The ball valves are essentially constituted by a ball provided with a cylindrical bore and rotating in the valve body.
The seal is effected between the outer surface of the sphere and two sealing ring mounted on the valve body in correspondence of the holes of the entry and exit of the sphere. The gaskets can be of different materials, but currently it is imposed almost universally the PTFE (Teflon) or PTFE reinforced with glass fibers.
As there is no metal contact between the ball and the body, the valve has a virtually unlimited duration, requiring the maximum, replace the seals. Thanks to the minimum friction coefficient in the contact between the PTFE and the polished metal surface of the sphere, is obtained the double advantage of very small wear of the seals and consequent long duration of the same and of the extremely small torque maneuver.
The ball is driven instead carried by a shaft mounted on bearings generally PTFE. As the thrust of the fluid on the sphere is discharged ui shaft bearings, the maneuver is even sweeter than for ball valves scillante. The sealing is due both to a slight forcing between initial ball and seals ia the effect of the fluid pressure differential on an area of the seals themselves.
In reference to how to mount the ball in the valve body, stand types "end entry" and "top entry ". The valves "end entry" have the body formed by at least two parts, connected by threads or flanges, for the insertion of the sphere.
In the valves with the body formed by parties related threads, you can not go to the ball and seals without removing the valve from the pipeline.
The valves "top entry " have the body of a single piece, provided with a top cover, through which is mounted the ball. In this case access to the ball and to uarnizioni is possible through the cover, without removing the valve from the pipeline. Some valves "top entry " also have devices for the resumption of play between beast and gaskets.
The ball valves can be 2, 3 or 4-way and allow an operation of closing, opening or deviation very rapid. As each transaction is carried out only with a quarter turn of the lever, this provides an instant view of the position of the ball.
The ball valves, both in total taste is reduced bore, causing the flow losses negligible. The flow may be always bi-directional, except in some types of valve na seal only. The ball valves can be used as valves adjustable preload, provided it does not throttle the flow excessively, in which case the portion of uarnizione exposed to the fluid flow could be undermined by the seat. Thanks to the compact obstruction, the ball valves can often be installed where space be insufficient for other types of valves.
The maximum operating temperature is imitated by the characteristics of the material forming the gasket.