the purging gas pressure has
been selected (defined as set-point), the actual purging gas pressure may deviate
±
10% from the set-point. As the purging cycle is time-controlled and is pro -
grammed during commissioning, the pressure set-point must be fixed before -
hand.
Purging gas
consumption volume
The inert gas consumption for one purging cycle must be a minimum of three
times the fuel gas pipe volume. The inert gas volume can be calculated with the
following equation:
V
i
= 3 V
a
[Nm
3
]
where:
V
i
.............. = minimum required inert gas volume [Nm
3
]
V
a
............. = total volume of the space to be purged, including the main en -
gine’s internal gas piping, the external gas supply piping and the rel -
evant fittings [m
3
]
The main engine’s internal gas piping volume, which must be purged, can be
found in the ‘Gas Fuel System’ of the MIDS,
 4-33 . The volume of the fuel gas
piping on the ship side must be calculated by the shipyard and must be based on
the piping layout. The main engine control system has a pre-set inert gas purging
cycle of 25 seconds. The value for this purging cycle must be adjusted during
commissioning.
Requirement Property Value
IGF requirements Content of mixture out of N
2
, CO
2
, Ar ≥ 95.0%
Oxygen content ≤ 5.0%
WinGD requirements Dew point (atmospheric pressure) ≤ -40°C
Inert gas pressure before purging valve Set-point ± 10%
Set-point selection range 5-15bar(g)
Requirement Property Value
IGF requirements Content of mixture out of N
2
, CO
2
, Ar ≥ 95.0%
Oxygen content ≤ 5.0%
WinGD requirements Dew point (atmospheric pressure) ≤ -40°C
Inert gas pressure before purging valve Set-point ± 10%
Set-point selection range 3-15bar(g)