LIGHT LOAD OPERATION & STANDBY GENERATING SETS
32 4
012/16 Diesel, February 1997
If an engine is operated on a load less than
25-30% of its rated output, certain symptoms
will be observed which may give cause for
concern.
The usual results of this operation are
heavier than normal lubricating oil
consumption, and oil leaks from the air and
exhaust manifolds. This condition is
particularly evident on stand-by generator
set applications where a weekly exercise on
no load is the usual practice.
These phenomena are due to the fact that:
1 Turbocharger oil seals are not fully
effective on light load which results in oil
being delivered together with the air into
the engine air manifolds.
2 The cylinder temperatures are too low to
ensure complete burning of all the fuel
delivered. This results in an unsightly
drip from the exhaust manifold
junctions. A further result is that of
abnormal carbon build-up on the valves,
piston crowns and exhaust ports, thus
the normal service interval of 2500
hours between top overhauls may have
to be reduced. Fuel dilution of the
lubricating oil will also occur.
To alleviate this condition the following
recommendations are made:-
1 Running on light load should be avoided
or reduced to the minimum period. If
weekly exercising on no load is carried
out, the running period should be kept
down to say, 10 minutes, or until the
battery charging rate returns to normal.
Periodically site load should be applied
(min 25%) through the year.
2 Every year the engine or generator set
should be run for four hours, to burn off
accumulations of carbon in the engine
and exhaust system. This will require
the use of a 'dummy load', which
should be built up gradually from zero to
the maximum over a four hour run.
On standby sets, air cleaner elements
should be changed annually.
Lubricating oil and fuel filter elements
should be changed every six months.
The fuel pump injectors should be
checked every 2 years.
