Why Radiant Tubes Fail Early

Radiant tubes used in gas-fired heat treating furnaces need to provide consistent heat transfer while at the same time offer maximum efficiency to reduce energy and operating expenses. As a maintenance manager, you’re looking for fast heat-up times and a long lifespan.

Radiant heat tubes can last anywhere from one to five years depending on the furnace and how it’s used. Early failure can cause a host of production delay issues that you want to avoid.

So, what should you be looking for? While it’s difficult to inspect and address issues once the tubes are installed, it’s helpful to know what causes premature failures and what can be done to avoid them.

Improper Joint Fusion

Joints in both cast and wrought tubes can be improperly prepared resulting in premature failure of the tube. During the design and manufacture of your radiant tubes, your supplier should be meticulous about properly preparing the areas to be welded in order to maximize the lifespan. Welding expertise and quality should be a top consideration when selecting a supplier for new or replacement tubes.

Constant Thermal Cycling

Radiant tubes are designed to run 24×7. Continually cycling your furnace on and off is very destructive to the life of the tube. Some manufacturers will cycle their furnaces, turning them down on holidays or weekends. While that’s one way to save on energy and operating costs, it could adversely affect the life of your radiant tubes so do this with the understanding that you might be sacrificing their lifespan.

Improper Burner Alignment and Calibration

Proper burner installation is imperative to the longevity of your radiant tubes. Improper alignment results in the flame contacting the tube – known as flame impingement – which will cause a hot spot. Remember that in optimal operation, the flame and the tube should not come into contact. As the flame attempts to burn through the tube, it will eventually fail.

Related to alignment is proper burner calibration. The correct gas and air ratios are necessary to avoid excessive carbon build-up within the tube. If the gas/air ratio aren’t correct, you risk the development of carbon deposit that will cause hot spots and rapid deterioration of the metal.

Radiant heat tubes are an important component to your manufacturing process. When it’s time for a replacement, make sure you carefully evaluate what led to the failure of your last set. This can provide helpful insight for the replacement. Make sure you consider joint fusion, thermal cycling and burner alignment/calibration during the design process. Don’t hesitate to contact Alloy Engineering for help with these evaluations.

Alloy Engineering fabricates tubes in any configuration and wall thickness and supports all furnace OEM tube designs. To learn more, contact us here or call us at 440.243.6800.