As fuel prices around the globe continue to rise, fuel savings generated by greater efficiency have become even more essential for businesses across the board.

Fire tube boiler manufacturers have made considerable advances in the last several years towards achieving an increasingly more efficient heat transfer area within the boiler. The use of the Wet-Back design, which converts dead area, in terms of heat transfer, into an active and effective heat transfer area, is a clear example of greater heat transfer area efficiencies. Additional noteworthy efficiency savings come from improvements to the burner of the boiler.

All boiler burners require an excess of air to achieve optimal combustion. The lesser the amount of excess air required, however, the greater the efficiency of the boiler’s combustion process. As burners begin to be equipped with new electronic controls, they become capable of achieving lower air excesses and greater efficiencies.

Below is an overview of boiler burner technologies, beginning with the most basic technology and leading up to the most recent technological developments in the field of burner unit design. The shortcomings of the more obsolete technologies become apparent as the benefits of implementing the most advanced applications available begin to stand out.

Level 1 - Linkages

Flame modulation system in which linkages are used to control the fuel valve and air hatch openings.

This type of equipment, the most basic technology available, is over 60 years old and is based on attaining a linear air-fuel ratio through a servomotor that operates the fuel valve and air hatch by means of linkages. It was the ideal means of achieving the efficient operation of the boiler burner in the 1940´s.

Nevertheless, this system had several negative points, including:

  • Mechanical misalignments
  • Mechanical system wear between the joint and the rods
  • Tendency to be mishandled by boiler operators

These negative features would cause the burner not to work properly, requiring the assistance of a technical specialist to get the burner operational again. For these reasons, as well as technical advancements that made this once cutting edge technology obsolete, the linkages flame modulation system is not the technology of choice for most of today’s boilers.

Level 2 - Linkage free

Micro modulation system with a microprocessor and servomotors that runs without linkages.

With the advancement of new, affordable technologies in the 1990´s, such as the microprocessor and the electronic motor, which manufacturers could integrate into their burner unit designs, the electronic, linkage free combustion unit was born.

By means of the digital PID reactive combustion control (smart control), the burner unit is completely operated via servomotors, eliminating the need for the linkages between the combustion valve and the air hatch.

The digital control establishes and maintains the optimal air-fuel ratio following parameters introduced during the commissioning of the machine in the form of optimal, predefined operating curves.

The electronic, linkage-free servomotors, which define an exact position at each operation point, adjust the following:

  • Air hatch
  • Fuel supply valve
  • Position of the combustion head (optional)

The operating technician, who is in turn the programmer of the combustion unit, inputs the operation parameters via an access code which serves as an additional security measure.

An exact electronic regulation is achieved with regards to reaching and maintaining the optimal operational air-fuel ratio in accordance with the prefixed values established during the commissioning of the boiler. This precision was lacking in the flame modulation system with linkages that did not rely on an electronic servomotor and resulted in reduced operational efficiencies.

Advantages of a Linkage Free Microflame Modulation System include:

  • Constant high efficiency operation, with fixed parameters along the entire operating curve.
  • Check against maladjustments due to operator mishandling or wear.

User-friendly screen on a module attached to the burner which provides the user with the following:

  • Current snapshot of boiler steam pressure
  • Boiler load (%)
  • Operational errors
  • Historical errors record
  • Setpoint of pressure/temperature
  • Fuel selection option (for dual burners)
  • Date/Time setting
  • Working time
  • Number of starts

Additional monthly savings in the consumption of fuel

Level 3 - O2 Trim

Micro modulation system that runs with an oxygen sensor.

Boiler burners need large amounts of air to achieve combustion. It is important to keep in mind, however, that the density of the air varies in relation to the temperature and as such, the quantity of air pumped into the boiler burner´s fan during the combustion process varies according to the temperature of the suctioned air.

Early burner unit technologies – even those using electronic servomotors and microprocessors that enabled the system to run linkage free – were not able to account for changes in outside air temperature. It was necessary, therefore, to find a type of automatic correction, something that would take into account the different temperatures, correcting at each moment the deviations of excess air brought about by changing outside air temperatures, in order to achieve an optimal combustion with low excess of air.

Adding a sensor to measure the oxygen in the boiler flue gases (combustion gases), and sending this signal to the boiler control unit for it to compare against ideal values and correct if any variations are found, allows the boiler burner to adjust automatically the air-fuel ration of the combustion based on the feedback it receives from the oxygen sensor installed in the smoke stack of the boiler. This system is called O2 Trim and is the latest development in boiler burner control technology.

Advantages of a O2-Trim System:

  • Constant high efficiency operation, with fixed parameters along the entire operating curve
  • Check against maladjustments due to operator mishandling or wear
  • Additional efficiencies
  • User-friendly screen on a module attached to the burner which provides the user with the following:
    • Current snapshot of boiler steam pressure (or temperature, for water tube boilers)
    • Boiler load (%)
    • Operational errors
    • Historical errors record
    • Setpoint of pressure/temperature
    • Fuel selection option (for dual burners)
    • Date/Time setting
    • Working time
    • Number of starts
    • Temperature of air entering boiler
    • Temperature of gases exiting boiler stack
    • Thermal Efficiciency
    • Instant value of the percentage of oxygen in the air exiting boiler stack
  • Additional monthly savings in the consumption of fuel

The importance of using the most cutting edge technology available cannot be overstated. As described above, not only do technology improvements lead to a reduction in user error, but they can also generate significant cost savings in terms of fuel consumption and maintenance repairs, while improving the overall operational efficiency of your boiler.