在流體管道系統中，閥門是控制元件，其主要作用是隔離設備和管道系統、調節流量、防止回流、調節和排泄壓力。

　　In fluid pipeline systems, valves are control components whose main functions are to isolate equipment and pipeline systems, regulate flow, prevent backflow, and regulate and discharge pressure.

　　閥門可用于控制空氣、水、蒸汽、各種腐蝕性介質、泥漿、油品、液態金屬和放射性介質等各種類型流體的流動。由于管道系統選擇最適合的閥門顯得非常重要，所以，了解閥門的特性及選擇閥門的步驟和依據也變得至關重要起來。

　　Valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metals, and radioactive media. Due to the importance of selecting the most suitable valve for pipeline systems, understanding the characteristics of valves and the steps and criteria for selecting valves have become crucial.

　　閥門的分類

　　Classification of valves

　　一、閥門總的可分兩大類：第一類自動閥門：依靠介質（液體、氣體）本身的能力而自行動作的閥門。如止回閥、安全閥、調節閥、疏水閥、減壓閥等。第二類驅動閥門：借助手動、電動、液動、氣動來操縱動作的閥門。如閘閥，截止閥、節流閥、蝶閥、球閥、旋塞閥等。

　　1、 Valves can be generally divided into two categories: the first category is automatic valves: valves that operate on their own by relying on the ability of the medium (liquid, gas) itself. Such as check valves, safety valves, regulating valves, drain valves, pressure reducing valves, etc. The second type of driven valve: a valve that is operated manually, electrically, hydraulically, or pneumatically. Such as gate valves, globe valves, throttle valves, butterfly valves, ball valves, plug valves, etc.

　　二、按結構特征，根據關閉件相對于閥座移動的方向可分：

　　2、 According to the structural characteristics, it can be divided into:

　　1.截門形:關閉件沿著閥座中心移動；

　　1. Truncated shape: The closing component moves along the center of the valve seat;

　　2.閘門形:關閉件沿著垂直閥座中心移動；

　　2. Gate shaped: The closing component moves along the center of the vertical valve seat;

　　3.旋塞和球形:關閉件是柱塞或球，圍繞本身的中心線旋轉；

　　3. Plug and ball: The closing component is a plunger or ball that rotates around its own centerline;

　　4.旋啟形:關閉件圍繞閥座外的軸旋轉；

　　4. Swing shape: The closing component rotates around the axis outside the valve seat;

　　5.碟形:關閉件的圓盤，圍繞閥座內的軸旋轉；

　　5. Disc shape: a circular disc of a closure that rotates around the axis inside the valve seat;

　　6.滑閥形:關閉件在垂直于通道的方向滑動。

　　6. Sliding valve shape: The closing element slides in a direction perpendicular to the channel.

　　三、按用途，根據閥門的不同用途可分：

　　3、 According to their different purposes, valves can be divided into:

　　1.開斷用：用來接通或切斷管路介質，如截止閥、閘閥、球閥、蝶閥等。

　　1. Disconnecting function: used to connect or cut off pipeline media, such as globe valves, gate valves, ball valves, butterfly valves, etc.

　　2.止回用：用來防止介質倒流，如止回閥。

　　2. Check valve: used to prevent medium backflow, such as a check valve.

　　3.調節用：用來調節介質的壓力和流量，如調節閥、減壓閥。

　　3. Regulating: Used to regulate the pressure and flow rate of the medium, such as regulating valves and pressure reducing valves.

　　4.分配用：用來改變介質流向、分配介質，如三通旋塞、分配閥、滑閥等。

　　4. Distribution: Used to change the flow direction and distribute media, such as three-way plugs, distribution valves, slide valves, etc.

　　5.安全閥：在介質壓力超過規定值時，用來排放多余的介質，保證管路系統及設備安全，如安全閥、事故閥。

　　5. Safety valve: Used to discharge excess medium when the medium pressure exceeds the specified value, ensuring the safety of pipeline systems and equipment, such as safety valves and emergency valves.

