Marine Installation Manual
2021-08
2-4
2 Engine Power and Speed
2.4 Power range
X72DF
Figure 2
-
2 Propeller curves and operational points
outlines the various engine limits, propeller curves and margins re
-
quired for engine optimisation. By incorporating the margins listed below, the
various operational points and subsequently the CMCR point can be determined
(see section
for detailed descriptions of the various line limits).
Sea trial power
The sea trial power must be specified.
shows the sea trial power to be
the power required for reaching service speed (point A) on the propeller curve
with a light running margin (Line 8).
Sea margin
The Sea Margin (SM) is defined as the increase in power to maintain a given
ship’s speed achieved in calm weather (point A in
) under average ser
-
vice condition (point B). This margin can vary depending on the owner’s and
charterer’s expectations, routes, season and schedules of the ship.
The location of reference point A and the magnitude of the sea margin are part of
the new building contract and are determined between the shipbuilder and the
owner. Typically, the sea margin is specified in the range of 10 to 25% of the sea
trial power.
SM-0026
Contracted maximum
continuous rating
CMCR (Rx)
Continuous service rating
Sea trial power
Ship speed [% service speed]
Engine speed [% CMCR rpm]
Engine power [% CMCR power]
EM
SM
LR
3
4
5
7
7
8
8
A
B
C
EM
LR
SM
Line 3
Line 4
Line 5
Line 7
Line 8
Power and ship speed during sea-trials - light running and ideal sea condition
Ship design point / Continuous service rating
Recommended point for adaptation of propeller pitch under sea-trial condition
Engine margin
Light running margin
Sea margin
Maximum engine speed limit for continuous operation
Maximum engine overspeed limit during sea-trials
Admissible torque limit
Nominal engine characteristic curve
Propeller curve with a light running margin
100
100
100
100
Maximum continuous power
Continuous service power
Sea trial power
Service speed
Service rpm
CMCR rpm
Sea trial rpm
Sea trial speed
A
B
C
A
B
C
