3.3.2 Fixed pitch propeller (FPP)
3.3.2.1 Continuous service rating
Point A (Figure 3-7) 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.
3.3.2.2 Engine margin / operational margin
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.
3.3.2.3 Load range limits
Fig 3-6 Schematic diagram - Relation Speed/Power (FPP)
110
100
95
90
80
70
60
50
40
65 70 80 90 95 104100 108
Engine power
[% Rx]
Engine speed
[% Rx]
Propeller curve
without SM
EM/OM
SM
4
3
1
2
5
6
CMCR (Rx)
B
A
D
Engine load range
Constant torque
Nominal propeller characteristic
LR
00117
When the engine has the best values at CMCR (R
X
), the limits that follow give the load range of
the engine:
•
Line 1 is a constant MEP or torque line through CMCR from 100% speed and power
down to 95% speed and power.
X92DF
AA00-0000-00AAA-042B-A
Operation Manual The relation between engine and propeller
Winterthur Gas & Diesel Ltd.
- 73 - Issue 002 2020-08
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