選用時須考慮的因素   選擇閥門是根據操作和安全及經濟的合理性，綜合平衡比較的經驗結果。在選擇閥門之前必須提出下述原始條件:1.1 物 性 (1) 物料狀態 a.氣體物料的物料狀態包括有關物性數據，純氣體還是混合物，是否有液滴或固體微粒，是否有易凝結的成份。 b.液體物料的物料狀態包括：有關物性數據，純組份或混合物是否含易揮發組份或溶解有氣體(壓力降低時可析出形成二相流)，是否含固體懸浮物，以及液體的粘稠度、凝固點或傾點等。 (2) 其它性質:包括腐蝕性、毒性、對閥門結構材料的溶解性，是否易燃易爆等性能。這些性能有時不只影響材質，還會引起結構上的特殊要求，或需要提高管道等級。

　　The factors to consider when selecting valves are based on the rationality of operation, safety, and economy, and the empirical results of comprehensive balance comparison. Before selecting a valve, the following original conditions must be proposed: 1.1 Physical properties (1) Material state a. The material state of gas materials includes relevant physical property data, whether it is pure gas or mixture, whether there are droplets or solid particles, and whether there are easily condensable components. b. The material state of liquid materials includes: relevant physical property data, whether pure components or mixtures contain volatile components or dissolved gases (which can precipitate into two-phase flow when pressure decreases), whether they contain solid suspensions, as well as the viscosity, solidification point or pour point of the liquid. (2) Other properties: including corrosiveness, toxicity, solubility in valve structural materials, flammability and explosiveness. These properties sometimes not only affect the material, but also cause special structural requirements or require an increase in pipeline grade.

　　1.2 操作狀態下的工作條件 (1) 按正常工作條件下的溫度和壓力，還需結合開停工或再生時的工作條件。 a.泵出口閥應考慮泵的最大關閉壓力等。 b.當系統再生溫度高出正常溫度很多，而壓力卻有所降低，對這種類型的系統，要考慮溫度和壓力綜合的影響。 c.操作的連續程度：即閥門開閉的頻率，也影響到對耐磨損程度的要求，開關較頻繁的系統，應考慮是否安裝雙閥。 (2) 系統允許的壓力降 a.系統允許壓力降較小，或允許壓力降不小但不需要進行流量調節時，則應選用、壓力降較小的閥型如閘閥、直通的球閥等。 b.需要調節流量，則應選擇調節性能較好，具有一定壓力降的閥型(壓力降占整個管道壓力降的比例與調節的靈敏度有關)。 (3) 閥門所處的環境:在寒冷地區的室外，特別是對化學物料，閥體材質一般不可用鑄鐵而應選用鑄鋼(或不銹鋼)。

　　1.2 Working conditions under operating conditions (1) The temperature and pressure under normal working conditions should also be combined with the working conditions during start-up, shutdown, or regeneration. a. The pump outlet valve should consider the maximum closing pressure of the pump, etc. b. When the regeneration temperature of the system is much higher than the normal temperature, but the pressure decreases, the combined effects of temperature and pressure should be considered for this type of system. c. The continuity of operation: that is, the frequency of valve opening and closing, also affects the requirements for wear resistance. For systems with frequent opening and closing, the installation of dual valves should be considered. (2) When the system allows for a small pressure drop, or allows for a significant pressure drop but does not require flow regulation, valve types with small pressure drops such as gate valves and straight through ball valves should be selected. b. If flow regulation is required, a valve type with good regulation performance and a certain pressure drop should be selected (the proportion of pressure drop to the entire pipeline pressure drop is related to the sensitivity of regulation). (3) The environment in which the valve is located: outdoors in cold regions, especially for chemical materials, the valve body material should generally not be cast iron but should be cast steel (or stainless steel).

　　1.3 閥門功能 (1) 切斷：幾乎所有的閥門都具有切斷功能。單純用于切斷而不需調節流量則可選用閘閥，球閥等，要求迅速切斷時，則以旋塞、球閥、蝶閥等較為適宜。截止閥則既可調節流量又可切斷。蝶閥也可適于大流量的調節。 (2) 改變流向：選用兩通(通道為L形)或三通(通道為T形)球閥或旋塞，可以迅速改變物料流向，且由于一個閥門起到兩個以上直通閥門的作用，可簡化操作，使切換準確無誤，并能減少所占空間。 (3) 調控：截止閥、柱塞閥可滿足一般的流量調節，針形閥可用于微量的細調；在較大流量范圍進行穩定(壓力、流量)的調節，則以節流閥為宜。 (4) 止回：需防止物料倒流時可選用止回閥。

　　1.3 Valve Function (1) Cut off: Almost all valves have a cut-off function. If it is only used for cutting off without adjusting the flow rate, gate valves, ball valves, etc. can be selected. When rapid cutting is required, plug valves, ball valves, butterfly valves, etc. are more suitable. The shut-off valve can adjust the flow rate and cut off the flow. Butterfly valves can also be suitable for regulating large flow rates. (2) Changing the flow direction: By using two-way (L-shaped channel) or three-way (T-shaped channel) ball valves or plugs, the material flow direction can be quickly changed. Moreover, since one valve serves as a direct passage for two or more valves, the operation can be simplified, the switching can be accurate, and the occupied space can be reduced. (3) Regulation: Globe valves and plunger valves can meet general flow regulation requirements, while needle valves can be used for micro fine adjustments; A throttle valve is suitable for stable regulation (pressure, flow) within a large flow range. (4) Check valve: When it is necessary to prevent material backflow, a check valve can be used.

　　(5) 不同生產過程可以選擇有附加功能的閥門，如有帶夾套、帶排凈口和帶旁路的閥門，有用于防止固體微粒沉降的帶吹氣口閥門等。

　　(5) Valves with additional functions can be selected for different production processes, such as valves with jackets, discharge ports, and bypass ports, as well as valves with blowing ports to prevent solid particle settling.

　　1.4 開關閥門的動力  就地操作的閥門絕大多數用手輪，對與操作帶有一定距離的，可采用鏈輪或加長桿。一些大口徑的閥門因啟動力矩過大在閥門設計時已帶有電機。在防爆區內要采用相應等級的防爆電機。  遙控閥門：采取的動力種類有氣動、液壓、電動等，其中電動又可分為電磁閥與電機帶動的閥。應根據需要和所能提供的能源來選擇。

　　1.4 Power for opening and closing valves: The vast majority of locally operated valves use handwheels. For valves that are at a certain distance from the operation, chain wheels or extension rods can be used. Some large-diameter valves are designed with motors due to excessive starting torque. Corresponding grade explosion-proof motors should be used in the explosion-proof area. Remote control valve: The types of power used include pneumatic, hydraulic, electric, etc. Among them, electric can be further divided into solenoid valves and motor-driven valves. The selection should be based on the needs and available energy.

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