MAN B&W 5L28/32H, Руководство пользователя

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08028-0D\H5250\94.08.12
B 13 00 0 External Cooling Water System
91.38
Design of External Cooling Water System
It is not difficult to make a system fulfil the require-
ments, but to make the system both simple and
cheap and still fulfil the requirements of both the
engine builder and other parties involved can be very
difficult. A simple version cannot be made without
involving the engine builder.
The diagrams on the following pages are principal
diagrams, and are MAN B&W's recommendation for
the design of external cooling water systems.
The systems are designed on the basis of the
following criteria:
1. Simplicity.
2. Separate HT temperature regulation for pro-
pulsion and alternator engines.
3. HT temperature regulation on engine outlet.
4. Preheating with surplus heat.
5. Preheating in engine top, downwards.
6. As few change-over valves as possible.
7. Possibility for Holeby ICS-system.
Ad 1) Cooling water systems have a tendency to be
unnecessarily complicated and thus uneconomic in
installation and operation. Therfore, we have attach-
ed great importance to simple diagram design with
optimal cooling of the engines and at the same time
installation- and operation- friendly systems result-
ing in economic advantages.
Ad 2) Cooling of alternator engines should be inde-
pendent of the propulsion engine load and vice
versa. Therefore, there should be separate cooling
water temperature regulation thus ensuring optimal
running temperatures irrespective of load.
Ad 3) The HT FW thermostatic valve should be
mounted on the engine's outlet side ensuring a
constant cooling water temperature above the en-
gine at all loads.
General
1613442-7.0
Page 1 (1)
If the thermostat valve is placed on the engine's inlet
side , which is not to be recommended, the tempera-
ture on the engine depends on the load with the risk
of overheating at full load.
Ad 4) It has been stressed on the diagrams that the
alternator engines in stand-by position as well as the
propulsion engine in stop position are preheated,
optimally and simply, with surplus heat from the
running engines.
Ad 5) If the engines are preheated with reverse
cooling water direction, i.e. from the top and down-
wards, an optimal heat distribution is reached in the
engine. This method is at the same time more
economic since the need for heating is less and the
water flow is reduced.
Ad 6) The systems have been designed in such a
way that the change-over from sea operation to
harbour operation/stand-by with preheating can be
made with a minimum of manual or automatic inter-
ference.
Ad 7) If the actual running situations demands that
one of the auxiliary engines should run on low-load,
the systems have been designed so that one of the
engines can be equipped with a cooling system for
ICS-operation(Integrated Charge air System).
Fresh Water Treatment
The engine cooling water is, like fuel oil and lubricat-
ing oil, a medium which must be carefully selected,
treated, maintained and monitored.
Otherwise, corrosion, corrosion fatigue and cavita-
tion may occur on the surfaces of the cooling system
which are in contact with the water, and deposits
may form.
Corrosion and cavitation may reduce the life time
and safety factors of parts concerned, and deposits
will impair the heat transfer and may result in thermal
overload of the components to be cooled.
The treatment process of the cooling water has to be
effected before the first commission of the plant, i.e.
immediately after installation at the shipyard or at the
power plant.