一、超全閥門選型技巧

　　1、 Selection Techniques for Ultra Full Valve

　　在流體管道系統中，調節閥是控制元件，其投資約占管道工程費用的30%～50%。閥門的主要功能為啟閉、節流、調節流量、隔離設備和管道系統、防止介質倒流、調節和排泄壓力等。閥門也是管路中最復雜的元件，它一般由多個零部件裝配而成，技術含量高。隨著石油化工工業的迅速發展，石油化工生產裝置中的介質大多具有毒性大、可燃、易爆和腐蝕性強的特點，運行工況較復雜苛刻，操作溫度和壓力較高，開工周期長，閥門一旦出現故障，輕者導致介質泄漏，既污染環境又造成經濟損失，重者導致裝置停工停產，甚至造成惡性事故。因而，在管道設計中，科學合理地選擇閥門既能降低裝置的建設費用，又保證生產安全運行。文章主要介紹了各種常用閥門如閘閥、截止閥、節流閥、旋塞閥、球閥、隔膜調節閥等的選型方法。

　　In the fluid pipeline system, the control valve is the control element, and its investment accounts for 30%~50% of the pipeline engineering cost. The main functions of valves are opening and closing, throttling, regulating flow, isolating equipment and pipeline systems, preventing medium backflow, regulating and discharging pressure, etc. Valves are also the most complex components in pipelines, usually assembled from multiple parts with high technical content. With the rapid development of the petrochemical industry, most of the media in petrochemical production facilities have the characteristics of high toxicity, flammability, explosiveness, and strong corrosiveness. The operating conditions are complex and demanding, with high operating temperatures and pressures, long operating cycles, and once valves fail, it can cause medium leakage, polluting the environment and causing economic losses. In severe cases, it can lead to equipment shutdown and even cause serious accidents. Therefore, in pipeline design, scientifically and reasonably selecting valves can not only reduce the construction cost of the device, but also ensure the safe operation of production. The article mainly introduces the selection methods of various commonly used valves such as gate valves, globe valves, throttle valves, plug valves, ball valves, diaphragm regulating valves, etc.

　　1、閥門選型的要點1、明確閥門在設備或裝置中的用途確定閥門的工作條件：適用介質的性質、工作壓力、工作溫度和操縱控制方式等。

　　1. Key points of valve selection: 1. Clarify the purpose of the valve in the equipment or device and determine the working conditions of the valve, including the properties of the applicable medium, working pressure, working temperature, and control mode.

　　2、正確選擇閥門的類型閥門型式的正確選擇是以設計者對整個生產工藝流程、操作工況的充分掌握為先決條件的，在選擇閥門類型時，設計人員應首先掌握每種閥門的結構特點和性能。

　　2. The correct choice of valve type is based on the designer's full understanding of the entire production process and operating conditions. When selecting valve types, designers should first grasp the structural characteristics and performance of each valve.

　　3、確定閥門的端部連接在螺紋連接、法蘭連接、焊接端部連接中，前兩種最常用。螺紋連接的閥門主要是公稱通徑在50mm以下的閥門，如果通徑尺寸過大，連接部的安裝和密封十分困難。法蘭連接的閥門，其安裝和拆卸都比較方便，但是較螺紋連接的閥門笨重，價格較高，故它適用于各種通徑和壓力的管道連接。焊接連接適用于較苛刻的條件下，比法蘭連接更為可靠。但是焊接連接的閥門拆卸和重新安裝都比較困難，所以它的使用僅限于通常能長期可靠地運行，或使用條件苛刻、溫度較高的場合。

　　3. Determine the most commonly used end connections for valves, including threaded connections, flange connections, and welded end connections. Valves with threaded connections are mainly those with a nominal diameter of less than 50mm. If the diameter size is too large, the installation and sealing of the connection part will be very difficult. Valves connected by flanges are relatively easy to install and disassemble, but they are bulky and expensive compared to valves connected by threads. Therefore, they are suitable for connecting pipelines of various diameters and pressures. Welding connections are suitable for more demanding conditions and are more reliable than flange connections. However, the disassembly and reinstallation of welded valves are relatively difficult, so their use is limited to situations where they can operate reliably for a long time or in harsh conditions with high temperatures.

　　4、閥門材質的選擇選擇閥門的殼體、內件和密封面的材質，除了考慮工作介質的物理性能（溫度、壓力）和化學性能（腐蝕性）外，還應掌握介質的清潔程度（有無固體顆粒），除此之外，還要參照國家和使用部門的有關規定。正確合理的選擇閥門的材質可以獲得閥門最經濟的使用壽命和最佳的使用性能。閥體材料選用順序為：鑄鐵-碳鋼-不銹鋼，密封圈材料選用順序為：橡膠-銅-合金鋼-F4。

　　4. The selection of valve material for the shell, internal components, and sealing surface of the valve should not only consider the physical properties (temperature, pressure) and chemical properties (corrosiveness) of the working medium, but also grasp the cleanliness of the medium (whether there are solid particles). In addition, relevant regulations of the country and the using department should also be referred to. The correct and reasonable selection of valve materials can achieve the most economical service life and optimal performance of the valve. The selection order of valve body materials is: cast iron carbon steel stainless steel, and the selection order of sealing ring materials is: rubber copper alloy steel-F4.

