A brief introduction to bellows seal valves
Release date:
2020-12-10
A brief introduction to bellows seal valves
1. Overview
Bellows sealed valves are mainly used in harsh conditions involving flammable, explosive, and toxic environments. The valve stem is sealed through the dual function of packing and bellows, achieving zero leakage between the valve and the outside. Since the bellows can only withstand tensile and compressive forces, it is only suitable for valves where the stem moves linearly during opening and closing. Therefore, bellows valves are usually limited to globe valves or gate valves. To broaden the application of the bellows sealing principle, bellows sealed ball valves have been developed.
2. Structure
Bellows sealed valves mainly consist of the valve body, upper valve stem, valve stem, bellows, lower valve stem, and pins. A pair of helical guide grooves (with the same helical direction) are opened on the upper and lower valve stems. Two pins are fixed on the valve stem, and these pins can move freely within the track grooves of the upper and lower valve stems. The lower valve stem is connected to the ball to control the opening and closing of the valve.
3. Working Principle
When the upper valve stem rotates, the pins installed on the valve stem tend to rotate as well. However, since the lower and upper helical grooves on the valve stem have the same rotational direction and apply opposing forces, this hinders the rotational movement. According to the principle of force balance, the valve stem only moves up and down under the action of the helical grooves. Because the bellows sealed valve is welded to the valve stem, the lifting of the valve stem ensures the safety of the bellows.
4. Conclusion
The bellows sealed valve is a relatively novel structure that effectively solves the problem of bellows rotation during the sealing process of ball valves. It uses two helical grooves with the same rotational direction, causing the external force to be transmitted three times during the transmission process. The two helical grooves have the same rotational direction and are easy to machine. No special configuration is required during assembly, effectively meeting the modern valve requirements for convenient machining, simple assembly, reliable operation, and safe handling.
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