Wartsila ?31DF Series Product Manual page 103

Wärtsilä 31DF Product Guide
6.4.1 Definitions Filtration term used
● mesh size: opening of the mesh (surface filtration), and often used as commercial name
at purchase. Only approximately related to Efficiency and Beta-value. Insufficient to compare
two filters from two suppliers. Good to compare two meshes of same filter model from
same supplier. Totally different than micron absolute, that is always much bigger size in
micron.
- e.g. a real example: 30 micron mesh size = approx. 50 micron ß50 = 75
● XX micron, nominal: commercial name of that mesh, at purchase. Not really related to
filtration capability, especially when comparing different suppliers. Typically, a totally
different value than XX micron, absolute.
- e.g. a real example: 10 micron nominal (e10 = 60%) = approx. 60 micron absolute.
● XX micron, absolute: intended here as ßxx = 75 ISO 16889 (similar to old exx = 98,7% )
- Beta value ßXX = YY : ISO name with ISO 16889 standardised test method. Weak
repeteability for dust bigger than 25..45 microns.
- Example: ß20 = 75 means "every 75 particles 20 micron ISO dust sent, one passes".
- Efficiency eXX = YY % : same meaning as Beta-value, but not any ISO standardised test
method, hence sometimes used for particles larger than 25..45 micron.
- Example: e20 = 98,7% means "every 75 particles 20 micron non-ISO dust sent, one
passes, which is 98,7% stopped."
6.4.2 Fuel heating requirements HFO
Heating is required for:
● Bunker tanks, settling tanks, day tanks
● Pipes (trace heating)
● Separators
● Fuel feeder/booster units
To enable pumping the temperature of bunker tanks must always be maintained 5...10°C
above the pour point, typically at 40...50°C. The heating coils can be designed for a temperature
of 60°C.
The tank heating capacity is determined by the heat loss from the bunker tank and the desired
temperature increase rate.
DBAE248994
In multiple engine installations, where several engines are connected to the same
fuel feed circuit, it must be possible to close the fuel supply and return lines
connected to the engine individually. This is a SOLAS requirement. It is further
stipulated that the means of isolation shall not affect the operation of the other
engines, and it shall be possible to close the fuel lines from a position that is not
rendered inaccessible due to fire on any of the engines.
NOTE
6. Fuel Oil System
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