led after the service tank, the supply pumps will
have to handle the pressure drop across the
MDO/MGO cooler which cannot be recommended.
The cooling medium used for the MDO/MGO cooler
is preferably fresh water from the central cooling
water system.
Seawater can be used as an alternative to fresh
water, but the possible risk of MDO/MGO leaking
into the sea water and the related pollution of the
ocean, must be supervised.
The horizontal axis shows the bunkered fuel viscos-
ity in cSt at 40°C, which should be informed in the
bunker analysis report.
If the temperature of the MGO is below the upper
blue curve at engine inlet, the viscosity is above 2.0
cSt. The black thick line shows the viscosity at ref-
erence condition (40°C) according to ISO8217,
marine distillates.
Example: MGO with viscosity of 4.0 cSt at 40°C
must have a temperature below 55°C at engine inlet
to ensure a viscosity above 3.0 cSt.
Example: MGO with a viscosity of 5.0 cSt at 40°C is
entering the engine at 50°C. The green curves
show that the fuel enters the engine at approxi-
mately 4.0 cSt.
Example: MGO with a viscosity of 2.0 cSt at 40°C
needs cooling to 18°C to reach 3.0 cSt.
The following items should be considered before
specifying the MDO/MGO cooler :
▪ The flow on the fuel oil side should be the same
as the capacity of the fuel oil circulating pump
( see D 10 05 0, List of Capacities )
▪ The fuel temperature to the MDO/MGO cooler
depends on the temperature of the fuel in the
service tank and the temperature of return oil
from the engine(s)
▪ The temperature of the cooling medium inlet to
the MDO/MGO cooler depends on the desired
fuel temperature to keep a minimum viscosity of
2.0 cSt
▪ The flow of the cooling medium inlet to the
MDO/MGO cooler depends on the flow on the
fuel oil side and how much the fuel has to be
cooled
The frictional heat from the fuel injection pumps,
which has to be removed, appears from the table
below.
Engine type
kW/cyl.
L16/24 0.5
L21/31 1.0
L27/38 1.5
L32/40 2.0
L23/30H 0.75
L28/32H 1.0
L28/32DF 1.0
V28/32S 1.0
Based on the fuel oils available in the market as of
June 2009, with a viscosity ≥ 2.0 cSt at 40°C, a fuel
inlet temperature ≤ 40°C is expected to be sufficient
to achieve 2.0 cSt at engine inlet
(see fig 1).
In such case, the central cooling water / LT cooling
water (36°C) can be used as coolant.
For the lowest viscosity MGO´s and MDO´s, a water
cooled MGO/MGO cooler may not be enough to
sufficiently cool the fuel as the cooling water availa-
ble onboard is typically LT cooling water (36°C).
In such cases, it is recommended to install a so-
called “Chiller” that removes heat through vapour-
compression or an absorption refrigeration cycle
(see fig 2).
MAN Diesel & Turbo
E 11 06 1
MDO / MGO cooler
1689458-7.3
Page 2 (3)
L28/32S, L27/38S, L23/30DF, L23/30S, L16/24S, L21/31S, L28/32DF, V28/32H,
V28/32S, L16/24, L21/31, L23/30H, L27/38, L28/32H
2016.03.03
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