Rotary seal, external sealing, Type RA
The external sealing rotary seal type RA is used as a double-acting seal for rotary unions, axes, actuators and shafts. The media used in these applications range from mineral oil-based hydraulic liquids, environment-friendly bio-oils and water to flame-resistant hydraulic liquids and air.
To create a lubricant reservoir and increase the surface pressure against the rod, one or two circumferential notches, depending on the profile cross section, are worked into the running surface of the PTFE profile ring.
With the PTFE profile ring, the rotary seal dynamically seals off the rod surface, and with the elastic O-ring, provides a static sealing between the profile ring and the groove base.
With different material combinations, it can be used reliably across the whole pressure, speed and temperature range while additionally ensuring stick-slip free running.
Notches
To ensure that the preload on the seal is maintained under sudden changes in pressure and in direction of motion, it can be provided with two radial notches on both sides.
Application media
- Mineral oil-based hydraulic liquids
- Water
- Air
Environment-friendly bio-oils- Flame-resistant hydraulic liquids
- Other media, depending on the O-ring material
Application range
Pressure: up to 30 Mpa (300 bar)
Speed: approx. up to 2 m/s
Temperature: – 30 °C to + +200 °C (depending on the O-ring material)
Surface finish
| Roughness depth | Ra | Rt |
| Running surface | ≤ 0,3 µm | ≤ 3,0 µm |
| Groove base | ≤ 1,6 µm | ≤ 16,0 µm |
| Groove flank | ≤ 1,6 µm | ≤ 16,0 µm |
Installation dimensions
| Cylinder ø D | Gap size S | |||||||
|---|---|---|---|---|---|---|---|---|
| Standard design | Light design | Groove base ø D | Groove width L +0,2 | Radius R | 10 Mpa max. | 30 Mpa max. | Number of notches | O-Ring line ø |
| 15,0 – 39,9 | 15,0 – 135,0 | ød – 4,9 | 2,2 | 0,4 | 0,15 | 0,1 | 0 | 1,78 |
| 40,0 – 79,9 | 14,0 – 250,0 | ød – 7,5 | 3,2 | 0,6 | 0,2 | 0,15 | 1 | 2,62 |
| 80,0 – 132,9 | 22,0 – 460,0 | ød – 11,0 | 4,2 | 1,0 | 0,25 | 0,2 | 1 | 3,53 |
| 133,0 – 329,9 | 40,0 – 675,0 | ød – 15,5 | 6,3 | 1,3 | 0,3 | 0,25 | 2 | 5,33 |
| 330,0 – 669,9 | 133,0 – 690,0 | ød – 21,0 | 8,1 | 1,8 | 0,3 | 0,25 | 2 | 7,0 |
| 670,0 – 900,0 | 670,0 – 900,0 | ød – 28,0 | 9,5 | 2,5 | 0,45 | 0,3 | 2 | 8,4 |
PTFE profile ring material
PTFE + bronze
The standard for hydraulic applications, good gliding behavior, particularly pressure and abrasion resistant, cannot be used in aqueous solutions or acids
PTFE + Glass-MoS2
Particularly good resistance to wear and abrasion, application is possible even with poor lubricating pressure fluids, in water and in water-oil emulsions
PTFE + carbon
Exceptional resistance to abrasion and extrusion; can be used in water-hydraulics
For other possible materials see our overview of PTFE materials in the technical information section.
O-ring material
- Nitrile rubber NBR: Temperature range − 30 °C to + 120 °C
- Fluororubber FPM: Temperature range − 25 °C to + 200 °C
Overview of materials for dynamic seals (PDF)
The following overview is a selection of typical PTFE materials used for seals, guide elements and wipers. Other PTFE materials are available for special applications.
Product data sheet (PDF)
Our data sheet for the Rotary seal, external sealing, Type RA can be found here.
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