MAN B&W
17.04
Page of
MAN Diesel
MAN B&W L35MC6
198 58 79-3.0
Power Related Unbalance
To evaluate if there is a risk that st and 2nd or-
der external moments will excite disturbing hull
vibrations, the concept Power Related Unbal-
ance (PRU) can be used as a guidance, see Table
7.04.0 below.
PRU =
External moment
___________
Engine power
Nm/kW
With the PRUvalue, stating the external moment
relative to the engine power, it is possible to give
an estimate of the risk of hull vibrations for a spe-
cific engine.
Based on service experience from a great number
of large ships with engines of different types and
cylinder numbers, the PRUvalues have been
classified in four groups as follows:
Table 17.04.01: Power Related Unbalance (PRU) values in Nm/kW
Calculation of External Moments
In the table at the end of this chapter, the exter-
nal moments (M
) are stated at the speed (n
) and
MCR rating in point L
of the layout diagram. For
other speeds (n
A
), the corresponding external mo-
ments (M
A
) are calculated by means of the formula:
M
A
= M
x
{
n
A
__
n
}
2
kNm
(The tolerance on the calculated values is 2.5%).
PRU Nm/kW
Need for compensator
0 - 60
Not relevant
60 - 20
Unlikely
20 - 220
Likely
220 -
Most likely
L35MC6 – 650 kW/cyl at 210 r/min
5 cyl.
6 cyl.
7 cyl.
8 cyl.
9 cyl.
10 cyl.
11 cyl.
12 cyl.
14 cyl.
PRU acc. to st order, Nm/kW
9.
0.0
3.9
5.7
0.3
2.3
.4
0.6
N.a.
PRU acc. to 2nd order, Nm/kW
88.0
5.0
2.6
0.0
.2
0.5
.8
0.3
N.a.
Based on external moments in layout point L
N.a.
Not applicable
Summary of Contents for B&W L35MC6-TII
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Page 19: ...MAN B W MAN Diesel Engine Design 1 ...
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Page 35: ...MAN B W MAN Diesel Engine Layout and Load Diagrams SFOC 2 ...
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Page 65: ...MAN B W MAN Diesel Turbocharger Selection Exhaust Gas By pass 3 ...
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Page 73: ...MAN B W MAN Diesel Electricity Production 4 ...
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Page 95: ...MAN B W MAN Diesel Installation Aspects 5 ...
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Page 147: ...MAN B W MAN Diesel List of Capacities Pumps Coolers Exhaust Gas 6 ...
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Page 171: ...MAN B W MAN Diesel Fuel 7 ...
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Page 187: ...MAN B W MAN Diesel Lubricating Oil 8 ...
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Page 203: ...MAN B W MAN Diesel Cylinder Lubrication 9 ...
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Page 213: ...MAN B W MAN Diesel Piston Rod Stuffing Box Drain Oil 10 ...
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Page 217: ...MAN B W MAN Diesel Central Cooling Water System 11 ...
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Page 223: ...MAN B W MAN Diesel Seawater Cooling System 12 ...
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Page 235: ...MAN B W MAN Diesel Starting and Control Air 13 ...
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Page 243: ...MAN B W MAN Diesel Scavenge Air 14 ...
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Page 257: ...MAN B W MAN Diesel Exhaust Gas 15 ...
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Page 273: ...MAN B W MAN Diesel Engine Control System 16 ...
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Page 289: ...MAN B W MAN Diesel Vibration Aspects 17 ...
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Page 305: ...MAN B W MAN Diesel Monitoring Systems and Instrumentation 18 ...
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Page 329: ...MAN B W MAN Diesel Dispatch Pattern Testing Spares and Tools 19 ...
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Page 361: ...MAN B W MAN Diesel Project Suppport and Documentation 20 ...
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Page 371: ...MAN B W MAN Diesel Appendix A ...
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