Bellows globe valves are generally used to fully open or fully close, while welded
gate valves, bellows gate valves and bellows globe valves are all sealed valves. So when they are closing in operation, we need to add pressure to the valve disc so that its sealing surface will not leak. When the medium enters valve six from below the valve disc, the resistance that the operating force needs to overcome is the friction force between the valve stem 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 valve The diameter of the stem should be large, otherwise the failure of the top of the valve stem will occur. In recent years, since the emergence of self-sealing valves, the medium flow direction of the globe valve has been changed from the top of the valve disc into the valve cavity. At this time, under the action of the medium pressure, the force to close the valve is small, while the force to open the valve is large, and the valve stem's force is small. The diameter can be reduced accordingly. At the same time, under the action of the medium, this form of valve is also tighter. my country's valve 'Three Chemicals' once stipulated that the flow direction of the globe valve should be from top to bottom. When the welded gate valve is opened, when the opening height of the valve disc is 25% to 30% of the nominal diameter, the flow rate has reached the maximum, indicating that the valve has reached the fully open position. Therefore, the fully open position of the globe valve should be determined by the stroke of the valve disc. The types of welded gate valves are divided into external thread type and internal thread type according to the position of the valve stem thread. According to the flow direction of the medium, there are straight-through type, direct-current type and angle type. Globe valve is divided into sealing form, there are packing bellows gate valve and bellows sealing globe valve. The installation and maintenance of the welded gate valve should pay attention to the following matters: The bellows globe valve operated by handwheel and handle can be installed in any position of the pipeline. The handwheel, handle and Weidong mechanism are not allowed to be used for lifting. The flow direction of the medium should be consistent with the direction of the arrow shown on the valve body. Welded gate valve, also known as cut gate, is the most widely used valve. The reason why it is popular is that the friction between the sealing surfaces is small during the opening and closing process, it is more durable, the opening height is not large, it is easy to manufacture, and it is easy to maintain. Convenient, not only for medium and low pressure, but also for high pressure. Its closing principle is that relying on the pressure of the valve stem, the sealing surface of the valve disc and the sealing surface of the valve seat are closely fitted to prevent the flow of the medium. Welded gate valves only allow the medium to flow in one direction, and have directionality during installation. Its structural length is longer than that of the gate valve, and at the same time, the fluid resistance is large, and the sealing reliability is not strong during long-term operation. Welded gate valves are divided into three categories: straight-through, right-angle and direct-current inclined globe valves. When the welded gate valve is opened, when the opening height of the valve disc is 25% to 30% of the nominal diameter, the flow rate has reached the maximum, indicating that the valve has reached the fully open position. Therefore, the fully open position of the globe valve should be determined by the stroke of the valve disc. Welded gate valve has the following advantages: 1. Simple structure, convenient to manufacture and maintain. 2. The working stroke is small and the opening and closing time is short. 3. Good sealing performance, small friction between sealing surfaces and long service life. The disadvantages of welded gate valves are as follows: 1. 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. 3. Poor adjustment performance. The above is the editor's description of the welding gate valve. I hope that what you need can help you understand the welding gate valve faster and more conveniently. Lianke Valve Co.,Ltd. is committed to valve innovation, creating more appropriate, more suitable and more comprehensive valves for everyone, which can be better applied in all aspects.
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