A Swivel Joint (also called a rotary union, rotating joint, rotary coupling, or rotary union) allows fluid (liquid, gas, or other media) to flow from a stationary supply line to a rotating component, while preserving a sealed connection. Internally it comprises a housing (stationary), a rotor or sleeve (rotating), bearings to permit smooth rotation under load, and seals to prevent leakage of the fluid being transferred under pressure. Some designs support a single flow passage; more advanced ones permit multiple independent flow paths (e.g. for different fluids, or fluid + hydraulic + electrical + pneumatic) through a single rotating joint.
