止回閥 - 工作原理/類型/材質(zhì)/選型/應(yīng)用等（中英文）
止回閥允許液體和空氣僅朝一個方向流動。止回閥的主要目的是防止系統(tǒng)中的回流。止回閥是解決潛在回流問題的廉價、有效且簡單的解決方案。如果流體受到污染，回流可能會造成問題，因為它會污染上游介質(zhì)。例如，下水道管線將有一個止回閥，以確保廢液可以離開系統(tǒng)（例如住宅管道系統(tǒng)），但不能重新進入。
A check valve allows liquid and air to flow in only one direction. The primary purpose of a check valve is to prevent backflow in the system. Check valves are inexpensive, effective, and easy solutions to the potential issue backflow. Backflow can cause a problem if the flow is contaminated because it can contaminate upstream media. For example, a sewer line will have a non-return valve to ensure that waste can leave a system (e.g., residential plumbing system) but cannot re-enter.
止回閥的工作原理
How does a check valve work
開啟壓力
Cracking pressure
止回閥需要入口和出口之間有最小壓差才能打開，從而允許介質(zhì)流過。閥門打開時的最小上游壓力稱為止回閥的開啟壓力。具體開啟壓力會根據(jù)閥門的設(shè)計和尺寸而變化，因此請確保系統(tǒng)壓力可以產(chǎn)生所選止回閥的開啟壓力。
A check valve requires a minimum pressure differential between the inlet and outlet to open, allowing media to flow through it. This minimum upstream pressure at which the valve opens is called the check valve's cracking pressure. The specific cracking pressure changes based on the valve design and size, so ensure that the system's pressure can generate the cracking pressure of the chosen check valve(s).
關(guān)閉
Closing
如果上游壓力低于開啟壓力或存在背壓（流體試圖從出口流向入口），單向止回閥將關(guān)閉。通常，止回閥有一個閘板、球、隔膜或圓盤壓在密封件上以關(guān)閉閥門并阻止流動。重力或彈簧可以協(xié)助關(guān)閉過程。
If the upstream pressure falls below the cracking pressure or there is back pressure (flow attempting to move from the outlet to the inlet), the one way check valve will close. Typically, check valves have a gate, ball, diaphragm, or disc pressed against a seal to close the valve and
block flow. Gravity or a spring can assist in the closing process.
安裝方向
Installation orientation
由于單向閥只允許一個方向的流動，因此了解正確的安裝方向至關(guān)重要。通常，閥門外殼上的箭頭指示流動方向。如果沒有箭頭，請檢查閥門以確保其安裝在預(yù)期的流動方向上。如果閥門安裝反了，介質(zhì)就無法在系統(tǒng)中流動，由此產(chǎn)生的壓力積聚可能會造成損壞。
As a one-way valve only allows flow in one direction, knowing the correct installation orientation is crucial. Typically, an arrow on the valve's housing indicates the flow direction. If there isn't an arrow, examine the valve to ensure it is installed in the intended flow direction. If the valve is installed backward, the media cannot move through the system, and the resulting pressure build-up can cause damage.
常開和常閉止回閥
Normally open and normally closed check valves
常開止回閥允許介質(zhì)自由流動，但在發(fā)生回流時會切斷流動。常閉止回閥會阻止介質(zhì)流過，直到破裂壓力積聚，此時閥門打開。
A normally open check valve allows the medium to flow freely but shuts off the flow in case of backflow. A normally closed check valve prevents the flow of media through it until the cracking pressure builds up, at which point the valve opens.
止回閥類型
Check valve types
止回閥的操作方式根據(jù)其設(shè)計而不同。最常見的止回閥是彈簧式直列止回閥。
Check valves operate differently depending on their design. The most common check valve is a spring-loaded in-line check valve.
