Tubular Electric Heater
Tubular electric heater (scientifically known as metallic tubular electric heating element, commonly called electric heating tube or heating tube, English: Tubular Heater / Sheathed Heating Element) is a resistance-type electric heating device with a metal tube as the shell, filled with heating wire and magnesium oxide insulating powder inside. It is one of the most basic and widely used heating elements in industrial heating and household appliances.
Working Principle
Based on Joule's law, when current passes through the spiral resistance wire inside the tube, heat is generated. The heat is conducted through the highly insulating and thermally conductive crystalline magnesium oxide powder to the surface of the metal tube shell, and then heats the external medium (air, liquid, or metal mold) through conduction, radiation, or convection.
Structural Composition
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Component Material/Description
Metal Sheath Tube In800, In840, 304, 316L, 310S stainless steel, aluminum, copper, low-carbon steel, titanium tube, etc.
Resistance Heating Wire Nickel-chromium alloy wire (Ni-Cr, temperature resistance 1400°C) or iron-chromium-aluminum alloy wire (Fe-Cr-Al, temperature resistance 1200°C)
Insulating Filler Crystalline magnesium oxide powder (MgO), divided into low-temperature type (below 400°C), medium-temperature type (400-600°C), and high-temperature type (600-850°C)
Sealing Material Epoxy, silicone, glass, etc.
Lead-out Rod/Terminal Stainless steel or free-cutting iron (brass lead-out rods are prohibited when surface temperature exceeds 450°C)
After the tube reduction process, the density of magnesium oxide powder reaches above 3.3g/cm³, ensuring the heating wire is centered and does not touch the wall, with high insulation (breakdown voltage ≥1500V) and high thermal conductivity.
Shape Classification
Straight single-end heating tube: single-end lead, suitable for molds, plastic machinery, etc.
Straight double-end heating tube: double-end lead, used for conventional liquid heating
U-shaped / W-shaped heating tube: bent structure, increasing heat exchange area
Spiral heating tube: used for pipeline heat tracing or special spaces
Fin-type heating tube: expands heat dissipation area, specially used for air heating
Special-shaped heating tube: custom bent shape according to equipment space
Main Technical Parameters
Working voltage: 12V, 24V, 36V, 48V, 110V, 220V, 380V, etc.
Maximum working temperature: up to 850°C
Design service life: generally over 10,000 hours
Electric energy conversion rate: over 95%
Insulation resistance: ≥1MΩ
Dielectric strength: 2KV/1min
Tube diameter range: φ6-φ30mm
Selection Reference (by Medium)
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Heating Medium Recommended Tube Material Surface Load
Clean water / Drinking water 304 stainless steel or copper 6-8 W/cm²
Oil / Heat transfer oil 304/321 stainless steel 2-4 W/cm²
Corrosive liquids 316L stainless steel or titanium alloy 3-5 W/cm²
Static air Fin-type 304 stainless steel 1-3 W/cm²
Flowing air Fin-type stainless steel 3-6 W/cm²
Typical Application Fields
Industrial fluid heating: oil tanks, water tanks, chemical solution circulation heating systems
Mold temperature control: constant temperature control for injection molding machines, die-casting machines
Pipeline anti-freezing: heat tracing and insulation for petroleum and chemical pipelines
Food processing: deep fryers (160-190°C), pasteurization equipment
Household appliances: electric water heaters, ovens, fan heaters, coffee makers
Special scenarios: semiconductor vacuum furnace heating, low-melting-point metal melting
Executive Standards
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Standard Number Name Scope of Application
JB/T 2379-2016 Metallic Tubular Electric Heating Elements Industrial use, voltage ≤440V
NB/T 10309-2019 Anti-corrosion Metallic Tubular Electric Heating Elements Working in corrosive media
GB/T 23150-2024 Tubular Heaters for Water Heaters Household water heaters (effective from April 1, 2025)
GB/T 8623-1988 Metallic Tubular Far-infrared Radiation Heaters Far-infrared heating scenarios
Usage Precautions
Strictly no dry burning: the effective heating zone of liquid heating type must be fully immersed in liquid or solid metal
Regular descaling: when water quality is hard, scale on the tube surface must be cleaned regularly to prevent affecting heat dissipation and shortening lifespan
Reliable grounding: the metal shell must be effectively grounded to prevent electric leakage
When heating fusible metals or solid nitrates: first reduce voltage, then raise to rated voltage after the medium melts
When heating air: elements should be arranged crosswise and evenly to ensure good heat dissipation conditions
Wiring part: should be placed outside the insulation layer to avoid contact with corrosive, explosive media and moisture
