外螺纹单向阀的工作原理是在一个方向流动的流体压力作用下，阀瓣打开；流体反方向流动时，由流体压力和阀瓣的自重合阀瓣作用于阀座，从而切断流动。H21X外螺纹单向阀又称为逆流阀、逆止阀、背压阀、止回阀。这类阀门是靠管路中介质本身的流动产生的力而自动开启和关闭的，属于一种自动阀门。止回阀用于管路系统，其主要作用是防止介质倒流、防止泵及其驱动电机机反转，以及容器内介质的泄放。H21X外螺纹单向阀是通过外螺纹焊接连接管道，具有安装方便 连接牢固 方便更换等优点。焊接形式又分为对焊和承插焊2种。用户可根据各自情况选购。

外螺纹单向阀

外螺纹单向阀是一种安装于管路系统中，用于防止介质（如液体、气体）倒流的自动阀门。其核心特点是阀体两端带有外螺纹，便于直接与内螺纹管件或接口连接，安装简便，密封性好。

该阀门内部通常包含一个阀瓣（如球体、锥体或碟片）和弹簧。当介质从进口端（入口）流入时，压力克服弹簧力及阀瓣自重，顶开阀瓣，形成通路。当介质停止流动或流向反向时，弹簧力和介质反向压力迅速将阀瓣压回阀座，关闭通道，从而有效阻止介质倒流，保护上游设备。

外螺纹单向阀因其结构紧凑、启闭迅速、维护简单等特点，被广泛应用于液压系统、气动系统、给排水、石油化工、暖通空调等诸多工业领域。

外螺纹单向阀主要特点：

外螺纹连接： 安装便捷，结构紧凑，占用空间小。

单向止回： 仅允许介质单向流动，有效防止逆流。

自动操作： 依靠介质自身压力及弹簧力自动启闭，无需外部控制。

低流阻： 设计流畅，对系统压力损失影响小。

多种材质： 可根据介质特性选择黄铜、不锈钢、碳钢等材质。

Product Name: External Thread Check Valve ( Male Thread Check Valve)

Product Overview:

An External Thread Check Valve is an automatic valve installed in pipeline systems to prevent the backflow of media (such as liquids  gases). Its key feature is the external (male) threads on both ends of the valve body, allowing for direct  easy connection to internal (female) threaded pipes  fittings, ensuring simple installation  reliable sealing.

The valve typically contains a disc (e.g., a ball, cone,  poppet)  a spring inside. When media flows in  the inlet side, its pressure overcomes the spring force  the weight of the disc, pushing the disc open to create a flow path. When the flow stops  reverses, the spring force  the reverse media pressure promptly push the disc back onto the seat, closing the passage  effectively preventing backflow, thereby protecting upstream equipment.

Due to their compact design, quick response,  simple maintenance, External Thread Check Valves are widely used in various industrial fields including hydraulic systems, pneumatic systems, water supply  drainage, petroleum  chemical industries,  HVAC systems.

Key Features:

External Thread Connection: Easy installation, compact structure,  small space requirement.

One-Way Check Function: Allows media flow in one direction only, effectively preventing reverse flow.

Automatic Operation: Opens  closes automatically based on media pressure  spring force, requiring no external control.

Low Flow Resistance: Streamlined design minimizes pressure drop in the system.

Variety of Materials: Available in materials like brass, stainless steel,  carbon steel to suit different media properties.