Radial Bearing Shaft Seals – AS and SA

AS and SA are radial oil seals for stainless steel bearing housings. They seal bearing housings against contaminants with long-lasting efficiency. There are two versions available, AS and SA. Each version has a specific design for specific applications.

The seals are made of nitrile rubber (NBR) which provides good resistance against mineral oils and greases, making them suitable for a wide range of standard industrial applications.

AS and SA radial bearing shaft seals – stainless steel bearing housing

AS Seal

AS oil seals are designed with asymmetric lip angles. The angle α between the shaft and lip on the air side is larger than the angle β on the lubricant side. This geometry is designed to prevent contamination from entering the bearing housing while retaining lubricant inside. Normally, seals are designed with a small angle β on the lubricant side and a large angle α on the air side. This prevents lubricant from leaking out of the system. However, when grease is used, the difference in angles is less important and often reversed to provide better sealing against contaminants from outside. This is what we call the AS version.

The AS seal provides reliable sealing for bearing housings in standard to moderately contaminated environments, especially suitable for use in closed bearing assemblies such as AS / AS-VK assembly. Used on places with none abrasive surrounding. Just to close and become a maintenance free bearing unit sealed against contaminants.

AS seal grease direction illustration

Mounting tip

It is necessary that, if you do the initial greasing, to keep the cap a little bit open. To ensure that air can escape.

SA Seal

SA oil seals are designed with asymmetric lip angles as shown in the illustration. The angle α between the shaft and lip on the air side is smaller than the angle β on the lubricant side to prevent lubricant from leaking out of the system. When grease is used, the difference in angles is less important and often reversed to provide better sealing against contaminants from outside. We call this seal version SA. Leakage is less of a concern here due to the consistency of grease, which prevents excessive loss of lubricant. Therefore the main purpose of the grease seal is to keep contaminants out.

To improve bearing life by the correct use of bearing shaft seals, it is recommended to use an automatic lubricator or lubricate regularly. Only a small quantity of grease is necessary when slowly flushed into the bearing cavity to force dust and moisture away from the seal lips.

SA seal grease direction illustration
Dirt build-up in bearing housing seal cavity

Note – SA Seal Is Not for Food Applications

The SA seal is not suitable for applications where high hygiene is demanded because the cavity in the lip can act as a chamber for collecting dirt. For high hygiene applications, use our CC design.

Not suitable for abrasive environments

The AS seal and, to a lesser extent, the SA seal are not suitable for applications where there is a risk of contamination from abrasive materials. For this type of application, use our CS design.

Grease Is a Great Help to Sealing Bearing Housings Against Contaminants

Grease can be a great help to sealing bearing housings against contaminants. The gaps between the lips of the centrifugal seal and the stator must be sealed to keep out dust and water. To improve bearing life for centrifugal bearing shaft seals, it is recommended to use an automatic lubricator or to lubricate regularly. Only a small quantity of grease is necessary when slowly flushed into the bearing cavity to force dust and moisture away from the working parts.

Conveyor belt in seawater environment with pillow block bearing and single-point greaser

Examples of Grease Diagrams Using AS Bearing Shaft Seals

If the contamination is only on one side of the bearing unit, a seal combination can be chosen that is based on refilling the grease on this side. In this way, the contamination along with the grease shall flow away from the sealing lips. An example of such an assembly, a CS-AS combination, is shown in one of the illustrations with the path of the grease shown by the red arrows.

Example of damage from incorrect greasing of a pressure-tight bearing unit

Important Information for Initial Greasing of Pressure-Tight Bearing Units

In some configurations, the bearing units from Extreme Bearing are bearing shaft seals pressure-tight. Therefore it is necessary to keep the cap a little bit open while you do the initial greasing. Otherwise problems like in the picture shown here can occur.

In addition, whenever it is necessary to add some more grease later, you should always take care not to create overpressure in the housing. The Extreme Bearing units are pressure-tight when used with the following configurations of seals: AS/AS, AS/VK, CL/CL and CL/VK.

Wogegen diese Dichtungen beständig sind – NBR (AS / SA / CS)

Die folgende Liste zeigt die Chemikalien, Flüssigkeiten und Gase, gegen die das NBR-Dichtelement (Nitrilkautschuk) der AS-, SA- und CS-Dichtungen zuverlässig beständig ist. Ein Häkchen in einer Temperaturspalte bedeutet, dass die Dichtung dieses Medium bei dieser Temperatur verträgt. Leere Felder bedeuten, dass das Medium bei dieser Temperatur nicht empfohlen wird — wählen Sie dann eine höherwertige Dichtung (FKM, Silikon oder PTFE).

Indikative Werte basierend auf industriellen Verträglichkeitstabellen (Parker O-Ring Handbook, Trelleborg, ERIKS). Der Endanwender ist für die Validierung der Eignung für seine spezifische Anwendung verantwortlich — Konzentration, Druck, mechanische Belastung und Einwirkdauer sind entscheidend. Im Zweifelsfall wenden Sie sich an Extreme Bearing für eine maßgeschneiderte Empfehlung.

