属于强制密封式阀门，所以在阀门关闭时，必须向阀瓣施加压力，以强制密封面不泄漏。 The national standard internal thread globe valve is a compulsory sealed valve, so when the valve is closed, pressure must be applied to the disc to force the sealing surface to not leak. 由于开闭过程中密封面之间摩擦力小，比较耐用，开启高度不大，制造容易，维修方便，不仅适用于中低压，而且适用于高压；一直广受欢迎。 The bellows globe valve has low friction between the sealing surfaces during opening and closing, is relatively durable, has a small opening height, is easy to manufacture, and is easy to maintain. It is not only suitable for low and medium pressure, but also for high pressure; it has been widely welcomed.
Second, the introduction of national standard internal thread globe valve
When the medium enters the valve from below the valve disc, the resistance to be overcome by the operating force is the friction 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. The diameter must be large, otherwise the valve top bending failure will occur.
属于强制密封式阀门，所以在阀门关闭时，必须向阀瓣施加压力，以强制密封面不泄漏。 Internally threaded globe valves are compulsory-sealed valves, so when the valve is closed, pressure must be applied to the disc to force the sealing surface to not leak. After the self-sealing valve appeared, the medium flow of the internal thread and flange cut-off valve changed from the upper part of the valve disc into the valve cavity. At this time, under the action of the medium pressure, the force to close the valve was small, and the force to open the valve was large. The diameter of the rod can be reduced accordingly. At the same time, this type of valve is also tight under the action of the medium. China's valve "three chemical supply" has stipulated that the flow direction of the shut-off valve will be used from top to bottom. This type of valve should generally be installed horizontally in the pipeline.
When the internal thread stop valve is opened, the opening height of the valve disc is 25% to 30% of the nominal diameter, and the flow has reached the maximum, indicating that the valve has reached the fully open position. Therefore, the fully open position of the shut-off valve should be determined by the stroke of the disc.
Advantages and disadvantages of national standard internal thread globe valve
The advantages of the GB internal thread globe valve are as follows:
1. Simple structure, easy to manufacture and maintain.
2. Small working stroke and short opening and closing time.
3. Good sealing performance, low friction between sealing surfaces and long life.
The disadvantages of the GB internal thread globe valve are as follows:
1. The fluid resistance is large, and the force required when opening and closing is large.
2. It is not suitable for media with particles, large viscosity and easy to coke.
3. Better regulation performance.
Types of internal thread stop valves are divided 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, direct-current and angular. The shut-off valve is divided into sealing forms, and it has a packing-sealed shut-off valve and a bellows-sealed shut-off valve.
Fourth, the national standard internal thread stop valve structure
The structural form of the internal thread cut-off valve body is straight-through, direct-current and right-angle. Straight-through is the most common structure, but its fluid resistance is greatest. DC fluids have low resistance and are mostly used for fluids with solid particles or high viscosity. Right-angle valve bodies are mostly forged and are suitable for globe valves with smaller passage and higher pressure.
Fifth, the operating principle of the national standard internal thread globe valve
1. When the handwheel is turned clockwise, the valve stem moves downward, and the valve flap is lowered to make the sealing surface close and cut off the passage. When it is reversed, it is opened, and the seal is effective at the highest point of the valve stem.
2. An upper seal is added to this valve. When the valve is open, it has a two-layer sealing effect with the packing and has a certain protective effect on the packing.
3. The valve adopts nylon products as the sealing surface, and the filler is a soft-shaped filler. The upper seal is also a soft material, which has a better sealing performance.
Performance Specifications of National Standard Internal Thread Globe Valves
Strength test pressure
Low pressure gas seal test pressure
High pressure seal test pressure
-16C J11W -16C
Water, oil, gas
200℃ ≤ 200 ℃
Material of main parts of national standard internal thread globe valve
-16C J11W -16C
8M 316. CF 8M
Eight, the main dimensions of the national standard internal thread globe valve
1 1/4 》