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What is a Rotary Union

Author: Yunus Shaikh
by Yunus Shaikh
Posted: Feb 24, 2022

A rotary union allows fluids to be transferred from a stationary supply passage to a rotating part by creating a seal. Depending on the industry and the application, it goes by a variety of names. Swivel joints, rotary couplings, fluid swivels, rotary manifolds, etc. are representative of these components. However, the purpose of a rotary union remains the same: delivering media from a stationary input to a rotating part.

The design of a Rotary Union Supplier in India will take into account the media to be transferred, rotational speed, pressure and temperature, and a number of flow paths. The basic components are:

Housing: It holds all the other components of the rotary union together. There is an inlet port to which the fluid supply line is connected.

Shaft: The medium passes through the device and into the rotating part.

Bearings: The shaft can rotate with the help of these. They can be roller bearings, such as a ball or tapered, or non-roller bearings, such as bronze or thermoplastic bushings.

Seals: There is no doubt that these are the most important components which are designed to prevent the media from leaking outside the rotary union while it is in use.

Where Are Rotary Unions Used?

In addition to industrial automation, food and beverage, alternative energy, oil and gas, and aerospace and defense, rotary unions are used in several other industries. In fact, they are used so extensively that it is easy to overlook their impact on equipment and systems.

Examples of a few applications include:

CNC (Computer Numerical Control) Machine Cooling

The coolant must be delivered to parts made of metal and other materials that are being machined. The fluid prevents overheating, maintains dimensional stability, and removes machined debris.

Bottle Filling and Capping

Automated systems are used to bottle and cap cough syrup, shampoo, and soda beverages. Rotating unions feed fluid from a central supply into these bottles as they move along a conveyor.

Hydro Dam Turbine Control

As water flows across turbine blades, hydroelectric dams siphon off the power. Hydraulic lines are used to control the opening and closing of gates and the subsequent flow of water.

Floating Production Storage and Offloading (FPSO)

Toroidal swivels are used in offshore vessel mooring systems that collect oil and gas from subsea reservoirs. Under extreme flow rates, these systems undergo substantial mechanical stress.

Liquefied Natural Gas (LNG) Loading Arms

Fluid cargo is loaded and unloaded from offshore vessels, tanker trucks, and railroad cars using loading arms. They must deliver the cargo in a leak-free manner.

Radar Cooling Systems

A mobile unit's electronic systems are constantly used, generate heat, and need cooling systems. Cooling electronic systems in these applications require specialized designs.

Depending on the specific application, the operating parameters may vary. Temperature can range from -150 to 400 F and pressure can range from 0 to 20,000 psi. Generally, rotational speeds range from 0 to 1000 rpm. Flowable media may include water, oil, coolant, or any other fluid intended to be transferred. Flow passages may range from one (1) to ten (10) or more. A number of factors must be considered in the design of a rotary union, but the sealing components may be the most crucial.

About the Author

I am an engineer serving in a leading valve manufacturing company. I love to share my knowledge here and I will try to keep posting articles.

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Author: Yunus Shaikh

Yunus Shaikh

Member since: May 25, 2021
Published articles: 3

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