Remarks:
The maximum output may have to be reduced depending on gas properties and gas pressure,
refer to section "Derating of output in gas mode". The permissible output will in such case be reduced with
same percentage at all revolution speeds.
Restrictions for low load operation to be observed.
2.2
Loading capacity
Controlled load increase is essential for highly supercharged engines, because the turbocharger needs
time to accelerate before it can deliver the required amount of air. Sufficient time to achieve even temper-
ature distribution in engine components must also be ensured. Dual fuel engines operating in gas mode
require precise control of the air/fuel ratio, which makes controlled load increase absolutely decisive for
proper operation on gas fuel.
The loading ramp “preheated, normal gas” (see figures) can be used as the default loading rate for both
diesel and gas mode. If the control system has only one load increase ramp, then the ramp for a preheated
engine must be used. The HT-water temperature in a preheated engine must be at least 60ºC, preferably
70ºC, and the lubricating oil temperature must be at least 40ºC.
The loading ramp “max. capacity gas” indicates the maximum capability of the engine in gas mode. Faster
loading may result in alarms, knock and undesired trips to diesel. This ramp can also be used as normal
loading rate in diesel mode once the engine has attained normal operating temperature.
The maximum loading rate “emergency diesel” is close to the maximum capability of the engine in diesel
mode. It shall not be used as the normal loading rate in diesel mode.
The load should always be applied gradually in normal operation. Acceptable load increments are smaller
in gas mode than in diesel mode and also smaller at high load, which must be taken into account in applic-
ations with sudden load changes. The time between load increments must be such that the maximum
loading rate is not exceeded. In the case of electric power generation, the classification society shall be
contacted at an early stage in the project regarding system specifications and engine loading capacity.
Electric generators must be capable of 10% overload. The maximum engine output is 110% in diesel mode
and 100% in gas mode. Transfer to diesel mode takes place automatically in case of overload. Lower than
specified methane number may also result in automatic transfer to diesel when operating close to 100%
output. Expected variations in gas fuel quality and momentary load level must be taken into account to
ensure that gas operation can be maintained in normal operation.
Product Guide Wärtsilä 34DF - 3/2012
9
Product Guide
2. Operating Ranges