The function of steam traps (III)

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This post was last edited by melamine on 2015-9-28 09:31. The function of steam traps (III): Another role of steam traps is to remove non-condensable gases such as air from the steam system. Sources of air in steam systems: 1. Vacuum is created when the steam system is shut down, allowing air to be drawn in. 2. Air is carried in by the water supplied to the boiler. 3. Make-up water and condensate come into contact with air. 4. The feeding and discharging areas of batch heating equipment. 5. Cold air carried by the materials and equipment during direct heating.

Harm of air to steam and condensate systems: It creates thermal resistance, affects heat transfer, reduces the efficiency of heat exchangers, increases heating time, and raises the required steam pressure. Due to air’s poor thermal conductivity, its presence leads to uneven heating of the product. The temperature of steam cannot be determined based on the pressure gauge, which is unacceptable for many manufacturing processes. The presence of 20% air in the heating space leads to a decrease in steam temperature as well as severe vapor locking in the hydrophobic system. The O2 and CO2 contained in the air can cause corrosion in valves, heat exchangers, and other components. When this air enters the condensate water system, it can cause water hammer. In Figure 1 shown above, among the three heat transfer resistance layers on the steam side – the water film, the air film, and the scale layer – the greatest heat resistance is provided by the air layer. The presence of an air film on the heat exchange surface can cause cold spots; in worse cases, it can completely prevent heat transfer, or at the very least it leads to uneven heating. In fact, the thermal resistance of air is more than 1,500 times that of iron and steel, and 13,000 times that of copper. As shown in Figure 2 above, when the cumulative air proportion in the heat exchanger space reaches 25%, the temperature of the steam drops significantly, which reduces the heat transfer efficiency; this can lead to failure in the sterilization process. Steam traps must be capable of promptly removing non-condensable gases such as air from the steam system during startup or normal operation, to ensure efficient heat transfer and protect the equipment. If you have any questions regarding the use or purchase of steam traps, please send a private message to the poster.