Key points of construction and installation of bellows gate valve

1) The installation position, height, inlet and outlet direction must meet the design requirements, and the connection shall be firm and tight.

2) The handle of various manual valves installed on the insulation pipeline shall not be downward.

3) The valve must be visually inspected before installation, and the nameplate of the valve shall comply with the provisions of the current GB standard general valve markings GB 12220. For the valves with working pressure greater than 1.0 MPa and the function of cutting off on the main pipe, strength and tightness tests shall be conducted 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 shell and packing shall be qualified if there is no leakage. During the tightness test, the test pressure shall be 1.1 times of the nominal pressure; The test pressure shall meet the requirements of GB 50243 during the test duration, and it shall be deemed as qualified if there is no leakage on the sealing surface of the valve disc.

Advantages of bellows gate valve:

1. The utility model has simple structure and convenient manufacture and maintenance.

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

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

The disadvantages of bellows gate valves 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 medium with particles, high viscosity and easy coking.

3. Poor regulation performance.

The types of bellows gate valves are divided into external thread type and internal thread type according to the position of valve stem thread. According to the flow direction of the medium, there are straight through type, DC type and angle type. Stop valves are divided into packing seal stop valves and bellows seal stop valves according to sealing forms.