MAN B&W S65ME-C8.2-GI-TII, Project Manual

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MAN B&W 7.09
Page 2 of 7
MAN Diesel MAN B&W ME-GI TII engines 198 86 39-0.2
Leakage detection and ventilation system
The purpose of the leakage detection and ventila-
tion system is to ensure that the outer pipe of the
double-wall gas pipe system is constantly ventilat-
ed by air. In this way securing gas leakages if any,
to be detected and transported to a secure place
outside the engine room the ventilation system is
required where double wall piping is applied, in all
enclosed areas on board the vessel.
General data for ventilation system
Medium: ................................................Ambient air
Minimum air supply inlet pressure: ....... 500 mBarg
(to be set at reduction valve)
Air supply quality: ........................ ISO 8573-1: 7 3 4
Pressure dewpoint Class 3
d
÷20 °C
Ventilation air pressure must always be less at-
mospheric pressure, so a ventilation fan is also
required to suck the supply air through the ventila-
tion system from the air supply inlet cover.
Minimum ventilation air pressure: ..........÷10 mBarg
Temperature range: ......................÷20 °C to +55 °C
Venting air fan capacity
To decide the necessary capacity for the fan, the
volume of the intermediate spaces of the pipe
system must be calculated. The complete volume
consists of:
• the volume of the annular spaces in the main
pipes
• the volume of the annular space in the chain
pipes
• the vented volume in the gas control block.
For further information regarding pipe sizes and
venting volume in the gas block for a specific en-
gine type, contact MAN Diesel & Turbo.
Based on the calculated volume, the capacity
must ensure a minimum of 30 air changes per
hour.
Fan requirements and installation guidelines
Ventilation is achieved by means of an electrically
driven extractor fan on deck. The fan must work
independently of any other fan installation in the
engine room/power plant.
The electric fan motor as well as the starters have
to be located outside the ventilated pipe and its
connected ducting.
The fan has to be protected with a wire mesh
(max 13 mm square mesh) in the outside opening
which is also to be protected against rain/water
entrance. In no case is the radial air gap between
the impeller and the casing to be less than 0.1
times the diameter of the impeller shaft in way of
the bearing but not less than 2 mm. It need not be
more than 13 mm.
The parts of the rotating body and of the casing
are to be made of spark free materiel and they are
to have antistatic properties. The installation of
the ventilation units is to made such as to ensure
the bonding to the structure/hull of the unit them-
selves.
The ventilation inlet is to be located in open air
away from ignition sources, and it is recommend-
ed to consider inlet and outlet as ATEX zone 1.
Venting air fan control
The fan is to be controlled from the GI-ECS, see
Fig. 16.02.03 ‘GI Extension Interface to External
Systems’, with reference to the signals going to
and from ‘Double Wall Pipe Ventilation’.
Two flow switches must be installed in the venting
air intake to monitor that air is flowing through the
ventilation system and the pipes are vented suf-
ficiently.