Man B&W S50ME-B9.3-TII User Manual

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 PRUvalue, 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 PRUvalues 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

Man B&W S50ME-B9.3-TII Specifications

General

Brand	Man
Model	B&W S50ME-B9.3-TII
Category	Engine
Language	English