Rotary union

Rotary union

This image shows the components needed to make a rotary union; a shaft, housing, bearings, seals and retaining clip. The independent shaft and housing allow for continuous rotation of either component. This is an example of a two passage rotary union with independent channels that allow both liquids and gases to transfer simultaneously. ^[1]

A rotary union is a union that allows for rotation of the united parts. It is thus a device that provides a seal between a stationary supply passage (such as pipe or tubing) and a rotating part (such as a drum, cylinder, or spindle) to permit the flow of a fluid into and/or out of the rotating part. Fluids typically used with rotary joints and rotating unions include various heat transfer media and fluid power media such as steam, water, thermal oil, hydraulic fluid, and coolants. A rotary union is sometimes referred to as a rotating union, rotary valve, roto rseal, rotary couplings, rotary joint, rotating joints, hydraulic coupling, pneumatic rotary union, through bore rotary union, air rotary union, electrical rotary union, vacuum rotary union

Rotary Joint Function, Types and Uses.

 

Function

A rotary union will lock onto an input valve while rotating to meet an outlet. During this time the liquid and/or gas will flow into the rotary union from its source and will be held within the device during its movement. This liquid and/or gas will leave the union when the valve openings meet during rotation and more liquid and/or gas will flow into the union again for the next rotation. Often functioning under high pressure and constant movement a rotary union is designed to rotate around an axis. A rotary union’s design can be altered to change this or to increase the psi or rpm it needs to withstand as well as the number of valves required.

Types of Rotary Unions

Many rotary unions incorporate multiple ports, some of which are designed to handle different types of material simultaneously. A rotary union with a straight port transfers the substance directly through the rotary union. Other designs include an elbow port, which causes the material to flow out at an angle, and multiple ports. A multiple port rotary union looks like a perforated cylinder. At the end of the cylinder is a threaded screw with seals that locks on to the output. The material being transferred flows into the cylinder and out of the input holes. In the case of a rotary union with multiple inputs, chambers separated by seals keep the materials from inadvertently mixing. This type of rotary union is often used in the manufacture of plastics and other petroleum products, for which multiple inputs may need to be streamlined, but kept separate.

Uses

Many assembly lines incorporate multiple rotary unions, because they are highly versatile and take up less space than other devices designed for a similar purpose. Rotary unions also appear in automobiles and other machines that require constant supplies of lubrication, air, or other liquids in order for moving parts to run smoothly. Brakes, for example, use rotary unions to maintain a constant supply of pressurized brake fluid. Rotary unions are also heavily used in crude oil processing, the chemical industry, commercial food production, and pharmaceutical applications.