How Do Rotary Unions Work

    How Do Rotary Unions Work

    For a motion to possible in machines, rotation must take place. It is easy to create a rotating motion. Achieving this is not so easy when liquid or air needs to be conveyed to the rotating part from a stationary one. The medium transferred is either air or liquid or both as required for various purposes. The uses of the mediums include:-

    • Lubrication
    • Transmission of fluid power (hydraulic)
    • Cooling
    • Heating

    Rotary unions are interfaces that enable the transfer of media in the form of liquid or air between a stationary component and a rotating component. Their design facilitates transfer varieties of media either in high or low temperatures.

    Rotary unions also work at different pressures, flows, and even in a vacuum. Transfer mechanism in rotary unions can be either be straight or at an angle.

    Other names used to refer to rotary union are rotary joint, swivel joint or rotating union. The variety of names depends on the environment the device is being used.

    How do Rotary Unions Work?

    The working principle of rotary unions is the same no matter the environment used and media.

    A rotary union connects to the source of the media using the non-rotating part. The rotating part transfers the media to another component of the assembly which is also rotating. The medium transfer occurs when the openings in the valves meet during the rotation. After the valves deposit, the media more flows into the union for the next output in the rotation. Injection of the media is capable because of the high pressures used with rotary unions.

    The input valve is on the stationary source while the outlet valves are on the rotating component constantly in rotation together with the machine during operation. This ensures uninterrupted fluid transfer constantly for an extended period.

    Rotary Unions Design

    The design of rotary unions is custom made according to the use. All rotary unions have four basic parts: the shaft, bearing, housing, and the seal.

    • The housing consists of the stationary part of the rotary union. It connects to the media supply. The housing encases all the other components of the rotary union.
    • The shaft is entirely an independent component that connects to the rotating part. The shaft acts as the assembly point for the bearings and the seal.
    • Bearings support the rotating part. Bearings found in rotary unions include roller, non-roller or tapered roller. The non-roller bearing includes graphite bearings and brushes made of bronze.
    • The sealing mechanism is the most vital component of the rotary union. The purpose of the seal is to ensure there is no leakage or bring it to a minimum. The seal is made to withstand wear and reduce friction. In a case where the leakage is unavoidable, a collection mechanism recovers the leaked media. The aim is to protect the operators and nature.

    Application of Rotary Unions

    Rotary unions are incorporation in assemblies is because they are more efficient and economical on space as compared to other inventions for a similar purpose. Rotary unions are in automobiles and also in machine requiring a constant supply of lubrication, other liquids, and air either to ensure the smooth running of the rotating part or for other purposes.

    The type of joints application is present in drilling & processing of crude oil, food productions in the field and industries, chemical industries, and pharmaceutical.

    Agricultural equipment used in harvesting use rotary unions. The equipment range from combine harvesters, grain carts, threshers, and tractors. Flaking mills, shredders, steam cooker, dryers, cutters, conveyers and rolling machines all use rotary unions.

    In oil drilling, the clutches and brakes use rotary unions. Mud is flushing from the drilling tip is through a rotary water union. In refinery batch mixers, blenders drying rolls and flaking mills all require rotary unions.

    In machines, rotary unions enable transmission of oil for lubrication, eg for cutting part, pressurized air and coolant.

    Choosing A Rotary Union For An Application

    Selection of the right rotary union for an application requires the following main considerations:

    • The physical size of the device in which the rotary union will be working.
    • Speed requirements in terms of rotation per minute (RPM) the machine are operating. Speed determines the setting the manufacturer will set for the rotary union. Speed, in some cases, falls within a range from low to highest possible.
    • The pressure the media will be traveling with through the device measured in(PSI). Pressure dictates the housing construction requirement for your rotary union to accommodate the maximum PSI the machine can operate well.

    Other considerations

    • Measurement: May influence the design of the rotary union due to their restrictions. These include the type of connectors, size of the fluid carrier, and thread types.
    • Material to use: this is especially important depending on the fluid used and operating temperatures. Some materials resistance to corrosion is minimal or affected by extreme fluctuations of temperatures.
    • Media transferred: type media, especially for rotary unions dealing with food, have restrictions on the material to use.
    • The number of passages: ranging from single, dual, or multiple.

    Moflon Rotary Unions

    Moflon manufactures rotary unions for use in different sectors such as

    • Medical equipment
    • Oil and gas equipment
    • Plastic molding
    • Aerospace
    • Construction machinery
    • Steel industry
    • Robots
    • Heavy & light machinery

    We are a leader in the design and manufacture of rotary unions. You can get a wide range of rotary unions which can fit your requirement from our products. We also offer services for custom made rotary unions as per your specifications.

    At moflon, we also manufacture parts to ensure that the maintenance of our products is possible. This ensures long service. The wide range of parts in our inventory ensures that you can rely on our products without worries of spare parts.


    Since the use of rotary union is essential in machines. You should look for reliable manufacturers like Moflon. This will not only ensure that you get a reliable product but also a serviceable rotary unit.

    Extended use of rotary unions is possible if you select the right one and install it properly.

    Do you have any question about rotatry unions? Leave them below in the comment section.

    Recent Articles


    Related Stories

    Leave A Reply

    Please enter your comment!
    Please enter your name here

    Stay on op - Ge the daily news in your inbox