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Hydraulic Rotary Unions — Rotary Joints for Machine Tools

Rotary Joints are required in almost all industries to transfer fluids from stationary to rotating machine parts. Some applications are simple to solve with standard rotary joint solutions. However, in more complex applications, such as machine tools, the performance of the machine depends to a large degree on the correct selection of the rotary joint. Maieroffers a complete range of rotary joints and sealing systems to suit individual customer specifications.

Cooling through the electro-spindle:

Traditionally, tool tips have been cooled by supplying coolant from an external source. However, in processes such as milling, this method of cooling does not provide optimum performance and decreases the service life of the tools, particularly in the case of high speeds of rotation. State-of-the-art machine tools use systems that supply cooling fluid through the electro-spindle.


  • Higher cutter speed
  • Better removal of the chips from the machining area
  • Improved lubrication/cooling of the tool and the machined pipe
  • Cleaning of the tool cone with air
  • Low coolant consumption
  • Longer service life of the tools

Selection of the rotary joint for coolant:

  • Fluid to transfer (i.e. coolant, minimal quantity lubrication, air, cutting oil)
  • Speed of the machine
  • Pressure and temperature
  • Type of connection to the machine: threaded rotor, self-supporting plug-in rotor or flange connection
  • Degree of filtration required for the fluid

TESS Technology:

The TESS technology (Thermal Expansion Sealing Systems) is an internationally patented Maier development. The system works like a classical closed seal when used with liquid coolant. In case of pressurized dry air, dry operation or minimal lubrication, the system detects an increase in temperature and reduces the specific closing pressure applied to the seal faces without separating the sealing surfaces.

K Series:

Series K consists of three basic versions: K 21, KT 21 and KT 41. Rotary joint type K 21 is only suitable for coolant. Rotary joint type KT 21 with TESS technology is resistant to pressure peaks. Suitable for coolant, dry operation without limitation, minimal quantity lubrication (MQL) and dry air under pressure and speed. Rotary joint type KT 41 with TESS is designed for high pressure and speed.

They share common characteristics such as:

  • Housing made of stainless steel and anodized aluminum
  • Adapted rotating mechanical seal with seal faces always in contact
  • Bearings protected by labyrinth seal and drain
  • Passages free from springs and corners
  • Possible stroke of driving rod of 19mm
  • All outside dimensions identical

K 21 C, KT 21 C and KT 41 C with axial inlet.
K 21 B, KT 21 B and KT 41 B with radial inlet.

KL Series:

Series KL rotary joints are designed for liquid coolants. Passage in one direction, closed seals. The housing is made of stainless steel and anodized aluminum. A labyrinth seal protects the bearings against fluid. Adapted rotating mechanical seals made of silicon carbide and carbon graphite. Ball bearings. Drain holes in the housing. KLT is the alternative with TESS technology with thermal relief of the seal. KLT is suitable for coolant, dry operation and MQL (minimal quantity lubrication). Outside dimensions identical to series KL.

KL 11 C and KLT 11 C with axial inlet.
KL 11 B and KLT 11 B with radial inlet.


With Combijoint, different types of rotary joints such as MP, MPV, K, DP and electric slip rings can be combined. Hydraulic oil, compressed air, gas, water, grease, coolant, current and electric signals can be transferred. Combijont versions are the most versatile and flexible way of transferring fluids. Frequently, only a single type of seal is selected for multi-passage rotary joints, usually a radial seal, to seal the passage of different media under different working conditions. This considerably reduces the service life of the rotary joint. Combijoint allows you to combine different seal technologies that best suit a specific fluid. Mounting several rotary joints in series also lets you select different materials, depending on the specific requirements. This results in a costeffective and reliable solution. In case of leaks, it is sufficient to repair the failed rotary joint without having to open the other rotary joints since only one housing is affected. The connecting flange can be sized to customer requirements for this solution.

Maier is a supplier and rotary union manufacturer for various applications including construction, mechanical, marine, and industrial.

