原文：
止回阀又称单向阀或逆止阀，其作用是防止管路中的介质倒流。水泵吸水的底阀也属于止回阀类。 启闭件靠介质流动和力量自行开启或关闭，以防止介质倒流的阀门叫止回阀。止回阀属于自动阀类，主要用于介质单向流动的管道上，只允许介质向一个方向流动，以防止发生事故。 一、止回阀的选用： 1、止回阀一般适用于清净介质，v不宜用于含有固体颗粒和粘度较大的介质。 2、对于DN50mm以下的低压止回阀，宜选用蝶式止回阀、立式升降止回阀和隔膜式止回阀；对于DN大于200mm、小于1200mm的中低压止回阀， 宜选用无磨损球形上回阀；对于DN大于50mm、小于2000mm的低压止回阀，宜选用蝶式止回阀和隔膜式止回阀。 3、隔膜式止回阀适用于易产生水的管路上，隔膜可以很好地xx介质逆流时产生的水，但受温度和压力限制，一般使用在低压常温管道上 4、对于要求关闭时水冲击比较小或无水的管路， 宜选用缓闭旋启式止回阀和缓闭蝶式止回阀。 二、止回阀的施工、安装 1、安装位置、高度、进出口方向必须符合设计要求，注意介质流动的方向应与阀体所标箭头方向一致，连接应牢固紧密 2、阀门安装前必须进行外观检查，阀门的铭牌应符合现行国家标准《通用阀门标志》GB 12220的规定。对于工作压力大于1.0 MPa及在主干管上起到切断作用的阀门，安装前应进行强度和严密性能试验，合格后方准使用。强度试验时，试验压力为公称压力的1.5倍，持续时间不少于5min，阀门壳体、填料应无渗漏为合格。严密性试验时，试验压力为公称压力的1.1倍；试验持续的时间符合GB 50243的要求。 3、在管线中不要使止回阀承受重量，大型的止回阀应独立支撑，使之不受管系产生的压力的影响。 三、止回阀的安装注意事顶： 1、在管线中不要使止回阀承受重量，大型的止回阀应独立支撑，使之不受管系产生的压力的影响。 2、安装时注意介质流动的方向应与阀体所票箭头方向一致。 3、升降式垂直瓣止回阀应安装在垂直管道上。 4、升降式水平瓣止回阀应安装在水平管道上。

“Valve Selection and Installation ”是由提供的阀门新闻，译文仅供参考。另外，中国止回阀网还提供相关产品搜索： 、 、 、 、 等。

译文：
Called one-way valve or check valve, check valve, its role is to prevent the line of medium back. The bottom valve pump water valve category also belong. Opening and closing pieces by medium flow and the forces to open or close the valve to prevent the media called back check valve. Check valves are automatic valves, mainly for one-way flow of media channels, only allowing media to flow in one direction, to prevent accidents. 1, valve selection: 1, check valve generally applicable to pure media, not for containing the solid particles and the medium viscosity. 2, low pressure valve for DN50mm below, should use butterfly valve, check valve and diaphragm vertical lift check valve; for DN larger than 200mm, less than 1200mm in the low pressure check valve should be chosen No wear on the back ball valve; for DN larger than 50mm, less than 2000mm of low pressure check valve, butterfly valve and the diaphragm should use check valves. 3, diaphragm check valves for water pipe in the road is easy to produce, could be eliminated medium diaphragm generated when the water upstream, but limited by the temperature and pressure, generally used in low temperature pipe 4, for required off the impact of small water or water pipeline, should use slow gentle swing check valve closed closed butterfly valve. Second, check the construction, installation 1, the installation location, height, must meet the design requirements of the import and export orientation, attention to the direction of media flow valve should be the same as the arrow direction, the connection should firmly close 2, the valve must be installed prior to visual inspection, the valve plate should be consistent with existing national standards, "Universal Valve logo" GB 12220 requirements. The working pressure greater than 1.0 MPa and in the main pipe on the role played off valve, the installation should be carried out before the performance test the strength and tight, qualified prospective use of the rear. Strength test, the test pressure for the nominal pressure of 1.5 times the duration of no less than 5min, the valve housing, packing should be no leakage in compliance. Tightness test, the test pressure for the nominal pressure of 1.1 times; test duration consistent with the requirements of GB 50243. 3 Do not check valve in the pipeline to withstand the weight of a large check valve should be independent of support, so that the pressure piping system from the impact. Third, the top valve installation for attention: 1 Do not check valve in the pipeline to withstand the weight of a large check valve should be independent of support, so that the pressure piping system from the impact. 2, installation, pay attention to the direction of media flow valve by the votes should be consistent with the direction the arrow. 3, vertical valve lift check valve should be installed in the vertical pipe. 4, the level of valve lift check valve should be installed in horizontal pipelines.