Plug valves and the ball valve are widely used and have similar functional characteristics, but there are still many differences between plug valves and the ball valve.
The ball valve is evolved from the plug valves, and the starting part of the ball valve is a sphere. Plug valves are mainly used to cut off, distribute and change the direction of medium flow.
The plug valves refer to the main part of the closing part plug valves are rotatable conical plug (plug) in the shape of a cone-shaped frustum, with a medium channel in it, have a rectangular cross-section, and a hole in the middle of the channel perpendicular to the axis of the plug. When the cock is rotated 90°, the fluid channel is completely closed. Plug valves are valves that use the conical plug with a hole to control the opening and closing. The conical cock is matched with the conical pressing surface formed on the inner surface of the valve body, and the upper part of the valve body is sealed with packing to seal the gap between the cock and the valve body. There is a square tenon on the top of the cock, and use a special square-hole wrench to turn the plug when in use. The valve is opened and closed by rotating at a certain angle. Types are straight-through cock, three-way cock and four-way cock, etc.
(1) Plug valves
The plug valves are characterized by simple structure, rapid opening and closing, and small resistance, but it is laborious to rotate, and it takes time to grind the plug during maintenance. The main difference between the plug valves and the ball valve is that the plug valves have better adjustment ability than the ball valve in terms of cutting off, but the advantage is not obvious. The sealing surface of the plug valves is much larger than that of the ball valve. The plug valves are closed or plunger-shaped rotary valve, which can be opened or closed by rotating 90 degrees to connect or separate the channel opening on the valve plug and the channel opening on the valve body.
Its valve plug can be cylindrical or conical in shape. In a cylindrical valve plug, the passage is generally rectangular. Whereas in a conical valve plug, the passage is trapezoidal. These shapes make the construction of the plug valves light, and are most suitable for shutting off and on the medium and for diverting. However, depending on the nature of the application and the erosion resistance of the sealing surface, it can sometimes be used for throttling.
(2) The ball valve
The opening and closing part (ball) of the ball valve is driven by the valve stem and rotates around the axis of the ball valve. It can also be used for fluid regulation and control, among which there is a strong shear force between the V-shaped ball core of the hard-sealed V-shaped ball valve and the metal valve seat of hard alloy surfacing, which is especially suitable for fibers and tiny solid particles. etc. medium. The multi-port ball valve on the pipeline can not only flexibly control the confluence, diversion, and switching of the flow direction of the medium, but also can close any channel and connect the other two channels. This type of valve should generally be installed horizontally in the pipeline. The ball valve is divided into pneumatic ball valve, electric ball valve, manual ball valve according to the driving method.
The sealing effect of the ball valve is slightly worse, but it can achieve a large diameter. With the improvement of technology, the sealing effect of the ball valve is getting better and better. Therefore, in general, plug valves are mostly used in occasions with strict sealing requirements, but the caliber is generally small. The ball valve is used in occasions where the sealing effect is not too strict and the caliber is required to be large.