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Burner Safety Measures

Burner Safety Diagram

As with any industrial process, safety is a major concern, especially with burner/boiler applications. The centerpiece of any burner/boiler safety system is the Flame Scanner. The following paragraph describes in detail the light-off sequence of a burner and explains the role of the Flame Scanner.

  1. The Burner Management System (BMS), which includes the Scanner and Signal Processor, is powered up. Once a fuel is selected and the Burner Start button is pressed, the BMS starts the fan and opens the fan damper to begin the air purge process. Once the purge cycle has completed, the BMS drives the air damper to the light-off position. This is typically 20-25% of the burner maximum heat input.
     
  2. The BMS then energizes a transformer connected to the pilot electrode, thereby causing it to begin sparking. At the same time, the BMS checks the pilot gas supply pressure to ensure that the appropriate heat input will be delivered to the pilot. Then, the BMS opens the two pilot gas shutoff valves and closes the pilot gas vent valve (This system is also know as Double Block and Bleed).
     
  3. At this point, the pilot should be lit and the scanner should be receiving a flame signal from the pilot flame. If the scanner does not pick up this signal within a 10 second trial for ignition, the BMS will shut the pilot gas shutoff valves, de-energize the transformer, and end the start-up sequence.
     
  4. If the pilot flame is "seen" by the scanner, the BMS proceeds to check the following interlocks: Loss of ID Fan, Loss of FD Fan, Combustion Airflow Low, Excess Furnace Pressure, Loss of Pilot Flame, High Burner Gas Pressure, Low Burner Gas Pressure. If all interlocks are proven, the BMS then opens the main gas shutoff valves and closes the main gas vent valve.
     
  5. After a five second trial for ignition, the pilot electrode is de-energized, the pilot gas shutoff valves are closed, and the pilot gas vent valve is opened. If the scanner continues to receive a strong flame signal from the main burner, the system will then be released for modulation. If the scanner fails to pick up a flame signal from the main burner, the main gas shut-off valves are closed and the vent valve opened. In this case, the entire light-off sequence must be re-started.

 

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