Analysis of the causes of overheating in the expansion tank of the heat transfer oil system

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This post was last edited by goldliyang on 2017-6-6 at 14:25. The heat transfer oil system mainly consists of a heating furnace, a circulation pump, an expansion tank (high-level tank), an oil storage tank (low-level tank), a filtration unit, and other auxiliary components (thermometers, pressure gauges, valves, etc.). In particular, the use of expansion tanks in heat transfer oil systems is crucial; they represent the main part of the system where the heat transfer oil comes into contact with the atmosphere. They not only help ensure the safe operation of the heating system but also contribute to extending the service life of the heat transfer oil. The main function of the expansion tank is to accommodate the volume increase of the heat transfer oil within the system, to replenish the oil lost due to consumption or accidental leaks, and to prevent the heat transfer oil from coming into contact with air and undergoing oxidative decomposition. During an emergency shutdown caused by an unexpected incident in the heating system, the hot oil inside the furnace is replaced to prevent the heat transfer oil from overheating and decomposing. Additionally, some units use the expansion tank as an oil filling tank during design. Since the oil in the expansion tank is in direct contact with air, it is recommended to install a nitrogen sealing device in such tanks to prevent the heat transfer oil from undergoing oxidation reactions with the oxygen in the air, which could accelerate decomposition. If the temperature of the heat transfer oil in the expansion tank is too high, it will also cause the oil to age rapidly, shortening its service life. Therefore, such things should be avoided as much as possible. The following reasons for overheating of the expansion tank have been identified: 1. An inappropriate angle of the expansion tube causes hot oil to enter the expansion tank during circulation, increasing the temperature of the heat transfer oil in the expansion tank. During installation, it must be carried out strictly in accordance with the boiler’s design and installation specifications. 2. The installation height of the expansion tank is insufficient, resulting in the heat transfer oil temperature in the system reaching the tank. The installation height of the expansion tank should be increased. 3. The auxiliary exhaust pipeline was not closed after dehydration and light removal were completed; as a result, the heat transfer oil entered the expansion tank through the auxiliary exhaust pipe during forced circulation, causing the expanded heat transfer oil to participate in the system circulation. The auxiliary exhaust valve should be closed once the heat transfer oil reaches the operating temperature.