17 Fully Metered Combustion Control
Mk8 MM Manual Page | 304
The current firing rate can be fed back to an external system via a 4-20mA output signal on terminals 16, 17
and 18.
17.4.2 Limitations
When using a volume flow meter, the mass flow rate is calculated using the volume flow rate and either
default pressure and temperature values, or the measured pressure and temperature values.
The MM’s fully metered combustion control is capable of controlling the most common hydrocarbon fuels
including methane, ethanol, ethane, butane, pentane, acetylene and 1-proponal.
For FGR, oxy fuels, hydrogen and special fuels, please contact Autoflame prior to use;
The fully metered combustion control will not work on oil combustion curves.
If fully metered combustion control is used, then neither an external 4-20mA sensor for auxiliary water level
control nor external fuel flow metering using 4-20mA input can be used. When using the fully metered
system, the fuel flow metering is automatically calculated from the flow rate.
If an EGA is optioned, a conflict will occur if the 3-parameter trim is activated.
The gas/air pressure sensor recommission feature is not available when using volume flow meters, if these
pressure sensors need to be recommissioned; a full recommission of the burner is required. This is due to
the pressures needing to be stored at the same time as the required volume flow.
Economiser or deaerator options for steam/heat flow metering cannot be used if the temperature sensors or
make-up flow meter inputs are being used for volume flow metering. The IO module can be used instead for
deaerator.
During running the system can adjust the channel 2 air servomotor from the commissioned closed and open
positions to bring the combustion to the commissioned fuel-air ratio, as the fuel servomotor moves. However,
the rest of the channels can only be moved from the low fire and high position, and not outside of this range.
This means that if the fuel servomotor is at the commissioned high fire position, it cannot move further. The
firing rate is limited to less than 100% and if it is critical to the system operation, then the actual firing rate
should be monitored.
The calorific value must be entered corrected to the 1013mbar and 15
O
C, see options 61 to 64.
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