Before introducing the material selection in their respective environment, let's learn a concept – the surface loading of heating tubes.
Surface load (sruface lord), defined in the machinery industry standard: power per unit area of heating surface, in watts per square centimeter (W/cm²)
When we know the heating tube power, dividing this power by the surface area of the heating part of the heating tube gives the surface load of the heating tube.
The maximum surface load that each material can withstand under different media is different, so surface load becomes an important element in material selection.
So the question is, how do you know the maximum surface load that a material can withstand?
As mentioned earlier, it is difficult to distinguish the true and false online information, and the mechanical industry standard JB/T2379-2016 lists the highest allowable surface load of commonly used heating tube materials in commonly used media, which is very professional and has great reference value, and is also consistent with the production experience of Heatwave Electric Thermal Technology for more than ten years:
Still air
Surface load≤ 5 W/cm² — SS304; SS321 ; SS316 ; SS316L
Surface load≤ 7.5 W/cm² — SS310S; IncoLoy840
Surface load≤ 10 W/cm² — IncoLoy800; IncoLoy800H ; Inconel600
Moving air (flow rate≥ 6m/s)
Surface load≤ 6 W/cm² — SS304 ; SS321 ; SS316 ; SS316L
Surface load≤ 8 W/cm² — SS310S; IncoLoy840
Surface load≤ 11 W/cm² — IncoLoy800; IncoLoy800H ; Inconel600
Water, weak acid, weak alkali solution boiling
Surface load≤7 W/cm² — copper (T4)
Surface load≤ 11 W/cm² — SS304 ; SS321 ; SS316 ; SS316L
Surface load≤ 13 W/cm² — SS310S; IncoLoy840
Surface load≤ 15 W/cm² — IncoLoy800; IncoLoy800H ; Inconel600
Edible oil, lubricating oil, hydraulic oil
Surface load ≤ 0.7 W/cm² at rest — SS304; SS321 ; SS316 ; SS316L
Surface load ≤ 1.5 W/cm² under flow — SS304; SS321 ; SS316 ; SS316L
Flow heat transfer fluid with a surface load ≤ 2.5 W/cm² — SS321
Components are cast, flushed, pressed in materials such as aluminum, copper, steel, etc
Surface load≤ 13 W/cm² — SS304 ; SS321 ; SS316L
High pressure, medium to high operating temperature water
Surface load≤ 2.5 W/cm² (2 W/cm² at high temperature≤ SS321; SS310S; IncoLoy840
Surface load≤ 3 W/cm² (2.5 W/cm² at high temperature≤) — IncoLoy800; IncoLoy800H ; Inconel600
Corrosive fluid environment (specific use requires reference materials and characteristics of corrosive fluid)
Surface load≤ 2 W/cm² — stainless steel clad Teflon (heating section up to 600 W per meter)
Surface load≤ 7 W/cm² — titanium alloys (TA1, TA2) (heating section power up to 2kW per meter)
It should be noted that the temperature of the material is also an important selection basis, such as:
Heating tube for dry burning in air: SS304 material has a maximum temperature resistance of 550 °C; S321, SS310S, IncoLoy840 materials have a maximum temperature resistance of 850°C
In water, water vapor or moist media with low corrosiveness: SS321 has a temperature resistance of up to 550°C
In a certain corrosive water and water vapor medium: SS316L has a maximum temperature resistance of 400 °C
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