What is the role of sealing in ball valves?

Adjustment of the pre-stress (gap) between the ball and the seal after valve assembly. If such a regulating valve is not installed, leakage will occur.

It is used for sealing between the valve body and the valve cover, and its main function is to prevent external leakage!

Two-piece flanged ball valve: how to achieve sealing without using gaskets between the valve bodies

Two-piece flanged ball valve: how to achieve sealing without using gaskets between the valve bodies

Asking this question suggests a lack of basic mechanical knowledge...

I’ve disassembled many ball valves from different manufacturers, and none of them had this sealing ring

This post was last edited by wangsir85 on 2018-7-3 at 16:15. Here is a comprehensive explanation for you: 1. The one in the front is a floating ball; just by looking at the valve seat, it can be seen that the pressure exerted by this type of floating ball is generally not very high. The one at the back is a fixed ball, with an integrated fixed spherical structure. The sealing ring you are referring to is the one at the sealing area of the middle flange. 2. The two gaskets you mentioned are both metal wound gaskets, and they serve a sealing function. 3. For the first floating ball, there is only one type of seal, namely a metal wound gasket seal; there is no O-ring seal. The reason is that the pressure is low, so a single wound gasket is sufficient for sealing. 4. For the second fixed ball, in addition to sealing with a metal wound gasket, an O-ring is also used for sealing; that black ring is the O-ring, and it is mainly the O-ring that provides the sealing effect. 5. Another reason why metal wound gaskets are used for sealing is fire prevention – it relates to the design of fire-resistant structures.

Here’s the professional term for it: it’s called planar sealing.

I would like to ask how floating balls and fixed balls can be distinguished structurally. Thank you!