Hidden dangers of quality degradation of thermal oil heaters

Thermal oil heaters operate at temperatures between 25°C and 390°C. They can control and maintain uniform temperatures, improving production processes and saving costs. With the need for improved production processes and environmental protection, they are widely used in the industrial sector.

Thermal oil heaters are a new, safe, efficient, and energy-efficient specialty industrial furnace that provides high-temperature heat at low pressure (at ambient or lower pressure). They use thermal oil as a heat carrier, which is circulated through a hot oil pump to transfer heat to the heat-consuming equipment. Organic heat carrier furnaces, a type of special equipment, can leak if mismanaged or operated in violation of regulations. This can cause accidents such as fires and explosions, resulting in unnecessary losses. Therefore, the safe operation and management of thermal oil heaters require high attention.

Regarding potential accidents with thermal oil heaters and preventative measures, the following points should be noted:

1. Potential Risk of Thermal Oil Quality Deterioration

Premature deterioration of thermal oil due to poor operation or management is a common problem with thermal oil heaters. Some thermal oils can experience significant performance degradation after only one or two years of use. Long-term operation of low-quality heat transfer fluid will cause carbon deposits to accumulate on the heated surface tube walls. This reduces the inner diameter of the tubes, resulting in a continuous decrease in heat transfer fluid flow, increasing circulation pump resistance, and declining heat transfer efficiency. This in turn leads to coking and blockage within the furnace tubes, resulting in serious accidents such as overheating, deformation, and tube bursts.

One of the main reasons for the decline in heat transfer fluid quality is local overheating and thermal cracking, and another is oil oxidation. When heat transfer fluid exceeds its specified upper operating temperature, it will locally overheat, causing thermal decomposition and polycondensation, which will precipitate carbon residue, lower its flash point, darken its color, increase its viscosity, reduce heat transfer efficiency, and cause coking and aging. Heat transfer fluid oxidizes when it comes into contact with oxygen in the air, generating organic acids that condense into a slurry, increasing its viscosity. This not only shortens the service life of the fluid but also causes acidic corrosion in the system.

Currently, domestic heat transfer fluid manufacturers have different quality standards, and the quality of the heat transfer fluids they produce varies greatly. The "Regulations on Safety and Technical Supervision of Organic Heat Carrier Furnaces" stipulate that the kinematic viscosity, flash point, carbon residue, and acid value of heat transfer fluids in use must be tested at least annually.

2. Hidden dangers of failed automatic control systems and inadequate safety protection. Currently, the current state of domestic thermal oil electric heater technology relies on a programmable logic controller (PLC) as the core control system. Thermal oil at a certain temperature enters the heater's inlet under the operating pressure of a circulating pump. The oil gradually heats up as it passes through the heater's heating chamber before flowing out the outlet, ultimately reaching the desired process temperature. This further enhances the equipment's automation level.
In this control system, thermal oil is pumped throughout the system via a gear pump. When the set magnetic level controller reaches the specified level, the gear pump automatically shuts off, activating the circulating pump and electric heater to begin heating. When the outlet oil temperature reaches the set value, it circulates into the user system. After use, the oil re-enters the device for heating, repeating this cycle. This cycle represents the thermal oil's operational state.
These automatic control systems are effective safeguards for the safe operation of thermal oil electric heaters. However, these safeguards often fail in practice due to a lack of safety awareness or economic reasons. Therefore, when selecting a thermal oil electric heater, in addition to the necessary functions, safety protection is indispensable: automatic power-off, over-temperature protection, high-voltage protection and other safety measures must be complete.