Modern burner designs incorporate years of technological development and improvements in reliability and repeatability. Most burner control systems have evolved away from actuators rotating jackshafts connected to linkage levers connected to gas valves and air actuators. These designs are quickly becoming obsolete, and have given way to digitally controlled, linkage-less designs which use highly precise servomotors directly driving gas control valves and precision air dampers.
Newer designs incorporate diffuser head servomotors to optimize the diffuser head position for ideal air pressure control, turbulence, and air-gas mixing for complete combustion with less excess air requirements. These factors allow more precise control, repeatability, and reliability over the entire load range and in a variety of conditions.
Highly efficient blower motors can be equipped with variable frequency drives (VFD’s) to maintain high static pressure in the area upstream of the diffuser, so a maximum pressure drop can be maintained to assure improved mixing and more complete combustion. All servomotors are controlled by a simple, but sophisticated, digital combustion control system.
Burner Sizing
Burner sizing is very important to achieving maximum efficiency and reliability. Many boilers that were designed for higher loads are now oversized for existing applications as heating loads have been removed or discontinued. Oversized burners tend to cycle on & off. Code required pre-purge and post-purge phases in the combustion cycle must replace the furnace volume four times with fresh air to prevent unburned fuel from accumulating in the furnace between ignition cycles so to eliminate furnace explosions.
On/off cycles cause heat losses from furnace and heat exchanger and reduce system efficiency. Correctly matching burner size with existing loads will prevent cycle losses and improve efficiency. In many cases, the resultant savings can pay for the cost of a replacement burner system. Additional problems associated with high cycling include thermal stresses due to constant expansion and contraction, which reduce the operating life of the equipment, and increased maintenance costs and higher fuel consumption.
Preventative Maintenance Programs
Preventative maintenance programs pay dividends. Users who engage in preventative maintenance (PM) programs experience lower overall maintenance and operating costs. Periodically checking safety devices, combustion tuning, and adjustments will increase productivity through reduced downtime and increased efficiency. Air density changes with seasons as humidity and temperatures vary. Higher temperature air will lower density and reduce the amount of excess air available to the burner. Conversely, lower air temperature will increase density and the amount of excess air to the burner system. Quarterly or Semiannual PM programs are recommended to maintain higher efficiency and to reduce downtime costs. Certified combustion technicians will go through the entire system to make sure it is running safely and reliably.
By understanding how combustion system operate, and the factors that make burners run more safely, reliably, and efficiently, we can choose the right burner system that is sized correctly for our applications, and properly maintain our systems, we can improve productivity and productivity.
Combustion & Control Solutions is a comprehensive sales and service provider for burner and combustion systems, boilers, heat exchangers, boiler room equipment, and controls. We service industrial, institutional, and commercial customers in Georgia, Tennessee, Alabama, Mississippi, and the Florida Panhandle.