　　6.其他特殊用途：如疏水閥、放空閥、排污閥等。

　　6. Other special purposes: such as drain valves, vent valves, drain valves, etc.

　　四、按驅動方式，根據不同的驅動方式可分：

　　4、 According to the driving method, it can be divided into:

　　1.手動：借助手輪、手柄、杠桿或鏈輪等，有人力驅動，傳動較大力矩時裝有蝸輪、齒輪等減速裝置。

　　1. Manual: With the help of a handwheel, handle, lever, or sprocket, it is manually driven and equipped with reduction devices such as worm gears and gears when transmitting large torque.

　　2.電動：借助電機或其他電氣裝置來驅動。

　　2. Electric: driven by a motor or other electrical device.

　　3.液動：借助（水、油）來驅動。

　　3. Hydraulic: driven by (water, oil).

　　4.氣動：借助壓縮空氣來驅動。

　　4. Pneumatic: driven by compressed air.

　　五、按壓力，根據閥門的公稱壓力可分：

　　5、 According to the nominal pressure of the valve, it can be divided into:

　　1.真空閥：絕對壓力<0.1Mpa 即 760mm 汞柱高的閥門，通常用 mm 汞柱或mm水柱表示壓力。

　　1. Vacuum valve: A valve with an absolute pressure<0.1Mpa, which is 760mm mercury column high, usually expressed in mm mercury column or mm water column to indicate pressure.

　　2.低壓閥：公稱壓力 PN≤1.6Mpa 的閥門（包括 PN≤1.6MPa 的鋼閥）

　　2. Low pressure valve: valves with nominal pressure PN ≤ 1.6Mpa (including steel valves with PN ≤ 1.6MPa)

　　3.中壓閥：公稱壓力 PN2.5-6.4MPa 的閥門。

　　3. Medium pressure valve: a valve with a nominal pressure of PN2.5-6.4MPa.

　　4.高壓閥：公稱壓力 PN10.0-80.0MPa 的閥門。

　　4. High pressure valve: a valve with a nominal pressure of PN10.0-80.0MPa.

　　5.超高壓閥：公稱壓力 PN≥100.0MPa 的閥門。

　　5. Ultra high pressure valve: a valve with a nominal pressure PN ≥ 100.0MPa.

　　六、按介質的溫度分，根據閥門工作時的介質溫度可分：

　　6、 According to the temperature of the medium, it can be divided into:

　　1.普通閥門：適用于介質溫度-40℃～425℃的閥門。

　　1. Ordinary valve: suitable for valves with medium temperatures ranging from -40 ℃ to 425 ℃.

　　2.高溫閥門：適用于介質溫度 425℃～600℃的閥門。

　　2. High temperature valve: suitable for valves with medium temperatures ranging from 425 ℃ to 600 ℃.

　　3.耐熱閥門：適用于介質溫度 600℃以上的閥門。

　　3. Heat resistant valve: Suitable for valves with medium temperatures above 600 ℃.

　　4.低溫閥門：適用于介質溫度-150℃～ -40℃的閥門。

　　4. Low temperature valve: Suitable for valves with medium temperatures ranging from -150 ℃ to -40 ℃.

　　5.超低溫閥門：適用于介質溫度-150℃以下的閥門。

　　5. Ultra low temperature valve: suitable for valves with medium temperatures below -150 ℃.

　　七、按公稱通徑分，根據閥門的公稱通徑可分：

　　7、 According to the nominal diameter, valves can be divided into:

　　1.小口徑閥門：公稱通徑 DN<40mm 的閥門。

　　1. Small caliber valves: valves with a nominal diameter of DN<40mm.

　　2.中口徑閥門：公稱通徑 DN50～300mm 的閥門。

　　2. Medium caliber valves: valves with a nominal diameter of DN50-300mm.

　　3.大口徑閥門：公稱通徑 DN350～1200mm 的閥門。

　　3. Large caliber valves: valves with a nominal diameter of DN350-1200mm.

　　4.特大口徑閥門：公稱通徑 DN≥1400mm 的閥門。

　　4. Extra large caliber valves: valves with a nominal diameter DN ≥ 1400mm.

　　八、按與管道連接方式分，根據閥門與管道連接方式可分：

　　8、 According to the connection method with the pipeline, it can be divided into:

　　1.法蘭連接閥門：閥體帶有法蘭，與管道采用法蘭連接的閥門。

　　1. Flange connected valve: The valve body is equipped with a flange and is connected to the pipeline using a flange.

　　2.螺紋連接閥門：閥體帶有內螺紋或外螺紋，與管道采用螺紋連接的閥門。

　　2. Threaded connection valve: The valve body has internal or external threads and is connected to the pipeline using threads.

