Single and multi-channel rotary unions for air, gases and fluids
Customised rotary unions for the most demanding requirements
Technical specifications
degree of protection
IP51 (higher on request)
rotational speed
0-300 rpm
case material
Aluminium, stainless steel
Number of implementations
1-24
additional services
Combination of different designs
Specification Media feed-through
- Number of pneumatic/liquid feed-throughs: 1 – 24
- Connection sizes: M5, 1/8″, ¼”, 3/8″, ½”, 5/8″, 1″, 1¼”
- Straight or angled connections
- Pressure: up to 1300 bar, 130 MPa; 20,000 psi, vacuum 0.01 torr, 30 HG
- Media: air, gas, vacuum, hydraulic-oil, return oil, water, hydrogen, Nitrogen, steam, cooling water, coolant, hot water, acids, bases, and much more
Product overview
All details about our slip rings clearly presented in our product overview
Single and multi-channel rotary unions for liquids, compressed air and vacuum
Unlike electrical slip rings for power, signal and data transmission, classic single-flow and multi-flow rotary unions are not designed to transmit signals and power between fixed and rotating components. Instead, they enable the sealed transfer of one or more liquids, a vacuum, or gases and compressed air (pneumatic and hydraulic energy) between stationary supply lines and/or rotating components (relative to each other). They are therefore primarily used for rollers, spindles and motors.
Depending on the area of application, multi-channel or single-channel rotary feedthroughs are used. Single-channel rotary feedthroughs are used almost exclusively in the private sector, e.g. in swivel taps or lawn sprinklers. Here, water must be fed exclusively into a movable or rotating component, but not back out again.
In industry, it is more complex. Here, for example, hydraulic fluid is fed under high pressure but also returned. For example, for the return of leak oil and return oil to the hydraulic oil tank. Rotary unions are also required for the pneumatics of a tyre pressure control system. This allows the tyre pressure of agricultural vehicles or construction site vehicles to be adjusted to the ground conditions while driving.
In addition, it may also be necessary to convey coolant – such as water – or pressure in the same rotary union, or to additionally transmit rotary movements through container walls, for example in vacuum technology. Accordingly, multi-channel rotary unions are required, which we offer at RotarX in 2-way, 3-way, 4-way, 6-way and up to 24-way versions.
However, the number of channels is not the only criterion. It is extremely important that the individual media are clearly separated from each other. At the same time, the friction of the sealing rings (seal friction) must not be too high. This increases wear and tear and also has a negative effect on the rotational speed. This friction is pressure-dependent, which must be taken into account when planning individual rotary feedthroughs – for example, for the drive torque of a rotary table. In addition, rotary feedthroughs, especially for hydraulics, pneumatics and vacuum, must withstand very high pressure. We guarantee this up to 1300 bar. The material of the sealing rings must also be variable, depending on whether acids, bases or other media are being conveyed.
Our rotary unions can therefore convey water, hydraulic fluid, cleaning agents, grease, emulsions, bases, acids, lubricants, coolants and oil, but can also withstand gas pressure, air pressure, vacuum and hydraulic pressure. Or they can carry hot steam, for example in the paper industry, where rotary unions with siphons are used. Hot steam is introduced, condensed and then “pressed out” again via a siphon to heat the large drying rollers.
rotary union
Different housing materials to choose from
Various connection sizes for media feed-throughs
Mounting and bolt circle roto
Optional rotary joint with hollow shaft
Configure requirements individually
Rotary unions are used in almost all industrial sectors – from the food industry to onshore and offshore wind power plants and construction machinery such as excavators. They therefore have to meet a wide range of requirements. Depending on what needs to be transferred, rotary joints must fulfil different criteria – from sealing and IP protection rating to material selection, vibration, acceleration and operating temperature. A classic rotary joint for fluids is therefore not automatically suitable for media transfer in hydraulics and pneumatics, because these applications, for example, must withstand significantly higher hydraulic or pneumatic pressure (bar). This does not apply to our combined electrical pneumatic/liquid rotary joints. They combine fluid media transfer with signal and power transmission – functions that are usually handled by separate slip rings – and can also be used as pneumatic and hydraulic rotary joints designed to withstand high pressure.
These are only a few of many criteria that have to be met in order to integrate rotary joints perfectly into each individual application. Together with our experts, we will find the optimal solution for every requirement. Or simply configure your individual slip ring online.
