WÄRTSILÄ WARTSILA 20, Product Manual

Page: 117 / 178

11.3 External exhaust gas system
Each engine should have its own exhaust pipe into open air. Backpressure, thermal expansion
and supporting are some of the decisive design factors.
Flexible bellows must be installed directly on the turbocharger outlet, to compensate for
thermal expansion and prevent damages to the turbocharger due to vibrations.
Diesel engine 1
Exhaust gas bellows 2
Connection for measurement of back pressure 3
Transition piece 4
Drain with water trap, continuously open 5
Bilge 6
SCR 7
Urea injection unit (SCR) 8
CSS silencer element 9
Fig 11-4 External exhaust gas
system
11.3.1 Piping
The piping should be as short and straight as possible. Pipe bends and expansions should
be smooth to minimise the backpressure. The diameter of the exhaust pipe should be increased
directly after the bellows on the turbocharger. Pipe bends should be made with the largest
possible bending radius; the bending radius should not be smaller than 1.5 x D.
The recommended flow velocity in the pipe is maximum 35…40 m/s at full output. If there are
many resistance factors in the piping, or the pipe is very long, then the flow velocity needs to
be lower. The exhaust gas mass flow given in chapter Technical data can be translated to
velocity using the formula:
where:
gas velocity [m/s] v =
exhaust gas mass flow [kg/s] m' =
exhaust gas temperature [°C] T =
exhaust gas pipe diameter [m] D =
Wärtsilä 20 Product Guide - a13 - 6 September 2016 11-3
11. Exhaust Gas System Wärtsilä 20 Product Guide