The function of the high-level tank of the thermal oil heater

During operation, an elevated tank must be installed at an appropriate height above the electric thermal oil boiler to serve as an expansion tank. Its main functions are as follows:

1. Oil filling: Replenishes thermal oil when new oil is added or when the system runs low. Thermal oil naturally loses 5-10% annually over time, requiring replenishment. When the elevated tank level drops, use a replenishment pump to refill it from the lower tank to the elevated tank to the normal level. Generally, a level of 1/3 at room temperature is maintained, and a level of less than 2/3 at operating temperature is considered normal. Failure to do so should raise concerns about design, installation, and operation errors. The elevated expansion tank must never be used without a level gauge during production.

2. Venting: After new oil enters the system, the thermal oil in the system separates into gas and vapor as it heats up. This venting (vaporization) and dehydration are removed through the expansion tank.

3. It is used to accommodate and compensate for the volume expansion or contraction of the thermal oil in the heating system and pipelines due to temperature changes, and to isolate the high-temperature thermal oil in the heating equipment from the air. Furthermore, the temperature of the thermal oil in the expansion tank that comes into contact with air should not exceed 70°C (Article 21, Paragraph 6 of the [Safety Technical Supervision Regulations for Organic Heat Transfer Furnaces]). This reduces the oxidation rate of the thermal oil (for thermal oil above 80°C, its oxidation rate doubles for every 10°C increase in temperature when in contact with air) and evaporation losses, thereby extending the service life and ensuring safe use of the thermal oil.

4. The expansion tank should be installed at least 1.5 meters above the heating system. Otherwise, the thermal oil in the high-level heating system will not be able to be filled. If forced to fill, the high-level tank will collapse. Despite the relatively large system and complex piping network, the inlet and outlet pressures and differential pressures of the organic heat transfer boiler are ideal, and pressure fluctuations are non-existent. Given the importance of expansion, dual level gauges (low-level alarm and magnetic flap level gauge) should be installed. To prevent oxidation of the thermal oil, an inert gas seal should be used. If these conditions are not met, the overflow pipe can be inserted directly below the liquid level in the low-level storage tank to form a cold oil seal to isolate the oil from oxygen in the air, thus extending the life of the thermal oil exponentially.