Wartsila ?31DF Series Product Manual page 176

14. Automation System
● Exhaust gas ventilation not performed
● HFO selected or fuel oil temperature > 70°C (Gas mode only)
● Charge air shut-off valve closed (optional device)
14.2.1.2 Start in gas operating mode
If the engine is ready to start in gas operating mode the output signals "engine ready for gas
operation" (no gas trips are active) and "engine ready for start" (no start blockings are active)
are activated. In gas operating mode the following tasks are performed automatically:
● A GVU gas leakage test
● The starting air is activated
● A combustion check (verify that all cylinders are firing)
● Gas admission is started and engine speed is raised to nominal
The start mode is interrupted in case of abnormalities during the start sequence. The start
sequence takes about 1.5 minutes to complete.
14.2.1.3 Start in diesel operating mode
When starting an engine in diesel operating mode the GVU check is omitted. The pilot
combustion check is performed to ensure correct functioning of the pilot fuel injection in order
to enable later transfer into gas operating mode. The start sequence takes about one minute
to complete.
14.2.1.4 Start in blackout mode
When the blackout signal is active, the engine will be started in backup operating mode. The
start is performed similarly to a diesel engine, i.e. after receiving start signal the engine will
start and ramp up to nominal speed using only the diesel fuel system. The blackout signal
disables some of the start blocks to get the engine running as quickly as possible. All checks
during start-up that are related to gas fuel system or pilot fuel system are omitted. Therefore
the engine is not able to transfer from backup operating mode to gas- or diesel operating
mode before the gas and pilot system related safety measures have been performed. This is
done by stopping the engine and re-starting it in diesel- or gas operating mode.
After the blackout situation is over (i.e. when the first engine is started in backup operating
mode, connected to switchboard, loaded, and consequently blackout-signal cleared), more
engines should be started, and the one running in backup mode stopped and re-started in
gas- or diesel operating mode.
14.2.2 Gas/diesel transfer control
14.2.2.1 Transfer from gas- to diesel-operating mode
The engine will transfer from gas to diesel operating mode at any load within 1s. This can be
initiated in three different ways: manually, by the engine control system or by the gas safety
system (gas operation mode blocked).
14.2.2.2 Transfer from diesel- to gas-operating mode
The engine can be transferred to gas at engine load below 80% in case no gas trips are active,
no pilot trip has occurred and the engine was not started in backup operating mode (excluding
combustion check).
Fuel transfers to gas usually takes about 2 minutes to complete, in order to minimize
disturbances to the gas fuel supply systems.
14-8
Wärtsilä 31DF Product Guide
DBAE248994