What type of valve is primarily used to control liquid flow in pipes?

A ball valve is primarily used to control liquid flow in pipes due to its design and functionality. It features a spherical disc, or ball, that is rotated within the valve body to either allow or restrict flow. When the ball's hole is aligned with the pipe, fluid can flow freely; when it is turned perpendicular to the flow, the valve is closed, stopping the flow. This mechanism provides a tight seal and allows for quick operation, making the ball valve a preferred choice for applications requiring reliable and efficient fluid control.

Ball valves are particularly advantageous because they can handle high pressure and maintain good flow characteristics. Their simple quarter-turn operation makes them easy to use, and they are often used in various settings, including residential, commercial, and industrial environments. This versatility and effectiveness in controlling flow make the ball valve the correct answer for the type of valve primarily used for this purpose.