　　5、其它除此之外，還應確定流經閥門流體的流量及壓力等級等，利用現有的資料（如閥門產品目錄、閥門產品樣本等）選擇適當的閥門。

　　5. In addition, the flow rate and pressure rating of the fluid flowing through the valve should also be determined, and appropriate valves should be selected using existing information such as valve product catalogs, valve product samples, etc.

　　二、常用閥門介紹閥門種類多、品種復雜，主要有閘閥、截止閥、節流閥、蝶閥、旋塞閥、球閥、電動閥、隔膜閥、止回閥、安全閥、減壓閥、蒸汽疏水閥和緊急切斷閥等，其中常用的有閘閥、截止閥、節流閥、旋塞閥、蝶閥、球閥、止回閥、隔膜閥。

　　2、 Introduction to commonly used valves: There are many types and complex varieties of valves, mainly including gate valves, globe valves, throttle valves, butterfly valves, plug valves, ball valves, electric valves, diaphragm valves, check valves, safety valves, pressure reducing valves, steam trap valves, and emergency shut-off valves. Among them, commonly used valves include gate valves, globe valves, throttle valves, plug valves, butterfly valves, ball valves, check valves, and diaphragm valves.

　　1、閘閥閘閥是指啟閉體（閥板）由閥桿帶動，沿閥座密封面作升降運動的閥門，可接通或截斷流體的通道。閘閥較截止閥密封性能好，流體阻力小，啟閉省力，具有一定的調節性能，是最常用的截斷閥門之一。缺點是尺寸大、結構較截止閥復雜，密封面易磨損，不易維修，一般不宜作節流用。按閘閥閥桿上螺紋位置分為明桿式和暗桿式兩類。按閘板的結構特點又可分為楔式和平行式兩類。

　　1. Gate valve refers to a valve whose opening and closing body (valve plate) is driven by the valve stem and moves up and down along the sealing surface of the valve seat, which can connect or cut off the passage of fluid. Gate valves have better sealing performance than globe valves, lower fluid resistance, easier opening and closing, and have certain regulating performance. They are one of the most commonly used shut-off valves. The disadvantages are large size, complex structure compared to globe valves, easy wear of sealing surfaces, difficult maintenance, and generally not suitable for throttling purposes. According to the thread position on the valve stem of the gate valve, it is divided into two types: rising stem type and hidden stem type. According to the structural characteristics of the gate, it can be divided into two types: wedge type and parallel type.

　　2、截止閥截止閥是向下閉合式閥門，啟閉件（閥瓣）由閥桿帶動沿閥座（密封面）軸線作升降運動的閥門。與閘閥相比，其調節性能好，密封性能差，結構簡單，制造維修方便，流體阻力較大，價格便宜，是一種常用的截斷閥，一般用于中、小口徑的管道。

　　2. Globe valve is a downward closing valve, and the opening and closing member (valve disc) is driven by the valve stem to move up and down along the axis of the valve seat (sealing surface). Compared with gate valves, it has good regulating performance, poor sealing performance, simple structure, easy manufacturing and maintenance, high fluid resistance, and low price. It is a commonly used block valve, generally used for medium and small diameter pipelines.

　　3、球閥球閥的啟閉件是帶圓形通孔的球體，球體隨閥桿轉動以實現啟閉的閥門。球閥的結構簡單，開關迅速，操作方便，體積小，重量輕，零部件少，流體阻力小，密封性好，維修方便。

　　3. The opening and closing component of a ball valve is a spherical body with a circular through-hole, which rotates with the valve stem to achieve opening and closing of the valve. Ball valves have a simple structure, quick opening and closing, easy operation, small size, light weight, few components, low fluid resistance, good sealing performance, and convenient maintenance.

　　4、節流閥節流閥除閥瓣以外與截止閥結構基本相同，其閥瓣是節流部件，不同形狀具有不同的特性，閥座的通徑不宜過大，因其開啟高度較小介質流速增大，從而加速對閥瓣的沖蝕。節流閥外形尺寸小、重量輕、調節性能好，但調節精度不高。

　　4. The structure of a throttle valve is basically the same as that of a globe valve, except for the valve disc. The valve disc is a throttling component, and different shapes have different characteristics. The diameter of the valve seat should not be too large because its opening height is small and the medium flow rate increases, thereby accelerating the erosion of the valve disc. The throttle valve has small external dimensions, light weight, and good adjustment performance, but the adjustment accuracy is not high.

　　5、旋塞閥旋塞閥是以帶通孔的塞體作為啟閉件，塞體隨閥桿轉動，以實現啟閉的閥門。旋塞閥結構簡單、開關迅速、操作方便、流體阻力小，部件少、重量輕。旋塞閥有直通式、三通式和四通式。直通式旋塞閥用于截斷介質，三通式和四通式旋塞閥用于改變介質方向或進行介質分流。

　　5. A plug valve is a valve that uses a plug body with a through-hole as the opening and closing member, and the plug body rotates with the valve stem to achieve opening and closing. The plug valve has a simple structure, quick opening and closing, easy operation, low fluid resistance, few components, and light weight. Plug valves have straight through, three-way, and four-way types. Direct type plug valves are used to cut off media, while three-way and four-way plug valves are used to change the direction of media or divert media.

