Wartsila 31 Product Manual page 111

Wärtsilä 31 Product Guide
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:
The exhaust pipe must be insulated with insulation material approved for concerned operation
conditions, minimum thickness 30 mm considering the shape of engine mounted insulation.
Insulation has to be continuous and protected by a covering plate or similar to keep the
insulation intact.
Closest to the turbocharger the insulation should consist of a hook on padding to facilitate
maintenance. It is especially important to prevent the airstream to the turbocharger from
detaching insulation, which will clog the filters.
After the insulation work has been finished, it has to be verified that it fulfils SOLAS-regulations.
Surface temperatures must be below 220°C on whole engine operating range.
10.3.2 Supporting
It is very important that the exhaust pipe is properly fixed to a support that is rigid in all
directions directly after the bellows on the turbocharger. There should be a fixing point on
both sides of the pipe at the support. The bellows on the turbocharger may not be used to
absorb thermal expansion from the exhaust pipe. The first fixing point must direct the thermal
expansion away from the engine. The following support must prevent the pipe from pivoting
around the first fixing point.
Absolutely rigid mounting between the pipe and the support is recommended at the first fixing
point after the turbocharger. Resilient mounts can be accepted for resiliently mounted engines
with long bellows, provided that the mounts are self-captive; maximum deflection at total
failure being less than 2 mm radial and 4 mm axial with regards to the bellows. The natural
frequencies of the mounting should be on a safe distance from the running speed, the firing
frequency of the engine and the blade passing frequency of the propeller. The resilient mounts
can be rubber mounts of conical type, or high damping stainless steel wire pads. Adequate
thermal insulation must be provided to protect rubber mounts from high temperatures. When
using resilient mounting, the alignment of the exhaust bellows must be checked on a regular
basis and corrected when necessary.
After the first fixing point resilient mounts are recommended. The mounting supports should
be positioned at stiffened locations within the ship's structure, e.g. deck levels, frame webs
or specially constructed supports.
The supporting must allow thermal expansion and ship's structural deflections.
Wärtsilä 31 Product Guide - a1 - 18 October 2016
v = gas velocity [m/s]
m' = exhaust gas mass flow [kg/s]
T = exhaust gas temperature [°C]
D = exhaust gas pipe diameter [m]
10. Exhaust Gas System
10-7