Emergency stop mode
The sequence of engine stopping in emergency stop mode is similar to shutdown mode, except that also
the pilot fuel injection is de-activated immediately upon stop signal.
Emergency stop is the fastest way of manually shutting down the engine. In case the emergency stop push-
button is pressed, the button is automatically locked in pressed position.
To return to normal operation the push button must be pulled out and alarms acknowledged.
14.2.5
Speed control
Main engines (mechanical propulsion)
The electronic speed control is integrated in the engine automation system.
The remote speed setting from the propulsion control is an analogue 4-20 mA signal. It is also possible to
select an operating mode in which the speed reference can be adjusted with increase/decrease signals.
The electronic speed control handles load sharing between parallel engines, fuel limiters, and various other
control functions (e.g. ready to open/close clutch, speed filtering). Overload protection and control of the
load increase rate must however be included in the propulsion control as described in the chapter "Operating
ranges".
For single main engines a fuel rack actuator with a mechanical-hydraulic backup governor is specified.
Mechanical back-up can also be specified for twin screw vessels with one engine per propeller shaft.
Mechanical back-up is not an option in installations with two engines connected to the same reduction
gear.
Generating sets
The electronic speed control is integrated in the engine automation system.
The load sharing can be based on traditional speed droop, or handled independently by the speed control
units without speed droop. The later load sharing principle is commonly referred to as isochronous load
sharing. With isochronous load sharing there is no need for load balancing, frequency adjustment, or gen-
erator loading/unloading control in the external control system.
In a speed droop system each individual speed control unit decreases its internal speed reference when it
senses increased load on the generator. Decreased network frequency with higher system load causes all
generators to take on a proportional share of the increased total load. Engines with the same speed droop
and speed reference will share load equally. Loading and unloading of a generator is accomplished by ad-
justing the speed reference of the individual speed control unit. The speed droop is normally 4%, which
means that the difference in frequency between zero load and maximum load is 4%.
In isochronous mode the speed reference remains constant regardless of load level. Both isochronous load
sharing and traditional speed droop are standard features in the speed control and either mode can be
easily selected. If the ship has several switchboard sections with tie breakers between the different sections,
then the status of each tie breaker is required for control of the load sharing in isochronous mode.
14.3 Alarm and monitoring signals
The number of sensors and signals may vary depending on the application. The actual configuration of
signals and the alarm levels are found in the project specific documentation supplied for all contracted
projects.
14.4 Electrical consumers
14.4.1
Motor starters and operation of electrically driven pumps
Separators, preheaters, compressors and fuel feed units are normally supplied as pre-assembled units with
the necessary motor starters included. The engine turning device and various electrically driven pumps require
separate motor starters. Motor starters for electrically driven pumps are to be dimensioned according to
the selected pump and electric motor.
Motor starters are not part of the control system supplied with the engine, but available as optional delivery
items.
Product Guide Wärtsilä 34DF - 3/2012
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Product Guide
14. Automation System
