The group of oil seals used in dynamic applications include radial shaft seals that seal a rotating shaft around its circumference. They are also known as lip seals, but in this blog we will use the term oil seals.
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Usually, these oil seals are used to seal lubricating oil or grease and contain it within the application, so that moving parts such as bearings are continually supplied with enough lubrication. However, such seals are also used for sealing other liquids, gases, and solids, such as powders or granules.
All are fitted with a spring to preload the sealing lip. All these types are for non-pressurised or low-pressure applications up to 0.5 bar for diameters of a limited size. For diameter of 500 mm or more, the maximum pressure is 0.1 bar. For higher pressures, special types or PTFE lip seals can be used.
ERIKS type M (type B according to the DIN standard) has a single metal casing and rubber sealing lip. Since the casing is made of metal, it must be fitted in a well-finished, undamaged groove. Large volumes of oil seals with metal casings are often cheaper, which is why they are often used as original equipment in machines. However, if an oil seal has to be replaced, types with a rubber exterior (type R or RST) are easier to fit. Type MST is similar to M and commonly used. The difference is the dust lip in the MST oil seal that prevents dust and dirt reaching the sealing lip, and extends its service life in dusty environments.
ERIKS type GV (type C according to DIN) is equivalent to type M, but is a heavy-duty version with a double metal casing. This can be a useful solution with larger diameters in more demanding applications. There is also a version of this type with a dust lip; the GVST (type CS according to DIN).
ERIKS type R (type A according to the DIN standard) is identical in shape to type M, but has a rubber outer case with metal reinforcement on the inside. The rubber creates a good seal in the housing, even if the housing has suffered minor damage or is not in its best condition for other reasons. The RST version has a dust lip. These types are often chosen to replace a type with a metal outer case because they are easier to install and can cope with minor damage to the groove, such as scratches.
ERIKS also supplies the types GR and GRST. These are virtually identical to the types R and RST, except in this case the metal inner ring is also completely encased in rubber. ERIKS uses FKM rubber here as standard, so these seals are ideal for use in acidic environments.
An overview of the different standard types of oil seals and their main characteristics is shown below.
Outer case
The metal used in the outer case of oil seals is usually made of carbon steel. Upon request, and depending on quantities, a different type of steel (such as stainless steel) can be used.
The quality of the rubber or rubber fabric used to make an outer case is the same as the quality of the rubber sealing lip. Fabric reinforced rubber is, as the name suggests, rubber reinforced with a fabric.
Spring
Standard springs are made of carbon steel. We use stainless-steel springs for our GR and GRST oil seals made from FKM rubber. In some rare cases, an O-ring is even used as a spring element. Standard PTFE lip seals are not fitted with springs.
Sealing lip
The sealing lip is always made of a rubber or synthetic material. For oil seals with a rubber outer case (R, RST, GR, GRST), the rubber quality of the sealing lip and the outer case are the same.
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.
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.
Most ERIKS oil seals, such as the types M, MST, R and RST, are made of NBR as standard.
Fluorine rubber (FKM, Viton')
FKM or FPM, which is in well-known brand Viton', can withstand higher liquid temperatures of up to 180 ˚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 -15 ˚C.
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.
EPDM
EPDM oil seals are less common. They are used in solvent, hot water and steam applications, EPDM resists low temperatures down to -50 °C and UV radiation well. Some types of EPDM are also suitable for higher temperatures up to +150 °C. EPDM oil seals are usually available upon request.
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VMQ (silicone)
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 fairly 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. VMQ oil seals are usually available on request.
To install an oil seal properly, the shaft must be undamaged. This is so the oil seal can do its job properly on the one hand, and to prevent it from being damaged during fitting on the other. In addition, it is very important to lubricate the shaft, the sealing lip and the bore with plenty of grease. This will allow the oil seal to slide more easily over the shaft and prevent dry running after the first rotation. The oil seal may also come into contact with the keyway, thread or other grooves when sliding over the shaft. By taping or covering the shaft at the location of these irregularities with oil-soaked paper, the oil seal can be mounted without damage to the sealing lip.
Other important factors are ensuring the hardness and roughness of the shaft are correct. A shaft hardness of HRC 45 is recommended for a rubber sealing lip, with a roughness of Ra 0.4-0.8. A higher shaft hardness of HRC 60 and shaft roughness of Ra 0.1-0.4 is recommended for a PTFE lip.