　　6、蝶閥蝶閥是蝶板在閥體內繞固定軸旋轉90°即可完成啟閉作用。蝶閥體積小、重量輕、結構簡單，只由少數幾個零件組成。而且只需旋轉90°;即可快速啟閉，操作簡單。蝶閥處于完全開啟位置時，蝶板厚度是介質流經閥體時唯一的阻力，因此通過該閥門所產生的壓力降很小，故具有較好的流量控制特性。蝶閥分彈性軟密封和金屬硬密封兩種密封型式。

　　6. Butterfly valve is a butterfly valve that can be opened and closed by rotating the butterfly plate 90 ° around a fixed axis inside the valve body. Butterfly valves are small in size, light in weight, and have a simple structure, consisting of only a few components. And only need to rotate 90 degrees; It can be quickly opened and closed, with simple operation. When the butterfly valve is in the fully open position, the thickness of the butterfly plate is the only resistance for the medium to flow through the valve body. Therefore, the pressure drop generated by this valve is very small, and it has good flow control characteristics. Butterfly valves are divided into two sealing types: elastic soft seals and metal hard seals.

　　彈性密封閥門，密封圈可以鑲嵌在閥體上或附在蝶板周邊，密封性能好，既可用于節流，又可用于中等真空管道和腐蝕性介質。

　　Elastic sealing valve, the sealing ring can be embedded on the valve body or attached around the butterfly plate, with good sealing performance. It can be used for throttling, as well as for medium vacuum pipelines and corrosive media.

　　采用金屬密封的閥門一般較彈性密封的閥門壽命長，但很難做到完全密封，通常用于流量和壓降變化大、要求節流性能好的場合。金屬密封能適應于較高的工作溫度，彈性密封則具有受溫度限制的缺陷。

　　Valves with metal seals generally have a longer lifespan than those with elastic seals, but it is difficult to achieve complete sealing. They are usually used in situations where flow and pressure drop changes are large and good throttling performance is required. Metal seals can adapt to higher operating temperatures, while elastic seals have the drawback of being limited by temperature.

　　7、止回閥止回閥是能自動阻止流體倒流的閥門，止回閥的閥瓣在流體壓力作用下開啟，流體從進口側流向出口側。當進口側壓力低于出口側時，閥瓣在流體壓差、本身重力等因素作用下，自動關閉，以防止流體倒流。按結構形式分升降式止回閥和旋啟式止回閥。

　　7. Check valve is a valve that can automatically prevent fluid backflow. The valve disc of the check valve opens under the action of fluid pressure, and fluid flows from the inlet side to the outlet side. When the pressure on the inlet side is lower than that on the outlet side, the valve disc automatically closes under the action of factors such as fluid pressure difference and its own gravity to prevent fluid backflow. Divided into lift check valves and swing check valves according to their structural forms.

　　升降式較旋啟式密封性好，流體阻力大。對于泵吸入管的吸入口處，宜選用底閥，其作用是：開泵前灌注水使泵的入口管充滿水；停泵后保持入口管和泵體充滿水，以備再次啟動。底閥一般只安裝在泵進口的垂直管道上，并且介質自下而上流動。

　　The lifting type has better sealing performance and greater fluid resistance than the rotary opening type. For the suction inlet of the pump suction pipe, it is advisable to use a bottom valve, which is used to fill the inlet pipe of the pump with water before starting the pump; Keep the inlet pipe and pump body filled with water after stopping the pump, in preparation for restarting. Bottom valves are generally only installed on the vertical pipeline at the pump inlet, and the medium flows from bottom to top.

　　8、隔膜閥隔膜閥的啟閉件是一塊橡膠隔膜，夾于閥體與閥蓋之間。隔膜中間突出部分固定在閥桿上，閥體內襯有橡膠，由于介質不進入閥蓋內腔，因此閥桿無需填料箱。隔膜閥結構簡單、密封性能好，便于維修，流體阻力小。隔膜閥分為堰式、直通式、直角式和直流式。

　　8. The opening and closing component of a diaphragm valve is a rubber diaphragm sandwiched between the valve body and the valve cover. The protruding part in the middle of the diaphragm is fixed on the valve stem, and the valve body is lined with rubber. Since the medium does not enter the inner cavity of the valve cover, the valve stem does not require a packing box. The diaphragm valve has a simple structure, good sealing performance, easy maintenance, and low fluid resistance. Diaphragm valves are divided into weir type, straight through type, right angle type, and direct flow type.

　　三、常用閥門選型說明

　　3、 Common Valve Selection Instructions

　　1、閘閥的選型說明一般情況下，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。

　　1. In general, the selection of gate valves should be preferred. 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；

　　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;

　　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；

　　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;

　　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。

　　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；

　　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;

　　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；

　　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;

　　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。

　　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。當≤40mm時，宜采用升降止回閥（僅允許安裝在水平管道上）；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）；

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

　　When DN ≥ 450mm, a buffer type check valve should be used; When DN=100-400mm, clamp type check valves can also be used; 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. 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；粘性流體、水泥漿以及沉淀性介質宜選用直通式隔膜閥；除特定要求，隔膜閥不宜用于真空管路和真空設備上。

　　Grinding granular media should choose weir type diaphragm valves, and the selection of weir type diaphragm valves should refer to their flow characteristics table; Viscous fluids, cement slurries, and sedimentary media should use straight through diaphragm valves; Unless otherwise specified, diaphragm valves are not suitable for use in vacuum pipelines and vacuum equipment.

