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2025.02.15

The plastic ball valve and cock

A ball valve is a type of valve that controls the flow of fluid by rotating a ball. The opening and closing part of the ball valve is a ball with a circular through-hole, which is connected to the valve stem. When the handle or driving device (such as electric, pneumatic, hydraulic, etc.) rotates the valve stem, the ball will also rotate accordingly. After the ball rotates 90 degrees, it can change the shape of the channel in the valve body, thereby realizing the opening or closing of the valve.
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Classification
Ball valves can be divided into many types according to different classification standards:
  1. Classified by the movement mode of the ball in the valve body:
  1. Classified by the material combination of the ball and the valve seat sealing surface:
  1. Classified by the channel mode of the valve:
  1. Classified by driving mode:
  1. Classified by connection mode:
Advantages and Disadvantages
  • Advantages:
    • It has a small resistance to fluid, and its resistance coefficient is equal to that of a pipe section of the same length.
    • Simple structure, small size and light weight.
    • Reliable sealing. At present, plastic is widely used as the sealing surface material of ball valves, which has good sealing performance and has been widely used in vacuum systems.
    • Easy to operate. It can be opened and closed quickly. It only needs to rotate 90° from fully open to fully closed, which is convenient for remote control.
    • Easy to maintain. The ball valve has a simple structure, and the sealing ring is generally movable, so it is easy to disassemble and replace.
    • When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, so the medium will not cause erosion of the valve sealing surface when passing through.
  • Disadvantages:
    • For hard-sealed ball valves, the valve core is spray-welded with alloy steel, and the sealing ring is surfacing-welded with alloy steel. Therefore, there will be no too much wear when the hard-sealed ball valve is switched.
    • For soft-sealed ball valves, a spring is used at the bottom of the sealing ring to make the sealing ring tightly embrace the valve core. Therefore, it is very easy to switch when the external force exceeds the preload of the spring.