7 семестр (Бормотов А) / 1man_bw_l23_30_chn_23_30_instruktsiya_po_ekspluatatsii_1 / MAN-BW L23-30h project-guide

General

This data sheet contains data regarding the necessary information for dimensioning of auxiliary machinery in the external cooling water system for the L23/30 type engine(s).The stated data are for one engine only and are specified at MCR.

For heat dissipation and pump capacities see D 10 05 0 "List of Capacities". Setpoints and operating levels for temperature and pressure are stated in B 19 00 0 "Operating Data and Setpoints".

External pipe velocities

For external pipe connections we prescribe the following maximum water velocties:

Pressure drop across engine

The pressure drop across the engines HT system, exclusive pump and thermostatic valve is approx. 0.5 bar.

Lubricating oil cooler

The pressure drop of cooling water across the builton lub. oil cooler is approx. 0.3 bar, the pressure drop may be different depending on the actual cooler design.

Thermostatic valve

The pressure drop across the built-on thermostatic valve is approx. 0.5 bar.

Charge air cooler

The pressure drop of cooling water across the charge air cooler is:

Pumps

The cooling water pumps should be of the centrifugal type.

Expansion tank

To provide against changes in volume in the closed jacket water cooling system caused by changes in tempera-ture or leakage, an expansion tank must be installed.

As the expansion tank also provides a certain suction head for the fresh water pump to prevent cavation, the lowest water level in the tank should be minimum 5 m above the centerlinie of the crankshaft.

Minimum recommended tank volume: 0.1 m³. For multiplants the tank volume should be min.:

V = 0.1 + ( exp. vol. per ekstra eng.) [m³]

Data for external preheating system

The capacity of the external preheater should be 0.8- 1.0 Kw/cyl. The flow through the engine should for each cylinder be approx. 1.4 l/min with flow from top and downwards and 10 l/min with flow from bottom and upwards. See also table 1 below.

Design of External Cooling Water System

It is not difficult to make a system fulfil the requirements, 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 propulsion 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 attached great importance to simple diagram design with optimal cooling of the engines and at the same time installationand operationfriendly systems resulting in economic advantages.

Ad 2) Cooling of alternator engines should be independent 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 engine at all loads.

If the thermostat valve is placed on the engine's inlet side , which is not to be recommended, the temperature 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 downwards, 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 interference.

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 lubricating oil, a medium which must be carefully selected, treated, maintained and monitored.

Otherwise, corrosion, corrosion fatigue and cavitation 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.