Do you know the working principle of the bellows stop valve?
Release date:
2021-02-03
Do you know the working principle of the bellows globe valve?
Bellows globe valve uses the lift of the valve stem to drive the valve head, thereby changing the distance between the valve disc and the valve seat to achieve opening and closing control. Bellows globe valves are the most widely used globe valves in chemical production. Globe valves are mainly used for controlling pipelines of water, steam, compressed air, etc., in actual production, but are not suitable for high-viscosity or easily crystallizing materials.
The structure of the bellows globe valve is relatively complex, but the actual operation is simple and labor-saving. It has good performance in regulating flow and cutting off the passage. The opening and closing speed is very slow, and water hammer is rarely seen. The globe valve has a compact structure and a distinct appearance. The top of the valve is equipped with a handwheel and valve stem, and the middle part has threads and a packing seal section.
During the use of the bellows globe valve, the main method to judge the valve's open and closed status is to observe the height of the valve stem exposed from the valve cover to control the valve operation. There may be gaps at the connection between the valve stem and the valve bonnet, which can easily cause medium leakage. This can be solved by packing seals. The valve stem threads of small globe valves are set inside the valve body, so they are in contact with the medium for a long time during use and are easily corroded by the medium.
Therefore, to prevent the short service life of globe valves, bellows globe valve manufacturers believe that the installation of globe valves should refer to the direction of fluid flow and pay attention to maintaining low inlet and outlet positions of the pipeline, that is, the fluid flows from bottom to top through the valve seat port. The purpose of this installation is to reduce fluid resistance inside the valve body, thereby reducing the force required to open and close the valve. At the same time, when the valve is closed, it can prevent the valve stem and packing from contacting the medium, thus reducing damage and leakage.
The opening and closing part of the bellows globe valve is a cylindrical valve disc, with a sealing surface that is flat or conical, and the valve disc moves linearly along the centerline of the fluid. The movement forms of the valve stem include the rising stem type (the valve stem rises and lowers, but the handwheel does not rise), and the rotating stem type (the handwheel and valve stem rotate and rise together, with the nut fixed on the valve body). Bellows globe valves are only suitable for fully open and fully closed positions, and allow adjustment and throttling when customized.
When the valve is closing or opening, when the opening height of the valve disc reaches 25% to 30% of the nominal diameter, the flow has reached its maximum value, indicating that the valve has reached the fully open position. Therefore, the fully open position of the bellows globe valve should be determined by the stroke of the valve disc.
More information
Contact Us
Email: mj@jsmjfy.com
Address: No.288,Huanghai RD,Haian City, Jiangsu Province,China
Mobile Website