Why do tubular heaters burn out?

Tubular heaters are a key component of heating systems in many industries — from plastics processing to the food industry to laboratories. Despite their widespread use, their premature failure can cause costly downtime and the need to replace components. Why do heaters burn out? Below is an analysis of the most common causes of failures and ways to reduce them.

1. Ageing degradation of materials

Each material from which the heater is made has a certain service life. Aging processes occur naturally, but their rate increases significantly at high temperatures. For standard tube heaters operating at 400-600°C, it can be assumed that their durability is about 3000 to 15,000 hours. When this value is exceeded, the heating elements can oxidize, crystallize and crack, resulting in failure.

Example: For applications requiring long-term operation at high temperatures, heaters with NiCr 80/20 resistance wire core are used, which has better oxidation resistance than FeCrAl.

2. Too much surface load

The surface load of the heater, defined in W/cm², is a key parameter for its durability. Too high a value leads to excessive heating of the resistance element and its damage. Each medium has its own permissible load value, for example:

• Water: 8-12 W/cm²
• Industrial oil: 2-4 W/cm²
• Air: 1-2 W/cm²

If the power of the heater is poorly selected for the medium, local overheating may occur, which leads to burnout of the insulator and damage to the wires.

Solution: In applications with high thermal requirements, it is used temperature control with thermocouples or PT100 sensors, which prevents overheating and allows you to optimize the process.

3. Incorrect execution of internal connections

In the manufacture of heaters, the quality of the connection of the resistance wire to the cold stem is of key importance. Disadvantages such as:

• Eccentric location of the heating spiral
• Too loose or poorly soldered connections
• Inadequate density of magnesium insulator (MgO)

can result in the formation of points of high resistance, which leads to local overheating and burnout of the insulation material.

Example: Heaters used in the chemical industry use precision MgO compaction, which provides better thermal conductivity and minimizes the risk of burns.

4. Power concentration in a small area

Too much concentration of power in a limited area causes uneven heating of the heater. An example can be poorly arranged heating spirals in elements of long length, which leads to point overheating.

Solution: Use of thermal simulations before production, it allows you to optimally distribute the heating spirals and evenly distribute the temperature.

5. Lack of proper control and security

Many breakdowns of heaters are due to Insufficient temperature control. Lack of thermal protection, such as temperature sensors, PID controllers or thermal switches, leads to a situation where the heater reaches too high a temperature and is destroyed.

 Example: In modern heating systems, PID controllers with automatic temperature compensation are used, which allow precise control of the heating process and extend the life of the heaters.

6. Failure of the heat receiving system

Tubular heaters are designed to work in a specific environment in which the medium receives heat. Failure of the ventilation system, blockage of air or liquid flow results in a sharp increase in the temperature of the heater and its burnout.

Example: In convection ovens, fans with high efficiency are used, which ensure uniform heat distribution and eliminate the risk of overheating of heaters.

7. Improper sealing of the heater

Heaters operating in conditions of high humidity or in contact with aggressive chemicals require proper sealing. Otherwise, there may be:

• Moisture penetration into the interior of the heater
• Corrosion of the heating element
• Short circuit and complete failure of the heater

 Solution: In applications requiring moisture resistance, heaters with silicone encapsulation or a cover with 316L type stainless steel, which provides maximum corrosion resistance.

summary

The causes of burnout of tubular heaters can be due to a variety of factors - from natural degradation of materials, through design and manufacturing errors, to improper operating conditions. Introduction of appropriate preventive measures, such as selection of suitable materials, temperature control, optimal placement of heating spirals or thermal protection, allows you to significantly extend the life of heating elements.

Photos presented in the article show damage typical for heaters operating in Thermal overload conditions — you can see traces of overheating, corrosion and local cracks in the protective coating. To avoid similar breakdowns, it is worth adhering to the recommendations on the surface load, control and encapsulation of heaters.

If your company is faced with the problem of rapid wear of heating elements, it is worth carrying out Diagnostics of working conditions and adapt the operating parameters to the real needs of the process.