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Hydraulic Rotary Unions — MP Series

The Maier MP Series is a multi-passage rotary joint for simultaneous supply of up to 10 different media. It is suitable for turntables, tools and forms. By means of many possible variations of sizes, materials and seals, MP Series covers a wide scope of applications. MP rotary joints can be combined with a slip ring or another rotary joint or with hollow shaft rotary joints. They can also be designed with multi-ports at the housing.

Hydraulic Rotary Union Product Features:

  • Design with radial shaft seal with elastic contact
  • Seal design to be selected according required media and performance
  • Rotor made of stainless steel, at sealing rear hardened or with metal ceramics
  • Housing of brass, aluminum, or steel — depending on application data
  • Threaded connections are G/BSP (ISO 228)
  • Other threads such as NPT (ANSI) are available on request
  • Ball bearings lubricated for lifetime
  • Flange of rotor can be custom-made on request

Combi-joint type MPE: MP rotary joint with two or four passages and slip ring with gold/gold contacts

Hollow shaft type MPH: Simplest version of series MP with one passage and hollow shaft. The radial connection at the housing corresponds to the customer’s shaft inlet. The technical characteristics are the same as series MP. Multi-passage versions are available on request.

Rotary joint type MPT: Two-way-design with two mechanical seals. Transfer of one fluid in and out, suitable for higher speed by means of mechanical seal. Custom-made design on request.

Rotary joint type MPV: One-to-four-way-designs with gap seal bushes – “hydrostatic relief”. Gap seals create controlled leakage recirculated to the hydraulic unit. With this technology it is possible to transfer the medium at high speed and high pressure simultaneously.

Maier is a supplier and rotary union manufacturer for various applications including construction, mechanical, marine, and industrial.

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Hydraulic Rotary Unions — M and DA Series

The Maier M Series is a sturdy rotary joint for polluted media at low speeds, suitable for water and steam.

Hydraulic Rotary Union Product Features:

  • Satisfactory results with heavily contaminated water due to extremely robust seal
  • Housing made of cast iron with spheroidal graphite, bearing housing made of cast iron
  • Rotor made of steel with polished abrasion and corrosion-protective coating of metal-ceramics in the sealing surface area
  • Packing with teflon impregnation, very rugged, may also be used with high-solids media
  • Compression spring made of chrome steel
  • High-quality ball bearing with easy access to lubrication nipple and corrosion-resistant support bearing in pressure chamber

The Maier DA Series is a shaft-supported rotary joint with maintenance-free, metal-impregnated sealing rings. These rotary joints are suitable for thermal oil, steam and water at low RPM.

Hydraulic Rotary Union Product Features:

  • Inexpensive design, since no bearings needed and available in large sizes, up to DN 300m nominal bore
  • Seal rings are resistant to fraction, even at high pressures
  • Maintenance-free, no lubrication necessary
  • Housing made of cast iron with spheroidal graphite, diameters DN 80 and above are made of steel
  • Rotor and sealing surface made of chrome steel, rotor pipe for diameters DN 65 and above made of steel
  • Cover, flange cover, butting ring, adjustment ring, and compression springs made of chrome steel

Maier is a supplier and rotary union manufacturer for various applications including construction, mechanical, marine, and industrial.

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Hydraulic Rotary Unions — H Series

The Maier H Series is a universal rotary joint to accommodate transfer of water, steam and thermal oil under temperature, rotation and pressure. These rotary joints are equipped with maintenance-free carbon sealing rings and carbon bushing. Metal-impregnated sealing rings for thermal oil and higher pressure loads are provided for hot water and steam applications.

The H3 type features an integrated vacuum valve for the steam cylinder. Maier offers the H Series in many different versions to meet the customers requirements. The new improved and fortified generation of the standard H series is faster and more robust and offers more flexibility, due to a modular system. It contains a low friction moment as well and a large variety of different designs, from 1/2″ up to 12″.

Hydraulic Rotary Union Product Features:

  • Easy to repair, maintenance-free, no relubrication
  • Ductile cast iron housing, chrome steel cover and root
  • Stainless steel used for sealing ace and high temperature resistant spring
  • Shatter-proofed sealing ring under high pressure thanks to compression-loaded wear-resistant graphite carbon
  • Series HW with metal impregnated graphite carbon, especially suited for thermal oil and considerably higher pressure, temperatures, and speeds
  • Connection to rotating pressurized system by means to standardized connecting piece with right-hand or left-hand male thread NPT, BSP threads (ISO228) available, K flange with conical inner ring for quick disconnection

Maier is a supplier and rotary union manufacturer for various applications including construction, mechanical, marine, and industrial.

