Swivel Joints or rotary unions are used combined with pressure vacuum vents in applications where a constant fluid transmission from a stationary source to a rotating one is required without leakage or cross-contamination. Swivel Joints 360-degree rotation while preserving hoses from getting tangled as components turn. As a result, mechanical stresses that result from the hose bending, stretching and twisting can be relieved. Swivel Joints are designed to operate at a wide range of temperatures and pressure for several environments and conditions. Based on application, the Swivel Joints can be engineered to have multiple passages and transfer several types of fluids simultaneously at various rotational speeds. As the number of passages increases, the size of a Swivel joint also increases, and the transmission speed will be lower. 

How Do Swivel Joints Work?

Swivel Joints come in different sizes and shapes and can be engineered according to the application and environment where they need to be used. While external factors require design considerations, all Swivel Joints have two main components, i.e., housing and a shaft. The concept behind a swivel joint allows the shaft to rotate, and the housing remains stationary. The shaft unit has holes of different depths and sizes starting from its top surface to ensure proper fluid flow. Variable hole markings and depths define the flow path of the fluid. The fluid is carried through the shaft into and out of the Swivel Joints through internal joints. The housing unit consists of grooves and passages to facilitate smooth fluid transfer and prevent leakages. Numbered markings are found on the housing surface, and the same is available on the shaft's top surface. These markings define where a user would expect the fluid to flow in slash out between the housing and shaft unit through the internal passages. A series of internal components are fitted between the housing and shaft at specific locations. These include O rings, bearings, snap rings, seals, etc. The selection of these components is essential while engineering a swivel, as attention has to be given to the internal design and tolerances of the housing grooves. Failure to adhere to the recommended design specifications and other requirements results in leakages. The passage of signals and power is required for particular industries and applications. Slip rings can be included in the joint through electric cables within the hollow inner diameter of the shaft. 

How to Choose a Swivel joint?

In contrast to other rotary components, a swivel joint and a product indicator endure internal loads while operational. It is a result of pressurized fluid flowing within the internal components. Multiple factors need to be considered to select the correct swivel fitting. 

The most influencing factor of swivel joints is the sealing solution between the housing and shaft. Precise tolerances should be maintained at the machining phase to create the required grooves for internal components and seals. Bearings, seals, O rings, wear rings, etc., are inserted in these grooves, and they must be strong enough to withstand the pressure created by the fluid. All swivel joints come with manufacturer ratings that recommend operating temperature, speed and pressure. These ratings are related to the geometric machining tolerances, internal component specifications and fluid type used. It is imperative to provide significant space and design consideration for swivel joints and their ports. Swivel joints may have up to nine ports to supply fluid based on application requirements. A higher number of passages result in increased material used and enhanced size. Swivel joints can be modified in terms of port sizes according to application requirements. Load requirements, environmental surroundings, space restrictions, etc., are considered while selecting an appropriate component. Engineers can provide the best solution that suits the application based on industrial requirements. Standard swivel joints can be modified to fit your application, and if required, engineers can provide a custom-built joint that suits your needs. 

Applications of Swivel Joints:

Several custom modifications are possible with a swivel for specific industrial applications. Thus, it can be found across many applications. Cranes and vacuum trucks that require their booms to rotate 360 degrees run into the problem of hose tangling or bending. Introducing swivel joints with a pressure vacuum vent to the system creates smooth fluid flow for continuous rotation. Bottling lines use swivel joints to deliver fluid to different locations. Design considerations are necessary for the various fluid viscosities to determine pressure requirements. The agricultural and farming industry utilizes swivel joints in many ways, including – waste recycling and herd feeding. Robotic arms and welding often require electric passage to allow electric transmission and mobility. 

How to Mount a Swivel joint?

Firstly, inspect the swivel joints to ensure that all the passages and connections are clean and free from physical damage during shipment. A flexible hose or connection must be used while installing swivel joints. While mounting the swivelensures that the housing or shaft is mounted in a manner that allows movement to accommodate any run-out during rotation or misalignment. It is advisable to fasten an anti-rotation arm to the stationary part of the unit. While mounting the housing and shaft, ensure that pipe thread sealant is used and the fittings are properly tightened. It is also necessary to ensure that the mounting surface should be concentric on the axis of the swivel assembly for the proper functioning of a swivel. Once fittings are installed, bolt the assembly using tapped holes or the mounting flange provided with the swivel joints. It is better to perform a dry run after installation to ensure proper mounting of the swivel assembly. It also verifies that there is an unintended movement of the swivel joint due to misalignment. Internal components and high-pressure seals contain the fluid from leaking out of the closed system. If any leakage is found on the surface of the swivel joints, it is imperative to inform the manufacturer immediately. 

Additionally, swivel joints are used in pneumatic systems that require rotation between flow lines. These joints provide 360-degree rotation in one, two, or three planes and are made of forged materials. Some swivels use ball bearings for better load distribution and spring seals to reduce torque drag. 

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