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MAN B&W 15.03
Exhaust Gas System for Main Engine
At the specified MCR of the engine, the total
back�pressure in the exhaust gas system after the
turbocharger (as indicated by the static pressure
measured in the piping after the turbocharger)
must not exceed 350 mm WC (0.035 bar).
In order to have a back�pressure margin for the
final system, it <strong>is</strong> recommended at the design
stage to initially use a value of about 300 mm WC
(0.030 bar).
The actual back�pressure in the exhaust gas
system at specified MCR depends on the gas
velocity, i.e. it <strong>is</strong> proportional to the square of the
exhaust gas velocity, and hence inversely proportional
to the pipe diameter to the 4th power. It has
by now become normal practice in order to avoid
too much pressure loss in the pipings to have an
exhaust gas velocity at specified MCR of about
35 m/sec, but not higher than 50 m/sec.
For dimensioning of the external exhaust pipe
connections, see the exhaust pipe diameters for
35 m/sec, 40 m/sec, 45 m/sec and 50 m/sec respectively,
shown in Table 5.07.02.
As long as the total back�pressure of the exhaust
gas system (incorporating all res<strong>is</strong>tance losses
from pipes and components) complies with the
above�mentioned requirements, the pressure
losses across each component may be chosen independently,
see proposed measuring points (M)
in Fig. 5.05.0 . The general design guidelines for
each component, described below, can be used
for guidance purposes at the initial project stage.
Exhaust gas piping system for main engine
The exhaust gas piping system conveys the gas
from the outlet of the turbocharger(s) to the atmosphere.
The exhaust piping <strong>is</strong> shown schematically in
Fig. 5.04.0 .
Page of
The exhaust system for the main engine compr<strong>is</strong>es:
• Exhaust gas pipes
• Exhaust gas boiler
• Silencer
• Spark arrester (if needed)
• Expansion joints (compensators)
• Pipe bracings.
In connection with dimensioning the exhaust gas
piping system, the following parameters must be
observed:
• Exhaust gas flow rate
• Exhaust gas temperature at turbocharger outlet
• Maximum pressure drop through exhaust gas
system
• Maximum no<strong>is</strong>e level at gas outlet to atmosphere
• Maximum force from exhaust piping on
turbocharger(s)
• Sufficient axial and lateral elongation ability of
expansion joints
• Util<strong>is</strong>ation of the heat energy of the exhaust gas.
Items that are to be calculated or read from tables
are:
• Exhaust gas mass flow rate, temperature and maximum
back pressure at turbocharger gas outlet
• Diameter of exhaust gas pipes
• Util<strong>is</strong>ation of the exhaust gas energy
• Attenuation of no<strong>is</strong>e from the exhaust pipe outlet
• Pressure drop across the exhaust gas system
• Expansion joints.
MAN B&W MC/MC�C, ME/ME�C/ME�GI/ME-B engines 198 40 74�6.3
MAN Diesel