　　四、各種閥門試壓方法一般情況下，工業閥門在使用時不做強度試驗，但修補過后閥體和閥蓋或腐蝕損傷的閥體和閥蓋應做強度試驗。對于安全閥，其整定壓和回座壓力及其他試驗應符合其說明書和有關規程的規定。閥門安裝之彰應作強度和密封性試驗。低壓閥門抽查20%，如不合格應100%的檢查;中、高壓閥門應100%的檢查。閥門試壓常用的介質有水、油、空氣、蒸汽、氮氣等，各類工業閥門含氣動閥門的試壓方法如下：

　　4、 In general, industrial valves do not undergo strength tests during use, but after repair, the valve body and valve cover, or those that have been corroded or damaged, should undergo strength tests. For safety valves, their set pressure, reseating pressure, and other tests should comply with their instructions and relevant regulations. The installation of valves should undergo strength and sealing tests. 20% of low-pressure valves shall be randomly inspected, and if they are found to be unqualified, 100% inspection shall be conducted; Medium and high pressure valves should be inspected 100%. The commonly used media for valve pressure testing include water, oil, air, steam, nitrogen, etc. The pressure testing methods for various industrial valves, including pneumatic valves, are as follows:

　　1、球閥的試壓方法氣動球閥的強度試驗應在球體半開狀態下進行。

　　1. The pressure test method for ball valves. The strength test for pneumatic ball valves should be conducted with the ball body in a semi open state.

　　①浮動式球閥密封性試驗：將閥處于半開狀態，一端引入試驗介質，另一端封閉；將球體轉動幾次，閥門處于關閉狀態時打開封閉端檢查，同時檢查填料和墊片處密封性能，不得有滲漏現象。然后從另一端引入試驗介質，重復上述試驗。②固定式球閥密封性試驗：在試驗前將球體空載轉動幾次，固定式球閥處于關閉狀態，從一端引人試驗介質至規定值；用壓力表檢查引入端密封性能，使用壓力表精度0．5～1級，量程為試驗壓力的1．5倍。

　?、?Floating ball valve sealing test: Place the valve in a semi open state, with one end introducing the test medium and the other end closed; Rotate the sphere several times, and when the valve is in the closed state, open the closed end for inspection. At the same time, check the sealing performance of the packing and gasket, and there should be no leakage. Then introduce the test medium from the other end and repeat the above experiment. ② Fixed ball valve sealing test: Before the test, rotate the ball several times without load, keep the fixed ball valve in the closed state, and introduce the test medium from one end to the specified value; Check the sealing performance of the inlet end with a pressure gauge, with an accuracy of 0.5-1 level and a range of 1.5 times the test pressure.

　　在規定時問內，沒有降壓現象為合格；再從另一端引入試驗介質，重復上述試驗。然后，將閥門處于半開狀態，兩端封閉，內腔充滿介質，在試驗壓力下檢查填料和墊片處，不得有滲漏。

　　If there is no pressure drop phenomenon within the specified time, it is considered qualified; Introduce the test medium from the other end and repeat the above experiment. Then, place the valve in a semi open position, seal both ends, and fill the inner chamber with medium. Check the packing and gasket under test pressure for any leakage.

　　③三通球閥應在各個位置上進行密封性試驗。2、止回閥的試壓方法止回閥試驗狀態：升降式止回閥閥瓣軸線處于與水平垂直的位置；旋啟式止回閥通道軸線和閥瓣軸線處于與水平線近似平行的位置。強度試驗時，從進口端引入試驗介質至規定值，另一端封閉，看閥體和閥蓋無滲漏為合格。密封性試驗從出口端引入試驗介質，在進口端檢查密封面處，填料和墊片處無滲漏為合格。

　　③ Three way ball valves should undergo sealing tests at various positions. 2. The pressure testing method for check valves: Check valve test status: The axis of the valve disc of the lift check valve is in a position perpendicular to the horizontal; The axis of the rotary check valve channel and the axis of the valve disc are located approximately parallel to the horizontal line. During the strength test, the test medium is introduced from the inlet end to the specified value, and the other end is closed. It is considered qualified if there is no leakage in the valve body and valve cover. The sealing test is conducted by introducing the test medium from the outlet end, and checking the sealing surface, packing, and gasket at the inlet end for no leakage, which is considered qualified.

　　3、減壓閥的試壓方法

　　3. Pressure testing method for pressure reducing valve

　?、贉p壓閥的強度試驗一般以單件試驗后組裝，亦可組裝后試驗。強度試驗持續時間：DN<50mm的lmin；dn65～150mm的大于2min；dn>150mm的大于3min。波紋管與組件焊接后，應用減壓閥后最高壓力的1．5倍、用空氣進行強度試驗。

　?、?The strength test of pressure reducing valves is generally conducted by assembling single pieces after testing, or by testing after assembly. Duration of strength test: 1 minute for DN<50mm; DN65-150mm for more than 2 minutes; DN>150mm for more than 3 minutes. After welding the corrugated pipe and components, apply a pressure reducing valve at 1.5 times the maximum pressure and conduct a strength test with air.

