MAN B&W
17.04
Page 1 of 1
MAN Diesel
MAN B&W S50ME-B9
198 76 80-1.1
Power Related Unbalance
To evaluate if there is a risk that 1st 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
17.04.01 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
1
) are stated at the speed (n
1
) and
MCR rating in point L
1
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
1
x
{
n
A
__
n
1
}
2
kNm
(The tolerance on the calculated values is 2.5%).
PRU Nm/kW
Need for compensator
0 - 60
Not relevant
60 - 120
Unlikely
120 - 220
Likely
220 -
Most likely
S50ME-B9 – 1,780 kW/cyl at 117 r/min
5 cyl.
6 cyl.
7 cyl.
8 cyl.
9 cyl.
10 cyl.
11 cyl.
12 cyl.
14 cyl.
PRU acc. to 1st order, Nm/kW
11.5
0.0
4.9
14.3
13.0
N.a.
N.a.
N.a.
N.a.
PRU acc. to 2nd order, Nm/kW
135.9
78.8
19.6
0.0
17.2
N.a.
N.a.
N.a.
N.a.
Based on external moments in layout point L
1
N.a.
Not applicable
Summary of Contents for B&W S50ME-B9.3-TII
Page 4: ......
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Page 11: ...MAN B W MAN Diesel Engine Design 1 ...
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Page 27: ...MAN B W MAN Diesel Engine Layout and Load Diagrams SFOC 2 ...
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Page 53: ...MAN B W MAN Diesel Turbocharger Selection Exhaust Gas By pass 3 ...
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Page 59: ...MAN B W MAN Diesel Electricity Production 4 ...
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Page 93: ...MAN B W MAN Diesel Installation Aspects 5 ...
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Page 133: ...MAN B W MAN Diesel List of Capacities Pumps Coolers Exhaust Gas 6 ...
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Page 155: ...MAN B W MAN Diesel Fuel 7 ...
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Page 171: ...MAN B W MAN Diesel Lubricating Oil 8 ...
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Page 189: ...MAN B W MAN Diesel Cylinder Lubrication 9 ...
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Page 199: ...MAN B W MAN Diesel Piston Rod Stuffing Box Drain Oil 10 ...
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Page 203: ...MAN B W MAN Diesel Central Cooling Water System 11 ...
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Page 209: ...MAN B W MAN Diesel Seawater Cooling System 12 ...
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Page 221: ...MAN B W MAN Diesel Starting and Control Air 13 ...
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Page 227: ...MAN B W MAN Diesel Scavenge Air 14 ...
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Page 239: ...MAN B W MAN Diesel Exhaust Gas 15 ...
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Page 255: ...MAN B W MAN Diesel Engine Control System 16 ...
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Page 265: ...MAN B W MAN Diesel Vibration Aspects 17 ...
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Page 281: ...MAN B W MAN Diesel Monitoring Systems and Instrumentation 18 ...
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Page 307: ...MAN B W MAN Diesel Dispatch Pattern Testing Spares and Tools 19 ...
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Page 323: ...MAN B W MAN Diesel Project Support and Documentation 20 ...
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Page 333: ...MAN B W MAN Diesel Appendix A ...
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