What parameters are required for selecting a steam trap?

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This post was last edited by 955559 on 2018-12-5 22:41. There are many types of drain valves, each with different performance characteristics. When selecting a steam trap, it is first necessary to ensure that its properties meet the requirements for optimal operation of steam heating equipment; only after that should other objective factors be considered. This approach ensures that the steam trap chosen is the right one and effective. When selecting a steam trap, it is necessary to provide operational parameters such as the steam consumption of the trap, operating pressure difference, operating temperature, and connection method. 1. Steam consumption of the drain valve: When selecting a drain valve, it is necessary to determine its drainage capacity by multiplying the equipment’s hourly steam consumption by a factor of 2–3, to obtain the maximum amount of condensate water. This ensures that the steam trap can discharge condensate as quickly as possible when it operates, thereby rapidly raising the temperature of the heating equipment. Insufficient discharge capacity of the steam trap results in delayed removal of condensate, thereby reducing the thermal efficiency of the heating equipment. When the steam heating equipment starts to supply steam, it is cold and filled with air; a steam trap is needed to quickly remove this air, as well as large amounts of low-temperature condensate, so that the equipment can gradually warm up and then enter its normal operating state. During startup, large amounts of air and low-temperature condensate, along with a low inlet pressure, cause the steam trap to operate under overload conditions. In such situations, the steam trap requires a larger drainage volume than during normal operation; therefore, the steam trap should be selected with a selection factor of 2–3 times. 2. Operating pressure difference of the steam trap: When selecting a steam trap, it is not possible to choose it based on its nominal pressure, as the nominal pressure merely indicates the pressure level that the steam trap’s casing can withstand; there is a significant difference between the nominal pressure of a steam trap and its operating pressure. Therefore, the drainage capacity of the steam trap should be selected based on the working pressure difference. The operating pressure difference refers to the difference between the operating pressure before the steam trap and the back pressure at the outlet of the steam trap. The back pressure behind the steam trap is calculated as follows: (when the condensate behind the steam trap is discharged into the atmosphere, the outlet back pressure of the steam trap is zero.) If the condensed water discharged by the steam trap is collected together, the back pressure at the outlet of the steam trap becomes the sum of the resistance in the return pipe, the elevation height of the return pipe, and the pressure inside the secondary evaporator (return water tank). ) 3. Operating temperature of the steam trap: When selecting a steam trap, it is necessary to choose one that can meet the requirements of the process conditions, based on the highest steam temperature in the pipeline. Steam in a pipeline whose maximum temperature exceeds the saturated steam temperature corresponding to its nominal pressure is known as superheated steam. When selecting a steam trap for such superheated steam pipelines, it is necessary to use a steam trap designed specifically for high-temperature and high-pressure superheated steam. 4. Connection method of the steam trap: Once the process conditions for the steam trap are determined, the size of the steam trap should be selected based on the working pressure difference before and after the steam trap, as well as the amount of steam to be drained, in accordance with the technical specifications provided by the steam trap manufacturer. It is not appropriate to choose a steam trap of the same size merely based on the connection dimensions of the equipment; the connection diameter of the steam trap does not indicate the amount of steam it can handle. Even steam traps with the same diameter can have significantly different drainage capacities. Therefore, when selecting a steam trap, it is necessary to base the choice on the process conditions of the equipment and refer to the parameters provided by the steam trap manufacturers – this is the correct approach.