04/06/2026
Detailed Explanation of 5 Types of Failure Modes for Tubular Heaters
1. Overheating Failure (Sheath Melt & Rupture)
Failure characteristics
Blue brown high-temperature tempering discoloration, bulging and thickening of the pipe wall, longitudinal cracks (as shown in Figure 1), and high-temperature creep deformation cracking of the metal shell appeared on the pipe wall in the U-shaped bend area.
Cause of Failure
Dry burning and lack of medium: Under liquid heating conditions, the liquid level is lower than that of the heating tube, and some areas are exposed to the air with poor heat dissipation. The surface temperature far exceeds the tolerance limit of the pipe material;
Air duct blockage/stagnant air: When the air is heated, the fan stops running, the air duct is blocked by dust accumulation, and the heat cannot be carried away by the airflow;
Temperature control failure: Temperature controller and thermocouple malfunction, continuous full power supply, long-term operation beyond rated temperature.
Principle of Destruction
Stainless steel/alloy sheath has coarse grains and decreased plasticity at high temperatures, resulting in thermal stress and internal magnesium oxide insulation powder thermal expansion and compression. The pipe wall first swells and then tears, and the electric heating wire short circuits and burns out after water v***r enters.
Improvement plan
Install liquid level protection, over temperature power-off temperature control, wind pressure interlock switch, and limit no-load power on.
2. Scale/Corrosion Buildup Failure (Sheath Failure)
Failure characteristics
The outer side of the pipe wall is covered with thick concave convex scale and rust layer, and the sheath is extensively corroded, cracked, and perforated. Under the corrosion layer, the pipe wall becomes thinner (Figure 2), and the corrosive medium seeps into the interior.
Cause of Failure
Water quality issues: High temperature precipitation and scaling of hard water calcium and magnesium ions, and electrochemical corrosion of pipe walls by acidic and alkaline corrosive liquids (electroplating solution, sewage, seawater);
Scale layer insulation vicious cycle: Scale has extremely poor thermal conductivity and cannot dissipate heat → pipe wall temperature further increases → corrosion and scaling accelerate.
Principle of Destruction
Corrosion under scale blockage (crevice corrosion), where the corrosive solution concentrates between the scale and the pipe wall, slowly corrodes through the sheath, and water ingress causes a short circuit to the grounding of the electric heating wire.
Improvement plan
316L/310S/Incoloy840 sheath is selected for corrosive working conditions, and a soft water device is installed for water circulation. Regular acid cleaning and descaling are carried out.
3. Moisture Ingress moisture infiltration failure (insulation breakdown)
Failure characteristics
The terminal threads cracked, the sealing adhesive aged, the magnesium oxide insulation powder inside the pipe mouth became damp, blackened, and carbonized, the root of the terminal post was damaged (Figure 3), the insulation resistance dropped sharply, and leakage tripping occurred.
Cause of Failure
End seal failure: Long term high-temperature aging and cracking of silicone rubber seals, shrinkage of rubber materials after cold and hot cycles;
Damp condensation in the environment: Wet water v***r and water v***r seep into the pipe through the wiring gaps;
Microcracks in the pipe body: Small gaps in the pipe wall allow water to enter, and magnesium oxide loses its insulation properties after absorbing moisture.
Principle of Destruction
Magnesium oxide insulation powder absorbs water and changes from insulation to conductivity. The electric heating wire leaks to the ground, and in severe cases, the local arc burns off the heating wire.
Improvement plan
Ceramic sealing and waterproof terminals are selected for high temperature conditions, and waterproof junction boxes are added for humid environments. Moisture resistant modified magnesium oxide powder is used.
4. Excess Watt Density power density exceeds the standard (localized burn out)
Failure characteristics
The sheath is melted through at a single point, forming a burnt black corrosion pit, surrounded by numerous small pitting holes. Electric heating wires can be seen inside the holes (Figure 4), and the pipe wall is locally burned by high temperature at a single point.
Cause of Failure
Selection error: The design of the unit surface area power (W/cm ²) exceeds the standard and exceeds the heat dissipation capacity of the medium; Choose air dry burning specifications for water heating;
Local wrapping: materials, fibers, and debris wrap around a single point, isolating local heat dissipation and forming hotspots;
Electric heating wire eccentric core: During manufacturing, the heating wire is eccentric and close to the pipe wall, causing local overheating and melting of the shell at close range.
Principle of Destruction
Local thermal load overload → instantaneous overheating of the pipe wall, melting and perforation, and instantaneous influx of medium causing short circuit and burning.
Improvement plan
Select power density according to the medium specifications: liquid is typically 10-25W/cm2, dry burning air is ≤ 8W/cm2; avoid foreign objects wrapping around the heating surface.
5. Physical Damage: Mechanical External Force Damage (Stress Cracks & Deformation)
Failure characteristics
The pipe body is bent, dented, wrinkled, and deformed, with fine stress cracks appearing at the bend (Figure 5). The plastic deformation of the pipe is accompanied by microscopic cracking.
Cause of Failure
Installation collision and bending: Hard prying or impact during equipment assembly, handling, and maintenance can cause deformation of bent pipes;
Thermal expansion and contraction stress: frequent alternation of cold and hot, the thermal expansion and contraction of the pipe are rigidly fixed and stuck, and the accumulated thermal stress tears the pipe wall;
Material erosion and impact: Particle materials and high-pressure fluids can cause long-term fatigue cracking of the pipe wall.
Principle of Destruction
The residual stress generated by deformation plus operational thermal stress superimposes, and the crack propagates from the outside to the inside, ultimately leading to water ingress failure at the crack opening.
Improvement plan
Install reserved thermal expansion allowance, install fixed brackets to prevent shaking, and avoid forcibly correcting deformed pipes.
Learn more about JMY Heaters: https://jmyheaters.com/
Whatsapp: 181 3660 3886
