MAN B&W L28/32H, Руководство пользователя

Страница: 129 / 218

91.32
General
1609535-5.1
Page 1 (2)
Exhaust Gas System B 16 00 0
Internal exhaust gas system
From the exhaust valves, the gas is led to the
exhaust gas receiver where the fluctuating pressure
from the individual cylinders is equalized and the
total volume of gas led further on to the turbocharger,
at a constant pressure. After the turbocharger, the
gas is led to the exhaust pipe system.
The exhaust gas receiver is made of pipe sections,
one for each cylinder, connected to each other, by
means of compensators, to prevent excessive stress
in the pipes due to heat expansion.
In the cooled intermediate piece a thermometer for
reading the exhaust gas temperature is fitted and
there is also possibility of fitting a sensor for remote
reading.
To avoid excessive thermal loss and to ensure a
reasonably low surface temperature the exhaust
gas receiver is insulated.
External exhaust gas system
The exhaust back-pressure should be kept as low as
possible.
It is therefore of the utmost importance that the
exhaust piping is made as short as possible and with
few and soft bends.
Long, curved, and narrow exhaust pipes result in
higher back-pressure which may affect the engine
combustion.
The exhaust back-pressure should not exceed 250
mmWC at MCR. An exhaust gas velocity through the
pipe of maximum 35 m/sec is often suitable, but
depends on the actual piping.
Holeby will be pleased to assist in making a calcula-
tion of the exhaust back-pressure.
The gas outlet of turbocharger, the expansion bel-
lows, the exhaust pipe, and silencer, (in case of
silencer with spark arrestor care must be taken that
the cleaning parts are accessible), must be insula-
ted with a suitable material.
The insulation should be shielded by a thin plating,
and should comply with the requirements of the
classification society and/or the local authorities.
Exhaust pipe dimensions
It should be noted that concerning the maximum
exhaust gas velocity the pipe dimension after the
expansion bellow should be increased for some of
the engines.
The wall thickness of the external exhaust pipe
should be min. 3 mm.
Exhaust pipe mounting
When the exhaust piping is mounted, the radiation of
noise and heat must be taken into consideration.
Because of thermal fluctuations in the exhaust pipe,
it is necessary to use flexible as well as rigid
suspension points.
In order to compensate for thermal expansion in the
longitudinal direction, expansion bellows must be
inserted. The expansion bellows should preferably
be placed at the rigid suspension points.
Note: The exhaust pipe must not exert any force
against the gas outlet on the engine.
One sturdy fixed-point support must be provided for
the expansion bellows on the turbocharger. It should
be positioned, if possible, immediately above the
expansion bellow in order to prevent the transmis-
sion of forces, resulting from the weight, thermal
expansion or lateral displacement of the exhaust
piping, to the turbocharger.
The exhaust piping should be mounted with a slope
towards the gas outlet on the engine. It is recom-
mended to have drain facilities in order to be able to
remove condensate or rainwater.