Swivels, also known as rotary unions, hydraulic swivels, swivel joints, and live swivels are used in applications where a constant transmission of fluid power from a stationary source to a rotating source is required without cross-contamination or leakage. Light and heavy-duty applications use swivels to allow for 360-degree rotation while preserving each hydraulic hose from getting tangled with other components in the machine structure. In return, mechanical stresses that would result from hose twisting, bending, and stretching can be relieved, the hose life is enhanced, and machine downtime is avoided.
Swivels are engineered to operate at a wide range of temperature and pressure ratings across a variety of conditions and environments. Based on industry requirements, a swivel is designed to have multiple fluid ports and hose fittings to transfer fluid simultaneously at various rotational speeds. Typically, as the number of ports increases, the body size increases, and the speed of a swivel will be lower. Internal ball bearings, seals, and other components preserve a swivel's function to withstand high pressure and temperature range.
Swivel joints come in a wide range of shapes and sizes based on the application and the environment where it is in use. While design consideration should be given to external factors, all swivels have two machine components: a shaft and housing.
To manufacture high-pressure swivels, stainless steel or hardened carbon-steel is used. A swivel would function as a hose routing mechanism where fluid power flows through one hose line to another through a hose connection on the swivel. During a swivel joint operation, the shaft rotates around its stem axis while the housing remains stationary in position.
An array of numbered markings is found on the housing outer diameter surface and the same can be found on the top surface of the shaft. Drilled holes of varying diameters and lengths create a passage between inlet and outlet fluid ports where hose ends are assembled onto swivel fittings. The housing unit includes machined passage and grooves to facilitate fluid power transfer within the swivel and preventing pressure drop.
The internal configuration of swivels includes different seal options, snaps rings, O rings, wearing, and small ball bearings in certain applications. Internal components fit onto high-tolerance machined grooves that push the fluid in the correct direction. Swivel Fittings are drilled on the external surfaces of swivels for hose ends to be assembled.
Swivels are used in many industries where applications require 360-degree rotation of equipment with. Through the configuration of swivels with hose fittings, rotation can be achieved over a wide range of operating pressures.
Due to a wide range of custom modifications that can be applied on swivels, they can be found across many applications. Occasionally a swivel would complement a slew ring or slew drive in operation as seen in vacuum trucks and cranes that require their booms to rotate 360 degrees using a slew drive.
While a hydraulic hose carries fluid across the system, the constant rotation would cause excessive bending. Introducing swivels to the system creates a smooth uninterrupted, leakproof flow of fluid power.
Bottling lines use swivels 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.
Power systems that require passage of signals integrate slip rings with swivels through passing electric cables of the hollow inner diameter of the shaft. These are also known as live swivels and are mainly used in welding and robotics arms. Failure to adhere to the recommended design and machining requirements, operating pressure, and internal recommended seals results in leaking components and machine downtime.
Although subject to axial and side loads, swivels operate under high internal pressure as a direct result of fluid power within. The service life of swivels is heavily dependent on its pressure rating and user handling. When selecting a swivel, a user must identify the number of fittings in use, hoses, operating speed, temperature, pressure rating, fluid power, fluid specifications, maximum allowable pressure drop, axial and side loading values, hose fittings size, and material.
The most common material used to manufacture swivels is carbon-steel, while stainless steel is also an option. Significant design and space considerations must be given for swivels and their fittings. Based on application requirements, swivels may have up to 9 different fluid ports with hose fittings. The more hoses required by the application, the larger a swivel will be. During the design of hydraulic power systems, space restrictions to swivel length and diameter, swivel load & pressure requirements, duty cycle, hydraulic hose capacity, and environmental surroundings all factors that are considered while selecting the correct swivels.
Based on the requirement provided Slewmaster will be able to provide the best solutions that suit the application. In most cases, our standard in-stock swivels can be modified to fit into your application, and if required Slewmaster can provide custom-built swivels that suit your needs. Further, Slewmaster can also cross-reference other manufacturers' swivels and provide equivalent solutions. Rebuild and swivel seal replacement kits are available upon request to avoid any operating downtime.