Man L23/30DF, Project Manual

Page: 197 / 392

General
This data sheet contains data regarding the neces-
sary information for dimensioning of auxiliary machi-
nery in the external cooling water system for the
L27/38 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".
Set points and operating levels for temperature and
pressure are stated in
B 19 00 0 "Operating Data
and Set Points".
Cooling water pressure
Max. cooling water inlet pressure before engine is
2.5 bar.
External pipe velocitiy
For external pipe connections we prescribe the fol-
lowing maximum water velocity:
Fresh water : 3.0 m/s
Pressure drop across engine
The engines have an attached centrifugal pump for
both LT and HT cooling water. The pressure drop
across the engine's system is approximately 0.5
bar. Therefore the internal pressure drops are negli-
gible for the cooling water pumps in the external
system. For engines installed in closed cooling
water systems, without any external cooling
water pumps, the pressure drop in the external
system should not exceed 1.0 bar.
Expansion tank
To provide against volume changes in the closed
jacket water cooling system, caused by changes in
temperature or leakage, an expansion tank must be
installed.
As the expansion tank also provides a certain suc-
tion head for the fresh water pump to prevent cavi-
tation, the lowest water level in the tank should be
minimum 8-10 m above the center line of the crank-
shaft.
The venting pipe must be made with continuous
upward slope of minimum 5°, even when the ship
heel or trim (static inclination).
The venting pipe must be connected to the expan-
sion tank below the minimum water level; this pre-
vents oxydation of the cooling water caused by
"splashing" from the venting pipe. The expansion
tank should be equipped with venting pipe and
flange for filling of water and inhibitors.
Minimum recommended tank volume: 0.15 m³.
For multi plants the tank volume should be min.:
V = 0.15 + (exp. vol. per extra eng.) [m³]
On engines equipped with 1-string cooling water
system, the LT system is vented via the HT system.
This means that both systems are connected to the
same expansion tank.
On engines equipped with 2-string cooling water
system, separate expansion tanks for the LT sys-
tem and HT system must be installed. This to
accommodate for changes of volume due to vary-
ing temperatures and possible leakage in the LT
system and/or the HT system. The separated HT
system and LT system facilitates trouble shooting.
Data for external preheating system
High pressure from external cooling water pumps
may disturb the preheating of the engine. In order to
avoid this, it is in most cases necessary to install
automatic shut off valve at cooling water inlet, which
close when the engine is stopped.
The capacity of the external preheater should be
3.0-3.5 kW/cyl. The flow through the engine should
for each cylinder be approx. 4 l/min with flow from
top and downwards and 25 l/min with flow from
bottom and upwards. See also table 1 below.
Cyl. No. 5 6 7 8 9
Quantity of water
in eng: HT and
LT system (litre) 150 180 210 240 270
Expansion vol.
(litre) 10 12 13 15 20
Preheating data:
Radiation area
(m2)
Thermal coeff.
(kJ/°C)
30
7200
33
8550
36
9970
39
11400
46
12820
Table 1: Showing cooling water data which are depending on
the number of cylinders.
MAN Diesel & Turbo
1665774-3.7
Page 1 (1)
Design data for the external cooling water system
B 13 00 0
L27/38S, L27/38
2015.01.05