止回阀，是一种自动阀门，仅允许流体（液体、气体）向一个方向流动，并能自动防止介质倒流。其核心原理是依靠介质自身的流动和压力来开启或关闭阀门，无需任何外部操作机构。

　　Check valve is an automatic valve that only allows fluid (liquid, gas) to flow in one direction and can automatically prevent medium backflow. The core principle is to rely on the flow and pressure of the medium itself to open or close the valve, without the need for any external operating mechanism.

　　一、核心结构与通用组件

　　1、 Core structure and common components

　　尽管种类繁多，但大多数止回阀都包含以下几个基本部件：阀体?：阀门的主要外壳，用于连接管道，承受管道压力。是流体通过的通道。阀瓣 ?或 关闭件：这是止回阀的核心运动部件。其名称和形状因类型而异（如圆盘、球体、两片瓣叶等）。它是直接阻止介质倒流的关键零件。阀座?：阀瓣闭合时与之紧密接触的密封面。阀座与阀瓣的配合质量决定了阀门的密封性能和内漏等级。辅助部件：根据类型不同，可能包括：弹簧?：提供额外的闭合力，帮助阀门快速关闭，防止水锤，并支持阀门在任意方向（水平、垂直向上、垂直向下）安装。摇臂与 枢轴?：用于旋启式止回阀，使阀瓣能像门一样摆动。球导向架?：用于球式止回阀，限制球的运动轨迹。

　　Although there are many types, most check valves include the following basic components: valve body: the main housing of the valve, used to connect pipelines and withstand pipeline pressure. It is a channel through which fluids pass. Valve disc or closure: This is the core moving component of a check valve. Its name and shape vary depending on the type (such as disc, sphere, two lobes, etc.). It is a key component that directly prevents the backflow of the medium. Valve seat: The sealing surface that tightly contacts the valve disc when it is closed. The quality of the fit between the valve seat and the valve disc determines the sealing performance and internal leakage level of the valve. Auxiliary components: Depending on the type, they may include: springs: providing additional closing force to help the valve close quickly, prevent water hammer, and support valve installation in any direction (horizontal, vertical up, vertical down). Swing arm and pivot: used for swing check valves, allowing the valve disc to swing like a door. Ball guide frame: used for ball check valves to restrict the movement trajectory of the ball.

　　二、主要结构类型（基于阀瓣运动方式）

　　2、 Main structural types (based on valve disc movement mode)

　　这是最基础也是最常见的分类方式，根据阀瓣如何运动来开启和关闭。1. 旋启式止回阀

　　This is the most basic and common classification method, which opens and closes based on how the valve disc moves. 1. Swing check valve

　　结构：阀瓣像一个铰链门，通过摇臂和枢轴连接在阀体顶部。阀瓣可以自由摆动。工作原理：流体正向流动时，压力将阀瓣推起；流动停止或反向时，阀瓣靠自重和回流压力关闭。特点：流阻小，压降低，适用于大流量、低流速的工况（如水泵出水口）。不适合流量频繁变化的场合，关闭时易产生水锤，通常要求安装在水平管道上。

　　Structure: The valve disc is like a hinged door, connected to the top of the valve body through a rocker arm and pivot. The valve disc can swing freely. Working principle: When the fluid flows forward, pressure pushes the valve disc up; When the flow stops or reverses, the valve disc closes by its own weight and reflux pressure. Features: Low flow resistance, reduced pressure, suitable for high flow and low flow conditions (such as water pump outlet). Not suitable for situations with frequent changes in flow, it is prone to water hammer when closed, and is usually required to be installed on a horizontal pipeline.

　　2. 升降式止回阀

　　2. Lift check valve

　　结构：阀瓣像一个活塞，通常带有导向机构，沿阀座通道轴线做垂直升降运动。其结构与截止阀非常相似。工作原理：流体压力顶起阀瓣；压力下降时，阀瓣靠自重落回阀座。特点：密封性能优于旋启式，但流阻较大。适用于高压、小口径场合（如锅炉给水系统、高压管道）。通常要求安装在水平管道上。

　　Structure: The valve disc is like a piston, usually equipped with a guiding mechanism, and moves vertically up and down along the axis of the valve seat channel. Its structure is very similar to a globe valve. Working principle: Fluid pressure lifts the valve disc; When the pressure drops, the valve disc falls back to the valve seat by self weight. Features: The sealing performance is better than that of the rotary opening type, but the flow resistance is relatively high. Suitable for high-pressure and small-diameter applications (such as boiler feedwater systems and high-pressure pipelines). It is usually required to be installed on a horizontal pipeline.