　　②密封性試驗時按實際工作介質進行。用空氣或水試驗時，以公稱壓力的1．1倍進行試驗；用蒸汽試驗時，以工作溫度下允許的最高工作壓力進行。進口壓力與出口壓力之差要求不小于0.2MPa。試驗方法為：進口壓力調定后，逐漸調節該閥的調節螺釘，使出口壓力在最大與最小值范圍內能靈敏地、連續地變化，不得有停滯、卡阻現象。對蒸汽減壓閥，當進口壓力調走后，關閉閥后截斷閥，出口壓力為最高和最低值，在2min內，其出口壓力的升值應符合表4.176—22中規定，同時，閥后管道容積符合表4.18中規定為合格；對水、空氣減壓閥，當進口壓力調定后，出口壓力為零時，關閉減壓閥進行密封性試驗，在2min內無泄漏為合格。

　?、?The sealing test shall be conducted according to the actual working medium. When testing with air or water, conduct the test at 1.1 times the nominal pressure; When conducting steam tests, use the maximum allowable working pressure at the operating temperature. The difference between the inlet pressure and the outlet pressure is required to be no less than 0.2 MPa. The experimental method is to gradually adjust the adjusting screw of the valve after setting the inlet pressure, so that the outlet pressure can change sensitively and continuously within the range of maximum and minimum values, without stagnation or blockage. For steam pressure reducing valves, when the inlet pressure is adjusted, the shut-off valve behind the valve is closed, and the outlet pressure is the highest and lowest values. Within 2 minutes, the increase in outlet pressure should comply with the provisions of Table 4.176-22. At the same time, the pipeline volume behind the valve should comply with the provisions of Table 4.18 to be qualified; For water and air pressure reducing valves, when the inlet pressure is set and the outlet pressure is zero, the pressure reducing valve should be closed for a sealing test. If there is no leakage within 2 minutes, it is considered qualified.

　　4、蝶閥的試壓方法氣動蝶閥的強度試驗與截止閥一樣。蝶閥的密封性能試驗應從介質流人端引入試驗介質，蝶板應開啟，另一端封閉，注入壓力至規定值；檢查填料和其他密封處無滲漏后，關閉蝶板，打開另一端，檢查蝶板密封處無滲漏為合格。作為調節流量用的蝶閥可不做密封性能試驗。

　　4. The pressure test method for butterfly valves is the same as the strength test for globe valves for pneumatic butterfly valves. The sealing performance test of butterfly valves should introduce the test medium from the end where the medium flows. The butterfly plate should be opened and the other end should be closed, and the pressure should be injected to the specified value; After checking that there is no leakage in the packing and other sealing areas, close the butterfly plate and open the other end. If there is no leakage in the sealing area of the butterfly plate, it is considered qualified. Butterfly valves used for regulating flow do not require sealing performance testing.

　　5、旋塞閥的試壓方法①旋塞閥進行強度試驗時，介質從一端引入，封閉其余通路，將塞子依次旋轉到全開的各工作位置進行試驗，閥體未發現滲漏為合格。②密封性試驗時，直通式旋塞應保持腔內與通路壓力相等，將塞子旋轉到關閉位置，從另一端進行檢查，然后將塞子旋轉180°重復上述試驗；三通式或四通式旋塞閥應保持腔內與通路一端壓力相等，將塞子依次旋轉到關閉位置，壓力從直角端引入，從其他端同時進行檢查。旋塞閥試驗前允許在密封面上涂一層非酸性稀潤滑油，在規定時間內未發現滲漏和擴大的水滴為合格。旋塞閥試驗時間可短一些，一般按公稱通徑規定為l～3min。煤氣用的旋塞閥應以1．25倍工作壓力進行空氣密封性試驗。6、隔膜閥的試壓方法隔膜閥強度試驗從任一端引入介質，開啟閥瓣，另一端封閉，試驗壓力升至規定值后，看閥體和閥蓋無滲漏為合格。然后降壓至密封性試驗壓力，關閉閥瓣，打開另一端進行檢查，無滲漏為合格。7、截止閥和節流閥的試壓方法截止閥和節流閥的強度試驗，通常將組裝好的閥門放在試壓架中，打開閥瓣，注入介質至規定值，檢查閥體和閥蓋是否冒汗和滲漏。也可單件進行強度試驗。密封性試驗只做截止閥。

　　5. The pressure testing method for plug valves: ① When conducting a strength test on a plug valve, the medium is introduced from one end, the remaining passages are closed, and the plug is rotated to each fully open working position for testing. If no leakage is found in the valve body, it is considered qualified. ② During the sealing test, the straight through plug should maintain equal pressure in the chamber and passage. Rotate the plug to the closed position, check from the other end, and then rotate the plug 180 ° to repeat the above test; A three-way or four-way plug valve should maintain equal pressure between the chamber and one end of the passage. The plug should be rotated to the closed position in sequence, and pressure should be introduced from the right angle end and checked simultaneously from the other ends. Before the plug valve test, it is allowed to apply a layer of non acidic lubricating oil on the sealing surface. If no leakage or enlarged water droplets are found within the specified time, it is considered qualified. The test time for plug valves can be shorter, generally ranging from 1 to 3 minutes according to the nominal diameter regulations. The gas plug valve should undergo an air tightness test at 1.25 times the working pressure. 6. The pressure test method for diaphragm valves is to introduce the medium from either end, open the valve disc, and seal the other end. After the test pressure rises to the specified value, the valve body and valve cover are considered qualified if there is no leakage. Then reduce the pressure to the sealing test pressure, close the valve disc, and open the other end for inspection. If there is no leakage, it is considered qualified. 7. The pressure testing method for globe valves and throttle valves. The strength test for globe valves and throttle valves usually involves placing the assembled valve in a pressure testing frame, opening the valve disc, injecting the medium to the specified value, and checking whether the valve body and valve cover are sweating and leaking. Strength tests can also be conducted on individual pieces. The sealing test is only conducted on globe valves.

