WÄRTSILÄ VASA 6L32, Instruction Manual

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Even if the above mentioned sensors are considered as standard
the amount and type of sensors can in special cases vary, depend-
ing on the needs for various installations. The actual set of sensors
and other electrical equipment mounted on the engine, as well as
alarm, load reduction and shutdown set points, can be found in
the installation specific documentation.
23.3 Functional testing
In this section there are described the procedures for testing of
overspeed trip and pressure sensors.
23.3.1 Testing of overspeed trip
There are two sensors measuring the engine speed. One sensor
(ST173) is connected to DCU1 and the other sensor (ST174) is
connected to the Relay Module. Overspeed is detected by both
sensors.
The overspeed limit set in the DCU is lower than the overspeed
limit set in the Relay Module. The limit of overspeed in the DCU
is 15 % above the engine nominal speed. The limit of overspeed
in the Relay Module is 18% above the engine nominal speed.
The overspeed trip can be tested by actually running the engine
at overspeed if that is possible. Otherwise the testing has to be
done by simulating the engine speed with a signal generator.
The overspeed trip should stop the engine when the overspeed
limit is exceeded. There is one exception to this. If a single main
engine exceeds the 15 % overspeed limit, the stop solenoids will
be activated only until the engine speed is below nominal speed.
The auxiliary engines will be stopped even when the lower
overspeed limit is exceeded. The overspeed limit of the Relay
Module is used as a backup and is always latching.
23.3.1.1 Testing of the overspeed trip by running the
engine
The overspeed trip can be tested by running the engine at
overspeed. The speed of the engine is not allowed to be increased
more than 60 rpm over the overspeed limit.
1 Increase the engine speed.
2 Check at what speed the overspeed is detected.
The limit of overspeed will be first exceeded in the DCU1. When
testing the overspeed trip of the Relay Module the speed sensor
of the DCU1 (ST173) has to be disconnected.
Note! Do not forget to connect the speed sensor after testing!
32-200115/II Instrumentation and Automation 23
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