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.

Ce à quoi ces joints résistent – NBR (joints AS / SA / CS)

La liste ci-dessous présente les produits chimiques, fluides et gaz auxquels l’élément d’étanchéité en NBR (caoutchouc nitrile) des joints AS, SA et CS résiste de manière fiable. Une coche dans une colonne de température indique que le joint convient à ce milieu à cette température. Les cases vides signalent que le milieu n’est pas recommandé à cette température — choisissez alors un joint de qualité supérieure (FKM, silicone ou PTFE).

Valeurs indicatives basées sur des tableaux industriels (Parker O-Ring Handbook, Trelleborg, ERIKS). L’utilisateur final est responsable de la validation de l’adéquation à son application spécifique — la concentration, la pression, la sollicitation mécanique et le temps d’exposition comptent. En cas de doute, contactez Extreme Bearing pour une recommandation sur mesure.

Substance chimique 20°C / 68°F 60°C / 140°F 100°C / 212°F
Formaldehyde (40%)
Ascorbic acide
Citric acide
Acides gras (>C6)
Oxalic acide
Phthalic acide
Stearic acide
Tannic acide (10%)
Tartaric acide
Boric acide
Carbonic acide
Silicic acide
Sulfites
Ammonia, aqueux
Soude caustique et potasse
Lime (CaO)
Alum
Aluminium chlorure
Aluminium sulfate
ammonium chlorure
Brines, saturé
Solution de bromure (K)
Calcium chlorure
Chlorates of Na, K, Ba
Chlorides of Na, K, Ba
Copper salts (most)
Ferric chlorure
Ferrous sulfate
Lead acetate
Mercuric chlorure
Mercury
Nickel salts
Nitrates de Na, K et NH3
nitrite (Na)
Silver nitrate
sodium carbonate
sodium silicate
sodium sulfure
Stannic chlorure
Sulphates (Na, K, Mg, Ca)
Zinc chlorure
Cyclohexane
Naptha
Petroleum spirits
Paraffin wax
Huiles diesel
Huiles minérales
Huiles végétales et animales
Alcohols
Methanol
Glycerine
Glycols
Glycol, ethylene
Acétylène
Fluides frigorigènes fluorés
Soufre
Eau distillée
Eau douce
Eau dure
Eau de mer
Air humide
Bière
Jus de fruits
Gelatine
Jus de viande
Produits laitiers
Molasses
Amidon
Sugar, syrups & jams
Suif
Urea (30%)
Levure
Detergents, synthetic
Silicone fluids
Agents mouillants (<5%)
Ethanol
Isopropanol (IPA)
Propylene glycol
eau/glycol coolant
Fluide hydraulique (HL, HLP, HM, minéral)
Fluide hydraulique HFA (huile dans eau)
Fluide hydraulique HFC (eau-glycol)
Liquide de frein (DOT 3/4, glycol)
essence / petrol
Kerosene
Jet carburant (JP-4/JP-5/JP-8)
fioul / carburant huile
LPG (propane, butane)
AdBlue (solution d’urée 32,5%)
Transformer huile
Turbine huile
Gear huile
Fluide de transmission ATF
Graisse silicone
Graisse au savon de lithium
comprimé air, sec
Nitrogen (N2)
Carbon dioxide (CO2)
Hydrogen (H2)
Helium (He)
Argon (Ar)
Ethylene (C2H4)
Propylene (C3H6)
Methane (CH4)
Gaz naturel
Carbon monoxide (CO)
Fluide frigorigène R22 (HCFC)
Fluide frigorigène R134a (HFC)
Fluide frigorigène R1234yf (HFO)
Fluide frigorigène R717 (ammoniac)
Fluide frigorigène R744 (CO2)
Vin
Café / thé
Jus de légumes
Nettoyant CIP alcalin (1-3%)
Pentane
Hexane
Heptane
Octane
Isobutylene
Butanol (n-butanol)
n-Propanol
Oleic acide
Palmitic acide
Adipic acide
Lauric acide
ammonium sulfate
ammonium nitrate
Copper sulfate
Zinc sulfate
Magnesium sulfate
Magnesium chlorure
Barium chlorure
potassium chlorure
sodium thiosulphate
Fluide frigorigène R32 (HFC)
Fluide frigorigène R410A (mélange HFC)
Fluide frigorigène R454B (mélange HFO)
Fluide frigorigène R1234ze (HFO)
Fluide frigorigène R290 (propane)
Fluide frigorigène R600a (isobutane)
Hexafluorure de soufre (SF6)
Nitrous oxide (N2O)
Olive huile
Soybean huile
Palm huile
Rapeseed (canola) huile
Fish huile
Beurre
Cheese curds / whey
Œufs (crus / liquides)
Moutarde
liquide sugar / glucose syrup
Quaternary ammonium compounds (QACs)
Solution de chlorhexidine
Cutting huile (eau-soluble emulsion)
Cutting huile (neat, minérale)
HVO renewable diesel
Marine heavy carburant huile (HFO)
Boue de forage (base eau)
Boue de forage (base huile)
Coulis de ciment
Coulis de cendres volantes
Solution de cyanure (extraction aurifère, 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.