Operation0070−1/A1
Winterthur Gas & Diesel Ltd.
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2. Fixed Pitch Propeller (FPP)
2.1 Continuous Service Rating (CSR)
Point A (see Fig. 1) shows the power and speed of a ship that operates at contractual
speed in calm seas with a new clean hull and propeller. A power / speed combination
at point D is necessary for the same ship at the same speed during service conditions
with aged hull and average weather. Point D is then the CSR point.
2.2 Engine Margin (EM) / Operational Margin (OM)
Most owners specify the contractual loaded service speed of the ship at 85% to 90%
of the contract maximum continuous rating (CMCR). The remaining 10% to 15% of
power can be used to catch up with changes in schedules or for the timing of dry-dock
intervals. This margin is usually subtracted from the CMCR. Thus, to get the 100%
power line, you divide the power at point D by between 0.85 to 0.90.
110
10% EM / OM
100
80
B
D
15% SM
CMCR (Rx)
Engine load range
65 70 80 90 95 100 104
108
93.8
95
90
76.5
70
60
50
40
A
4
5
6
3
2
1
F10.5249
Engine power
[% Rx]
Engine speed
[% Rx]
103.2
Propeller curve
without SM
Constant
torque
Load range limits with load diagram of an
engine related to a specified rating point Rx
EM Engine Margin
OM Operational Margin
SM Sea Margin
Fig. 1: Schematic Diagram of Speed / Power Relation (FPP)
2014
The Relation between Engine and Propeller
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