Marine Installation Manual
2021-08
4-79
4 Ancillary Systems
4.6 Fuel oil system
X72DF
Separators without
gravity discs
These separators are self-adjusting to the fuel properties and self-cleaning. Sep
-
arators without gravity discs operate as combined purifiers-clarifiers; thus water
and sediment separation is integrated in one unit. The manufacturers claim ex
-
tended periods between overhaul. Compared to the outdated separators with
gravity discs, the reliability is greatly improved, enabling unattended onboard
operation. As it is usual to install a standby separator as a back-up, it is of advan
-
tage to use both units in parallel to improve the separation result.
For further details and information regarding the separators please refer to the
manufacturer’s instructions.
Separation efficiency
The separation efficiency is a measure of the separator's capability to remove
specified test particles. The separation efficiency is defined as follows:
where:
n
............... = separation efficiency [%]
C
out
........... = number of test particles in cleaned test oil
C
in
............ = number of test particles in test oil before separator
Certified Flow Rate
To express the performance of separators according to a common standard, the
term Certified Flow Rate (CFR) has been introduced. CFR is defined as the flow
rate in litres/hour, 30 minutes after sludge discharge, at which the separation ef
-
ficiency is 85% when using defined test oils and test particles. CFR is defined for
equivalent fuel oil viscosities of 380 and 700cSt at 50°C.
More information can be found in the CEN document CWA 15375:2005 (E) of
the European Committee for Standardization.
Throughput capacity
The required minimum effective throughput capacity (litres/hour) of the separa
-
tors is determined by the formula 1.2
•
CMCR
•
BSFC
•
10
-3
[litres/hour] as shown
in the following example. The nominal separator capacity and the installation
are to comply with the recommendations of the separator manufacturer.
(The MDO separator capacity can be estimated using the same formula.)
Example
•
8-cyl. engine
•
CMCR /R1: 25,800kW
•
BSFC/R1: 182.0 g/kWh
•
Throughput:
1.2
•
25,800
•
182.0
•
10
-3
=
5,635 litres/hour
Oil samples
To ensure that representative samples of fuel oil can be taken, dedicated sam
-
pling points (cocks) are provided on engine side. Such cocks need also to be in
-
stalled on system side according to the relevant system proposal drawing in
100 1
out
in
C
n
C
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