Ultimate Guide to Oil Seals | Part-2: by CV Technik
The following blog gives additional information to Blog 1. This blog will cover an overview of oil seals with an explanation of Oil seal types, oil seal materials, and their uses.
Types of Oil Seal
Types of Oil Seal
Oil Seals can be categorized in different types. As per interactional standards it normally is categorized as per their design aspect.
Oil seal type or shape-depending on Metal Case
Oil seal type or shape-depending on Lip Design
Oil seal type or shape-depending on Metal Case
The oil seal consists of a supporting body i.e., a metal case. The metal insert will give rigidity and strength to the seal while it is being held in the bore or recessed groove. It is normally made of cold-rolled steel sheets or other materials such as stainless steel 304, 316 or brass may be used depending on the application. Metal may be either inside or outside.
Oil Seal Type A | Oil Seal Type B | Oil Seal Type B1 | Oil Seal Type C
Oil Seal Types-Depending on Metal Case
Oil seal type or shape-depending on Lip Design
The Seal lip is the most important part of oil seal which is always in contact with the shaft and is responsible for providing required sealing. Lip selection is determined by media type, shaft speed, pressure, temperature, and contamination parameters. The media used in most applications are oil or grease. Lip designs generally include a spring when the media is oil because of its higher viscosity than grease. There is also a double spring design when there is media on both sides of the oil seal. Lip designs can also include a secondary lip which purpose is to mitigate particulates from reaching the sealing lip. For added protection of the oil seal from external particles, a V-Ring can be used in conjunction with the oil seal to eliminate particles. Check out our V-Ring section.
Oil Seal A | Oil Seal Type AS | Oil Seal Type D | Oil Seal Type DS | Oil Seal Type DL
Oil Seal Types-Depending on Lip Design
Oil Seal-Garter Spring
Oil seal garter spring
A helically coiled wire with its ends connected to form a ring is fitted into a lip seal. It is used in tension for maintaining a radial sealing force between the sealing element of a radial lip seal and shaft. The spring also prevents the deterioration of the main lip sealing performance caused by heat or others. Spring steel is the normal material for garter springs. Stainless steel is used where resistance to corrosion is required.
Oil Seal Materials
Oil seal material selection chart
The sealing lip is always made of a rubber or synthetic material. The material of the sealing lip is chosen according to the liquid to be sealed and the rotational speed. For larger shafts, an NBR sealing lip can cope with surface speeds of up to 10-12 m/s, while an FKM lip is suitable for speeds of up to 35-38 m/s.
NBR Oil Seal / Nitrile Butadiene Rubber / NBR / Nitrile
NBR, also known as nitrile rubber or nitrile, is the most popular material for an oil seal because of its good resistance to many oils and greases, such as mineral grease and hydraulic oil. Depending on their composition, synthetic oils and greases, such as those based on glycol, can damage NBR rubber materials. Depending on the amount of glycol, a PTFE lip seal may be the best choice. NBR is also unable to cope with contact with acids and solvents. The rubber is suitable for oil and grease at temperatures from -35 °C to 100 °C.
Temperature Range: -30°C to +100°C
NBR Oil Seal Advantages: Heat resistant, good mechanical properties, good abrasion resistance.
NBR Oil Seal Suitable for: Fuel, oil, acids, fat, grease, hydraulic fluids, chemicals.
NBR Oil Seal Not-Suitable for: Ozone, aromatics, chlorinated hydrocarbons, ketones, esters, and ethers.
HNBR Oil Seal / HSN / HYDROGENATED NITRILE-BUTADIENE
The properties of HNBR depend upon the acrylonitrile content and the degree of hydrogenation of the butadiene copolymer. They have rather better oil and chemical resistance than Nitrile Rubber and can withstand much higher temperatures. It has excellent resistance to sour oil and gas, steam, hot water, and ozone. Physical properties (e.g. tensile and tear strength, elongation, abrasion resistance, compression set, etc.) are also excellent and compounds exhibit good dynamic behaviour at elevated temperatures. Limitations include poor electrical properties, poor Flame resistance, and attack by aromatic oils and polar organic solvents.