The seal makes the difference
The primary goal of our technology and individual consultation: High availability, simple installation, low maintenance requirements and a long service life. Achieving these goals for pneumatic rotary unions, including normal media feed-throughs, or combined electrical rotary unions is significantly more challenging than for purely electrical slip rings or simple rotary unions. Not least because of the seal and wear caused by friction. The biggest design challenges are the precise separation of all media-carrying lines and the wear of the seals. The rotation of the inner and outer housings generates constant friction. This is not a major problem with purely electronic slip rings. However, where absolute tightness is essential, friction between rubber rings and plastic or aluminium is a limiting factor for the service life of the component. But we at rotarX have already mastered these and other challenges for a wide range of industrial sectors.
The principle behind it: the unloaded mechanical seal. In rotary feedthroughs for pneumatics or hydraulics, for example, this means that only the actuating and return forces act on the seal, rather than the pressure, which significantly increases its service life. In addition, we offer various seal pairings such as ceramic, graphite or silicon carbide on request in order to respond optimally to individual requirements and thus reduce maintenance costs and seal friction.
Differences between classic, hybrid and electric rotary unions
Since modern industrial and agricultural businesses often require a combined rotary union for pneumatics/hydraulics and fluids, more and more customers are opting for hybrid rotary unions. The media guides are then not exclusive. Hybrid pneumatic rotary unions can therefore convey both liquids and compressed gas.
This enables very interesting combinations. In addition to transferring pneumatic or hydraulic energy, gas, compressed air and vacuum, they can also be used to convey auxiliary and operating materials such as coolants, cleaning agents, lubricants and hydraulic fluids under high pressure. They can withstand up to 1300 bar at 300 revolutions per minute.
This means that media supplies, which previously could only be carried out at standstill or at low speeds, are now also possible at high speeds. The degree of automation and productivity of the overall system are significantly increased. In addition, they can be used from -30 °C to +80 °C (other temperature ranges on request). For the reusable rotary unions, up to 24 channels are available for different media – from water to pneumatics and gases. Everything is combined in one slip ring body. The possible applications are therefore practically unlimited.
Our hybrid electric rotary unions for pneumatics, hydraulics & fluids offer even greater combination possibilities. Not only do they combine media feed-through with the transmission of pneumatic and hydraulic energy, they can also transmit data, control signals and electricity. One possible area of application is in wind turbines, primarily for pitch control. The electrical rotary unions can be used here for the hydraulic control of the rotor blade angle adjustment in order to adapt it to the wind speed. To do this, they must simultaneously transmit the sensor data from the control system or anemometer, luminous flux, hydraulic pressure and hydraulic fluid, as well as any relevant auxiliary materials, and return used materials. This is the only way to optimally turn the rotor blades into the wind and achieve power limitation at high wind speeds in order to prevent damage to the drive train. This approach also saves space, as an electrical slip ring does not need to be installed as a separate component, but is already integrated into the rotary union.
Your path to a customised rotary union
The basic prerequisite for the optimal solution is a detailed consultation. Together, we define the framework conditions, specifying the required media and operating data. We need information from you about detailed process sequences, e.g. when which medium is pressurised, temperature influences, space conditions, but also the range of necessary channels, which, for example, must be variable on permanently installed workbenches (with milling machines or other tools) depending on the user. A central interface for media and power supply with a modular design is then required here.
Areas of application for rotary unions
In the context of Industry 4.0, automation and digitalisation, combinations of slip rings and rotary unions are becoming increasingly popular, as more and more measured values and control signals need to be transmitted in addition to fluids, gases or compressed air.
One example of this is a so-called milking carousel. Compared to the classic herringbone milking parlour, a rotating milking carousel enables almost completely automated milking of dairy cattle. However, this requires not only the milk to be transported through a classic rotary union, but also the measured values, data and, of course, electricity necessary for automation and control.
Another application for these particularly powerful slip rings can be found in wind turbines. Here, they are mainly used for the hydraulic control of rotor blade adjustment. They can transmit sensor data or luminous flux simultaneously with hydraulic pressure, which is used to optimally turn the rotor blades into the wind.