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Hydraulic Rotary Unions — DX and DXS Series

The Maier DX and DXS Series is a water rotary joint with mechanical seal and ball bearings, suitable for cooling water (DX and DXS) and hot water (DXS). The DXS is equipped with highly resistant ceramics-coated sealing surface for higher temperatures and speeds as well as prolonged service life.

Hydraulic Rotary Union Standard Product Features:

  • Optimized cross-sections of housing connections thanks to serape one way flow and two way flow versions
  • Easy to repair
  • Safe sealing even in applications with adverse conditions
  • Brass housing, cast housing consisting of two parts for DN 100 and larger
  • Chrome steel rotor and counter-running surfaces, DXS Series feature counter-running surfaces made of metal ceramics
  • Compact mechanical seal, DN 100 and larger as well as DSXB equipped with easy-to-replace rotor seal
  • Factory-lubricated and maintenance free (up to 176°F) bearings, easily accessible lubrication point for higher temperatures

Maier is a supplier and rotary union manufacturer for various applications including construction, mechanical, marine, and industrial.

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Hydraulic Rotary Unions — DP Series

The Maier DP series is an universal rotary joint for hot and cold water and thermal oil, with balanced mechanical seal and ball bearings. Thanks to a low frictional torque high speeds are possible. Various application-specific seal combinations can be selected according to the application. The small series is also suitable for hydraulic oil and compressed air.

The Maier DP Series meets the special requirements of the printing and plastics industries. It is available in four variants, including different sizes from small to large and a stainless steel series.

Hydraulic Rotary Union Standard Product Features:

  • Low friction torque, no anti-rotational devices required
  • Long service life with easy field repair and maintenance
  • Rotor made of chrome steel
  • Housing and Elbow made of brass and glass beaded without harming environment
  • Series -750 for thermal oil equipped with heat-stabilized ball bearings, Viton O-Rings, and axial shaft seal for additional bearing protection
  • Connection to rotating pressure system by means of standardized connection pieces with right-hand or left-hand male thread NPT (ANSI), K-Flange, and conical inner ring (DN 1 1/2 and larger), fixed flange (DN 1 1/2 and larger), and sealing with groove and O-Ring
  • Radial housing connection with right-hand thread NPT (ANSI), axial with right-hand thread NPT (ANSI) and screw plug. For series -750 radial and axial housing connections with right-hand thread NPT (ANSI). Axial thread with screw plug.

The Small Series DP 1/4:

  • Housing made of anodized aluminum, Atet-Design without anodization
  • Ball bearings factory-lubricated for life

The Large Series DP 2 1/2 to 4:

  • Housing made of lacquered steel, for one way flow, two way flow, non-rotating and rotating inner pipe. No elbow required.
  • Maintained advantages of low frictional torque, high speeds possible

The Stainless Steel Series DPN:

  • Suitable for food industry or aggressive media or areas
  • Standard design made of 430F (1.4104) steel, for demanding applications of 316Ti (1.4571)

Maier is a supplier and rotary union manufacturer for various applications including construction, mechanical, marine, and industrial.

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Hydraulic Rotary Unions — DQ Series

The Maier DQ series is a rotary joint for thermal oil and high temperature and speed ranges with balanced mechanical seal. The DQ, DQT and DQTX types up to 752 °F work as “leak-free” solutions with additional cooling units for cooling and lubrication of bearings and seals by using the same heat transfer medium as in the main circuit. The DQL type and the 5th generation of DQ don’t require additional cooling units.

The DQ series offers a patented system to avoid seal damage and meets the requirements of specialized industries and processes including polymer, coating and lamination applications, paper and textile manufacturing processes including non-woven and textile calendars, industrial dryers and in rotary reaction vessels.

