Standard & Custom Rotary Unions

Overview

DSTI rotary unions (rotary joints) reliably seal and transfer fluid such as water, air, hydraulic oil, coolant, steam, and other media types from stationary sources to rotating parts.

Our rotary union products are used across a wide range of industries including factory automation, heavy equipment, machine tool, packaging, medical, oil and gas, defense, and aerospace.

We offer standard rotary union product lines grouped by function and feature exclusive sealing technology selected for compatibility to each application’s operating pressure, temperature, speed, media, and required service life.

If our inventory of standard products isn’t a fit for your project, we can provide a custom-tailored rotary union solution designed to meet your exact application’s requirements for operating performance, cost, and delivery - in fact, it’s what we do best! Our fluid sealing experts will assist with a solution that meets your needs, which may include making modifications to a standard product, providing improvement recommendations to an existing design, or developing a new prototype to your exact project’s specifications.

Rotary Union FAQs

What is a rotary union?

A rotary union (or swivel joint) is a device used to transfer fluid under pressure or vacuum from a stationary inlet to a rotating outlet, preserving and isolating the fluid connection. Learn more about What is a Rotary Union?

How do I choose a rotary union?

Proper selection of a rotary union solution requires details about your application's operating parameters including pressure, speed, media type(s), number of flow passages (channels), and connection size(s) / type(s). A good place to start your search is with our Standard Rotary Unions. If you are confident that a custom / modified solution is most likely required or need assistance in your selection, contact us to Get Started. Our experts are here for you.

Do you offer custom rotary unions?

Yes, it's what we do best! We can meet your exact fluid rotary union requirements from modifying our standard products to complete, custom design and manufacturing. For more information see Custom Solutions

What is your process for a custom rotary union solution?

First, contact us to Get Started. Our team will reach out to you to start learning more about your project's technical and delivery requirements. We will consider all aspects of your application and work together to develop the best solution. We typically start by evaluating our in-stock standard product options, reviewing our extensive library of custom rotary union designs, and examining a complete custom solution.

We will present a detailed proposal including proposed design, cost breakdown, and project timeline. You will be assigned a sales engineer and project manager so you know who to go to with any questions throughout the process. For more information see Custom Solutions

Do you offer compatible options for replacing another manufacturer's fluid rotary union?

Yes, we can cross reference other manufacturer's fluid rotary unions to find an equivalent solution. Contact us to Get Started

Can your standard rotary unions be modified to meet the requirements of my application?

We can modify our standard rotary unions to fit your needs. Custom modifications to our standard products are quite common and easier than you may think. Modifications include changes to housing / shaft dimensions and materials, seal types, mounting configurations, connection sizes and types, and flow passage configurations. For more information see Standard Rotary Union Modifications

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Do you offer replacement seals and/or bearings for rebuilding your rotary unions?

Yes, seal and bearing kits are available for our rotary union products for on-location rebuilding and repair. Contact us to Get Started

Do you offer fluid rotary union / electrical slip ring combination assemblies?

Yes, DSTI fluid rotary union and electrical slip ring technology can be integrated together into one complete solution for fluid, power, signal, and data transfer. We offer both standard (in-stock) assemblies and custom solutions designed to meet your exact requirements. For more information see Fluid + Electrical Solutions.

Can I use a different media than what is listed on your site?

DSTI products are only recommended for use with the specific media types listed. This ensures proper compatibility with all components; shaft / housing, bearings and seals.

How do I install/mount my rotary union into my equipment?

CAUTION: DSTI does not recommend mounting the rotary union with both the shaft & housing components solidly bolted into place. One of the two components should be mounted in a manner that allows for some movement in the event of misalignment. Using only the supply lines or hoses to fix the stationary component in place is also not recommended. An anti-rotation arm that attaches to the stationary part of the rotating union assembly and rests against part of the equipment framework is recommended.

