6.
Fuel System
6.1
Acceptable fuel characteristics
6.1.1 Gas fuel specification
As a dual fuel engine, the Wärtsilä 34DF engine is designed for continuous operation in gas operating mode
or diesel operating mode. For continuous operation without reduction in the rated output, the gas used as
main fuel in gas operating mode has to fulfill the below mentioned quality requirements.
Table 6.1 Fuel Gas Specifications
Value
Unit
Property
28
MJ/m
3
N
2)
Lower heating value (LHV), min
1)
80...90
Methane number (MN), min
3)
70
% volume
Methane (CH
4
), min
0.05
% volume
Hydrogen sulphide (H
2
S), max
3
% volume
Hydrogen (H
2
), max
4)
25
mg/m
3
N
Ammonia, max
50
mg/m
3
N
Ch Fluorines, max
50
mg/m
3
N
Particles or solids at engine inlet, max
5
um
Particles or solids at engine inlet, max size
0…60
°C
Gas inlet temperature
Water and hydrocarbon condensates at engine inlet not allowed
5)
The required gas feed pressure is depending on the LHV (see section Gas feed pressure in chapter Fuel system).
1)
Values given in m³
N
are at 0°C and 101.3 kPa.
2)
The methane number (MN) is a calculated value that gives a scale for evaluation of the resistance to knock of
gaseous fuels. Above table is valid for a low Methane Number optimized engine. Minimum value is depending
on engine configuration, which will affect the performance data.
However, if the total content of hydrocarbons C5 and heavier is more than 1% volume Wärtsilä has to be con-
tacted for further evaluation.
3)
Hydrogen content higher than 3% volume has to be considered project specifically.
4)
Dew point of natural gas is below the minimum operating temperature and pressure.
5)
6.1.2 Liquid fuel specification
The fuel specifications are based on the ISO 8217:2010 (E) standard. Observe that a few additional properties
not included in the standard are listed in the tables. For maximum fuel temperature before the engine, see
chapter "Technical Data".
The fuel shall not contain any added substances or chemical waste, which jeopardizes the safety of install-
ations or adversely affects the performance of the engines or is harmful to personnel or contributes overall
to air pollution.
Marine Diesel Fuel (MDF)
Distillate fuel grades are ISO-F-DMX, DMA, DMZ, DMB. These fuel grades are referred to as MDF (Marine
Diesel Fuel).
The distillate grades mentioned above can be described as follows:
•
DMX: A fuel which is suitable for use at ambient temperatures down to -15°C without heating the fuel.
Especially in merchant marine applications its use is restricted to lifeboat engines and certain emer-
gency equipment due to the reduced flash point. The low flash point which is not meeting the SOLAS
requirement can also prevent the use in other marine applications, unless the fuel system is built ac-
36
Product Guide Wärtsilä 34DF - 3/2012
Product Guide
6. Fuel System
