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6
6. ENGINE EXHAUST
Engine exhaust must be directed to the outside
through a properly designed exhaust system that
does not create excessive back pressure on the
engine. A suitable exhaust silencer should be
connected into the exhaust piping. Exhaust system
components located within the engine room should
be insulated to reduce heat radiation. The outer
end of the pipe should be equipped with a rain cap
or cut at 60° to the horizontal to prevent rain or
snow from entering the exhaust system. If the
building is equipped with a smoke detection
system, the exhaust outlet should be positioned so
it cannot set off the smoke detection alarm.
6.1 Exhaust Piping
For both installation economy and operating
efficiency, engine location should make the exhaust
piping as short as possible with minimum bends
and restrictions. Usually the exhaust pipe extends
through an outside wall of the building and
continues up the outside of the wall to the roof.
There should be a sleeve in the wall opening to
absorb vibration and an expansion joint in the pipe
to compensate for lengthways thermal expansion or
contraction. See figure 6.1.
It is not normally recommended that the engine
exhaust share a flue with a furnace or other
equipment since there is danger that back pressure
caused by one will adversely affect operation of the
others. Such multiple use of a flue should be
attempted only if it is not detrimental to
performance of the engine or any other equipment
sharing the common flue.
The exhaust can be directed into a special stack that
also serves as the outlet for radiator discharge air
and may be sound-insulated. The radiator
discharge air enters below the exhaust gas inlet so
that the rising radiator air mixes with the exhaust
gas. See figures 6.2 and 6.3. The silencer may be
located within the stack or in the room with its tail
pipe extending through the stack and then outward.
Air guide vanes should be installed in the stack to
turn radiator discharge air flow upward and to
reduce radiator fan air flow restriction, or the sound
insulation lining may have a curved contour to
direct air flow upward. For a generating set
enclosed in a penthouse on the roof or in a separate
outdoor enclosure or trailer, the exhaust and
radiator discharges can flow together above the
enclosure without a stack. Sometimes for this
purpose the radiator is mounted horizontally and
the fan is driven by an electric motor to discharge
air vertically.
FIG 6.1 TYPICAL EXHAUST SYSTEM INSTALLATION
EXHAUST
SILENCER
WALL SLEEVE
AND EXPANSION
JOINT
SILENCER/PIPEWORK
SUPPORTS
RAIN CAP