Sheathed Electric Heater
Sheathed electric heater (also known as armored heater, tubular electric heater) is a structured electric heating element that completely encloses the resistance heating wire core within a metal sheath, isolated from the sheath by high-temperature inorganic insulating material.
Core Structure
Adopts a three-layer coaxial structure of "core wire – insulation – sheath":
Resistance heating core wire: Nickel-chromium alloy (NiCr), iron-chromium-aluminum alloy (FeCrAl), etc.
High-temperature insulation layer: High-purity magnesium oxide (MgO) powder filling, providing both insulation and thermal conductivity
Metal sheath: 304/316L stainless steel, Incoloy 800/840, titanium alloy, Hastelloy, etc.
Main Model Series
Common sheathed electric heaters include HRY series and SRY6 series, covering multiple sub-models such as HRY1~HRY14, with power range generally 1kW~8kW and rated voltage 220V/380V. Among them, HRY6 type adopts a double-layer split structure (internal heating core + outer independent sheath tube), allowing the heating core to be individually extracted and replaced without draining the oil tank.
Key Technical Parameters
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Parameter Typical Range
Rated Voltage 220V / 380V
Power 1kW ~ 6000kW (pipe type)
Surface Power Density ≤0.7~3.8 W/cm²
Operating Temperature ≤300℃ (conventional), high-temperature type up to 983℃
Working Pressure ≤0.8MPa (conventional), high-pressure custom up to 20MPa
Protection Rating IP54~IP65, explosion-proof type up to Ex db IIC T1-T6
Electrothermal Conversion Efficiency ≥98%
Core Advantages
Medium Protection: The sheath isolates the heating core from the medium, preventing oil carbonization and deterioration, extending medium service life
Easy Maintenance: Replacing the core does not require draining the oil tank, significantly reducing downtime costs
Safe and Reliable: Supports flameproof design, suitable for sealed oil and gas environments
Corrosion Resistance: Sheath materials can be selected from stainless steel, titanium alloy, etc., adapting to corrosive conditions
Long Service Life: Up to 10,000~50,000 hours
Typical Application Scenarios
Hydraulic and Lubrication Systems: Hydraulic stations, lubricating oil tanks, reducer oil heating for viscosity reduction
Chemical and Petrochemical: Reactor jackets, thermal oil heating, heavy oil/diesel preheating
Pipeline Heat Tracing: Natural gas decompression stations, high-rise building hot water circulation, solar pipeline anti-freezing
New Energy: Lithium battery material sintering furnaces, hydrogen energy electrolyzer preheating
Food and Pharmaceutical: High-pressure steam sterilizers, dairy sterilization conveying
Special Research Environments: Space simulation chambers, nuclear fusion experimental devices
Selection Key Points
When selecting, four dimensions need to be focused on:
Heating medium: Clean water choose 304 stainless steel, oil control at 1~3W/cm², corrosive media choose 316L or titanium tube
Power density: Strictly control according to medium type, oil ≤3W/cm², air heating requires fins
Power and voltage: Comprehensively calculated based on medium mass, specific heat capacity, target temperature rise, matching on-site power supply
Installation method: Threaded connection (hydraulic oil tank), flange connection (reactor/large storage tank), straight tube/U-type/W-type, etc.
The industry implementation standards are "Armored Electric Heater" (JB/T 12233-2015) and JBT2379-93.