Hydraulic Rotary Union Product Features:

  • Longer service life than other rotary joints
  • Longer uninterrupted run-times and no unscheduled maintenance due to constant monitoring of rotary joint function via cooling unit
  • Significantly reduced risk of thermal oil leakage and escape of oil vapors
  • Pressure balanced and free running primary seal
  • Seal protector disk provides protection against coarse contamination
  • Even more safety due to the externally loaded mechanical seal
  • Secondary seal protected by cooled barrier fluid
  • Double wall rotor protects bearings form extended high temperature exposure and prevents energy loss
  • Function of rotary joints are monitored continuously via control elements on the cooling unit
  • In case of leakage, production can be continued until next scheduled shut-down due to temporary containment of reusable filtered oil within cooling unit

Maier is a supplier and rotary union manufacturer for various applications including construction, mechanical, marine, and industrial.

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Hydraulic Rotary Unions — DC Series

The Maier DC Series is a rotary joint for steam and hot water at high pressures and speeds. The patented system includes balanced mechanical seal with external water cooling. It meets the special requirements of applications as coating and laminating systems, paper, non-woven and textile calendars as well as driers.

Hydraulic Rotary Union Product Features:

  • Considerable longer service life
  • Greater application data range compared to other rotary joints
  • Longer machine running times
  • Easily predictable maintenance due to temperature sensor at mechanical seal
  • Sensor monitors function of mechanical seal in the rotary joint
  • Mechanical seal is pressurized from outside for superior reliability and low friction torque
  • Usage of cooling water for the integrated cooling system
  • Insulating disk protects mechanical seal from abrasive pollutants and prevents dissipation of heat from heating circuit to the cooled seal area
  • Rapid tapered roller bearings for high speed, pressure, and additional loads
  • DCL and DC bearing lubrication with high temperature grease up to 428°F, 362psi

Maier is a supplier and rotary union manufacturer for various applications including construction, mechanical, marine, and industrial.

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Custom Rotary Union

Multiple passage rotary unions are available in 1-44 passage models. Modified or custom configurations are also available. The rotary unions incorporate a patented seal design that is suitable for vacuum and bi-directional pressures up to 7,500 psi. All passages are individually sealed to allow use with dissimilar medias. The rotary unions can also be ordered as a combination rotary union/electrical slip ring assembly. Some of the options available include:

  • Single Passage
  • Multiple Passage
  • Inline
  • Threaded Shaft Mount
  • Flange Mount

Maier Heidenheim provides special solutions which safely connect pressurized pipes and rotating systems – for heating or cooling with water, steam or thermal oil, for the passage of cooling lubricants or for controlling production processes with hydraulic oil or compressed air. Please contact IC-Fluid Power to learn more about their customized products.

Maier is a supplier and rotary union manufacturer for various applications including construction, mechanical, marine, and industrial.

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Hydraulic Rotary Unions – Electrical Slip Ring

IC-Fluid Power can offer integrated electrical slip rings, which are useful for power, signal and data transfer. In addition to the standard slip rings illustrated below, IC Fluid Power can also supply custom slip rings ranging from high to low current designs with ultra low electrical noise.

Many slip ring assemblies are available with sealed protective covers. These covers can also include IP67 rated pin style connectors if needed; please contact your IC Fluid power sales representative to discuss the specifics of your application.

Standard Slip Ring Features:

  • High quality gold on gold contacts
  • Low electrical noise
  • Compact size
  • Transfers analog and digital signals
  • Compatible with data bus protocols
  • Standard designs with up to 56 circuits
  • Custom designs with 100+ circuits

The Maier SRK electric slip rings are equipped with gold-gold contacts. They can be used to transfer digital data such as Interbus, Profibus, Canbus or Ethernet up to the Gbit/s range. The slip rings are also suitable for high-precision analog measurement signals, PT100, DMS or encoders as well as currents of several amperes. Maier Slip rings can also be connected to rotary joints to work as a Combijoint solution and transfer current, signals, digital data, etc. Other slip ring configurations are available. Please contact IC-Fluid Power to discuss your specific slip ring requirements.

Maier is a supplier and rotary union manufacturer for various applications including construction, mechanical, marine, and industrial.

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