Iveco Marine Diesel Engines, Installation Handbook

Page: 93 / 132

MARCH 2004 DISCHARGE
9.93
MARINE ENGINES INSTALLATION
9.1 OVERVIEW
The discharge system of marine engine exhaust gases can be divided in two categories:
■
Dry discharge
■
Mixed discharge
The choice of the type of discharge is the staff ’s decision and it depends on the vessel structure and
on the desired comfort. Dry discharge is generally chosen by high power engines in professional ves-
sels, while mixed discharge is chosen for pleasure vessels that need more comfort in terms of noise and
fumes in passenger areas.
9.2 DRY DISCHARGE
Exhaust gases are expelled through pipes; for safety reasons and to avoid heat radiation these pipes
should be fitted with an appropriate thermal insulation made of non-flammable, fuel-proof and lubri-
cant oil-resistant.
An alternative system to protect discharge conduits consists of lining the pipes to make water run
through the interstice.This solution requires the regulation of the flow of refrigeration water to avoid
exhaust gases excessive cooling, since this would form acid condensations and fumes during exhaus-
tion.
The three-way valve regulation allows the engine circuit water drainage without causing throttling in the
water circuit.
If secondary circuit water is used, this should be drained at the circuit outlet, paying special attention to
avoid spillage that would reduce the pump water flow. Coolant from the engine primary circuit must
not be used.
In the case of engines mounted on rigid supports, the pipes must be fitted with a joint to compensate
thermal dilatation. The expansion joints, generally shaped as stainless steel bellows, must axially com-
pensate dilatations and must not vibrate (Fig. 1).
Insulating exhaust pipes with thermal lining, not only aims to avoid the vibration caused by the engine
and the thrust of the exhaust gases, but also thermal dilatations due to high temperature.Therefore, it
is important to provide flexible insulation to reduce vibration without hindering dilatation movements.
Figure 1