A paper rotary joints or rotary union (also called rotary couplings, rotary swivels) is a tool designed to direct liquid and gases from one point to another, under very high pressure. It provides a mechanical seal between a supply pipe to rotating cylinder or drum. Paper rotary joints are used in several manufacturing processes to heat, cool, or transfer liquid (pneumatic or hydraulic) power. Rotary unions are used in a wide range of equipment; from small rotary unions for semiconductor industry, to large rotary unions for industrial applications.
Rotary unions come in numerous shapes and sizes. Some are designed so that the material passes directly through the rotary union on a single port, while others are designed for multiple ports. Many rotary unions come in custom designs. There are four basic components of rotary union: Mechanical seal, bearing, shaft and housing.