To mount shaft-mounted units with O-ring face seal glands (-OF option in product code):

1) Make sure the rotating union shaft face & equipment mounting surface is clean and free from dents or chips to insure proper installation. Equipment pilot bore needs to be concentric to the center line of the rotating union shaft to assure proper function.
2) Install face mount O-rings into seal gland on shaft face. General assembly grease can be used as needed to hold O-rings into place during assembly.
3) Align rotating union shaft with equipment pilot bore and flow passages, then insert into place.
4) Bolt assembly into place using tapped holes or optional mounting flange (see below) on rotating union face.

To mount shaft-mounted units with threaded connections:

1) Make sure all fittings are properly tightened & pipe thread tape is used as required. Equipment mounting surface needs to be concentric to the center line of the rotating union shaft to assure proper function.
2) After all fittings are in place, bolt assembly into place using tapped holes or optional mounting flange (see below) on rotating union shaft.

Optional Mounting Flanges: DSTI shaft and housing mounting flanges are available for purchase. To order, contact a member of our Sales Support Team.

Customer Interface Adapters: DSTI does not manufacture customer interface adapters for stock products. If ordering a custom rotary union, DSTI can design the union to integrate directly into your equipment.

What do the letters R.A in the Product Code mean?

The letters R.A are an abbreviation for Revision A. This gives DSTI the ability to manage revision control on all products.

Can I use more than one media type in a rotary union at the same time?

Yes, if all media types are suitable for that specific rotary union. However, if using air/gas and another fluid, DSTI recommends using a rotary union with an extra passage (empty) between the two to avoid cross contamination. Please speak with a member of our Sales Support Team to discuss your application in detail.

Can I run air and fluid in the same rotary union?

DSTI recommends using a rotary union with an extra passage (empty) between the two to avoid cross contamination. Please speak with a member of our Sales Support Team to discuss your application in detail.

What causes a rotary union to fail?

Common causes of early failure are dirty, unfiltered media, vibration, exceeding operating parameters, excessive heat, improper installation, etc.

Can a rotary union be rebuilt?

Yes. All standard DSTI rotary unions can be rebuilt assuming no damage to sealing surfaces have occurred. There are two options for rebuilding:

1) Purchase a do-it-yourself service kit that includes either seals (only) or seals and bearings. Contact a member of our Sales Support Team for pricing and availability.

2) Send the unit to DSTI for repair evaluation. A Return Merchandize Authorization (RMA) number is required prior to returning any DSTI products. Request a RMA Number.

What is a through bore?

A through bore is a hollow, center-bore that provides routing space for passing electrical wires or other components through the middle of the rotary union. It can also be used to mount the rotary union to a custom interface.

What is the life expectancy of a rotary union?

The life expectancy of a rotary union varies widely depending on many application variables: media type, pressure, rotational speed, duty cycle, temperature, and more. If you need further assistance contact a member of our Sales Support Team.

Is there a quantity price break if I order multiple units?

To discuss quantity price breaks, contact a member of our Sales Support Team.

How much torque is require to rotate a rotary union?

It varies by series and model number. After selecting a specific standard rotary union model, view the mininum torque needed to rotate at zero pressure within the Available Configurations table under the column called, "Min. Torque".

Can I rotate the rotary union dry (no media flowing)?

Yes. Although there may be some adverse effects if it is run dry for a prolonged period of time under extreme conditions, for example, high rotational speeds and/or elevated temperatures. Contact a member of our Sales Support Team to discuss this topic more in detail.

What do the letters -OF in the Product Code mean?

The letters -OF in the product code is for an optional "O-ring Face Seal Gland" for flush mounting the rotary union to the customer’s interface. When this option is ordered the side connections on the shaft are plugged (if applicable).

Can an axial and/or radial load be placed on a rotary union?

In most cases, some degree of load can be placed on a rotary union, but please contact a member of our Sales Support Team to better understand your application needs.

Which part of the rotary union stays stationary and which part rotates?

Functionally it makes no difference whether the shaft or the housing rotates. It is all dependent on how the assembly is mounted and installed on your machine or equipment.

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Questions?

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