止回阀是所有阀门中为特殊的一类——它是为数不多的不需要外部动力即可自动工作的阀门。止回阀的启闭件（阀瓣）依靠介质自身的流动力量来开启或关闭，其核心功能是只允许介质向一个方向流动，并自动阻止反向流动。正因如此，止回阀又被称为单向阀、逆止阀或回流阀。

Check valve is a special type of valve among all valves - it is one of the few valves that can work automatically without external power. The opening and closing components (valve disc) of a check valve rely on the flow force of the medium itself to open or close. Its core function is to allow the medium to flow only in one direction and automatically prevent reverse flow. That's why check valves are also known as one-way valves, check valves, or return valves.

止回阀的工作原理基于流体压力与阀瓣自重（或弹簧力）的平衡。当介质正向流动时，流体压力克服阀瓣的自重或弹簧阻力，将阀瓣推开，阀门开启。一旦正向流动停止或出现反向流动趋势，阀瓣在背压、重力或弹簧作用下迅速关闭，切断倒流通道。整个过程完全自动完成，无需人工操作或外部能源。

The working principle of a check valve is based on the balance between fluid pressure and the self weight (or spring force) of the valve disc. When the medium flows forward, the fluid pressure overcomes the self weight or spring resistance of the valve disc, pushes the valve disc open, and the valve opens. Once the forward flow stops or a reverse flow trend occurs, the valve disc quickly closes under back pressure, gravity, or spring action, cutting off the reverse flow channel. The entire process is completely automated, without the need for manual operation or external energy.

根据阀瓣的运动方式，止回阀主要分为旋启式和升降式两大类。旋启式止回阀的阀瓣围绕一个铰链轴旋转——介质正向流动时将阀瓣推开（阀瓣绕轴旋起），反向流动时阀瓣在自重和背压下旋回关闭。旋启式止回阀流阻较小，适用于大口径管道。升降式止回阀的阀瓣沿阀体中心线作直线升降运动——正向流动时将阀瓣顶起，反向流动时阀瓣落下关闭。升降式止回阀密封性能更好，但流阻较大，适用于小口径管道。

According to the movement mode of the valve disc, check valves are mainly divided into two categories: swing type and lift type. The valve disc of a swing check valve rotates around a hinge axis - when the medium flows forward, the valve disc is pushed open (the valve disc rotates around the axis), and when the medium flows backward, the valve disc rotates and closes under its own weight and back pressure. Swing check valves have low flow resistance and are suitable for large-diameter pipelines. The valve disc of the lift check valve moves in a straight line along the centerline of the valve body - lifting the valve disc when flowing forward and closing it when flowing backward. Lift check valves have better sealing performance but higher flow resistance, making them suitable for small-diameter pipelines.

此外，还有蝶式止回阀（阀瓣为圆盘形，类似蝶阀的蝶板）、隔膜式止回阀（依靠隔膜的弹性变形实现启闭）等多种特殊结构。部分止回阀还可在特殊情况下安装外部配重和阻尼装置，以改善关闭特性。

In addition, there are various special structures such as butterfly check valves (with disc shaped valve discs similar to butterfly valves) and diaphragm check valves (which rely on the elastic deformation of the diaphragm to achieve opening and closing). Partial check valves can also be equipped with external counterweights and damping devices in special circumstances to improve their closing characteristics.

止回阀在管道系统中的重要性常常被低估，但其作用却至关重要。在泵出口管道上，止回阀可以防止停泵时介质倒流导致泵反转损坏。在容器出口管道上，止回阀可以防止容器内的介质意外泄放。在并联运行的泵系统中，止回阀可以防止一台泵运行时介质从另一台停运泵中倒流。

The importance of check valves in pipeline systems is often underestimated, but their role is crucial. On the pump outlet pipeline, a check valve can prevent the medium from flowing back and causing damage to the pump due to reverse rotation when the pump is stopped. On the outlet pipeline of the container, a check valve can prevent accidental release of the medium inside the container. In a parallel running pump system, check valves can prevent the medium from flowing back from another stopped pump when one pump is running.

良工阀门生产的止回阀产品线覆盖多种类型。H41W系列止回阀为升降式结构，公称压力2.5MPa。H44H系列旋启式止回阀采用WCB碳钢材质，口径可达DN450mm。良工智能消声止回阀采用“头”形阀瓣和“腰鼓”形阀体设计，改善了介质流向，降低了流阻系数。橡胶瓣止回阀则以圆形橡胶阀瓣为启闭件，靠自身重量及介质压力动作。此外，良工还提供黄铜法兰止回阀等铜阀门产品。在材质方面，可提供铸铁、碳钢、不锈钢、铜合金等多种选择。

The check valve product line produced by Lianggong Valve covers multiple types. The H41W series check valve is a lifting structure with a nominal pressure of 2.5MPa. The H44H series swing check valve is made of WCB carbon steel material, with a diameter of up to DN450mm. The Lianggong intelligent noise reduction check valve adopts a "head" shaped valve disc and a "waist drum" shaped valve body design, which improves the flow direction of the medium and reduces the flow resistance coefficient. Rubber flap check valves use circular rubber flaps as opening and closing components, which operate based on their own weight and medium pressure. In addition, Lianggong also provides copper valve products such as brass flange check valves. In terms of materials, there are various options available, such as cast iron, carbon steel, stainless steel, copper alloy, etc.

止回阀在石油、化工、电力、给排水等行业的泵出口、设备出口和管道分支点上有广泛应用。正确选型和安装止回阀，是保障管道系统安全运行的重要环节。

Check valves are widely used in pump outlets, equipment outlets, and pipeline branching points in industries such as petroleum, chemical, power, and water supply and drainage. Correctly selecting and installing check valves is an important step in ensuring the safe operation of pipeline systems.

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