What's the difference between needle valve and ball valve

Needle valve is a kind of throttling valve, with higher regulation precision. The valve is needle-shaped, along the water flow direction action, change the cross-flow area, used to cut off or adjust the flow of the valve. Needle valve is a kind of fine-tuning valve, its valve plug is needle-shaped, mainly used as a regulator of gas flow. Fine-tuning valve requires the valve opening gradually become larger, from closed to open can be continuously fine-tuning.

Needle valve plug is generally hardened steel needle, and the valve seat is made of tin, copper and other soft materials. Valve needle and the valve seat ask the seal is to rely on its taper surface close fit to achieve. Needle taper 1:50 and 60 cone angle of two kinds, cone surface to be fine grinding. Valve stem and valve seat seal is realized by bellows.

Ball valve: it is evolved from plug valve. It has the same rotary 90 ° action, the difference is that the plug body is a sphere, there is a circular through hole or channel through its axis. The ratio of the sphere to the passage opening should be such that when the ball is rotated 90°, it should all present a spherical surface at the inlet and outlet, thus intercepting the fluid flow.

Needle valves can adjust the size of the flow, ball valves can not regulate the flow; needle valves fully open the handle needs to be twisted a few turns, while the ball valve only need to turn 90 °. In the appearance of the difference is more obvious, needle valve has a hand wheel, ball valve has a handle. In the liquid, pneumatic control pipeline if you want to regulate the flow of needle valves, if the rapid cut-off flow of ball valves.