Wartsila 31 Product Manual page 54

6. Fuel Oil System
type filters instead. A coalescing filter is usually installed on the suction side of the circulation
pump in the fuel feed system. The filter must have a low pressure drop to avoid pump cavitation.
Separator mode of operation
The best separation efficiency is achieved when also the stand-by separator is in operation
all the time, and the throughput is reduced according to actual consumption.
Separators with monitoring of cleaned fuel (without gravity disc) operating on a continuous
basis can handle fuels with densities exceeding 991 kg/m3 at 15°C. In this case the main and
stand-by separators should be run in parallel.
When separators with gravity disc are used, then each stand-by separator should be operated
in series with another separator, so that the first separator acts as a purifier and the second
as clarifier. This arrangement can be used for fuels with a density of max. 991 kg/m3 at 15°C.
The separators must be of the same size.
Separation efficiency
The term Certified Flow Rate (CFR) has been introduced to express the performance of
separators according to a common standard. CFR is defined as the flow rate in l/h, 30 minutes
after sludge discharge, at which the separation efficiency of the separator is 85%, when using
defined test oils and test particles. CFR is defined for equivalent fuel oil viscosities of 380 cSt
and 700 cSt at 50°C. More information can be found in the CEN (European Committee for
Standardisation) document CWA 15375:2005 (E).
The separation efficiency is measure of the separator's capability to remove specified test
particles. The separation efficiency is defined as follows:
where:
C
6.3.3.2 Separator unit (1N02/1N05)
Separators are usually supplied as pre-assembled units designed by the separator
manufacturer.
Typically separator modules are equipped with:
● Suction strainer (1F02)
● Feed pump (1P02)
● Pre-heater (1E01)
● Sludge tank (1T05)
● Separator (1S01/1S02)
● Sludge pump
● Control cabinets including motor starters and monitoring
6-10
n = separation efficiency [%]
= number of test particles in cleaned test oil
out
C = number of test particles in test oil before separator
in
Wärtsilä 31 Product Guide
Wärtsilä 31 Product Guide - a1 - 18 October 2016