Recognizing and Correcting Burner Problems- Lifting Flames and Flashback

14 Feb, 2010 Blog,Instrumentation

In dealing with oven or furnace problems, it’s important to understand that, because the main component – the burner – is designed to produce a controlled or regulated flame, it has to be well maintained. This is true regardless of whether an oven or furnace is used for industrial, commercial or residential applications. If control is compromised, it could lead to damage to the unit itself, damage to property, or worse, personal injury.

An oven or furnace operator should be able to recognize the signs and symptoms of burner problems as this will help a great deal during troubleshooting and repair by maintenance personnel and qualified service technicians.

In this series we will discuss burner problems, their associated symptoms, and possible effects if not properly addressed. Almost all of these symptoms can be recognized by observing flame behavior, shape, color, and distinct sounds, during operation. The recommended procedures to correct these burner problems are also included for reference.

Lifting Flames, as the name suggests, describes how part of the flame seems to lift or “dance” at a considerable distance above a portion of the burner. Normally, a cone of flame will stabilize near the burner port. However, when the velocity of gas-in-air flow is greater than the flame velocity, this lifting will occur, accompanied by a roaring sound. If left unchecked, the cones of flame could break completely, allowing unburned gas to escape, thus reducing the efficiency of the burner. Decreasing the burner’s primary air will usually solve Lifting Flames. Keep in mind that when the burner gets enough primary air, it will produce a conical blue flame.

Flashback is the igniting of the gas-air mixture while still inside the burner orifice or opening. This premature combustion produces a blowtorch-like noise and should be addressed immediately because it will produce carbon monoxide, a colorless, odorless, tasteless and highly toxic gas, as well as other aldehydes. Over time, a Flashback problem will cause the over-accumulation of soot inside the burner and will lead to irreparable damage. As with Lifting Flames, decreasing primary air in the burner will correct the problem. When Flashback occurs in multi-section furnaces that use an array of burners, check the size of the troublesome burner’s orifice against those of the others. If there is some difference, then the burner needs to be replaced. Valve leaks may also cause Flashback. Check and replace them if needed.

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