Temperature Range: -30°C to +150°C
HNBR Oil Seal Advantages: Good mechanical and physical properties, better oil and chemical resistance than NBR.
HNBR Oil Seal Suitable for: Oil and gas, steam, hot water, and ozone sour gasoline, fats, acids and alkalis.
HNBR Oil Seal Not-Suitable for: Ketones, strong hydrocarbons, aromatic oils and polar organic solvents.
FKM Oil Seal / Fluorine Rubber / FKM / Viton / FPM
FKM or FPM, which is in well-known brand of Viton can withstand higher liquid temperatures of up to 220 ˚C. FKM is highly resistant to strong acids and bases, as well as to synthetic oils and greases. Glycol-based oil and grease, however, can also damage FKM. Because of the higher temperature resistance of FKM, this material is also chosen for applications where higher speeds play a role, which raise the temperature at the sealing lip considerably. Usually, using FKM will result in a longer life than using NBR. This compensates the higher price of FKM compared to NBR, as an FKM does not have to be replaced as frequently. The low temperature resistance of standard FKM is limited to -40 ˚C.
Temperature Range: -40°C to +220°C
FKM Oil Seal Advantages: Good resistance to high temperatures and chemical stability.
FKM Oil Seal Suitable for: Oils, greases, hydrocarbon, chlorinated Hydrocarbons, most organic acids, hot water and steam.
FKM Oil Seal Not-Suitable for: Methanol, ketones, esters, and nitro-containing compound.
EPDM Oil Seal / ETHYLENE PROPYLENE DIENE RUBBER
EPDM oil seals are less common. They are used in solvent, hot water and steam applications, EPDM resists low temperatures down to -40 °C and UV radiation well. Some types of EPDM are also suitable for higher temperatures up to +120 °C.
Temperature Range: -40°C to +120°C
EPDM Oil Seal Advantages: Excellent ozone, heat, chemical and aging resistance.
EPDM Oil Seal Suitable for: Ozone, hot water, oxidizing chemicals.
EPDM Oil Seal Not-Suitable for: Petrol, mineral oils, aromatics and chlorinated hydrocarbons.
Silicone Oil Seal / VMQ
VMQ, also known as silicone, is also used for oil seals, but this is less common because the mechanical strength of VMQ is low and this material has poor wear resistance This makes it less suitable for dynamic applications, but it can withstand low and high temperatures from -60 °C to 200 °C. Many types of VMQ are also suitable for contact with pharmaceutical and food products, so VMQ is an option worth considering.
Temperature Range: -60°C to +220°C
Silicone Oil Seal Advantages: Withstands continuous heating without hardening, good cold flexibility, very good resistance to oxygen and ozone attack.
Silicone Oil Seal Suitable for: Ozone and oxidizing chemicals.
Silicone Oil Seal Not-Suitable for: Oils, fuels, concentrated acids.
PTFE Oil Seal / Polytetrafluoroethylene / PTFE / Teflon
PTFE, which is used in the well-known brand Teflon is less commonly used, but it is the preferred material for specific rotating seals in the chemical, food and pharmaceutical industries. This material is notable for having a very low frictional resistance and the best chemical resistance. It can also withstand a very wide range of temperatures in these types of seals; -80 ˚C to 200 ˚C. The shafts on which oil seals with PTFE lips are used require a harder and finer finish. Something like an axle sleeve can also be used to meet this requirement.
Oil Seal Material Table
CV Technik Oil Seal Material Table
Conclusion:
In summary, in the blog Ultimate Guide to Oil Seals | Part-2 explains various types of oil seals, how they are categorized depending on the design or shape of the seal. We also have seen various materials used for manufacturing oil seals and how material selection is important as per industrial application.
