The opening and closing part of the bellow seal gate valve is a plug-shaped disc, the sealing surface is flat or conical, and the disc moves in a straight line along the center line of the fluid. The movement forms of the valve rod include lifting rod type (the valve rod is lifted and the handwheel is not lifted), and lifting rotating rod type (the handwheel rotates and lifts with the valve rod, and the nut is set on the valve body). Corrugated tube stop valve is only applicable to full opening and full closing, and regulation and throttling are not allowed. This type of valve shall be installed horizontally in the pipeline.
Bellows gate valve is a forced sealing valve, so when the valve is closed, pressure must be applied to the valve disc to force the sealing surface not to leak. When the medium enters the valve body from below the valve disc, the resistance to be overcome by the operating force is the friction force between the valve rod and the packing and the thrust generated by the pressure of the medium. The force to close the valve is greater than the force to open the valve, so the diameter of the valve rod should be larger, otherwise the valve rod jacking failure will occur. In recent years, after the emergence of self sealing valve, the medium flow direction of stop valve changes from above the valve disc to enter the valve cavity. At this time, under the action of medium pressure, the force to close the valve is small, while the force to open the valve is large, and the diameter of valve rod can be reduced accordingly. At the same time, under the action of medium, this form of valve is also more tight. The “three modernizations” of valves in China once stipulated that the flow direction of stop valves should be from top to bottom. When the bellow seal gate valve is opened, when the opening height of the valve disc is 25% ~ 30% of the nominal diameter, the flow has reached the maximum, indicating that the valve has reached the fully open position. Therefore, the full open position of the stop valve shall be determined by the stroke of the valve disc. The electric gate valve is sensitive, safe and reliable. Many factories with high control requirements set up compressed air stations for pneumatic instrument control elements. Electric means electricity. And can control its flow.
Types of bellow seal gate valves
The types of bellow seal 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. The stop valve is divided into packing seal stop valve and bellows seal stop valve according to the sealing form.
Advantages and disadvantages of bellow seal gate valve
Advantages of bellow seal gate valve
The utility model has the advantages of simple structure and convenient manufacture and maintenance.
Small working stroke and short opening and closing time.
Good sealing performance, small friction between sealing surfaces and long service life.
Disadvantages of bellow seal gate valve
The fluid resistance is large, and the force required for opening and closing is large.
It is not suitable for media with particles, high viscosity and easy coking.
Poor regulation performance.
Installation points of bellow seal 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. Visual inspection must be carried out before valve installation, and the nameplate of the valve shall comply with the provisions of the current national standard general valve marks (GB 12220). For the valves with working pressure greater than 1.0 MPa and cut-off effect on the main pipe, the strength and tightness test 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 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 is qualified if there is no leakage on the sealing surface of the valve disc.
The installation and maintenance of bellow seal gate valve shall pay attention to the following matters:
1. Hand wheel and handle operated stop valve can be installed at any position of the pipeline.
2. Handwheel, handle and servo mechanism are not allowed to be used for lifting.
3. The flow direction of medium shall be consistent with the arrow direction shown on the valve body.
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