A rotary union is a mechanical device that allows the transfer of fluids or gases between stationary and rotating parts of a machine. It typically consists of a rotating component and a stationary component, enabling the flow of substances while minimizing wear and tear. Rotary unions are commonly used in applications such as industrial machinery, robotics, and aerospace. These devices are essential in systems where continuous rotation is required, such as in turbines or printing presses. By providing a reliable connection, rotary unions help maintain efficiency and prevent leaks, ensuring smooth operation in various engineering applications.