彈簧式直通止回閥
Spring-loaded in-line check valve
直通式彈簧式止回閥很常見，易于理解，設(shè)計簡單。圖 2 顯示了彈簧式直通止回閥處于打開和關(guān)閉位置的情況。箭頭表示流動方向。當流體進入閥門的輸入端口時，它應(yīng)該具有足夠的壓力（力）來克服開啟壓力和彈簧力。壓力推動閥瓣（圖 2 標記為 B），打開孔口并允許流體通過閥門。當輸入壓力不再足夠高或有足夠的背壓時，背壓和彈簧（圖 2 標記為 C）將閥瓣推向孔口并密封閥門。彈簧和閥瓣的短行程距離允許快速關(guān)閉反應(yīng)時間。彈簧止回閥設(shè)計還可以防止管路中的壓力激增，從而防止水錘。
常見的彈簧式直列止回閥類型也稱為：
? 噴嘴止回閥
? 提升式止回閥
? 軸向止回閥
? 過流止回閥
? 靜音止回閥
? 防水錘止回閥
In-line spring-loaded check valves are common, easy to understand, and have a simple design. Figure 2 shows a spring-loaded in-line check valve in the open and closed positions. The arrows indicate flow direction. When flow enters the input port of the valve, it should have enough pressure (force) to overcome the cracking pressure and the spring force. The pressure pushes the disc (Figure 2 labeled B), opening the orifice and allowing flow through the valve. When the input pressure is no longer high enough, or there is enough back pressure, the back pressure and spring (Figure 2 labeled C) push the disc against the orifice and seal the valve shut. The spring and the short travel distance for the disc allow for a quick reaction time for closing. The spring check valve design also prevents pressure surges in the line, preventing water hammer.
Common types of spring-loaded in-line check valves are also called:
? nozzle check valves
? poppet check valves
? axial check valves
? excess flow check valves
? silent or quiet check valves
? anti-water hammer check valves
彈簧加載 Y 型止回閥
Spring-loaded Y-check valve
彈簧加載 Y 型止回閥的工作原理與直列彈簧加載止回閥類似。不同之處在于彈簧和可移動閥瓣呈一定角度放置。這形成了一個“y”形，因此得名。它的工作原理與直列閥相同，但由于可移動部件呈一定角度，因此可以在閥門連接到系統(tǒng)時對其進行檢查和維修。這些閥門更大，在系統(tǒng)內(nèi)占用更多空間。
Spring-loaded y-check valves operate similarly to in-line spring-loaded check valves. The difference is that the spring and movable disc are positioned at an angle. This creates a ‘y’ shape, hence the name of the valve. It works the same way as an in-line valve, but since the moveable components are at an angle, they can be inspected and serviced while the valve is connected to the system. These valves are larger and take up more room within the system.
球形止回閥
Ball check valve
球形止回閥使用自由浮動或彈簧加載的球，該球位于密封座上以關(guān)閉孔口。密封座通常呈錐形，以將球引導到閥座中并形成正密封，從而阻止反向流動。當入口側(cè)的流體壓力超過開啟壓力時，球會從閥座上移開，從而允許流動。當入口壓力不超過開啟壓力或存在背壓時，球?qū)⑼ㄟ^背壓或彈簧關(guān)閉，從而有效地關(guān)閉孔口。真正的聯(lián)合球形止回閥可以輕松拆卸和更換球，無需購買新閥門。
A ball check valve uses a free-floating or spring-loaded ball that rests on the sealing seat to close the orifice. The sealing seat is normally conically tapered to guide the ball into the seat and create a positive seal, thereby stopping reverse flow. When the pressure of the fluid in the inlet side exceeds the cracking pressure, the ball is dislodged from its seat, which permits flow. When the inlet pressure doesn’t exceed the cracking pressure, or there is back pressure, the ball will close with the back pressure or via the spring, effectively closing the orifice. True union ball check valves allow for easy removal and replacement of balls, eliminating the need to buy a new valve.
