Several common parameters and selection methods for selecting steam traps

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This post was last edited by MIYAWAKI Han Jie on 2019-7-4 at 10:47. 1 Types of steam traps: The commonly used steam traps are divided into three categories: thermostatic, thermodynamic, and mechanical. Common types of thermostatic types: diaphragm type, bimetallic type (Miyawaki temperature control type). Common type of thermodynamic type: disc type. When selecting a trap, if the type of trap is not specified, the type can be initially determined based on the location where the trap will be used and its drainage capacity. 2 Connection methods and diameters: The common connection methods include threaded connection (Rc/Rp), flanged connection (FF/RF), and socket weld connection (SW). Common units for diameter: inch/innches (1/8, 1/4, 3/8, 1/2…….), mm/millimeters (6, 8, 10, 15........). Flange standards are divided into: Japanese standards (JIS5K, JIS10K……), American standards (ANSI150lb, ANSI300lb…..), German standards (PN10, PN16……), and Chinese standards (PN0.25Mpa, PN0.6Mpa……). When selecting, choose a trap that meets the requirements based solely on the diameter and connection method. If the diameter is too large while the amount of condensate to be removed is low, considering reducing the diameter may be appropriate; the same logic applies in reverse. 3 Valve body material: Standards for valve body materials include Japanese standards (JIS), American standards (ASTM), German standards (DIN), and Chinese standards (GB). Traps with different valve body materials can withstand different temperatures and pressures; if a socket welding connection is used, it is also necessary to consider whether the valve body material and the pipeline material are compatible for welding. When selecting a material, if there are specific requirements regarding the material type, it should be given top priority to meet those requirements; if this is not possible, then alternative materials should be sought as long as they can satisfy the pressure and temperature requirements. When it comes to clean steam, food-grade stainless steel must be used; there is no alternative. 4 Pressure and temperature: The pressure and temperature parameters of steam traps – PMA: Maximum allowable pressure: The highest pressure that the valve body of a steam trap can withstand, also known as the design pressure. PMO – Maximum operating pressure: The highest pressure at which the steam trap can operate. PMX – Maximum operating pressure difference: The highest working pressure difference that a steam trap can withstand, with the operating pressure difference being equal to the inlet pressure minus the back pressure. TMA – Maximum Allowable Temperature: The highest temperature that the body of a steam trap can withstand, also known as the design temperature. TMO – Maximum operating temperature: The highest temperature at which the steam trap can operate. When selecting a valve, the operating pressure difference is typically calculated based on the design requirements, and this pressure difference serves as the standard for determining the flow rate of the steam trap. 5 Flow rate: When selecting a steam trap, the most important parameter is the flow rate, also known as the condensate discharge volume. The required flow rate as per the design specifications is multiplied by the safety factor specified in the design to obtain the safe flow rate; thereafter, the model of the steam trap that meets this safe flow rate at the given operating pressure difference is selected based on its flow rate chart. The safety factor is usually 3 times; if there are no design specifications, it must not be less than 1.5 times. The presence of a safety factor ensures that condensate water can be drained promptly when the equipment or pipes are started up and warmed up. In summary, when selecting a steam trap, the first thing to consider is choosing the appropriate type; next, it is necessary to check whether it meets the requirements regarding temperature, pressure, and material; finally, it is important to verify that the flow rate meets the specified standards.