How to distinguish between various piece ball valves?
Distinguish from the structure.

One-piece ball valve is inside the ball, PTFE ring, lock nut composition, the ball slightly smaller diameter than the pipe diameter, similar to the Cantonese-style ball.
Two-piece ball valve is composed of two parts; the seal is better than a ball valve, ball diameter and pipe the same diameter, than a ball valve for easy disconnection.
Three-piece ball valve is composed of three parts; the middle of both sides of the valve cover and valve body, three-piece ball valve is different from the two-piece ball valve ball valve and where is the demolition of maintenance.

     Distinguish from the pressure
Three-piece pressure is much higher than the one-and two ball valves. Outside the main three-piece ball valve fixed by four bolts, fastening to play a good role. Casting pressure valve can be reached 1000psi