That depends on where it is used! No one knows how many kinds of valves. If you have water, you can use gas, food, and so on.
Valve difference, or you should ask the classification of valves, valve classification, there are several sub methods, some according to the model, and some are by use, then each kind of valve is divided into several categories and models. Take the trap for example, it is a kind of valve, and then it is divided into steam traps, air traps, float traps, and so on. If you really want to know the difference between the valve you search the Internet under the classification of the valve, there are a lot of articles, or you directly to the trap inside www.ssfmsh find an article on the valve type article, can not give you a specific address, is not allowed here. You work hard, go find kazakhstan. I hope my answer will be helpful to you.
