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The Ultimate Guide to Select Swivel Joints

Author: Jessica

Sep. 17, 2022

67 0 0

Tags: Mechanical Parts & Fabrication Services

What is a Swivel Joint?

Swivel joints, also known as rotary unions are used in applications where a constant transmission of fluids from a stationary source to a rotating source is required without cross-contamination or leakage. Typical applications use swivel joints to allow for 360-degree rotation while preserving hoses from getting tangles as components turn. In return, mechanical stresses that would result from hose twisting, bending, and stretching can be relieved.


Swivel joints are engineered to operate at a wide range of pressure and temperature for a variety of conditions and environments. Based on industry requirements, the swivel joint can be designed to have multiple passages and can transfer different types of fluid simultaneously at various rotational speeds. Typically, as the number of passages increases, the size increases, and speed will be lower.


Here's a thought:What Are Hydraulic Hose Rotary Joints?


How Does a Swivel Joint Work?

Swivel Joints come in different shapes and sizes based on the application and the environment where it is subjected to. While design consideration should be given to external factors, all the swivel joints have two main components: a shaft and housing.


The concept behind a swivel allows the shaft to rotate while the housing remains stationary in position. The shaft has drilled holes of varying size and depth starting from its top surface. Variable hole depths and markings define the flow path of fluid within the swivel. Through internal design, the fluid is carried through the shaft into and out of the swivel joint.


The housing unit includes machined passage and grooves to facilitate fluid transfer within the swivel and preventing cross leaks. Numbered markings are found on the housing outer diameter surface and the same can be found on the top surface of the shaft.


These numbers define where a user would expect the fluid to flow in/out between shaft and housing through the machined internal passages. A series of carefully selected internal components are fitted between the shaft and housing at specified locations. These include seals, snaps rings, O rings, wearings, small bearings in certain applications.


The selection of internal components is of vital importance while designing a swivel joint as extreme attention has to be given to the tolerances and internal design of the housing grooves. Failure to adhere to the recommended design and machining requirements results in leaking components.


Passage of power and signals are sometimes required for particular applications and industries. Slip rings can be integrated with the swivel joint through passing electric cables within the hollow inner diameter of the shaft.


How to Select a Swivel Joint?

As opposed to other rotary components in the same industries, a swivel joint mostly endures internal loads while operational. This is a direct result of pressurized fluid flowing within its internal components. To select an appropriate swivel joint, multiple influencing factors must be considered.


The most influencing factor on a swivel joint is the internal sealing solution between the shaft and housing. Very precise tolerances must be maintained during the machining phase to create the required grooves for seals and internal components to be fit.


Seals, o-rings, wear rings, and bearings are inserted within these internal grooves and must be able to withstand the pressures induced by the fluid Swivel joints are rated by the manufacturer as to their recommended operating pressures, temperatures, and speeds.


These values are directly related to the internal components specifications, geometric machining tolerances, and type of fluid used significant design and space considerations must be given for a swivel joint and its ports.


Based on application requirements, a swivel joint may have up to 9 different ports to supply fluid through different passages. A higher number of passageways result in significant size and material increase.  


Swivel joints can be modified in size and port sizes with respect to application requirements. Space restrictions, load requirements, duty cycle, and environmental surroundings all factors that are considered while selecting an appropriate component


Based on the requirement provided CSIEQUIPT will be able to provide the best solution that suits the application.


In most cases, our standard in-stock swivels can be modified to fit into your application, and if required CSIEQUIPT can provide a custom-built swivel that suits your needs. Further, CSIEQUIPT can also cross-reference other manufacturers' Swivel Joint and provide an equivalent solution.


What are the Different Applications That Use Swivel Joints?

Due to a wide range of custom modifications that can be applied on a swivel joint, it can be found across many applications. Vacuum trucks and cranes that require their booms to rotate 360 degrees using a slew drive run into the problem of hose bending and tangling.


Introducing swivel joints to the system creates a smooth fluid flow for continuous rotation. Bottling lines use swivel joints to deliver fluid across to the different end locations. Design considerations are given to the different fluid viscosities to determine operating pressure requirements.


Farming and agricultural equipment utilize swivel joints in several ways including herd feeding and waste recycling. Welding and robotic arms often require electric passage and slip rings are used to allow for mobility and electric transmission.


How is a Swivel Joint Mounted?

Inspect the swivel joints and make sure that all the connections and passages are clean and free from any physical damage during shipment.


A flexible connection/ hose should always be used while installing a Swivel joint. While mounting the Swivel Joint, ensure that either shaft or housing are mounted in a manner that allows for some movement in order to accommodate any misalignment or run-out during rotation. It is recommended to fasten an anti-rotation arm to the stationary part of the rotary union.


When mounting the shaft and the housing make sure that pipe thread sealant is used on fittings and the fitting is properly tightened. For proper functioning of a swivel, it is required to ensure that the mounting flange or surface should be concentric to the axis of the swivel assembly.


After all, fittings are installed bolt the assembly down using the mounting flange or tapped holes provided on the swivel joint. It is recommended to perform a dry run after the swivel is installed to ensure proper mounting of the swivel joint assembly and to verify that there is an unintended movement of the swivel joint due to misalignment.


High pressure selected seals and internal components contain the fluid from leaking out of the closed system. If any leakage is found around any surfaces of the swivel joint, the manufacturer must be alerted immediately.


How To Maintain High Speed Rotary Union To Extend Service Life?

Maintenance Methods

1. Sealing surface

Check the wear condition and thickness change of the sealing surface (generally, the normal wear is 5-10mm); observe the friction track of the sealing surface to see if there are three-point discontinuity or scratches. If these problems occur, don't hesitate to replace the rotary joint immediately.


2. Clean regularly

Special attention should be paid to the inside of the rotary joint drum and pipeline, and a filter should be added when necessary. This is because many foreign objects will cause strong wear on the rotary joint, and frequent cleaning can effectively extend the service life of the rotary joint.


3. Long-term non-use

If the general machine is not used for a long time, it will cause scaling and rust inside the rotary joint. If it is used suddenly, it will get stuck or drip.


4. Regular oil injection

The oil injection device should be oiled regularly to ensure the reliability of the rotary joint bearing operation. Rotary joints that circulate heating medium should gradually generate temperature to avoid sudden temperature changes.


Changsong Industrial Equipment Shandong Ltd. (CSIEQUIPT) is committed to providing industrial equipment for global high-quality industrial enterprises, including complete sets of equipment and parts, fluid equipment manufacturing, centralized procurement of mechanical equipment, instruments and meters for large enterprises, and global procurement.If you are interested in our products, please contact us now!


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