However, electric pneumatic-liquid rotary unions are also increasingly being used for classic applications where non-electric multi-channel rotary feeders were previously used. In a tyre pressure control system, for example, the rotary union can transmit not only the compressed air but also the measured values of the current tyre pressure. In an excavator with a rotating upper carriage, not only can return oil be fed back and hydraulic fluid be moved back and forth under high pressure, but the fill level of the hydraulic oil tank can also be transmitted, for example.
Further application examples for hybrid multi-way rotary unions:
- Workpiece and tool detection
- Clamping and loosening
- Cooling (e.g. spindle cooling)
- System control
- Tyre pressure control system
- Recirculation of leak oil and return oil (hydraulics)
- Turning and milling work (also in combination)
Why RotarX?
Our many years of experience pay off when it comes to the special challenges involved in designing hybrid rotary unions. Our modular design principle and individual consultation by our experts based on your process parameters and environmental requirements enable over 50,000 different combination options. Compared to pure electrical or fluid feedthroughs, the feedthrough of gas pressure or hydraulic pressure through a rotary connection is an enormous challenge. A complex channel system is created between the rotor and the stator for the passage of media. In addition, a central media line ends in a rotary coupling. The weak point in this design is the seal. However, through the use of high-quality sealing rubbers and sophisticated engineering, these lines can withstand up to 1300 bar – at 300 revolutions per minute. This is made possible by combining different sealing technologies. Whether it’s a mechanical seal, a hydrostatic seal or an elastomer or “plastomer seal”. This allows us to respond explicitly to the requirements of our customers’ media, operating and process parameters. The most suitable sealing technology is used for each media channel. In special cases, all seals can also be combined in one housing if required.
Multi-channel rotary feedthroughs for machine tools
Early on, it became necessary to insert, execute or carry out more than just one medium in a rotating machine tool part on corresponding workbenches. Sophisticated multi-flow hybrid rotary feedthroughs not only enable simultaneous turning and milling, but also allow for system control or cleaning of the table or machine parts, e.g. with compressed air. And all this via a single central interface, which is not affected by the individual channel allocation, depending on the needs of the person currently working at the table. This allows the operation to react flexibly to changes in channel allocation at any time. Multi-channel rotary unions are available for all conceivable variants, whether hydraulics, pneumatics, vacuum or a fluid passage, e.g. for coolant, is required.
The increased demand for hybrid rotary unions actually arose from machining processes to ensure the central supply of compressed air or hydraulic fluid. Initially, the advantages were mainly for machinists and for clamping and unclamping workpieces, such as higher productivity and the possibility of combining a wide variety of functions during rotation. For example, the supply of media to the workpiece spindle during turning, or in combined milling and turning operations, where rotary unions supply media to workpiece clamps, for example. The most common application here is the hybrid supply of coolant, compressed air or hydraulic oil to the tool spindle. Multi-channel rotary unions are also used on rotary tables with hydraulic chucks. They are always necessary when a central supply for several flexible channels is required.
Based on our discussions, we develop an individual solution for each customer. Starting out as specialists in wind energy, we have built up a wealth of experience in a wide range of industries over the last few decades – from the construction industry and the food industry to robotics and medical technology.
Pneumatic rotary unions – compressed air for tools and agriculture
A pneumatic rotary union for compressed air is also necessary in almost all industrial operations that use cutting technology. This is because, for example, in turning and milling work, it is not only the supply of coolant, grease, oil or – in the case of combined electrical rotary unions – measured values, power and control signals that is crucial. Compressed air also ensures that the spindle operates so that the milling head can work. This calls for hybrid multi-channel rotary unions that can simultaneously convey compressed air, coolant and lubricating oil – without leaking. Pneumatics also enable simple and gentle cleaning of the components without having to remove individual parts from the machine tool. Compressed air is also used in robotics, namely whenever gripping and transfer movements are coupled with rotary movements.
Multi-channel rotary unions for pneumatics are not only used to simultaneously feed and return different media in a selective manner, but also to feed compressed air – or another single medium – to different points in a machine tool. This is the case, for example, with dynamic tyre pressure control for commercial vehicles.
Dynamic tyre pressure control is a basic requirement for modern agricultural and construction vehicles.
