Calorised Emitter Tube

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Why do SPACE-RAY use Calorised Emitter tubes? The comparison tables below show the relative merits of emitter tube materials.

Tube Material	Internal Absorptivity	External Emissivity	Radiation Performance	Corrosion Resistance
				INTERNAL	EXTERNAL
Calorised	Very Good	Very Good (0.86)	Very Good	Excellent	Excellent
Stainless Steel	Very Poor	Very Poor (0.20-0.25)	Very Poor	Excellent	Excellent
Stainless Steel Painted	Very Poor	Very Good (0.85)	Average	Excellent	Excellent
Aluminised Steel	Very Poor	Poor (0.25-0.30)	Very Poor	Good	Good
Aluminised Steel Painted	Very Poor	Very Good (0.80)	Good	Very Good	Very Good
Mild Steel (Hot Rolled)	Average	Average (0.66)	Average	Poor	Poor
Mild Steel Painted	Average	Good (0.75)	Good	Poor	Average

Tube Material	Peeling and Flaking Resistance		Scratch Resistance	Site Time to Clean & Paint Each Tube
	At Burner	Downstream
Calorised	Excellent	Excellent	Very Good	n/a
Stainless Steel	Excellent	Excellent	n/a	n/a
Stainless Steel Painted	Poor	Average	Extremely Poor	15 Minutes
Aluminised Steel	Good	Good	Good	n/a
Aluminised Steel Painted	Poor	Average	Poor	15 Minutes
Mild Steel (Hot Rolled)	Poor	Average	n/a	n/a
Mild Steel Painted	Poor	Average	Extremely Poor	20 Minutes

• Calorising gives protection to ferrous metal by providing a self-forming, self-healing coating of practical infusible material (alumina) which is impervious to oxygen , carbon, sulphur and the products of combustion of all common fuels.
• Various grades of the process are available according to the article and the use for which it is intended up to maximum metal temperature of 950 degrees centigrade for calorised aluminised mild steel or cast steel.
• The process is accomplished by fusing aluminium into the surface of the base metal with which it forms a homogenous alloy.
• The protective action is due to the aluminium oxide formed on the surface by the action of heat.
• Under working conditions the exposed surface of the alloy is converted to alumina which has a fusion point in excess of 1,000 degrees centigrade.
• Due to the protection given to the base metal, calorised aluminised mild steel has improved resistance to deformation and scaling at elevated temperatures.
• It is particularly useful for parts subjected in service, at elevated temperature, to sulphurous gases and for case-hardening boxes and pots, cyanide, salt and lead baths. Also for steel protection tubes for thermo-couples.

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