The opening and closing part of the bellows gate valve is a plug-shaped valve disc, the sealing surface is flat or conical, and the valve disc moves linearly along the center line of the fluid.  The movement form of the valve stem has a lifting rod type (the valve stem is raised and lowered, the hand wheel does not rise), and there is a lifting rotating rod type (the hand wheel and the valve stem rotate and rise together, and the nut is set on the valve body).  The corrugated pipe shut-off valve is only suitable for fully open and fully closed, adjustment and throttling are not allowed.  This type of valve should generally be installed horizontally in the pipeline.  What are the specific functions of the internal bellows of the bellows gate valve? 　　 Bellows safety valve: The bellows can eliminate the influence of back pressure fluctuations on the valve performance, and can also protect the spring and other internal parts from corrosion by the medium.  And can effectively prevent the leakage of the medium.

    　　 Bellows globe valve: The bellows and the valve packing form a double seal to prevent the medium from leaking. It is mostly used for toxic media.

    　　 Bellows trap: The bellows is made into a heat-sensitive element to control the valve to drain and block gas.

    Key points of construction and installation of bellows gate valve 　　 1) The installation position, height, and direction of inlet and outlet must meet the design requirements, and the connection should be firm and tight.

    　　2). All kinds of manual valves installed on the thermal insulation pipeline must not handle downwards.

    　　3). The valve must be visually inspected before installation. The nameplate of the valve should comply with the current national standard "General Valve Marking" GB 12220.  For valves with a working pressure greater than 1.0 MPa and a cut-off effect on the main pipe, the strength and tightness performance test should be carried out before installation, and the valve can be used only after it is qualified.  During the strength test, the test pressure is 1.5 times the nominal pressure, and the duration is not less than 5 min. The valve housing and packing should be qualified without leakage.  During the tightness test, the test pressure is 1.1 times the nominal pressure; the test pressure should meet the requirements of the GB 50243 standard during the test duration, and no leakage on the valve flap sealing surface is qualified.

    The advantages of bellows gate valve: 　　 1. Simple structure, convenient manufacturing and maintenance.

    　　2. Small working stroke and short opening and closing time.

    　　3. Good sealing, small friction between the sealing surfaces, and long life.

    The disadvantages of the bellows gate valve are as follows: 　　 1. The fluid resistance is large, and the force required for opening and closing is large.

    　　 2. It is not suitable for media with particles, high viscosity and easy to coke.

    　　 3. Poor adjustment performance.

    　　 Bellows gate valves are classified into external thread type and internal thread type according to the position of the stem thread.  According to the flow direction of the medium, there are straight-through type, direct-flow type and angle type.  The stop valve is divided into sealing form, there are packing seal stop valve and bellows seal stop valve.

    The installation and maintenance of the bellows gate valve should pay attention to the following items: 　　 1. The handwheel and handle operated stop valve can be installed at any position of the pipeline.

    　　 2. Handwheels, handles and dynamic mechanisms are not allowed for lifting.

    　　3. The flow direction of the medium should be consistent with the arrow direction shown on the valve body.