　　3.焊接連接閥門：閥體帶有焊口，與管道采用焊接連接的閥門。

　　3. Welded connection valve: The valve body has a welded joint and is connected to the pipeline by welding.

　　4.夾箍連接閥門：閥體上帶有夾口，與管道采用夾箍連接的閥門。

　　4. Clamp connected valve: The valve body has a clamp mouth and is connected to the pipeline using clamps.

　　5.卡套連接閥門：采用卡套與管道連接的閥門。

　　5. Card sleeve connected valve: a valve that uses a card sleeve to connect to the pipeline.

　　閥門的特性閥門的特性一般有兩種，使用特性和結構特性。

　　The characteristics of valves generally have two types: usage characteristics and structural characteristics.

　　使用特性：它確定了閥門的主要使用性能和使用范圍，屬于閥門使用特性的有：

　　Usage characteristics: It determines the main performance and scope of use of the valve, and the valve usage characteristics include:

　　閥門的類別（閉路閥門、調節閥門、安全閥門等）；

　　Types of valves (closed-circuit valves, regulating valves, safety valves, etc.);

　　產品類型（閘閥、截止閥、蝶閥、球閥等）；

　　Product type (gate valve, globe valve, butterfly valve, ball valve, etc.);

　　閥門主要零件（閥體、閥蓋、閥桿、閥瓣、密封面）的材料；閥門傳動方式等。

　　The materials of the main components of the valve (valve body, valve cover, valve stem, valve disc, sealing surface); Valve transmission mode, etc.

　　結構特性：它確定了閥門的安裝、維修、保養等方法的一些結構特性，屬于結構特性的有：閥門的結構長度和總體高度、與管道的連接形式（法蘭連接、螺紋連接、夾箍連接、外螺紋連接、焊接端連接等）；密封面的形式（鑲圈、螺紋圈、堆焊、噴焊、閥體本體）；閥桿結構形式（旋轉桿、升降桿）等。

　　Structural characteristics: It determines some structural characteristics of the installation, maintenance, and upkeep methods of the valve, including the structural length and overall height of the valve, and the connection form with the pipeline (flange connection, threaded connection, clamp connection, external threaded connection, welded end connection, etc.); Form of sealing surface (insert ring, threaded ring, overlay welding, spray welding, valve body); Valve stem structure forms (rotating rod, lifting rod), etc.

　　選擇閥門的步驟和依據選擇步驟：

　　Steps and criteria for selecting valves:

　　1、明確閥門在設備或裝置中的用途，確定閥門的工作條件：適用介質、工作壓力、工作溫度等等。

　　1. Clarify the purpose of the valve in the equipment or device, determine the working conditions of the valve: applicable medium, working pressure, working temperature, etc.

　　2、確定與閥門連接管道的公稱通徑和連接方式：法蘭、螺紋、焊接等。

　　2. Determine the nominal diameter and connection method of the pipeline connected to the valve: flange, thread, welding, etc.

　　3、確定操作閥門的方式：手動、電動、電磁、氣動或液動、電氣聯動或電液聯動等。

　　3. Determine the method of operating the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electrical linkage or electro-hydraulic linkage, etc.

　　4、根據管線輸送的介質、工作壓力、工作溫度確定所選閥門的殼體和內件的材料：灰鑄鐵、可鍛鑄鐵、球墨鑄鐵、碳素鋼、合金鋼、不銹耐酸鋼、銅合金等。

　　4. Determine the materials for the shell and internal components of the selected valve based on the medium transported by the pipeline, working pressure, and working temperature: gray cast iron, malleable cast iron, ductile iron, carbon steel, alloy steel, stainless acid resistant steel, copper alloy, etc.

