Marine Installation Manual
2021-08
2-6
2 Engine Power and Speed
2.5 Power range limits
X72DF
2.5
Power range limits
Once an engine is optimised at CMCR (Rx), the working range of the engine is
limited by the following border lines (see
).
Figure 2
-
3 Power range limits
Line 1
100% Torque Limit
Constant MEP or torque line through CMCR from 100 % (speed and power)
down to 96% (speed and power).
Line 2
Overload Limit
Available in diesel mode for testbed operation and emergency operation ac
-
cording to SOLAS Regulation II-1/3.6. It is a constant MEP line, connecting
point P07 (102.3 % power and 96 % speed) to point P08 (110% power and
103.2% speed). Point P08 is the point of intersection between Line 7 and 110 %
power. Overload is not permitted in gas mode. If overload is attempted in gas
mode, then the engine’s safety system will automatically initiate a gas trip to
diesel mode at 102 % power.
Line 3
Speed Limit
Maximum speed limit for continuous engine running is set to 104% of CMCR
speed. However, in diesel mode this limit can be extended to 106% (Line 3a) if
Rx speed is reduced (
n
CMCR
≤
0.98
n
MCR
), provided that the specified torsional
vibration limits are not exceeded.
Line 4
Overspeed Limit
The overspeed range, from Line 3 at 104 % (or Line 3a at 106% for selected en
-
gines in diesel mode) can extend to an upper speed limit of 108 %. If needed for
demonstration of 100% CMCR power operation during sea trials, operating in
this overspeed range is only permissible in the presence of an authorised engine
builder representative. However, the specified torsional vibration limits must not
be exceeded.
SM-0323
0
10
20
30
40
50
60
70
80
90
100
110
0
10
20
30
40
50
60
70
80
90
100
110
Engine speed [% Rx]
Engine power [% Rx]
8
7
6
5
4
2
1
P09
P07
P06
P05
P04
(CMCR)
P03
P02
P01
P01
P02
P03
P04 (CMCR)
P05
P06
P07
P08
P09
40
60
96
100
40
60
96
103.2
108
20
36
96
100
24
40
102.3
110
110
Breakpoints
Engine
Speed [%Rx]
Engine
Power [%Rx]
P08
9
13
3
3a