旋啟式止回閥
Swing check valve
旋啟式止回閥又稱為“傾斜閥瓣”或“擋板”止回閥。它們在鉸鏈（或耳軸）上有一個閥瓣，閥瓣會隨著入口壓力擺動打開。當入口壓力降低或出現(xiàn)回流時，閥瓣會擺動關(guān)閉。如果沒有彈簧協(xié)助關(guān)閉，則必須考慮安裝方向，以確保閥瓣在重力作用下擺動關(guān)閉。圖 5 顯示了旋啟式止回閥的示例。
Swing check valves are called ‘tilting-disc’ or ‘flapper’ check valves. They have a disc on a hinge (or trunnion) that swings open with an inlet pressure. The disc swings shut as the inlet pressure decreases or if there is backflow. If there is no spring to assist in closing, mounting orientation is important to consider to ensure that the disc swings shut with gravity. Figure 5 shows an example of a swing check valve.
底閥
Foot valve
底閥是一種與入口側(cè)的過濾器組合的止回閥。過濾器可防止雜物進入止回閥，以免堵塞或損壞下游設(shè)備。由于該閥的入口沒有連接點，因此安裝在一段管道的末端。底閥中常見的止回閥類型是直列彈簧輔助止回閥或直列球形止回閥。它們通常安裝在水井、油箱或任何其他吸入管線位于泵下方的應(yīng)用的泵吸入管線末端。它們可以保持泵處于啟動狀態(tài)，防止液體虹吸回流，并防止雜物進入管線。圖 6 顯示了底閥的示例。
A foot valve is a check valve combined with a strainer on the inlet side. The strainer prevents debris that could clog or damage something downstream from entering the check valve. This valve is installed at the end of a section of piping as its input doesn't have a connection point. Common check valve types included in a foot valve are in-line spring assisted or an in-line ball check valve. They are typically installed at the end of a pump suction line of a water well, fuel tank, or any other application where the suction line is situated below the pump. They can keep pumps primed, prevent liquid from siphoning back, and keep debris out of the line. Figure 6 shows an example of a foot valve.
止回閥材質(zhì)
Check valve materials
不銹鋼止回閥
Stainless steel check valve
不銹鋼止回閥以其出色的耐腐蝕、耐熱和耐低溫性能而聞名，是苛刻環(huán)境的選擇。它們具有出色的機械性能，包括高強度和耐用性，有助于延長使用壽命。這些閥門非常適合涉及高溫和高壓的應(yīng)用，例如工業(yè)加工、化工廠以及石油和天然氣工業(yè)。
不銹鋼止回閥有多種等級，最常見的是 304 和 316。316 級不銹鋼具有增強的抗氯化物和其他腐蝕性物質(zhì)的能力，使其適用于海洋和沿海應(yīng)用。
雖然不銹鋼止回閥具有出色的性能，但對于不需要如此高耐用性或耐性的應(yīng)用，它們可能不是最具成本效益的解決方案。在這種情況下，PVC 或黃銅等替代材料可能更經(jīng)濟。
主要特點
? 耐腐蝕性：對各種腐蝕介質(zhì)具有出色的耐受性，包括酸、堿和氯化物。
? 耐高溫性：能夠承受極端溫度，從 -25 °C 到 200 °C（-13 °F 到 392 °F）的高溫和低溫。
? 機械強度：高強度和耐用性，適用于高達 64 bar（928 psi）的高壓應(yīng)用。
? 多功能性：有各種等級可供選擇，以滿足特定的應(yīng)用要求。
應(yīng)用
? 工業(yè)加工
? 化工廠
? 石油和天然氣工業(yè)
? 海洋和沿海環(huán)境
? 高溫高壓系統(tǒng)
Stainless steel check valves are renowned for their superior resistance to corrosion, heat, and low temperatures, making them ideal for demanding environments. They exhibit excellent mechanical properties, including high strength and durability, contributing to their long service life. These valves are well-suited for applications involving high temperatures and pressures, such as in industrial processing, chemical plants, and oil and gas industries.
Stainless steel check valves are available in various grades, with 304 and 316 being the most common. Grade 316 stainless steel offers enhanced resistance to chlorides and other corrosive substances, making it suitable for marine and coastal applications.
While stainless steel check valves provide exceptional performance, they may not be the most cost-effective solution for applications that do not require such high durability or resistance. In such cases, alternative materials like PVC or brass may be more economical.
Key Features
? Corrosion resistance: Excellent resistance to a wide range of corrosive media, including acids, alkalis, and chlorides.