　　5、選擇閥門的種類：閉路閥門、調節閥門、安全閥門等。

　　5. Choose the type of valve: closed-circuit valve, regulating valve, safety valve, etc.

　　6、確定閥門的型式：閘閥、截止閥、球閥、蝶閥、節流閥、安全閥、減壓閥、蒸汽疏水閥等。

　　6. Determine the type of valve: gate valve, globe valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap valve, etc.

　　7、確定閥門的參數：對于自動閥門，根據不同需要先確定允許流阻、排放能力、背壓等，再確定管道的公稱通徑和閥座孔的直徑。

　　7. Determine the parameters of the valve: For automatic valves, determine the allowable flow resistance, discharge capacity, back pressure, etc. according to different needs, and then determine the nominal diameter of the pipeline and the diameter of the valve seat hole.

　　8、確定所選用閥門的幾何參數：結構長度、法蘭連接形式及尺寸、開啟和關閉后閥門高度方向的尺寸、連接的螺栓孔尺寸和數量、整個閥門外型尺寸等。

　　8. Determine the geometric parameters of the selected valve: structural length, flange connection form and size, height direction size of the valve after opening and closing, size and quantity of bolt holes for connection, overall dimensions of the valve, etc.

　　9、利用現有的資料：閥門產品目錄、閥門產品樣本等選擇適當的閥門產品。

　　9. Use existing materials such as valve product catalogs and valve product samples to select appropriate valve products.

　　選擇閥門的依據：在了解掌握選擇閥門步驟的同時，還應進一步了解選擇閥門的依據。

　　Basis for valve selection: While understanding and mastering the steps of valve selection, it is also necessary to further understand the basis for valve selection.

　　1、所選用閥門的用途、使用工況條件和操縱控制方式。

　　1. The purpose, operating conditions, and control mode of the selected valve.

　　2、工作介質的性質：工作壓力、工作溫度、腐蝕性能，是否含有固體顆粒，介質是否有毒，是否是易燃、易爆介質，介質的黏度等等。

　　2. The properties of the working medium include working pressure, working temperature, corrosion performance, whether it contains solid particles, whether the medium is toxic, whether it is flammable or explosive, viscosity of the medium, and so on.

　　3、對閥門流體特性的要求：流阻、排放能力、流量特性、密封等級等等。

　　3. Requirements for valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, sealing grade, etc.

　　4、安裝尺寸和外形尺寸要求：公稱通徑、與管道的連接方式和連接尺寸、外形尺寸或重量限制等。

　　4. Installation dimensions and external dimensions requirements: nominal diameter, connection method and dimensions with the pipeline, external dimensions or weight limitations, etc.

　　5、對閥門產品的可靠性、使用壽命和電動裝置的防爆性能等的附加要求。

　　5. Additional requirements for the reliability, service life, and explosion-proof performance of valve products and electric devices.

　　在選定參數時應注意：如果閥門要用于控制目的，必須確定如下額外參數：操作方法、最大和最小流量要求、正常流動的壓力降、關閉時的壓力降、閥門的最大和最小進口壓力。

　　When selecting parameters, it should be noted that if the valve is to be used for control purposes, the following additional parameters must be determined: operating method, maximum and minimum flow requirements, pressure drop for normal flow, pressure drop when closing, and maximum and minimum inlet pressure of the valve.

　　根據上述選擇閥門的依據和步驟，合理、正確地選擇閥門時還必須對各種類型閥門的內部結構進行詳細了解，以便能對優先選用的閥門做出正確的抉擇。管道的最終控制是閥門。閥門啟閉件控制著介質在管道內的流束方式，閥門流道的形狀使閥門具備一定的流量特性，在選擇管道系統最適合安裝的閥門時必須考慮到這一點。

　　According to the above criteria and steps for selecting valves, it is necessary to have a detailed understanding of the internal structure of various types of valves when selecting valves reasonably and correctly, so as to make the correct choice for the preferred valve. The ultimate control of pipelines is valves. The valve opening and closing components control the flow of the medium in the pipeline, and the shape of the valve channel gives the valve certain flow characteristics. This must be taken into account when selecting the most suitable valve for installation in the pipeline system.

