1 Mk8 MM Overview, Specifications and Wiring
Mk8 MM Manual Page | 15
1.1.2 Overview of Micro-Modulation (MM)
To ensure maximum efficiency and reliability of the boiler plant operation, two requirements are of
paramount importance, the air to fuel ratio and the target temperature or pressure:
• The air to fuel ratio must be kept to the minimum to ensure complete combustion within the
limitations of the combustion head design. A very high air to fuel ratio will be an indication of high
excess air, which decreases the overall efficiency of the boiler. The fuel valve and air damper
positions set for this minimum air to fuel ratio along the whole commission curve must be infinitely
repeatable to an incredibly high degree of accuracy.
• The target temperature or pressure of the boiler must be monitored by the combustion system and at
all times, with exactly the right amount of fuel and air fired to achieve this target value. Irrespective of
load changes, the burner/boiler system should be able to meet the target temperature or pressure.
The burner’s fuel to air ratio was traditionally governed by mechanical systems which involved multiple cams,
shafts and linkages controlled by one motor. The inherent hysteresis that occurred from the system design
allowing components to be loose, which made the level of accuracy required impossible. With this poor
accuracy, the response of the fuel input to the monitored temperature/ pressure of the boiler meant that the
set target value at most times would overshoot or fall short.
The Micro-Modulation module is the basic building block of the Autoflame System. The Autoflame MM
provides an easily programmable and flexible means of optimising combustion quality throughout the load
requirement range of the burner/boiler unit whilst ensuring the temperature is accurate to within 1°C (°F) and
pressure to within 1 PSI (0.1Bar). Using direct drive motors to individually control the air damper and fuel
valve(s), gives the optimum combustion of the burner at every point along the firing range. The allowed error
in angular degrees of rotation between the two servomotors at any position in the load range is 0.1°.
This automated system of burner control can achieve ‘locked on’ near stoichiometric air to fuel mixing
throughout the fuel input range of the boiler while maintaining exact temperature or pressure target values.
The load control incorporates user-variable Proportional Integral Derivative control. The PID control is
infinitely adjustable to match any boiler room requirements.
To Next Page
Loading...
Need help?
General