? Temperature tolerance: Capable of withstanding extreme temperatures, both high and low from -25 °C to 200 °C (-13 °F to 392 °F).
? Mechanical strength: High strength and durability, suitable for high-pressure applications up to 64 bar (928 psi).
? Versatility: Available in various grades to meet specific application requirements.
Applications
? Industrial processing
? Chemical plants
? Oil and gas industries
? Marine and coastal environments
? High-temperature and high-pressure systems
PVC（聚氯乙烯）止回閥
PVC (Polyvinyl Chloride) check valve
PVC 止回閥經(jīng)常用于灌溉和水管理系統(tǒng)。它們對大多數(shù)腐蝕性介質(zhì)（如海水、酸、堿、氯化物溶液和有機溶劑）具有耐腐蝕性。但是，它們對芳香烴和氯化烴并非免疫，并且通常最高耐溫約為 60°C。
主要特點
? 耐腐蝕性：對各種腐蝕性介質(zhì)具有出色的耐受性，包括海水、酸、堿和氯化物溶液。
? 耐高溫性：能夠承受高達 60°C (140°F) 的溫度。
? 機械強度：強度足以滿足低壓至中壓應(yīng)用。
? 多功能性：適用于各種水管理和灌溉系統(tǒng)。
應(yīng)用
? 灌溉系統(tǒng)
? 水管理系統(tǒng)
? 涉及非芳香烴和非氯化烴的化學加工
? 廢水處理
PVC check valves are frequently used in irrigation and water management systems. They are corrosion-resistant to most corrosive media like seawater, acids, bases, chloride solutions, and organic solvents. However, they are not immune to aromatic and chlorinated hydrocarbons and typically have a max temperature resistance of around 60 °C.
Key features
? Corrosion resistance: Excellent resistance to a wide range of corrosive media, including seawater, acids, bases, and chloride solutions.
? Temperature tolerance: Capable of withstanding temperatures up to 60 °C (140°F).
? Mechanical strength: Adequate strength for low to moderate pressure applications.
? Versatility: Suitable for a variety of water management and irrigation systems.
Applications
? Irrigation systems
? Water management systems
? Chemical processing involving non-aromatic and non-chlorinated hydrocarbons
? Wastewater treatment
黃銅止回閥
Brass check valve
黃銅止回閥非常適合空氣、水、油或燃料應(yīng)用。但是，它們不耐海水、純凈水或氯化水。與不銹鋼相比，黃銅的耐熱性和耐腐蝕性較差，通常用于低壓應(yīng)用。
主要特點
? 耐腐蝕性：中等耐腐蝕性，但不適用于海水、純凈水或氯化水。
? 耐高溫性：有限的耐高溫性，通常適用于低溫應(yīng)用。
? 機械強度：強度足以滿足低壓應(yīng)用。
? 多功能性：適用于涉及空氣、水、油或燃料的各種應(yīng)用。
應(yīng)用
? 低壓系統(tǒng)
? 家用水系統(tǒng)
? 燃油管路
? 空氣壓縮機
Brass check valves are excellent for air, water, oil, or fuel applications. However, they are not resistant to seawater, purified water, or chlorinated water. Compared to stainless steel, brass is less resistant to heat and corrosion and is typically used for applications with low pressure.
Key features
? Corrosion resistance: Moderate resistance to corrosion, but not suitable for seawater, purified water, or chlorinated water.
? Temperature tolerance: Limited temperature tolerance, generally suitable for low-temperature applications.
? Mechanical strength: Adequate strength for low-pressure applications.
? Versatility: Suitable for a variety of applications involving air, water, oil, or fuel.
