Xylem Fire diesel pump D Series GEN D Series - Manual (Page 44)

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Mount a rubber expansion joint between the engine exhaust manifold outlet (or the turbo-
blower exhaust outlet for the supercharged types) and the downstream pipe, to absorb the
thermal expansions and engine vibrations and protect the pipe from damage.
Using a rubber expansion joint, fasten the exhaust pipe to suitable brackets independent
from the diesel engine. Secure the pipes to the walls or ceiling using suitable pipe hangers
capable of supporting the weight of the pipes external to the engine without weighing onto
the engine (exhaust manifold or turbo-blower), and enabling expansion.
EXHAUST SILENCER
Normally, the exhaust silencer is already mounted with the exhaust manifolds. Only high
power engines require separate installation of the silencer.
Whenever possible, the silencer can also be installed outside the room.
The position of the silencer can generate resonances with the pipe resulting from the
pulsations of the gas; in this case you should adjust the distance of the silencer from the
engine along the pipe.
In case of installation in hospitals, residential units and similar applications, where lower noise
levels are required, special silencers should be used to ensure greater noise dampening
performances than those provided by the original silencers. Moreover, suitable plenum
chambers should be used whenever possible.
SIZING OF THE EXHAUST GAS PIPES
The engine’s exhaust counterpressure has a major effect on the power output of the engine
and its thermal load; excessive values (measured at the exhaust manifold outlet for aspirated
engines and at the turbine outlet for supercharged engines) cause power output reductions,
higher exhaust gas temperatures, higher grade of smoke, high fuel consumption, overheating
of the cooling water and lubricant deterioration, with the consequent negative repercussions
on the engine parts.
The pipes must be as short as possible and with the least possible number of elbows. When
elbows are needed, they must have wide bends (ideally, the radius of the bend should be 2.5
to 3 times the internal diameter of the pipe). Elbows must be counted along the overall
length of the pipe based on the equivalent length Lo. The table below provides guidelines for
various types of bends.
The piping must be sized based on the length of the pipe, its characteristics and the
admissible counterpressure value. Specific tables and normograms can be used for the
calculation. A typical calculation normogram is shown below. Remember to take into
account also the silencer counterpressure.
In any case, the exhaust pipe must never have a smaller diameter than that of the engine
exhaust manifold.