05

2023

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01

Introduction to valve connection end structure form

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The valve end connection structure and size are very important for the installation and use of the valve. Improper selection may cause mismatch in size or connection structure during the installation process, resulting in failure to install. Therefore, when selecting valves, special attention should be paid to selecting the correct and appropriate connection end structure to ensure smooth installation of the valve.

The valve end connection structure and size are very important for the installation and use of the valve. Improper selection may cause mismatch in size or connection structure during the installation process, resulting in failure to install. Therefore, when selecting valves, special attention should be paid to selecting the correct and appropriate connection end structure to ensure smooth installation of the valve.

    The connection forms of valve end faces are usually divided into three types; welded end connection , threaded end connection and flange end connection . Among them, flange end connection is the most commonly used structural form.

 

1. Flange connection structure

   It realizes connection with the help of flanges, gaskets and bolts. Flange-connected valves are very convenient to install and disassemble. It is suitable for a wide range of nominal diameters and pressures. The flange connected to the valve can be divided into flat welding flange, butt welding flange, socket welding flange, integrated flange, etc.; according to the sealing surface form, it can be divided into full plane flange, raised table flange, Concave and convex face flanges, grooved and grooved face flanges and ring and grooved face flanges. The selection of various flange structural forms and sealing surface forms depends on different operating conditions. Generally speaking, flat welding flanges are mostly used under relatively mild operating conditions due to their low structural strength and rigidity, such as low-pressure circulating water valves, general low-pressure compressed air valves, etc. Their advantages are low price and easy installation. convenient. The neck and tapered transition structure, strength and rigidity of the butt welding flange are relatively good, and it can be connected with the pipe for non-destructive testing, so it can be used in occasions with harsh working conditions, such as oil, gas and chemical media. Socket welding structure is commonly used in pipelines with PN≤10.0MPa and DN≤40. The sealing surface of the valve is also selected based on its operating conditions. The full-plane structure is often used with the flat welding structure. When the conditions are relatively mild, the boss surface is often used with the butt welding and socket welding structures, which are widely used. . The convex and concave surfaces are often used with butt welding and socket structures. The use of grooved and tenon surfaces is similar to that of convex and concave structures. The ring and groove surface structures are often used with butt welding structures.

 

2. Threaded connection

   Threaded connections are detachable connections and are often used in situations where welding is not suitable or disassembly is required. Threaded connections are divided into internal threaded connections and external threaded connections. For internal thread connections, the end of the valve body is usually processed into a tapered or straight female thread, and the pipe connected to it is processed into a tapered or straight male thread. External thread connection is a valve whose end of the valve body is processed into a male thread to facilitate the installation and removal of the threaded end. Compared with the welding connection method, the threaded connection of the valve has low strength and strong sealing. Therefore, when applied in petrochemical equipment, it is often restricted by the following conditions:

    Mostly used in pipelines with DN≤40;

    Threaded pipe fittings should use tapered pipe threads;

    Valves with threaded connections must not be used for the management of highly toxic media;

    Threaded connection valves are not recommended for use when the medium temperature is above 200°C and below -45°C;

    Threaded connection valves are not recommended for use in locations where stress corrosion, crevice corrosion, or variable loads may occur due to vibration, pressure pulsation, and temperature changes;

    When threaded connection valves are used on combustible gas pipelines, seal welding should be used for sealing.