　　選擇閥門應遵循的原則1、截止和開放介質用的閥門流道為直通式的閥門，其流阻較小，通常選擇作為截止和開放介質用的閥門。向下閉合式閥門（截止閥、柱塞閥）由于其流道曲折，流阻比其他閥門高，故較少選用。在允許有較高流阻的場合，可選用閉合式閥門。

　　Principles to be followed when selecting valves: 1. Valves used for shut-off and opening media should have straight through flow channels with low flow resistance, and are usually selected as valves for shut-off and opening media. Downward closing valves (globe valves, plunger valves) are less commonly used due to their tortuous flow paths and higher flow resistance compared to other valves. In situations where high flow resistance is allowed, closed valves can be used.

　　2、控制流量用的閥門通常選擇易于調節流量的閥門作為控制流量用。向下閉合式閥門（如截止閥）適于這一用途，因為它的閥座尺寸與關閉件的行程之間成正比關系。旋轉式閥門（旋塞閥、蝶閥、球閥）和撓曲閥體式閥門（夾緊閥、隔膜閥）也可用于節流控制，但通常只能在有限的閥門口徑范圍內適用。閘閥是以圓盤形閘板對圓形閥座口做橫切運動，它只有在接近關閉位置時，才能較好地控制流量，故通常不用于流量控制。

　　2. Valves used for controlling flow are usually chosen to be easy to adjust. A downward closing valve (such as a globe valve) is suitable for this purpose because its seat size is proportional to the stroke of the closing member. Rotary valves (plug valves, butterfly valves, ball valves) and flex valve body valves (clamp valves, diaphragm valves) can also be used for throttling control, but are usually only applicable within a limited range of valve diameters. Gate valve is a disc-shaped gate that performs transverse movement on a circular valve seat. It can only effectively control flow when approaching the closed position, so it is usually not used for flow control.

　　3、換向分流用的閥門根據換向分流的需要，這種閥門可有三個或更多的通道。旋塞閥和球閥較適用于這一目的，因此，大部分用于換向分流的閥門都選取這類閥門中的一種。但是在有些情況下，其他類型的閥門，只要把兩個或更多個閥門適當地相互連接起來，也可作換向分流用。

　　3. The valve used for directional diversion can have three or more channels according to the needs of directional diversion. Plug valves and ball valves are more suitable for this purpose, therefore, most valves used for directional diversion choose one of these types of valves. However, in some cases, other types of valves can also be used for directional diversion as long as two or more valves are appropriately connected to each other.

　　4、帶有懸浮顆粒的介質用閥門當介質中帶有懸浮顆粒時，最適于采用其關閉件沿密封面的滑動帶有擦拭作用的閥門。如果關閉件對閥座的來回運動是豎直的，那末就可能夾持顆粒，因此這種閥門除非密封面材料可以允許嵌入顆粒，否則只適用于基本清潔的介質。球閥和旋塞閥在啟閉過程中對密封面均有擦拭作用，故適宜用在帶有懸浮顆粒的介質中。

　　4. Valves for media with suspended particles are most suitable when the media contains suspended particles, and valves with sliding closure along the sealing surface and wiping function are most suitable. If the back and forth movement of the closure against the valve seat is vertical, it may clamp particles, so this type of valve is only suitable for basic clean media unless the sealing surface material allows particles to be embedded. Ball valves and plug valves have a wiping effect on the sealing surface during the opening and closing process, making them suitable for use in media with suspended particles.

　　閥門選型說明1、閘閥的選型一般情況下，應首選閘閥。閘閥除適用于蒸汽、油品等介質外，還適用于含有粒狀固體及粘度較大的介質，并適用于放空和低真空系統的閥門。對帶有固體顆粒的介質，閘閥閥體上應帶有一個或兩個吹掃孔。對低溫介質，應選用低溫專用閘閥。

　　Valve selection instructions: Generally, gate valves should be the preferred choice for valve selection. Gate valves are not only suitable for media such as steam and oil, but also for media containing granular solids and high viscosity, and are suitable for valves in venting and low vacuum systems. For media with solid particles, the gate valve body should have one or two blowdown holes. For low-temperature media, low-temperature dedicated gate valves should be selected.