Chemischer Stoff 20°C / 68°F 60°C / 140°F 100°C / 212°F
Formaldehyde (40%)
Ascorbic Säure
Citric Säure
Fettsäuren (>C6)
Oxalic Säure
Phthalic Säure
Stearic Säure
Tannic Säure (10%)
Tartaric Säure
Boric Säure
Carbonic Säure
Silicic Säure
Sulfite
Ammonia, wässrig
Natronlauge und Kalilauge
Lime (CaO)
Alum
Aluminium Chlorid
Aluminium Sulfat
Ammonium Chlorid
Brines, gesättigt
Bromide (K) Lösung
Calcium Chlorid
Chlorates of Na, K, Ba
Chlorides of Na, K, Ba
Copper salts (most)
Ferric Chlorid
Ferrous Sulfat
Lead acetate
Mercuric Chlorid
Mercury
Nickel salts
Nitrate von Na, K und NH3
Nitrit (Na)
Silver Nitrat
Natrium Carbonat
Natrium silicate
Natrium Sulfid
Stannic Chlorid
Sulphates (Na, K, Mg, Ca)
Zinc Chlorid
Cyclohexane
Naptha
Petroleum spirits
Paraffin wax
Dieselöle
Mineralöle
Pflanzliche und tierische Öle
Alcohols
Methanol
Glycerine
Glycols
Glycol, ethylene
Acetylene
Fluorierte Kältemittel
Sulphur
Destilliertes Wasser
Weiches Wasser
Hartes Wasser
Meerwasser
Moist Luft
Beer
Fruchtsäfte
Gelatine
Fleischsäfte
Milk products
Molasses
Starch
Sugar, syrups & jams
Tallow
Urea (30%)
Yeast
Detergents, synthetic
Silicone fluids
Netzmittel (<5%)
Ethanol
Isopropanol (IPA)
Propylene glycol
Wasser/glycol coolant
Hydraulikflüssigkeit (HL, HLP, HM, mineralisch)
Hydraulikflüssigkeit HFA (Öl in Wasser)
Hydraulikflüssigkeit HFC (Wasser-Glykol)
Bremsflüssigkeit (DOT 3/4, Glykol)
Benzin / petrol
Kerosene
Jet Kraftstoff (JP-4/JP-5/JP-8)
Heizöl / Kraftstoff Öl
LPG (propane, butane)
AdBlue (urea Lösung 32.5%)
Transformer Öl
Turbine Öl
Gear Öl
ATF-Getriebeöl
Silikonfett
Lithiumseifenfett
komprimiert Luft, trocken
Nitrogen (N2)
Carbon dioxide (CO2)
Hydrogen (H2)
Helium (He)
Argon (Ar)
Ethylene (C2H4)
Propylene (C3H6)
Methane (CH4)
Erdgas
Carbon monoxide (CO)
Kältemittel R22 (HCFC)
Kältemittel R134a (HFC)
Kältemittel R1234yf (HFO)
Kältemittel R717 (Ammoniak)
Kältemittel R744 (CO2)
Wein
Kaffee / Tee
Gemüsesaft
CIP-Reiniger alkalisch (1-3%)
Pentane
Hexane
Heptane
Octane
Isobutylene
Butanol (n-butanol)
n-Propanol
Oleic Säure
Palmitic Säure
Adipic Säure
Lauric Säure
Ammonium Sulfat
Ammonium Nitrat
Copper Sulfat
Zinc Sulfat
Magnesium Sulfat
Magnesium Chlorid
Barium Chlorid
Kalium Chlorid
Natrium thiosulphate
Kältemittel R32 (HFC)
Kältemittel R410A (HFC-Gemisch)
Kältemittel R454B (HFO-Gemisch)
Kältemittel R1234ze (HFO)
Kältemittel R290 (Propan)
Kältemittel R600a (Isobutan)
Sulphur hexafluoride (SF6)
Nitrous oxide (N2O)
Olive Öl
Soybean Öl
Palm Öl
Rapeseed (canola) Öl
Fish Öl
Butter
Cheese curds / whey
Eggs (raw / flüssig)
Senf
flüssig sugar / glucose syrup
Quaternary Ammonium compounds (QACs)
Chlorhexidine Lösung
Schneidöl (wasserlösliche Emulsion)
Schneidöl (pur, mineralisch)
HVO renewable Diesel
Marine heavy Kraftstoff Öl (HFO)
Bohrspülung (wasserbasiert)
Bohrspülung (ölbasiert)
Zementschlämme
Flugascheschlämme
Cyanide Lösung (gold mining, NaCN)

Service instruction

Please inform your maintenance crew about this special service operating instruction. It could be helpful to dismount the grease nipples and exchange them with a standard stainless screw, so it will be impossible to make mistakes.