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.

Frente a qué resisten estos sellos – NBR (sellos AS / SA / CS)

La lista siguiente muestra los productos químicos, fluidos y gases frente a los que el elemento de sellado de NBR (caucho nitrílico) de los sellos AS, SA y CS es fiablemente resistente. Una marca en una columna de temperatura indica que el sello es apto para ese medio a esa temperatura. Las celdas vacías indican que el medio no se recomienda a esa temperatura — elija un sello de mayor grado (FKM, silicona o PTFE).

Valores indicativos basados en tablas industriales (Parker O-Ring Handbook, Trelleborg, ERIKS). El usuario final es responsable de validar la idoneidad para su aplicación específica — concentración, presión, esfuerzo mecánico y tiempo de exposición importan. En caso de duda, contacte con Extreme Bearing para una recomendación a medida.

Sustancia química 20°C / 68°F 60°C / 140°F 100°C / 212°F
Formaldehyde (40%)
Ascorbic ácido
Citric ácido
Ácidos grasos (>C6)
Oxalic ácido
Phthalic ácido
Stearic ácido
Tannic ácido (10%)
Tartaric ácido
Boric ácido
Carbonic ácido
Silicic ácido
Sulfitos
Ammonia, acuoso
Sosa cáustica y potasa
Lime (CaO)
Alum
Aluminium cloruro
Aluminium sulfato
amonio cloruro
Brines, saturado
Bromide (K) solución
Calcium cloruro
Chlorates of Na, K, Ba
Chlorides of Na, K, Ba
Copper salts (most)
Ferric cloruro
Ferrous sulfato
Lead acetate
Mercuric cloruro
Mercury
Nickel salts
Nitratos de Na, K y NH3
nitrito (Na)
Silver nitrato
sodio carbonato
sodio silicate
sodio sulfuro
Stannic cloruro
Sulphates (Na, K, Mg, Ca)
Zinc cloruro
Cyclohexane
Naptha
Petroleum spirits
Paraffin wax
Aceites diésel
Aceites minerales
Aceites vegetales y animales
Alcohols
Methanol
Glycerine
Glycols
Glycol, ethylene
Acetylene
Refrigerantes fluorados
Sulphur
Agua destilada
Agua blanda
Agua dura
Agua de mar
Aire húmedo
Beer
Zumos de fruta
Gelatine
Jugos de carne
Milk products
Molasses
Starch
Sugar, syrups & jams
Tallow
Urea (30%)
Yeast
Detergents, synthetic
Silicone fluids
Agentes humectantes (<5%)
Ethanol
Isopropanol (IPA)
Propylene glycol
agua/glycol coolant
Fluido hidráulico (HL, HLP, HM, mineral)
Fluido hidráulico HFA (aceite en agua)
Fluido hidráulico HFC (agua-glicol)
Líquido de frenos (DOT 3/4, glicol)
Gasolina
Kerosene
Jet combustible (JP-4/JP-5/JP-8)
combustibleóleo / combustible aceite
LPG (propane, butane)
AdBlue (urea solución 32.5%)
Transformer aceite
Turbine aceite
Gear aceite
Fluido de transmisión ATF
Grasa de silicona
Grasa de jabón de litio
comprimido aire, seco
Nitrogen (N2)
Carbon dioxide (CO2)
Hydrogen (H2)
Helium (He)
Argon (Ar)
Ethylene (C2H4)
Propylene (C3H6)
Methane (CH4)
gas natural
Carbon monoxide (CO)
Refrigerante R22 (HCFC)
Refrigerante R134a (HFC)
Refrigerante R1234yf (HFO)
Refrigerante R717 (amoníaco)
Refrigerante R744 (CO2)
Vino
Café / té
Zumo vegetal
Limpiador CIP alcalino (1-3%)
Pentane
Hexane
Heptane
Octane
Isobutylene
Butanol (n-butanol)
n-Propanol
Oleic ácido
Palmitic ácido
Adipic ácido
Lauric ácido
amonio sulfato
amonio nitrato
Copper sulfato
Zinc sulfato
Magnesium sulfato
Magnesium cloruro
Barium cloruro
potasio cloruro
sodio thiosulphate
Refrigerante R32 (HFC)
Refrigerante R410A (mezcla HFC)
Refrigerante R454B (mezcla HFO)
Refrigerante R1234ze (HFO)
Refrigerante R290 (propano)
Refrigerante R600a (isobutano)
Sulphur hexafluoride (SF6)
Nitrous oxide (N2O)
Olive aceite
Soybean aceite
Palm aceite
Rapeseed (canola) aceite
Fish aceite
Mantequilla
Cheese curds / whey
Eggs (raw / líquido)
Mostaza
líquido sugar / glucose syrup
Quaternary amonio compounds (QACs)
Chlorhexidine solución
Aceite de corte (emulsión soluble en agua)
Aceite de corte (puro, mineral)
HVO renewable diésel
Marine heavy combustible aceite (HFO)
Lodo de perforación (base agua)
Lodo de perforación (base aceite)
Lechada de cemento
Lechada de ceniza volante
Cyanide solución (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.