The ball valve defined in 2.GB/T21465-2008 "Valve Terminology" is a valve whose opening and closing parts (spheres) are driven by the valve stem and rotate around the axis of the ball valve. It can also be used for fluid regulation and control. The V-shaped ball valve with hard seal has a strong shear force between its V-shaped ball core and the metal valve seat of hard-faced cemented carbide, which is especially suitable for media containing fibers and tiny solid particles. The multi-way ball valve can not only flexibly control the confluence, diversion and flow direction switching of the medium in the pipeline, but also close any channel and connect the other two channels. Generally, this valve should be installed horizontally in the pipeline. Ball valves are divided into pneumatic ball valves, electric ball valves and manual ball valves according to the driving mode.
3. Cut-off valve, also known as cut-off valve, is a forced sealing valve, so when the valve is closed, pressure must be applied to the disc to force the sealing surface not to leak. When the medium enters the valve from below the 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 medium pressure. The force to close the valve is greater than the force to open the valve, so the diameter of the valve stem should be larger, otherwise the valve stem will bend.