　　2、 截止閥選型說明截止閥適用于對流體阻力要求不嚴的管路上，即對壓力損失考慮不大，以及高溫、高壓介質的管路或裝置，適用于DN＜200mm的蒸汽等介質管道上；小型閥門可選用截止閥，如針形閥、儀表閥、取樣閥、壓力計閥等；截止閥有流量調節或壓力調節，但對調節精度要求不高，而且管路直徑又比較小時，宜選用截止閥或節流閥；對于劇毒介質，宜選用波紋管密封的截止閥；但截止閥不宜用于粘度較大的介質和含有顆粒易沉淀的介質，也不宜作放空閥及低真空系統的閥門。

　　2. Selection instructions for globe valves: Globe valves are suitable for pipelines that do not have strict requirements for fluid resistance, with little consideration for pressure loss, as well as pipelines or devices for high-temperature and high-pressure media. They are suitable for steam and other media pipelines with DN<200mm; Small valves can use globe valves, such as needle valves, instrument valves, sampling valves, pressure gauge valves, etc; Globe valves have flow regulation or pressure regulation, but do not require high regulation accuracy, and the pipeline diameter is relatively small. Globe valves or throttle valves should be selected; For highly toxic media, it is advisable to use bellows sealed globe valves; However, globe valves should not be used for media with high viscosity and media containing particles that are prone to precipitation, nor should they be used as vent valves or valves for low vacuum systems.

　　3、球閥選型說明球閥適用于低溫、高壓、粘度大的介質。大多數球閥可用于帶懸浮固體顆粒的介質中，依據密封的材料要求也可用于粉狀和顆粒狀的介質；全通道球閥不適用于流量調節，但適用于要求快速啟閉的場合，便于實現事故緊急切斷；通常在密封性能嚴格、磨損、縮口通道、啟閉動作迅速、高壓截止（壓差大）、低噪音、有氣化現象、操作力矩小、流體阻力小的管路中，推薦使用球閥；球閥適用于輕型結構、低壓截止、腐蝕性介質中；球閥還是低溫、深冷介質的最理想閥門，低溫介質的管路系統和裝置上，宜選用加上閥蓋的低溫球閥；選用浮動球球閥時其閥座材料應承接球體和工作介質的載荷，大口徑的球閥在操作時需要較大的力，DN≥200mm的球閥應選用蝸輪傳動形式；固定球球閥適用于較大口徑及壓力較高的場合；另外，用于工藝劇毒物料、可燃介質管道的球閥，應具有防火、防靜電結構。

　　3. Ball valve selection instructions: Ball valves are suitable for media with low temperature, high pressure, and high viscosity. Most ball valves can be used in media with suspended solid particles, and can also be used in powder and granular media depending on the sealing material requirements; Full channel ball valves are not suitable for flow regulation, but are suitable for situations that require quick opening and closing, making it easy to achieve emergency shutdown in case of accidents; Ball valves are recommended for pipelines with strict sealing performance, wear, constricted channels, rapid opening and closing actions, high pressure cutoff (large pressure difference), low noise, gasification phenomenon, low operating torque, and low fluid resistance; Ball valves are suitable for lightweight structures, low-pressure shut-off, and corrosive media; Ball valves are still the most ideal valves for low-temperature and cryogenic media. For pipeline systems and devices for low-temperature media, low-temperature ball valves with valve covers should be selected; When selecting a floating ball valve, its seat material should bear the load of the ball and working medium. Large diameter ball valves require greater force during operation, and ball valves with DN ≥ 200mm should use worm gear transmission; Fixed ball valves are suitable for larger diameters and high-pressure applications; In addition, ball valves used for the production of highly toxic materials and flammable medium pipelines should have fire-resistant and anti-static structures.

　　4、節流閥選型說明節流閥適用于介質溫度較低、壓力較高的場合，適用于需要調節流量和壓力的部位，不適用于粘度大和含有固體顆粒的介質，不宜作隔斷閥。

　　4. Throttle valve selection instructions: Throttle valves are suitable for situations where the medium temperature is low and the pressure is high. They are suitable for areas where flow and pressure need to be adjusted. They are not suitable for media with high viscosity and solid particles, and should not be used as block valves.

　　5、旋塞閥選型說明旋塞閥適用于要求快速啟閉的場合，一般不適用于蒸汽及溫度較高的介質，用于溫度較低、粘度大的介質，也適用于帶懸浮顆粒的介質。

　　5. Plug valve selection instructions: Plug valves are suitable for situations that require quick opening and closing, and are generally not suitable for steam and high-temperature media. They are used for media with low temperature and high viscosity, and are also suitable for media with suspended particles.

