Abstract
An ordinary-looking metal tube contains complex electro-thermodynamic design inside. This article takes you through the core construction of industrial electric heaters.
Industrial electric heating tubes (metal-clad heating elements) use a metal tube as the outer sheath. Inside the core is a spiral electric heating alloy wire (typically nickel-chromium or iron-chromium-aluminum alloy).
Heating Mechanism
According to Joule’s law Q = I²Rt, heat is generated when current flows through the alloy wire.
Importance of the Filler Layer
Between the alloy wire and the outer sheath is compacted magnesium oxide powder. This powder must provide extremely high insulation performance while rapidly conducting heat to the metal tube wall.
The seal at both ends of the tube is the “lifeline” of the electric heater. We typically use specialty silicone or industrial ceramics for sealing.
Because magnesium oxide powder is highly hygroscopic, once the seal fails, the insulation resistance will drop rapidly.
High-Performance Characteristics
High-quality electric heating tubes can operate stably in high-pressure environments, vacuum conditions, and even corrosive liquids – thanks to the high corrosion resistance of the outer sheath materials (such as SUS316L, Incoloy 800).