Iveco Marine Diesel Engines, Installation Handbook

Page: 15 / 132

MARCH 2004 INTRODUCTION
1.15
MARINE ENGINES INSTALLATION
Since there are no established rules for the calculation of the heavy duty rate according to the load fac-
tor, it is possible to consider the following elements:
■
Light work load factor below 50%
■
Medium work load factor from 50 to 70%
■
Heavy work load work above 70%
Therefore, the work factor is an index of the work heaviness.
The definition of load factor already includes the time parameter. However, it is important to stress the
concept of “continuous” work or “intermittent” work (see figure 5):
■
As continuous work it is usually meant the engine constant operation at maximum load (24 hours
a day), with minor load and speed variations, or having no variations at all.
■
As intermittent work it is meant the use of the engine with frequent and substantial load and/or
speed variations.
In the marine sector, for example:
■
The continuous work corresponds to that of work boats
(fishing, tug-boats, ferry-boats).
■
The intermittent work corresponds to that of commercial boats
(coastguard and sea rescue, crew transport, etc.).
Finally, there is the definition of:
■
Pleasure boats (yachts), where the engine use is intermittent and limited to the typical life of yachts,
for which maximum powers higher than the previous cases are accepted.
In this respect, see the power classification included in the technical-commercial documentation of each
engine.
The above mentioned points are fundamental for the choice of the engine in terms of piston displace-
ment, power, overhaul intervals, engine and transmission foreseeable duration.
In particular, it is important to bear in mind that the engine load, i.e. its real average pressure, influences
the engine overhaul intervals.
Figure 5
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
Load per
centage
Heavy continuous Heavy intermittent Medium variable
A B C