Mobile agricultural machinery in particular – above all tractors and combine harvesters – travel on a wide variety of surfaces. This also applies to some extent to construction vehicles. In agriculture, a tractor may have to travel over sand, clay soil, asphalt, fields, meadows and forest floors during a single trip. At the same time, machines are becoming heavier and trailers are carrying ever-increasing volumes. It is therefore a basic requirement for modern machines that tyre pressure can be dynamically regulated during operation and adapted to the ground surface in order to extend the service life of the tyres and at the same time protect the soil. If the air pressure cannot be adjusted, the requirements for safety and tyre life and the requirements for protecting roads, farmland and forest soil are almost incompatible.
High tyre pressure on the road ensures longer tyre life and greater safety when steering and braking. However, in the field or on soft ground such as forest floors or meadows, it promotes the so-called bulldozing effect, i.e. a large track depth and the associated high fuel consumption. Low tyre pressure would increase the tyre contact area and counteract the bulldozing effect.
In addition, high tyre pressure leads to greater compaction on soft ground, thereby impairing subsequent crops, while at the same time hindering the infiltration of rainwater, which increases the risk of soil erosion and flooding. Dynamic tyre pressure control during operation makes it possible to increase tyre pressure on the road and reduce it on soft ground. Rule of thumb: 0.5 bar to 1.2 bar in the field, around 2 bar to 2.5 bar on the road.
However, in everyday operation, the machine switches between field work and transport so frequently that manually adjusting the air pressure each time is very labour-intensive. This is where the dynamic tyre pressure control system comes into play. It must be possible to adjust the air pressure at the touch of a button via the control system in the driver’s cab – while the machine is in operation and the tyres are rotating. This requires multi-flow pneumatic rotary unions, both for single-circuit and dual-circuit systems. The interface between the compressed air supply line and the rotating tyre is always the rotary feed. It receives the compressed air from the compressor (stator side) and feeds it through the rotor into the tyres. Combined electrical rotary feedthroughs also make it possible to transmit the measured values to the driver’s cab so that the current tyre pressure can be displayed. This eliminates the need for an additional electrical slip ring.
Incidentally, this function can also be retrofitted to older agricultural machinery, for which the rotary union is mounted on the front edge of the axle hub. However, compact rotary unions such as those from rotarX also allow the rotary feeders to be installed inside the axle (in-axle designs). Only the connection thread is then visible from the outside.
Hydraulic rotary joints for excavators or wind turbines
The powerful rotary unions are particularly popular. If electrical hydraulic rotary unions are used, measurement and sensor data as well as control signals can also be transmitted via the rotary union, for example to display the fill level of the hydraulic oil tank on a screen. They are also used in wind power for pitch control. Here, they can be used for hydraulic rotor blade adjustment and simultaneously transmit measurement data from the anemometer. Construction machinery such as large hydraulic excavators also benefit from particularly powerful and resistant multi-channel rotary unions.
Rotary unions for water
Rotary unions for water can be used in a wide variety of areas, whether the water is used for cleaning, as a coolant or as fire-fighting water. In its simplest form, water is used in single-flow rotary unions for sprinkler systems or lawn sprinklers when these need to be swivelling or rotating. The same applies to swivelling taps.
However, water can also be used in multi-channel rotary feedthroughs, for example for the intermittent partial cleaning of components in lathe and milling machines. Here, it is usually combined with the passage of compressed air, vacuum, hydraulic fluid, emulsions or greases, naturally clearly separated by high-quality sealing rings to prevent the media from mixing. In addition, our rotary unions are pressure-resistant up to a maximum of 1300 bar, making them suitable for high-pressure cleaning systems, for example in washing systems.
Vacuum rotary feedthroughs
A rotary union for vacuum technology is designed to transmit rotary movements between the atmosphere and a vacuum. For example, the rotary movements of a motor shaft can be transmitted into a hermetic chamber, i.e. a vacuum. To do this, the rotary feed is installed in the wall of the chamber, forming the transition to the vacuum and acting as a passage for the movement. This is required, for example, in the field of glass processing. For example, to move glass substrates in a coating system or to rotate optical glass during processing in the vacuum chamber. Vacuum technology is also indispensable in the high-tech sector and the computer industry for the manufacture of individual components.
Practical slip ring solutions for your application
Product catalogue for all slip rings
Find out about the different slip rings in our current overview. Transmission technology for complex industrial and safety-relevant applications form the core of our product range. All products can be individually adapted to the applications in order to offer you added value. Premium engineering - that is our claim for every single product we manufacture. We would like to convince you of this.
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