6.3.2 External fuel gas system
Before the gas is supplied to the engine, it passes a Gas Valve Unit (GVU).
The Gas Valve Unit (GVU) supplies filtered gas at proper pressure to the engine, and contains
safety functions, and has several block & bleed valves. The unit includes a manual shut-off
valve, inerting connection, filter, fuel gas pressure control valve, shut-off valves, venting valves,
pressure transmitters/gauges, a gas temperature transmitter and control cabinets.
The off-engine venting valves vent or purge the gas pipes inner section that are inside and
before GVU. They can remain closed at engine venting (MCC de-gassing valve open), or act
in coordination with the MCC de-gassing valve, according to need. Off-engine venting valves
for inner gas pipes acts also at purging. The off-engine venting valves that are for annular
space are for ventilation. No corresponding valve is on-engine. The gas supply system on
engine is equipped with double wall gas pipes. A Gas Valve Unit (GVU) is required for each
engine and has to be located as close the engine as possible.
Fig 6-4 Gas supply system with the Gas Valve Unit (GVU) and the main components
6.3.2.1 Requirements on the external gas system equipment
The design of the external gas system may vary from installation to installation but every
system shall be designed to provide the engine with gas of correct flow, pressure and according
to fuel specification in the Product Guide.
Design, manufacturing and installation of pipes and other equipment has to fulfil all local
authority requirements.
Piping material before the engine and after the external gas filter has to be in stainless steel.
The gas connections to/from engine have to be flexible. No external loads on the engine gas
inlet/outlet connections are allowed.
The pipe diameter of the outlet gas ventilation connection on the engine is DN50. The external
ventilation pipe is recommended to be one size larger in order not to influence negatively on
the programmed engine gas venting sequences.
DBAD209883 6-15
6. Fuel SystemWärtsilä 46DF Product Guide
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