　　6、蝶閥選型說明蝶閥適用于口徑較大（如DN﹥600mm）及結構長度要求短，以及需要進行流量調節及啟閉要求快速的場合，一般用于溫度≤80℃、壓力≤1.0MPa的水、油品和壓縮空氣等介質；由于蝶閥相對于閘閥、球閥壓力損失比較大，故蝶閥適用于壓力損失要求不嚴的管路系統中。

　　6. Butterfly valve selection instructions: Butterfly valves are suitable for larger diameters (such as DN>600mm), shorter structural length requirements, and situations that require flow regulation and quick opening and closing. They are generally used for media such as water, oil, and compressed air with temperatures ≤ 80 ℃ and pressures ≤ 1.0MPa; Due to the relatively large pressure loss of butterfly valves compared to gate valves and ball valves, butterfly valves are suitable for pipeline systems with less stringent pressure loss requirements.

　　7、止回閥選型說明止回閥一般適用于清凈介質，不宜用于含有固體顆粒和粘度較大的介質。

　　7. Selection instructions for check valves: Check valves are generally suitable for clean media and should not be used for media containing solid particles and high viscosity.

　　當DN≤40mm時，宜采用升降止回閥（僅允許安裝在水平管道上）；

　　When DN ≤ 40mm, it is advisable to use a lift check valve (only allowed to be installed on horizontal pipelines);

　　當DN＝50～400mm時，宜采用旋啟式升降止回閥（在水平和垂直管道上都可安裝，如安裝在垂直管道上，介質流向要由下而上）；

　　When DN=50-400mm, it is advisable to use a rotary lift check valve (which can be installed on both horizontal and vertical pipelines. If installed on a vertical pipeline, the flow direction of the medium should be from bottom to top);

　　當DN≥450mm時，宜采用緩沖型止回閥；當DN＝100～400mm也可選用對夾式止回閥；

　　When DN ≥ 450mm, a buffer type check valve should be used; When DN=100-400mm, clamp type check valves can also be used;

　　旋啟式止回閥可以做成很高的工作壓力，PN可以達到42MPa，根據殼體及密封件的材質不同可適用于任何工作介質和任何工作溫度范圍。

　　Swing check valves can be designed for high working pressures, with PN reaching up to 42MPa. Depending on the material of the shell and seal, they can be suitable for any working medium and any working temperature range.

　　介質為水、蒸汽、氣體、腐蝕性介質、油品、藥品等。介質工作溫度范圍在-196～800℃之間。

　　The medium includes water, steam, gas, corrosive medium, oil, medicine, etc. The working temperature range of the medium is between -196 and 800 ℃.

　　8、隔膜閥選型說明隔膜閥適用于工作溫度小于200℃、壓力小于1.0MPa的油品、水、酸性介質和含懸浮物的介質，不適用于有機溶劑和強氧化劑介質；

　　8. Diaphragm valve selection instructions: Diaphragm valves are suitable for oil products, water, acidic media, and media containing suspended solids with working temperatures less than 200 ℃ and pressures less than 1.0MPa. They are not suitable for organic solvents and strong oxidant media;

　　研磨顆粒性介質宜選堰式隔膜閥，選用堰式隔膜閥要參照它的流量特性表；

　　Grinding granular media should choose weir type diaphragm valves, and the selection of weir type diaphragm valves should refer to their flow characteristics table;

　　粘性流體、水泥漿以及沉淀性介質宜選用直通式隔膜閥；

　　Viscous fluids, cement slurries, and sedimentary media should use straight through diaphragm valves;

　　除特定要求，隔膜閥不宜用于真空管路和真空設備上。

　　Unless otherwise specified, diaphragm valves are not suitable for use in vacuum pipelines and vacuum equipment.

　　閥門應用、操作頻率和服務千變萬化，要控制或杜絕那怕是低微的泄漏，最重要、最關鍵的設備還數閥門。學會正確選擇閥門至關重要。

　　The applications, operating frequencies, and services of valves are constantly changing. To control or eliminate even minor leaks, the most important and critical equipment is the valve. Learning to choose valves correctly is crucial.