Common Accident Hazards and Treatment Measures for Electric Heating Thermal Oil Furnaces
1. Hazard of Deterioration of Thermal Oil Quality
Premature deterioration of thermal oil quality due to poor production process operation management is one of the most common problems in electric heating thermal oil furnaces. Some thermal oils deteriorate severely in performance indicators after only one or two years of use. Long-term operation with deteriorated thermal oil leads to increasing carbon deposition on the heated surface tube walls, reduced inner diameter of tubes, decreased thermal oil flow, increased resistance of the circulating pump, and continuously reduced heat transfer efficiency, eventually causing coking, blockage, and malignant accidents such as overheating, deformation, and tube bursting. One cause of thermal oil quality degradation is local overheating leading to thermal cracking, and the other is oxidation of the thermal oil. When the thermal oil exceeds its specified maximum operating temperature, local overheating occurs, resulting in thermal decomposition and polycondensation, precipitation of residual carbon, flash point drop, color darkening, viscosity increase, heat transfer efficiency decrease, coking, and aging. The thermal oil reacts with oxygen in the air to undergo oxidation, generating organic acids and polycondensing into sludge, increasing viscosity, not only reducing the service life of the medium but also causing acidic corrosion of the system. Currently, different domestic thermal oil manufacturers have their own quality standards, and the quality of produced thermal oils varies greatly. For thermal oil in use, the "Safety Technical Supervision Regulations for Organic Heat Transfer Material Heaters" stipulate that kinematic viscosity, flash point, residual carbon, and acid value should be tested at least once a year.
2. Hazard of Automatic Control System Failure
Currently, the status of domestic thermal oil electric heater technology is that the thermal oil control system uses a programmable logic controller (PLC) as the control core. Thermal oil at a certain temperature enters the heater from the inlet under the working pressure of the circulating pump, passes through the heating chamber of the heater, gradually increases in temperature, and then flows out from the outlet, thereby achieving the required process temperature, further improving the automation level of the equipment.
In the control system, the thermal oil is sent into the entire system through a gear pump. When the preset magnetic flip column level controller reaches the specified level, the gear pump automatically shuts off, and then the circulating pump and electric heater are started to begin heating. When the outlet oil temperature reaches the set value, it enters the user system for circulation. After being used by the equipment, the oil returns to the device for heating again, repeating the cycle, which is the working state of the thermal oil.
These automatic control systems are effective checkpoints to ensure the safe operation of electric heating thermal oil furnaces, but it is often these checkpoints that fail in actual operation due to weak safety awareness or economic reasons.
3. Hazard of Air and Moisture Ingress
Air and moisture are prone to enter during new oil filling, oil change, and maintenance of electric heating thermal oil furnaces. During heating, these air and moisture expand and evaporate, and their volume change far exceeds the thermal expansion of the thermal oil itself. When relative pressure is zero, the volume expansion of water evaporation is about 1600 times its original volume, and air expands about 5 times when heated to 270°C. If these air and moisture cannot be discharged in time, they will inevitably cause an increase in operating pressure, seriously threatening system safety. Therefore, the moisture and other components in the thermal oil should be strictly controlled. During the heating start-up process, the vent valve should be repeatedly opened to discharge the air, water, and thermal oil mixed steam in the system, and attention should be paid to controlling the heating rate of the thermal oil.
