Precautions for operating heat transfer oil furnaces

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Precautions for operating a heat transfer oil furnace I. Preparations before startup 1. Inspect and verify all installed equipment and components to ensure they meet the design requirements, including valves, filters, pumps； Whether the pipes and other components are installed correctly. 2. Check whether the electrical control cabinet is wired in accordance with the electrical schematic, whether the automatic control and safety alarm systems are functioning properly, and whether the rotation direction of the circulation pump is correct. 3. Check whether water, electricity, steam, gas, etc. meet the requirements ； Are the safety and fire-fighting facilities complete, functional, and properly stored? ； Are there any flammable or explosive materials in the area, and are there any piles of debris around? II. First-time driving and commissioning 1. Filling with oil: Once the system is ready for oil filling, turn on the oil injection pump and pour heat transfer oil into the system until 1/3 of the level is reached in the high-level tank. 2. Cold operation: Start the circulation pump and check whether the direction of the oil pump, pressure, and liquid level are normal. Operate in the cold oil condition for more than 2 hours until all air in the system is completely removed. 3. Oven drying: Before using the boiler for the first time, it is necessary to dry it out first. For coal-fired heat transfer oil furnaces, it is required to use firewood for heating the furnace, with the temperature rise rate controlled at 10°C/h and not exceeding 100°C. The furnace drying time depends on the type of furnace, but it generally should not be less than 72 hours. 4. Dehydration: Systems that are being used for the first time or to which new oil has been added require dehydration first. Open the valve of the system’s dehydration line (auxiliary steam discharge pipeline), raise the temperature to the range of 100–110°C to start the dehydration process. At this point, there will be significant fluctuations in the pressure of the circulation pump, and vapor will be discharged from the exhaust port at the top of the high-level tank. Maintain a constant temperature until the pressure stabilizes, after which gradually increase the temperature by 3–5°C to continue the dehydration process... Repeat these operations until the temperature reaches 150°C and the pressure remains stable, at which point the dehydration is complete. The dehydration time depends on the conditions of the system; do not attempt to speed up the dehydration process to avoid oil spraying from the high-level tank. After dehydration is complete, the dehydration valve must be closed promptly; otherwise, the heat transfer oil will age rapidly until it becomes unusable. III. Normal shutdown: Upon receiving the shutdown command, the hot oil furnace begins to cool down at a rate of 2°C per minute, until it is no longer possible to maintain an open flame; at that point, the fire is extinguished or the ash is removed from the furnace, and the flue dampers and ventilation openings are opened. The circulation pump can be stopped only after the temperature of the heat transfer oil has dropped by 100°C. IV. Precautions 1. The temperature of the heat transfer oil must be strictly kept within the allowable operating temperature range. 2. The oil level in the expansion tank should always remain above 1/3 of its capacity. The temperature of the heat transfer oil inside the expansion tank must be checked regularly, and it should be kept below 60°C. 3. The heating rate should not be too fast; the temperature difference between the boiler’s inlet and outlet should be ≤ 30°C. 4. Ensure proper circulation of the heat transfer oil; the filters should be cleaned regularly, and lubrication should be applied to all mechanical parts such as pumps as specified, along with regular maintenance of these components. 5. When starting the ignition, the circulation pump should be turned on first; heating should only be carried out after the pressure stabilizes ； When shutting down the furnace, it is generally required that the temperature of the heat transfer oil be reduced below 100°C before stopping the operation of the circulation pump. V. Judgment and handling of abnormal situations 1. Abnormal pressure difference at the inlet and outlet of the heat transfer oil furnace. 1) When the inlet pressure increases, the outlet pressure decreases, and the pressure difference between the inlet and outlet rises, it indicates that coking has occurred within the furnace tubes of the heating furnace, causing blockages. 2) When the inlet pressure rises, the outlet pressure also rises, and the pressure difference between inlet and outlet drops sharply, it indicates that coking and blockage have occurred in the external pipes at the outlet of the heating furnace. 3) When the inlet pressure drops, the outlet pressure also drops, and the pressure difference between inlet and outlet falls sharply, it indicates that coking has occurred in the external pipes at the inlet of the heater, causing a blockage. 2. The return oil temperature of the boiler is high, preventing the heat-using equipment from reaching the desired temperature. 1) When heat equipment is operated in parallel, the oil circuit design is unreasonable, resulting in uneven flow distribution. Readjust the management design to ensure a reasonable distribution of traffic. 2) Coking of equipment pipes, severe cracking of heat transfer oil. Clean the system and replace the heat transfer oil. It is strictly prohibited to raise the export temperature in order to ensure the heat supply, as this will exacerbate coking in the system and accelerate the cracking of the heat transfer oil, creating a vicious cycle that can ultimately lead to the rupture of the furnace tubes. VI. Several emergency measures in case of a sudden power outage: When there is a sudden power outage, the heat transfer oil inside the oil furnace coils stops flowing, which leads to an increase in the temperature of the heat transfer oil and localized overheating, severely affecting its service life. To minimize the damage caused by sudden power outages to oil products, it is recommended to take the following emergency measures. 1. Install a diesel generator to power the circulation pump motor. 2. Open the furnace door and quickly remove the burning coal ash (or extinguish it by using pre-prepared wet coal before removing it), then cool the furnace interior through natural ventilation. 3. Open the cold oil replacement valve to allow the heat transfer oil in the furnace to flow into the lower oil storage tank.