　　3. 球式止回阀

　　3. Ball check valve

　　结构：用一个球体作为阀瓣。阀体内部通常有一个锥形阀座来容纳球体。工作原理：流体压力顶起球体；反向流动时，球体滚回锥形阀座并密封。特点：结构简单，密封可靠，适用于高粘度、带悬浮颗粒的介质（如泥浆、造纸浆液）。但噪音和水锤现象可能较明显。

　　Structure: Use a sphere as the valve disc. There is usually a conical valve seat inside the valve body to accommodate the ball. Working principle: Fluid pressure lifts the sphere; When flowing in reverse, the sphere rolls back to the conical valve seat and seals. Features: Simple structure, reliable sealing, suitable for media with high viscosity and suspended particles (such as mud and paper pulp). But noise and water hammer phenomena may be more pronounced.

　　4. 瓣式（对夹式）止回阀

　　4. Flap type (clamp type) check valve

　　结构：由两个半圆形的弹簧加载瓣片和一个中央销轴组成。结构非常紧凑，重量轻。工作原理：流体压力推开两个瓣片；流动停止时，弹簧力和回流压力迅速将瓣片关闭。特点：启闭速度快，能有效减小水锤压力；体积小、重量轻、成本低。广泛应用于石油、化工、水处理等行业的空间受限场合。

　　Structure: Composed of two semi-circular spring-loaded flaps and a central pin shaft. The structure is very compact and lightweight. Working principle: Fluid pressure pushes apart two flaps; When the flow stops, the spring force and reflux pressure quickly close the flap. Features: Fast opening and closing speed, effectively reducing water hammer pressure; Small size, light weight, and low cost. Widely used in space constrained environments in industries such as petroleum, chemical, and water treatment.

　　三、特殊类别与高性能类型

　　3、 Special categories and high-performance types

　　这些是为了满足特定苛刻工况而设计的止回阀。

　　These are check valves designed to meet specific harsh operating conditions.

　　1. 轴流式止回阀

　　1. Axial flow check valve

　　特点：阀瓣的开启和关闭沿管道轴线方向运动，流道呈直线型，极其通畅。优势：流阻极低，压降非常小。开启和关闭平稳迅速，水锤效应极低。应用：对压力损失要求极高的场合，如长输石油/天然气管道、大型泵的出口、压缩机系统。

　　Features: The opening and closing of the valve disc move along the axis of the pipeline, and the flow channel is linear and extremely smooth. Advantages: Extremely low flow resistance and very small pressure drop. Smooth and rapid opening and closing, with extremely low water hammer effect. Application: In situations where high pressure loss is required, such as long-distance oil/gas pipelines, large pump outlets, and compressor systems.

　　2. 缓闭式止回阀

　　2. Slow closing check valve

　　特点：带有阻尼机构（如液压油缸、弹簧和阻尼孔），可以控制阀瓣的关闭速度。优势：主动防止水锤。它先快速关闭大部分行程（约80-90%）以防止倒流，最后一段行程缓慢关闭以消除压力波动。应用：防止水锤危害至关重要的系统，如大型水泵站、电厂冷却水系统、高层建筑给水系统。

　　Features: Equipped with damping mechanisms (such as hydraulic cylinders, springs, and damping holes), it can control the closing speed of the valve disc. Advantage: Proactively prevent water hammer. It first quickly closes most of the stroke (about 80-90%) to prevent backflow, and then slowly closes the last stroke to eliminate pressure fluctuations. Application: It is crucial to prevent water hammer hazards in systems such as large pump stations, power plant cooling water systems, and high-rise building water supply systems.

　　3. 截止止回阀

　　3. Cut off check valve

　　特点：它是截止阀和止回阀的结合体。它有一个额外的外部手轮或执行机构。优势：具有两种模式：止回模式：手轮完全抬起，阀瓣可自由活动，作为普通止回阀使用。截止模式：通过手轮强行将阀瓣压紧在阀座上，充当截止阀，可以完全手动切断流动。应用：锅炉给水泵出口、汽轮机抽汽管路等需要双重保障的关键场合。

　　Characteristic: It is a combination of a globe valve and a check valve. It has an additional external handwheel or actuator. Advantage: It has two modes: check mode: when the handwheel is fully raised, the valve disc can move freely and is used as a regular check valve. Cut off mode: By forcefully pressing the valve disc onto the valve seat with the handwheel, it acts as a shut-off valve and can completely manually cut off the flow. Application: Key occasions that require dual protection, such as the outlet of boiler feedwater pumps and the extraction pipelines of steam turbines.

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