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Selection guide for heating tubes’ material

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Corrosion: In addition to choosing a sheath material compatible with the heating medium, other factors that affect corrosion need to be considered:

 

The temperature of the corrosive agent-as the temperature increases, the degree of corrosion also increases. Also keep in mind that usually the component temperature is higher than the material it heats.

The degree of corrosive aeration-stagnation will deprive stainless steel of oxygen, which is necessary to maintain its corrosion-resistant surface.

Corrosive speed-increasing the speed can increase the corrosion rate.

 

Standard element sheath material

Incoloy®800 — nickel (30-35%), chromium (19-23%), iron alloy. The high nickel content of this alloy helps it resist scaling and corrosion. Used for air heating (see also Incoloy®840) and immersion heating for drinking water and other liquids that are not corrosive to Incoloy®800 sheath.

Low carbon steel-applications include fluid heat transfer media, tar, high to low viscosity petroleum, asphalt, wax, molten salt and other solutions that are not corrosive to the steel sheath.

316 stainless steel—chromium (16-18%), nickel (11-14%), iron alloy and molybdenum (2-3%) are added to improve the corrosion resistance in certain environments, especially those that may be due to the following reasons The presence of environmental chlorides that cause pitting corrosion. Applications include deionized water.

Copper—It is mainly used for heating pure water for antifreeze protection in toilets, showers, flushing pools and storage tanks.

 

Optional sheath material

304 stainless steel-chromium (18-20%), nickel (8-11%), ferroalloys used in the food industry, disinfectant, air heating, and many organic and inorganic chemicals.

321 stainless steel-chromium (17-20%), nickel (9-13%), iron alloy, modified by adding titanium to prevent carbide precipitation and intergranular corrosion that may occur in certain media when operating in 800 . -1200°F (427-649°C) temperature range.

Incoloy®840 — nickel (18-20%), chromium (18-22%), iron alloy. Incoloy840® contains 10% less nickel than Incoloy 800. Used in many air heating applications, it has better oxidation resistance and lower cost than Incoloy 800®.

Incoloy®825 — nickel (38-46%), chromium (19.5-23.5%), molybdenum (2-3%) iron alloy.

2020年9月3日 17:29
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