
126 SEBU8088-06
Reference Information Section
Engine Ratings
Reference Information
Section
Engine Ratings
i00727327
Engine R atin
g Con dit ions
SMCS Code: 1000
All engine ratings are in compliance with the following
standard ambient air conditions of “SAE J1349”:
•
99 kPa (29.3 inches of Hg)
•
30 percent re
lative humidity
•
A temperature of 25 °C (77 °F)
Ratings relate to the standard conditions of
“ISO8665”, of “ISO3046/1”, of “DIN6271”, and of
“BS5514”.
The engine ratings are based on the following fuel
specificati
ons:
•
Low heat value (LHV) of the fuel of 42 780 kJ/kg
(18,390 Btu
/lb) at 29 °C (84 °F)
•
Gravity (API) of 35 degrees at 15 °C (60 °F)
•
Specific gravity of .849 at 15 °C (60 °F)
•
Density of
850 kg/m
3
(7.085 lb/US gal)
The engine ratings are gross output ratings.
Gross Output Ratings – The total output capability
of the engine that is equipped with standard
accessori
es.
Standard accessories include the following
component
s:
•
Oil pumps
•
Fuel pumps
•
Water pump
s
Subtract the power that is required to drive auxiliary
component
s from the gross output. This will produce
the net power that is available for the external load
(flywheel).
i01250210
Engine Rating Definitions
SMCS Code: 1000
The ratings mus
t be reduced in order to accommodate
changes in the altitude. The ratings must be reduced
according to the data for derating that is obtained
from the test s
pecification for the engine.
All of the ratings that are definedhavea
manufacturin
g tolerance of ± three percent.
Use the following guidelines in order to determine the
applicable e
ngine rating.
NOTICE
Operating an engine at a greater power output than
the engine is r
ated for will reduce the service life of
the engine before overhaul.
Ratings for Generator Set Engines
Load Factor –
The sum of the loads divided by the
number of hours of operation. Idle time and down
time are not part of the calculation.
Power Interruption – Unexpected failure of the
utility power supply.
Operating Cycle – Unless the operating cycle
is specified differently, the operating cycle for
calculatin
g the load factors and the peak load limits is
not to exceed 24 hours. The operating cycle does not
include the time when the engine is not operating.
Continuous – This rating allows a constant load
or a load that varies for an unlimited number of
hours per y
ear. The normal load factor is up to 100
percent for an unlimited number of hours per year.
The following applications are suggested: base load,
utility, c
ogeneration, and parallel operation.
Prime – This rating allows a load that varies for an
unlimite
d number of hours per year. The normal load
factor is up to 80 percent for an unlimited number of
hours per year. A 100 percent load is only allowed
for 5 perc
ent of the operating cycle. The following
applications are suggested: industrial, pumping,
construction, and cogeneration.