Views:3 Author:Site Editor Publish Time: 2019-05-21 Origin:Site
Ball valves are evolved from plug valves. It has the same 90° rotation action, except that the plug body is a sphere with a circular through hole or passage through its axis. The ratio of the spherical surface to the passage opening should be such that when the ball is rotated by 90°, all of the spherical surfaces should be present at the inlet and outlet to intercept the fluid flow.
The needle valve is a type of throttle valve with high adjustment accuracy. The valve is needle-shaped, moves in the direction of water flow, changes the flow area, and is used to cut or adjust the flow of the valve.
The needle valve is a trim valve with a needle plug that is primarily used to regulate air flow. The trim valve requires that the valve opening be gradually enlarged, and the maximum fine adjustment can be continuously performed from the closing to the opening.
The needle valve plug is generally made of a hardened steel long needle, and the valve seat is made of a soft material such as tin or copper. The sealing of the valve needle and the valve seat is achieved by the close fitting of the tapered surface.
The valve needle has a taper of 1:50 and 60 taper angles, and the surface of the cone is finely ground. The sealing between the valve stem and the valve seat is realized by the bellows.
The needle valve can adjust the flow rate, the ball valve can not adjust the flow; the needle valve needs to be screwed a few times when the needle valve is fully opened, and the ball valve only needs to turn 90°.
The difference in appearance is more obvious. The needle valve has a hand wheel and the ball valve has a handle.
If the flow rate is to be adjusted on the liquid and air pressure control pipes, the needle valve is selected. If the flow rate is quickly cut off, the ball valve is selected.