　　試驗時截止閥的閥桿成垂直狀態，閥瓣開啟，介質從閥瓣底下一端引入至規定值，檢查填料和墊片處；待合格后關閉閥瓣，打開另一端檢查是否有滲漏。如果閥門強度和密封性試驗都要做時，可先做強度試驗，然后降壓至密封性試驗規定值，檢查填料和墊片處；再關閉閥瓣，打開出口端檢查密封面是否滲漏。8、閘閥的試壓方法閘閥的強度試驗與截止閥一樣。閘閥的密封性試驗有兩種方法。①閘板開啟，使閥內壓力升至規定值；然后關閉閘板，立即取出閘閥，檢查閘板兩側密封處有否滲漏或者直接往閥蓋上的堵頭內注入試驗介質至規定值，檢查閘板兩側密封處。以上方法叫做中間試壓。這種方法不宜在公稱通徑DN32mm以下的閘閥做密封試驗。②另一種方法是將閘板開啟，使閥門試驗壓力升至規定值；然后關閘板，打開一端盲板，檢查密封面是否滲漏。再倒頭，作以上重復試驗至合格為止。氣動閘閥填料和墊片處密封性試驗應在閘板密封性試驗之前進行。9、安全閥的試壓方法①安全閥的強度試驗與其他閥門一樣，是用水作試驗的。試驗閥體下部時，壓力從進I=I端引入，密封面封閉；試驗閥體上部和閥蓋時，壓力從出El端引入，其他端封閉。在規定時間內閥體和閥蓋無滲漏現象為合格。②密封性試驗和定壓試驗，一般使用介質是：蒸汽用安全閥以飽和蒸汽為試驗介質；氨或其他氣體用閥以空氣為試驗介質；水和其他非腐蝕性液體用閥以水為試驗介質。對于一些重要位置的安全閥常用氮氣為試驗介質。密封試驗以公稱壓力值為試驗壓力進行試驗，其次數不少于兩次，在規定時間內無滲漏為合格。驗漏方法有兩種：一是將安全閥各連接處密封，用黃油把薄紙封貼在出El法蘭上，薄紙鼓起為漏，不鼓起為合格；二是用黃油把薄塑料板或其他板封貼在出口法蘭下部，灌水封住閥瓣，檢驗水中不冒泡為合格。安全閥定壓和回座壓力試驗次數不少于3次，符合規定為合格。安全閥的各項性能試驗見GB／T12242–1989安全閥性能試驗方法》。閥門選型總結通過以上分析可知，一般情況下，應首選閘閥。

　　During the experiment, the valve stem of the shut-off valve is in a vertical position, the valve disc is open, and the medium is introduced from the bottom end of the valve disc to the specified value. Check the packing and gasket; After passing the inspection, close the valve disc and open the other end to check for any leakage. If both the strength and sealing tests of the valve need to be conducted, the strength test can be conducted first, and then the pressure can be reduced to the specified value for the sealing test, and the packing and gasket can be checked; Close the valve disc again and open the outlet end to check if there is any leakage on the sealing surface. 8. The pressure testing method for gate valves is the same as that for globe valves in terms of strength testing. There are two methods for the sealing test of gate valves. ① Open the gate to increase the pressure inside the valve to the specified value; Then close the gate valve, immediately remove the gate valve, check whether there is any leakage at the sealing points on both sides of the gate valve, or directly inject the test medium into the plug on the valve cover to the specified value, and check the sealing points on both sides of the gate valve. The above method is called intermediate pressure testing. This method is not suitable for conducting sealing tests on gate valves with a nominal diameter of DN32mm or less. ② Another method is to open the gate and increase the test pressure of the valve to the specified value; Then close the gate, open one end blind plate, and check whether the sealing surface leaks. Invert the head again and repeat the above test until it is qualified. The sealing test of the packing and gasket of the pneumatic gate valve should be conducted before the sealing test of the gate valve. 9. The pressure testing method for safety valves ① The strength test for safety valves, like other valves, is conducted using water. When testing the lower part of the valve body, pressure is introduced from the inlet I=I end, and the sealing surface is closed; When testing the upper part of the valve body and valve cover, pressure is introduced from the outlet end El, and the other ends are closed. If there is no leakage in the valve body and valve cover within the specified time, it is considered qualified. ② The sealing test and constant pressure test generally use saturated steam as the test medium for steam safety valves; Valves for ammonia or other gases use air as the test medium; Valves for water and other non corrosive liquids use water as the test medium. Nitrogen is commonly used as the test medium for safety valves in important locations. The sealing test shall be conducted at the nominal pressure value as the test pressure, and the number of times shall not be less than two. If there is no leakage within the specified time, it is considered qualified. There are two methods for leak detection: one is to seal the connections of the safety valve, and use butter to seal the thin paper on the outlet flange. If the thin paper bulges, it is considered a leak, and if it does not bulge, it is considered qualified; The second method is to seal a thin plastic or other board with butter under the outlet flange, fill it with water to seal the valve disc, and check that there is no bubbling in the water to be qualified. The safety valve shall undergo at least 3 pressure tests for constant pressure and reseating pressure, and shall be deemed qualified if it meets the requirements. The performance tests of safety valves can be found in GB/T12242-1989 Safety Valve Performance Test Methods. Based on the above analysis, it can be concluded that in general, gate valves should be the preferred choice for valve selection.