Oil seals are crucial components in sealing systems, especially in high-pressure and high-temperature environments. Choosing the right oil seal for such demanding applications is essential to ensure effective sealing, prevent leakage, and prolong the service life of your machinery. In this article, we will explore the key considerations and factors that affect the selection of oil seals for high-pressure and high-temperature applications.
Before selecting an oil seal, it's important to understand the specific challenges posed by high-pressure and high-temperature applications:
High-Pressure Applications: Oil seals in high-pressure environments must maintain a reliable barrier to prevent leaks and withstand significant forces. These seals must not deform or lose contact with the sealing surface under pressure.
High-Temperature Applications: When exposed to high temperatures, oil seals must retain their sealing properties without degrading. High-temperature seals must resist thermal expansion, ensure material integrity, and remain flexible enough to handle changes in temperature.
Selecting the right oil seal for high-pressure and high-temperature applications depends on several factors:
The material used in the construction of the oil seal plays a critical role in its performance in extreme environments. Here are the best materials for high-pressure and high-temperature applications:
Viton (FKM): Known for its high resistance to both high temperatures and aggressive chemicals, Viton is ideal for sealing in environments where both heat and pressure are present. It can withstand temperatures up to 250°C and is suitable for aggressive fluids.
PTFE (Polytetrafluoroethylene): PTFE seals offer excellent resistance to high temperatures (up to 260°C) and are highly chemically resistant. Their low friction properties also make them ideal for high-speed applications under pressure.
Nitrile Rubber (NBR): NBR seals are ideal for oil-based applications, offering good resistance to oils, fuels, and greases. Although their temperature tolerance is generally lower than that of Viton or PTFE, they can perform effectively in high-pressure conditions with temperatures ranging from -40°C to 120°C.
EPDM: EPDM seals are known for their excellent resistance to heat, ozone, and weathering. They are suitable for water, steam, and certain chemical applications, but they are not ideal for petroleum-based oils.
It is essential to select an oil seal material that can withstand the maximum temperature and pressure your machinery will be exposed to. Consider the following:
For High Pressure: Seals for high-pressure applications require materials with good compression set resistance and the ability to retain shape under pressure. Viton, PTFE, and metal-cased seals are excellent choices for this purpose.
For High Temperature: Viton and PTFE are the best choices for high-temperature environments. Viton seals can handle continuous temperatures up to 250°C, while PTFE seals perform well up to 260°C and are ideal for extreme conditions.
For high-pressure and high-temperature applications, minimizing friction is crucial to extend the service life of the oil seal and the machinery. PTFE oil seals are excellent for low friction applications, while Viton and NBR seals may be more suitable for moderate-speed environments.
The design of the oil seal is another important factor. Common seal designs for high-pressure and high-temperature applications include:
Spring-Loaded Seals: These seals use an internal spring to maintain constant pressure on the sealing surface, ensuring effective sealing even in fluctuating pressure conditions.
Metal-Cased Seals: These seals provide enhanced strength and are often used in high-pressure applications where the oil seal is exposed to external forces.
In addition to temperature and pressure, it is important to consider the chemical compatibility of the oil seal with the fluids it will be exposed to. For example:
At DXTSEALS, we specialize in providing high-performance oil seals designed to withstand even the most challenging conditions. Our oil seals are manufactured from top-quality materials like Viton, PTFE, NBR, and more, ensuring long-lasting and reliable sealing for high-pressure and high-temperature applications.
Whether you need spring-loaded, metal-cased, or custom-designed oil seals, DXTSEALS can provide the right solution for your needs. Our team works closely with you to understand your requirements and deliver tailored sealing solutions that ensure your machinery operates at peak performance.
Choosing the right oil seal for high-pressure and high-temperature applications is essential for maintaining the efficiency and longevity of your machinery. Key factors like material selection, pressure, temperature range, and seal design play a critical role in ensuring effective sealing under extreme conditions. DXTSEALS offers a wide range of high-quality oil seals, including Viton, PTFE, and NBR, designed to meet the toughest industrial requirements.
Contact us to discuss your requirements of TC Oil Seal. Our experienced sales team can help you identify the options that best suit your needs.