Ball Valve - How They Work
A ball valve is a shut off valve that controls the flow of a liquid or gas by means of a rotary ball having a bore. By rotating the ball a quarter turn (90 degrees) around its axis, the medium can flow through or is blocked. They are characterized by a long service life and provide a reliable sealing over the life span, even when the valve is not in use for a long time. As a result, they are more popular as a shut off valve then for example the gate valve. For a complete comparison, read our gate valve vs ball valve article. Moreover, they are more resistant against contaminated media than most other types of valves. In special versions, ball valves are also used as a control valve. This application is less common due to the relatively limited accuracy of controlling the flow rate in comparison with other types of control valves. However, the valve also offers some advantages here. For example, it still ensures a reliable sealing, even in the case of dirty media. Figure 1 shows a sectional view of a ball valve.
Standard floating ball valves consist of the housing, seats, ball and lever for ball rotation. They include valves with two, three and four ports which can be female or male threaded or a combination of those. Threaded valves are most common and come in many varieties: with approvals for specific media or applications, mini ball valves, angled ball valves, ISO-top ball valves, with an integrated strainer or a bleed point and the list goes on. They have a wide range of options and a large operating range for pressure and temperature.
For more information on a threaded connection, read our trunnion ball valve connection types article.
Hydraulic
Hydraulic ball valves are specially designed for hydraulic and heating systems due to their high operating pressure rating and hydraulic and heating oil resistance. These valves are made of either steel or stainless steel. Besides these materials, the seats also make hydraulic valves suitable for high operating pressure. The seats of these valves are made of polyoxymethylene (POM), which is suitable for high pressure and low temperature applications. The maximum operating pressure of hydraulic ball valves goes above 500 bar while the maximum temperature goes up to 80°C.
Flanged
Flanged ball valves are characterized by their connection type. The ports are connected to a piping system via flanges that are usually designed in accordance with a certain standard. These valves provide a high flow rate since they typically have a full-bore design. When choosing a flanged ball valve, besides the pressure rating, you also have to check the flange compression class which indicates the highest pressure this connection type can withstand. These ball valves are designed with two, three or four ports, they can be approved for specific media, have an ISO-top and everything else a standard quarter turn valve could have. They are typically made out of stainless steel, steel, or cast iron.