Free Shipping on orders over R3,999. T's&C's Apply.
Rotary unions are rarely seen, yet almost every machine that turns while it is fed with water, oil, air or steam depends on one: car washes, hose reels, surface cleaners, production lines and hydraulic systems. A rotary union, also called a swivel, rotary joint or rotary coupling, carries the fluid from a fixed supply into the part that turns, and keeps the joint sealed while it does.
Kränzle South Africa is a supplier of Mosmatic rotary unions. The range comes in two groups:
Inline and 90°
Low-speed swivels, up to about 200 rpm, for guns, hoses, hose reels and booms. Large bore sizes for high flow, and compact high-pressure swivels up to 500 bar.
High RPM
High-speed swivels up to 2000 rpm and 500 bar for surface cleaners, rotating heads, parts washers and tyre cleaners, including saltwater and underwater versions. Ceramic or carbide seals and up to four bearings.
Rotary unions are a Mosmatic speciality. The company has designed and made them for more than 40 years, and its swivels are designed, produced and assembled in Switzerland, on modern machinery and from high-quality materials, around a patented sealing system and in a clean, compact design. They turn with low torque even at full pressure, run on sealed, self-lubricating bearings with a warning system for seal wear, and are quality-checked with 3D measurement technology.
Choosing a rotary union
The range is wide, so a swivel is chosen by the job it has to do, not by the thread size alone. Mosmatic asks for these points before a swivel is specified:
- 90° or inline
- Pressure (max. bar)
- Mounting design
- Speed (max. rpm)
- Forces: axial, radial or both
- Flow volume (L/min)
- Connections
- Flow medium and pH value
- Fluid temperature (°C)
- Duty cycle (hours per day)
Mosmatic swivels suit fluids with a pH between 3 and 12 and filtration to 10 µm, and compressed air up to 20 bar. Where no standard swivel fits, Mosmatic can design a custom one with its own R&D team. Request a quote with these details and the Kränzle team will match the Mosmatic family and part number.
Find a swivel by application
This is Mosmatic’s own selection chart. Click an application to show the swivels Mosmatic recommends for it in the listing below, or click a green square to show one swivel family.Choose an application to show the swivels Mosmatic recommends for it in the listing below.
OptimalAlternative
| Application | |||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Source: Mosmatic 2026 catalogue, “Select by application”. The final choice is always checked against pressure, speed, flow, temperature and load. If your application isn’t on the chart, request a quote and we will match the part.
Rotary unions by industry
Mosmatic's own application guide is the starting point for choosing a family; the final choice is always checked against the pressure, speed, flow, temperature and load.
| Industry or application | Mosmatic families |
|---|---|
| Food processing and pharmaceutical | DGEI, DGL, DYCI / DYDI, steam swivels DXLS / DXGS / DXFS |
| Truck, bus, fleet and container washing | DXTI, DYT / DYU |
| Mining | DXTI |
| Agriculture | DYF, DYCI / DYDI, DYT / DYU |
| Municipal vehicles and fire service | DXTI, DYCI / DYDI, DGV, DGVI, DGE |
| Hose reels | DGE, DGEI, WDE, WDEI, WDC |
| High pressure guns, lances and hose connections | DGV, DGVI, DGK, DGS |
| Surface cleaners | DGF, DXF, DYF, DYW, DYCI / DYDI |
| Parts washers, tyre and wheel cleaning | DGG, DXTI, DYF, DYT / DYU |
| Pipe and duct cleaning | DGG, DXG, DYG, DGE, DGEI |
| Hydraulics, pneumatics and paint guns | DGV, DGVI, DGS, DGK |
| Saltwater and underwater equipment | DYKI |
Mosmatic swivels also turn up in less obvious places: drone and facade cleaning, wind-turbine cleaning, paper and semiconductor machinery, and paint and coatings systems, wherever a moving part needs a reliable fluid supply.
Service and seal kits
A Mosmatic rotary union has no fixed service interval: its life depends on pressure, speed, water quality and hours of use, and good filtration is the simplest way to extend it. On the high-speed swivels, water running steadily from the weep holes is the signal to replace the seals, because continued running washes the lubricant out of the bearings. Seal kits are available across the range, with bearing and repair kits for selected families. When opening a swivel, clamp it in soft aluminium jaws so the housing and threads are not damaged.
Frequently asked questions
What does a rotary union do?
A rotary union transfers a fluid such as water, oil, air or steam from a stationary supply into a part that rotates or moves, and keeps the connection sealed under pressure while it does. It is what lets a surface cleaner's rotor arm, a hose reel or a tank-cleaning head turn freely while it is still being fed.
What is the difference between a rotary joint and a rotary union?
They are the same component. Rotary union, rotary joint, rotary coupling, swivel joint and swivel are all names for a joint that passes a fluid between a fixed part and a turning one. Mosmatic calls its range rotary unions or swivels.
Which rotary union is used for water?
Most of the Mosmatic range is built for water, hot or cold, up to about 120 °C. The choice then comes down to pressure, speed and flow: low-speed inline and 90° swivels for guns, hoses and hose reels, high-flow swivels for large volumes, and ceramic or carbide-seal high-speed swivels for surface cleaners and self-rotating heads. The DYKI is built for saltwater and underwater use.
Can Mosmatic rotary unions be used for air, oil or steam?
Yes. Many families handle water, oil or air, and many O-ring designs can be supplied with NBR, EPDM or FKM seals to suit the medium. The DGK air swivels are made for compressed-air and paint guns, and the DXLS, DXGS and DXFS steam swivels are rated to about 20 bar of steam at 180 °C.
How much does a rotary union cost?
It depends on the family, size, material and connections, so Mosmatic rotary unions are quoted per part. Send the pressure, speed, flow, connections, medium and temperature with a request for a quote, and Kränzle South Africa will price the right part.
Do Mosmatic rotary unions need maintenance?
Very little. The bearing compartments are sealed and the bearings self-lubricating, so there is no regreasing and no fixed service interval: service life depends on pressure, speed, water quality and hours of use. On high-speed swivels, water running steadily from the weep holes means the seals should be replaced as soon as possible. Seal kits are available, and bearing and repair kits for selected families.
Where can I buy rotary unions in South Africa?
Kränzle South Africa supplies Mosmatic rotary unions and swivels from Brackenfell, Cape Town. Request a quote with the application details and the team will match the Mosmatic family and part number.