　　截止閥適用于對流體阻力要求不嚴的管路上，以及高溫、高壓介質的管路或裝置，不宜用于粘度較大和含有顆粒的介質，也不宜作放空閥及低真空系統的閥門。

　　Globe valves are suitable for pipelines that do not have strict requirements for fluid resistance, as well as pipelines or devices for high temperature and high pressure media. They are not suitable for media with high viscosity and containing particles, nor are they suitable as vent valves or valves for low vacuum systems.

　　球閥適用于低溫、高壓、粘度大的介質，通常用在密封性能嚴格、磨損、縮口通道、啟閉動作迅速、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。

　　Ball valves are suitable for media with low temperature, high pressure, and high viscosity. They are usually used in pipelines with strict sealing performance, wear, constricted channels, rapid opening and closing action, large pressure difference, low noise, gasification phenomenon, low operating torque, and low fluid resistance.

　　節流閥適用于介質溫度較低、壓力較高的場合，不適用于粘度大和含有固體顆粒的介質，不宜作隔斷閥。

　　Throttle valves are suitable for situations where the medium temperature is low and the pressure is high. They are not suitable for media with high viscosity and solid particles, and should not be used as block valves.

　　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。蝶閥一般用于溫度≤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。

　　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. Butterfly valves 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.

　　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。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。

　　Check valves are generally suitable for clean media and should not be used for media containing solid particles and high viscosity. 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 oxidizing agents.

　　在石油、化工及其它行業的管道系統，閥門應用、操作頻率和服務千變萬化，要控制或杜絕低微的泄漏，最重要、最關鍵的設備是閥門。合理的選擇閥門能夠降低裝置的建設費用、保證生產安全運行。

　　In pipeline systems in the petroleum, chemical, and other industries, valve applications, operating frequencies, and services are constantly changing. To control or eliminate minor leaks, the most important and critical equipment is the valve. Reasonable selection of valves can reduce the construction cost of the device and ensure safe production operation.

　　固定球閥，通過旋轉閥門中的球體來控制閥門的打開和關閉，球體中間有一個通孔，可以旋轉90°，通孔的直徑等于或小于管道的直徑，當球體旋轉90°時，管道進出口面都是球面，從而關閉閥門，截斷流體。

　　Fixed ball valve, which controls the opening and closing of the valve by rotating the ball in the valve. There is a through-hole in the middle of the ball, which can be rotated 90 °. The diameter of the through-hole is equal to or smaller than the diameter of the pipeline. When the ball rotates 90 °, the inlet and outlet surfaces of the pipeline are spherical, thereby closing the valve and cutting off the fluid.

　　當球閥回轉90°時，管道進出口面都是球孔面，流體通過閥門，球閥可旋轉到不同的角度，從而可控制流體的大小；固定球閥常用于一般管線上，如輸送水，油，蒸汽等。

　　When the ball valve rotates 90 degrees, both the inlet and outlet surfaces of the pipeline are ball hole surfaces, and the fluid passes through the valve. The ball valve can rotate to different angles, thereby controlling the size of the fluid; Fixed ball valves are commonly used on general pipelines, such as conveying water, oil, steam, etc.

　　截止閥，又稱截門閥，通過旋轉閥桿施加壓力，可以完全密封掉閥座出口，從而阻止流體流通；截止閥常用在天然氣，液化氣，硫酸等一些腐蝕性氣體，液體管路中。閘閥，就像一個閘門一樣，通過旋轉閥桿，控制閘做上下垂直運動來控制流體，閘板兩邊的密封圈能完全密封整個截面，閘閥只能做全開和全關，不能作為調節流量的閥門使用；閘閥主要用在自來水，污水，船舶等管道上作為截流裝置使用。旋啟式止回閥，是靠流體的壓力將閥蓋打開，當閥門進出口管道內流體的壓力均衡時，閥蓋又能靠自身的重力關閉，阻止流體通過，其主要作用是防止流體倒流，屬于自動閥類；主要用于石油，化工，制藥等管路上。

　　Globe valve, also known as shut-off valve, can completely seal off the valve seat outlet by rotating the valve stem to apply pressure, thereby preventing fluid flow; Globe valves are commonly used in corrosive gases such as natural gas, liquefied gas, sulfuric acid, and liquid pipelines. A gate valve, like a gate valve, controls the fluid by rotating the valve stem to make vertical movements up and down. The sealing rings on both sides of the gate valve can completely seal the entire section. A gate valve can only be fully opened and fully closed, and cannot be used as a valve for regulating flow; Gate valves are mainly used as shut-off devices on pipelines such as tap water, sewage, and ships. Swing check valve is a type of automatic valve that opens the valve cover by the pressure of the fluid. When the pressure of the fluid in the inlet and outlet pipelines of the valve is balanced, the valve cover can be closed by its own gravity to prevent fluid from passing through. Its main function is to prevent fluid backflow; Mainly used in pipelines for petroleum, chemical, pharmaceutical, and other industries.

