Page 27 - Uninterruptible Power Supplies

Standby Power Generating Sets
Standby Power Generating Sets 25

If the temperature within the engine room is not maintained above 0°C
trace heating of the engine pipework and filters should be considered, or
discuss with the fuel supplier the possibility of using an antiwaxing addi-
tive. There are practical difficulties in ensuring that additives are dis-
persed throughout the store of fuel.
If the bulk tank is installed outside of the building, the filter at the out-
let should be a coarse filter that will not clog under cold conditions, oth-
erwise some trace heating of the filter pipework run will be required.

Long-Term Storage of Diesel Fuel
If a strategic quantity of fuel is stored on site for emergency purposes,
there are two hazards which may be encountered, microbiological growth
and chemical degradation. Water will inevitably collect at the base of the
tank due to internal condensation and microbiological growth occurs at
the oil/water interface. The water should be drained off as necessary and
any significant biological growth will be observed as sludge. If sludge is
observed specialist attention may be required. It is sometimes recom-
mended that 25 percent of the contents of a tank should be used and
replaced with new fuel each year.
Chemical degradation occurs independently of microbiological growth
and results in a darkening of the color of the fuel.
The problems are best avoided by good housekeeping involving regu-
lar draining of water from the tank, regular testing of the contents by
an experienced specialist organization, and regular usage so that new
oil can be added. These remarks are mainly directed at bulk tanks, but
water (and any sludge) should be regularly drained from service tanks.

Engine Cooling Systems
Water-Cooled Diesel Engines
Up to 40 percent of the energy of the fuel used by a modern diesel engine
is transferred to the crankshaft, the remaining energy is dispersed from
the exhaust gases, the radiator, and the engine casing. Manufacturers’
data for these losses vary widely but guideline figures may be consid-
ered as:

Useful energy transferred to generator 38.5 percent
Energy used by engine driven radiator fan 1.5 percent
Heat lost in exhaust gases 30.0 percent
Heat lost from radiator 25.0 percent
Heat lost from engine casing 5.0 percent

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