閥門作為流體控制系統的關鍵部件，其尺寸選擇直接影響管道系統的運行效率與安全性。合適的尺寸能確保流體通暢流動，減少能耗與故障風險；尺寸不當則可能導致壓力損失過大、流量不足或閥門損壞。選擇閥門尺寸需綜合考慮管道參數、介質特性及工作條件，通過科學分析確定最優規格。

　　As a key component of fluid control systems, the size selection of valves directly affects the operational efficiency and safety of pipeline systems. Appropriate size can ensure smooth fluid flow, reduce energy consumption and fault risks; Improper size may result in excessive pressure loss, insufficient flow, or valve damage. The selection of valve size should comprehensively consider pipeline parameters, medium characteristics, and working conditions, and determine the optimal specifications through scientific analysis.

　　管道直徑是選擇閥門尺寸的基礎依據。閥門的公稱直徑應與所在管道的公稱直徑相匹配，確保流體在管道與閥門之間平穩過渡。若閥門尺寸小于管道直徑，會形成流通瓶頸，導致流體受阻，增加管道內的壓力損失，不僅降低系統效率，還可能因流速過快引發閥門內部沖刷磨損，縮短使用壽命。反之，若閥門尺寸大于管道直徑，雖能減少阻力，但會造成材料浪費，且閥門與管道的連接部位易出現湍流，長期運行可能導致密封件損壞，增加泄漏風險。因此，常規情況下，閥門公稱直徑應與管道公稱直徑保持一致，特殊場景需通過水力計算調整。

　　The diameter of the pipeline is the basic basis for selecting valve size. The nominal diameter of the valve should match the nominal diameter of the pipeline it is in, ensuring a smooth transition of fluid between the pipeline and the valve. If the valve size is smaller than the diameter of the pipeline, it will form a flow bottleneck, causing fluid obstruction and increasing pressure loss inside the pipeline. This not only reduces system efficiency, but may also cause internal erosion and wear of the valve due to excessive flow rate, shortening its service life. On the contrary, if the size of the valve is larger than the diameter of the pipeline, although it can reduce resistance, it will cause material waste, and the connection between the valve and the pipeline is prone to turbulence. Long term operation may cause seal damage and increase the risk of leakage. Therefore, under normal circumstances, the nominal diameter of the valve should be consistent with the nominal diameter of the pipeline, and special scenarios require adjustment through hydraulic calculations.

　　介質特性對閥門尺寸選擇有重要影響。對于黏度較高的介質（如原油、糖漿），需適當放大閥門尺寸，避免因介質流動性差導致堵塞。這類介質在管道中流速較慢，若閥門尺寸過小，易在閥體內形成淤積，影響控制精度。而對于含顆粒雜質的介質（如污水、礦漿），除需匹配管道直徑外，還需考慮閥門流道的通暢性，選擇直通式流道的閥門時，其尺寸應保證顆粒順利通過，防止卡堵；若顆粒含量較高，可適當增大閥門尺寸，降低流速以減少顆粒對閥門的沖擊磨損。

　　The characteristics of the medium have a significant impact on the selection of valve size. For media with high viscosity (such as crude oil and syrup), the valve size should be appropriately enlarged to avoid blockage caused by poor fluidity of the medium. This type of medium has a slow flow rate in pipelines. If the valve size is too small, it is easy to form sedimentation inside the valve body, which affects the control accuracy. For media containing particulate impurities (such as sewage and slurry), in addition to matching the pipeline diameter, the smoothness of the valve flow channel also needs to be considered. When choosing a valve with a straight through flow channel, its size should ensure that the particles pass smoothly and prevent blockage; If the particle content is high, the valve size can be appropriately increased and the flow rate can be reduced to minimize the impact and wear of particles on the valve.

　　工作壓力與溫度是不可忽視的因素。高壓系統中，閥門尺寸需結合壓力等級核算，確保閥門殼體強度與管道系統匹配。壓力較高時，若閥門尺寸過大，其壁厚需相應增加以承受高壓，不僅增加成本，還會降低啟閉靈活性；壓力較低的系統則可根據流量需求適當調整尺寸，在滿足流通的前提下簡化結構。溫度對閥門尺寸的影響體現在材料熱脹冷縮特性上，高溫環境下，閥門與管道的連接部位可能因熱膨脹出現間隙，選擇尺寸時需預留一定的補償空間，避免因尺寸剛性匹配導致密封失效。

　　Work pressure and temperature are factors that cannot be ignored. In high-pressure systems, valve size needs to be calculated based on pressure rating to ensure that the strength of the valve housing matches the pipeline system. When the pressure is high, if the valve size is too large, its wall thickness needs to be increased accordingly to withstand high pressure, which not only increases costs but also reduces the flexibility of opening and closing; Systems with lower pressure can be adjusted in size according to flow requirements, simplifying the structure while meeting flow requirements. The influence of temperature on valve size is reflected in the thermal expansion and contraction characteristics of materials. In high temperature environments, there may be gaps at the connection between valves and pipelines due to thermal expansion. When selecting the size, a certain compensation space should be reserved to avoid sealing failure caused by rigid size matching.

　　流量需求是確定閥門尺寸的核心參數。通過計算管道系統的設計流量，結合閥門的流量系數（Kv 值）確定合適尺寸。流量系數反映閥門的流通能力，數值越大，單位時間內通過的流體量越多。在已知設計流量和允許壓力損失的情況下，可通過公式計算所需的最小 Kv 值，再對照閥門廠家提供的 Kv 值表選擇對應尺寸。例如，大流量系統需選擇 Kv 值較大的閥門，確保流體能按設計要求通過；小流量精確控制場景則需選擇小尺寸閥門，提高調節精度。

　　Flow demand is the core parameter for determining valve size. Determine the appropriate size by calculating the design flow rate of the pipeline system and combining it with the flow coefficient (Kv value) of the valve. The flow coefficient reflects the flow capacity of the valve, and the larger the value, the more fluid passes through per unit time. Given the known design flow rate and allowable pressure loss, the minimum required Kv value can be calculated using a formula, and the corresponding size can be selected by comparing it with the Kv value table provided by the valve manufacturer. For example, for high flow systems, valves with larger Kv values need to be selected to ensure that the fluid can pass through according to design requirements; For small flow precise control scenarios, small-sized valves need to be selected to improve regulation accuracy.

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