　　蝶閥，又叫翻板閥，可以旋轉90°，通過旋轉閥桿帶動碟板轉動，改變碟板的角度就能控制流體的流量，可用于截斷，接通，調節管路中的流體；常用于供水，供氣等管路中，作為調節和截流裝置。

　　Butterfly valve, also known as flap valve, can rotate 90 °. By rotating the valve stem to drive the disc plate to rotate, the angle of the disc plate can be changed to control the flow rate of the fluid. It can be used to cut off, connect, and regulate the fluid in the pipeline; Commonly used in water and gas supply pipelines as regulating and shut-off devices.

　　調節閥，又叫控制閥，用于控制流體的大小，當閥門調節部位收到調節信號，閥桿會根據信號自動控制閥門的開關程度，從而達到對流體流速及壓力的調節；常用于供熱，燃氣，石化等管路中。

　　Regulating valve, also known as control valve, is used to control the size of fluid. When the regulating part of the valve receives a regulating signal, the valve stem will automatically control the opening and closing degree of the valve according to the signal, thereby achieving the regulation of fluid flow rate and pressure; Commonly used in heating, gas, petrochemical and other pipelines.

　　溢流閥和減壓閥的作用

　　The function of overflow valve and pressure reducing valve

　　溢流閥是防止系統超載,保證安全。減壓閥是在保證系統不過載的前提下,降低系統壓力.

　　Overflow valve is used to prevent system overload and ensure safety. A pressure reducing valve reduces system pressure while ensuring that the system is not overloaded

　　可以說溢流閥是被動工作,而減壓閥是主動工作.1、減壓閥保持出口處壓力不變，而溢流閥保持進口處壓力不變；

　　It can be said that the relief valve works passively, while the pressure reducing valve works actively. 1. The pressure reducing valve maintains a constant pressure at the outlet, while the relief valve maintains a constant pressure at the inlet;

　　2、在不工作時，減壓閥進出口互通，而溢流閥進出口不通；3、非工作狀態時，減壓閥的閥口是敞開的，而溢流閥是常閉的溢流閥和減壓閥的區別

　　2. When not working, the inlet and outlet of the pressure reducing valve are interconnected, while the inlet and outlet of the overflow valve are not connected; 3. When not in operation, the valve port of the pressure reducing valve is open, while the relief valve is normally closed. The difference between relief valve and pressure reducing valve

　　溢流閥是壓力控制閥，主要是控制系統壓力，還起卸荷的作用：減壓閥是一種使閥出口壓力低于進口壓力的壓力調節閥。1、減壓閥主要是用來降低液壓系統某一分支油路的壓力，使分支壓力比主油 路壓力低且穩定，在調定壓力的范圍內，減壓閥也像溢流閥那樣是關閉的。但是隨著系統壓力的升高當達到減壓閥調定的壓力時，減壓閥打開，部分油液會經過他返回油箱（此時有一定壓力的油回油箱，油箱的油溫會上升），這一支路的油壓是不會上升了。它起到對本支路的減壓與穩壓作用！溢流閥則不同，它裝在泵的出口處會保證系統的整體壓力穩定且不會超壓。所以他有安全、調壓、穩壓等作用！2、溢流閥一般并聯在系統的支路中起調壓、穩壓與減壓作用，而減壓閥一般串聯在某一支路上起減壓與保壓本支路的作用！

　　Overflow valve is a pressure control valve that mainly controls the system pressure and also plays a role in unloading. A pressure reducing valve is a pressure regulating valve that makes the outlet pressure of the valve lower than the inlet pressure. 1. A pressure reducing valve is mainly used to reduce the pressure of a branch oil circuit in a hydraulic system, so that the branch pressure is lower and more stable than the main oil circuit pressure. Within the set pressure range, the pressure reducing valve is also closed like an overflow valve. However, as the system pressure increases and reaches the set pressure of the pressure reducing valve, the valve opens and some of the oil will pass through it back to the tank (at this time, there is a certain pressure of oil returning to the tank, and the oil temperature in the tank will rise). The oil pressure in this branch will not increase. It plays a role in reducing and stabilizing the pressure of this branch! The overflow valve is different. It is installed at the outlet of the pump to ensure the overall pressure stability of the system and prevent overpressure. So he has functions such as safety, voltage regulation, and stabilization! 2. Overflow valves are generally connected in parallel in the system's branches to regulate, stabilize, and reduce pressure, while pressure reducing valves are generally connected in series in a certain branch to reduce and maintain pressure in this branch!

　　溢流閥是常閉的，只是當系統超壓才動作；減壓閥是常通的，通過狹窄通道減壓。

　　The overflow valve is normally closed and only operates when the system is overpressure; The pressure reducing valve is normally open and reduces pressure through a narrow channel.

　　溢流閥的作用是：穩壓、溢流、過載保護。減壓閥是減小壓力，，液壓系統某一部分壓里減小。用途不一樣。所以不能代替。

　　The function of the overflow valve is to stabilize voltage, overflow, and overload protection. A pressure reducing valve is used to decrease the pressure in a certain part of the hydraulic system. The purpose is different. So it cannot be replaced.

　　溢流閥控制進油口壓力，減壓閥控制出油口壓力

　　The overflow valve controls the inlet pressure, and the pressure reducing valve controls the outlet pressure

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