What is the definition for grinding valves?

Grinding valves are a type of valve that use a rotating disc or wheel to control the flow of a fluid. The disc or wheel is positioned in the flow path and can be rotated to open or close the valve. The grinding action of the disc or wheel against the seat creates a tight seal, preventing any leakage of fluid. Grinding valves are often used in high-pressure applications where a tight seal is required.