Valve bellowsThe structure is simple, and the manufacturing and maintenance are relatively convenient. Small working stroke, short switching time. Good sealing performance, low friction on the sealing surface and long service life. The valve bellows has high fluid resistance and the force required to open and close is large. It is not suitable for medium with particles, high viscosity and easy coking. Poor regulation performance. According to the position of the valve stem thread, the type of valve bellows is divided into external thread type and internal thread type. According to the flow direction of the medium, there are straight-through type, DC type and angle type. According to the sealing form, the globe valve is divided into packing seal globe valve and bellows seal globe valve.

The installation and maintenance of the valve bellows should pay attention to the following matters: Handwheel and handle operated shut-off valve can be installed in any position of the pipeline. Do not use handwheels, handles and lifting mechanisms for lifting. The flow direction of the medium should be consistent with the direction of the arrow shown on the valve body. Metal bellows valve: Metal bellows can eliminate the impact of back pressure fluctuations on the performance of the gate valve, and can also protect the main components such as torsion springs from medium erosion. Can effectively prevent material leakage. The installation method, relative height and import and export trade direction shall conform to the design points, and the connection shall be firm and tight.

The handle of various manual valves installed in the directly buried insulation pipe shall not be downward. Valves must be visually inspected prior to installation and gate valve nameplates shall comply with current standards. Gate valves with working pressure greater than 1.0MPa and disconnected from the main pipe shall be subjected to strength sealing test before construction, and can be used only after passing the test. During the compressive strength test, the test working pressure shall be 1.5 times of the nominal diameter, and the duration shall not be less than 5min. The gate valve housing and packing shall be qualified without leakage. The type of valve bellows is divided into pipe thread type and thread type according to the position of valve seat thread. According to the medium inflow amount, there are a direct connection type, a direct current type and an angle type. According to the sealing form of the globe valve, there are rotary seal globe valve and bellows seal globe valve. Valve bellows installation and maintenance should pay attention to the following:

Handwheel and handle operated shut-off valves can be installed in all parts of the pipeline. Handwheels, handles and small actuators cannot be used for lifting. The inflow of medium shall be consistent with the arrow indication on the oil circuit plate. The installation position, height and import and export direction must meet the design requirements, and the connection is firm and tight.

The handle of various manual valves installed on the insulation pipeline shall not be downward. The valve must be visually inspected before installation, and the valve nameplate should comply with the current national standard "General Valve Mark" GB 12220. For valves with working pressure greater than 1.0MPa and cut-off function on the main pipe, strength and tightness tests shall be carried out before installation, and they can be used only after they are qualified. During the strength test, the test pressure shall be 1.5 times of the nominal pressure, and the duration shall not be less than 5min. The valve housing and packing shall be leak-free and acceptable. During the sealing test, the test pressure shall be 1.1 times of the nominal pressure. During the test, the test pressure shall meet the requirements of GB 50243 standard, and the valve disc sealing surface shall be qualified without leakage.