A ball valve is a metal sphere inside of a pipe and it has a hole through the middle of it. It is attached to a handle outside the pipe. The actual ball part is chrome-plated, though the body it sits in can be made of metal, plastic or ceramic. And it typically comes in two sizes: the 14-inch model and the12-inch model.
The body of the valve could be assembled from typical two or three main parts sealed and bolted together, or alternatively welded together to increase the safety, especially used in the pipeline industry. There are a lot of different designs; however the basic principle is the same for all of them.
It consists of a highly polished ball place within the body of the valve. The ball is either floating or trunnion mounted. A floating ball has only one support from the top of the ball, and it is free to move against the downstream seat while the pressure is rising. The higher pressure the tighter valve is the basic principle with floating ball. A new floating ball valve will seal off both on the upstream and downstream seat. On a trunnion, the ball has support on both top and bottom, and the ball will not move under pressure. And a trunnion valve has springs pushing the seats against the ball both up and downstream.