Burner Efficiency - linkageless controls
Posted in Burner Efficiency by Boiler Guy on April 16th, 2008 Burner turndown ratios have been promoted, with great success, over the years. The term turndown ratio may be defined as the ratio of maximum fuel input rate to minimum fuel input rate on a variable input burner. Typically these rates have been 5:1 with newer burner designs offering 10:1 turndown ratio or more.
Why would anybody want a high turndown burner can be answered in the advantages offered by closely controlling firing rates. These advantages include:
• Reducing stand-by losses
• Eliminating thermal cycling
• Minimizing wear and tear on the burner
When a boiler is in idle, that is to say not firing, air is drawn through the vessel as a result of the stack effect. This air robs precious heat from the system. During boiler start-up and shut down this stand-by loss is magnified as a result pre and post purge cycles.
Another advantage to higher turndown is the reducing thermal cycling. Boilers that are quickly heated up and cooled down are more susceptible to material failure due to the expansion and contraction associated with on again off again operation. This is especially rough on refractory and other brittle materials used in boiler construction. By gradually increasing or decreasing firing rates, these effects are greatly minimized.
It goes without saying that the wear and tear on burner linkages, motor starters, pilot gas valves and main gas valves are also minimized. But, perhaps the most important reason to consider a high turndown burner is the money you would save.
Another avenue to explore is upgrading your burner to linkageless controls. In many cases an upgrade such as this would improve turndown performance as well as low-fire combustion efficiency.
We read a great article online that addresses this very subject in a clear concise manner. The Article, Upgrading Burner Controls, was published by Heating/Piping?Air Conditioning Engineering in the June 2007 issue. It was written by Bertram Leng, Director of the Combustion Controls Product Group, Group Region Americas for Siemens Building Technologies, Inc.
Mr. Leng makes a strong case for upgrading burners and burner controls to improve efficiencies. He points out that, with limited budgets, facilities managers can still improve boiler performance without buying new boilers. He sites a specific example in which a hospital was faced with the dilemma many of us face when trying to deal with older equipment.
It is a worthwhile article and we suggest you take a moment to read through it.
The article can be found at http://www.hpac.com/GlobalSearch/Article/67895/
