WÄRTSILÄ 31SG Product Manual Download

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14.4.1.7 Stand-by pump, LT cooling water (if applicable) (4P05)

The engine control system starts the pump automatically via a motor starter, if the cooling water

pressure drops below a preset level when the engine is running.

14.4.1.8 Circulating pump for preheater (4P04)

The preheater pump shall start when the engine stops (to ensure water circulation through the

hot engine) and stop when the engine starts. The engine control system handles start/stop of
the pump automatically.

14.5

System requirements and guidelines for gas-electric

propulsion

Typical features to be incorporated in the propulsion control and power management systems

in a gas-electric ship:

1. The load increase program must limit the load increase rate during ship acceleration and

load transfer between generators according to the curves in chapter

2.2 Loading Capacity

●

Continuously active limit: “normal max. loading in operating condition”.

●

During the first 6 minutes after starting an engine: “preheated engine”

If the control system has only one load increase ramp, then the ramp for a preheated engine

is to be used.

The load increase rate of a recently connected generator is the sum of the load transfer

performed by the power management system and the load increase performed by the
propulsion control, if the load sharing is based on speed droop. In a system with
isochronous load sharing the loading rate of a recently connected generator is not affected
by changes in the total system load (as long as the generators already sharing load equally
are not loaded over 100%).

Rapid loading according to the “emergency” curve in chapter

2.2 Loading Capacity

may

only be possible by activating an emergency function, which generates visual and audible
alarms in the control room and on the bridge.

3. The propulsion control should be able to control the propulsion power according to the

load increase rate at the gas generators. Controlled load increase with different number of
generators connected and in different operating conditions is difficult to achieve with only
time ramps for the propeller speed.

4. The load reduction rate should also be limited in normal operation. Crash stop can be

recognised by for example a large lever movement from ahead to astern.

5. The power management system performs loading and unloading of generators in a speed

droop  system,  and  it  usually  also  corrects  the  system  frequency  to  compensate  for  the
droop offset, by adjusting the speed setting of the individual speed control units. The speed
reference  is  adjusted  by  sending  an  increase/decrease  pulse  of  a  certain  length  to  the
speed  control  unit.  The  power  management  should  determine  the  length  of  the
increase/decrease pulse based on the size of the desired correction and then wait for 30
seconds or more before performing a new correction, in particular when performing small
corrections.

The relation between duration of increase/decrease signal and change in speed reference

is usually 0.1 Hz per second. The actual speed and/or load will change at a slower rate.

6. The full output of the generator is in principle available as soon as the generator is

connected to the network, but only if there is no power limitation controlling the power