Case Studies · Iron & Steel

Radiant Tube High Emissivity Coating: Exit-Gas Temperature Down 70°C at Oxelösund

Radiant tube (Kanthal chrome-nickel)·Oxelösund, Sweden

A radiant tube at an integrated Swedish steel mill showed 500°C exit-gas temperatures, hot spots, and premature oxidation. The tube was grit-blasted, coated externally with Emisshield, and sintered before installation. Exit-gas temperature dropped to 430°C, indicating more heat transferred to the steel, hot spots and oxidation diminished, and tube life is projected three to five times longer.

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Exit gas 500 to 430°C
: Life projected 3 to 5×
: Natural gas

The Challenge

Improve heat transfer to the steel, reduce tube temperature, and extend service life.

What Was Applied

External coating of the chrome-nickel tube, sintered at 815°C, then returned to natural-gas service for evaluation.

Glowing forgings in front of an open reheat chamber

Why It Worked

A high emissivity tube surface radiates more of the combustion energy to the load, so less leaves as hot exit gas, and uniform surface temperature slows oxidation. See Energy Savings.

Summary of Results

Metric	Uncoated	Coated
Exit-gas temperature	500°C	430°C (−70°C)
Heat flux to steel	Baseline	Improved
Hot spots and oxidation	Present	Reduced
Projected tube life	Baseline	3 to 5×

Operators noted the coated tube outperformed more exotic and expensive alternatives, improving energy efficiency and reducing replacement downtime.

Next step

Operating the Same Asset?

Radiant tubes failing early? Send us the tube alloy, geometry, and exit-gas data. We project the result from comparable documented installations.

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