Applications
? Low-pressure systems
? Domestic water systems
? Fuel lines
? Air compressors
選擇標準
Selection criteria
在為某一應(yīng)用選擇止回閥時，需要考慮以下標準：
? 材料與介質(zhì)的兼容性
? 連接點的管線尺寸
? 最大壓力和開啟壓力要求
? 安裝方向水平或垂直
? 外殼尺寸
? 檢查和維修的可達性需求
? 溫度（外部和介質(zhì)）
Check valves have the following criteria to consider when selecting one for an application:
? Material compatibility with the medium
? Line size for connection points
? Max pressure and cracking pressure requirement
? Installation orientation horizontal or vertical
? Envelope dimensions
? Accessibility needs for inspections and repairs
? Temperature (external and media)
應(yīng)用
Applications
由于止回閥的功能，它們通常在各種應(yīng)用中用于以下四個不同原因之一：
? 保護下游設(shè)備免受回流損壞
? 防止因反向流動而造成的污染
? 防止虹吸
? 保持真空密封
由于其功能，它們幾乎用于所有行業(yè)。它們用于常見的家用電器，如洗碗機、洗衣機和廢水管線。對于工業(yè)用途，它們用于鍋爐、熔爐、氣體系統(tǒng)、泵送應(yīng)用或真空系統(tǒng)。它們還經(jīng)常用作水和二氧化碳管線上的水族館止回閥。此外，微型止回閥是一種流行的選擇，因為空間有限，但可靠的操作是必不可少的。兩種最常見的止回閥應(yīng)用是水和空氣，下面將更深入地討論它們。
Due to how check valves function, they are typically used for one of four different reasons in various applications:
? To protect equipment downstream from backflow damage
? To prevent contamination due to reverse flow
? To prevent siphoning
? To keep a vacuum seal
Due to their function, they are used in almost every industry. They are used on common household appliances, like dishwashers, washing machines, and wastewater lines. For industrial purposes, they are used on boilers, furnaces, gas systems, pumping applications, or vacuum systems. They are also frequently used as aquarium check valves on water and CO2 lines. Also, a miniature check valve is a popular choice where the space is limited, yet a reliable operation is essential. Two of the most common check valve applications are for water and air, which are discussed in more depth below.
水用止回閥
Check valves for water
水用止回閥用于多種水應(yīng)用，如飲用水和廢水。這些閥門簡稱為單向水閥。用于飲用水應(yīng)用的管道止回閥可確保沒有任何環(huán)境介質(zhì)（閥門出口側(cè)）可以隨安全、清潔的飲用水進入系統(tǒng)并污染系統(tǒng)。對于廢水應(yīng)用，它們可確保廢水不會重新進入系統(tǒng)并導致溢流或其他污染。對于水泵應(yīng)用，通常使用底閥來確保沒有雜物進入管道并保持內(nèi)部壓力以用于啟動目的。污水泵止回閥可確保在泵關(guān)閉時，排出的水不會因重力而回流到污水泵中。
A water check valve is used in numerous water applications, like drinking water and wastewater. These valves are simply called one-way water valves. Plumbing check valves for drinking water applications ensure that no environmental media (outlet side of the valve) can enter the system with the safe, clean drinking water and contaminate it. For wastewater applications, they ensure that the wastewater cannot re-enter the system and cause an overflow or additional contamination. For water pumping applications, a foot valve is often used to ensure no debris enters the line and keep internal pressure for priming purposes. Sump pump check valves ensure that the discharged water does not come back into the sump pump with gravity when the pump is turned off.
氣動止回閥
Pneumatic check valve
氣動止回閥或空氣止回閥允許氣流通過并防止氣流流出。它們通常簡稱為單向空氣閥。最常見的應(yīng)用是空氣壓縮機。氣動止回閥允許壓縮機保持某些部件加壓，而其他部件減壓。它們可以位于空氣接收器、排氣管上，或作為活塞壓縮機入口和出口側(cè)的活塞止回閥。
A pneumatic check valve, or air check valve, allows airflow and prevents it from going out. They are often simply called one-way air valves. The most common application is for an air compressor. A pneumatic check valve allows the compressor to keep certain parts pressurized and other parts de-pressurized. They can be located on an air receiver, discharge pipe, or as a piston check valve on the piston compressor's inlet and outlet sides.
止回閥符號
Check valve symbols
止回閥的 P&ID 符號如圖 7 所示。
The P& ID symbol for check valves is shown in Figure 7.
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