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.
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.
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What is Oil seal:
Oil seals play a crucial role in preventing the leakage of lubricants or fluids in a wide range of applications. From automotive engines and transmissions to industrial machinery and equipment, oil seals ensure proper functioning and avoid damage caused by leaks. These essential components are designed to tightly seal the gaps between moving parts, thus keeping contaminants out and lubricants in.
An oil seal, also known as a rotary shaft seal, consists of a flexible, circular lip made from materials such as rubber or metal. The lip is pressed against the shaft or housing in which it is installed to create a seal. The lip's contact with the rotating or stationary parts prevents the escape of fluids, such as oil or grease, while allowing the shaft to rotate smoothly.
One key aspect of oil seals is their ability to withstand high temperatures and pressure conditions. They are made from materials that can handle the demands of various applications, ensuring optimal performance and longevity. These materials often include elastomers such as nitrile rubber (NBR), fluoroelastomers (FPM), or silicone rubber (VMQ).
Oil Seal Product Description:
Introducing our high-quality oil seals engineered to provide exceptional performance and reliability in a variety of industrial and automotive applications. Our oil seals are meticulously designed with precision and constructed with durable materials to effectively seal and protect against the ingress of oil, grease, and other contaminants.
Function:
Oil seals, also known as rotary shaft seals or lip seals, function as essential components in mechanical systems. They are primarily used to prevent the leakage of lubricants, such as oil or grease, and to retain fluids within a system. By creating a barrier between the stationary and rotating components of machinery, oil seals effectively minimize friction, extend the longevity of equipment, and ensure its optimal function. Moreover, they provide protection against external contaminants, such as dirt, dust, moisture, and corrosive fluids, which could potentially lead to damage and wear.
Features:
1. Superior Sealing Performance: Our oil seals are engineered with precision to deliver exceptional sealing performance, ensuring that lubricants stay within the system and contaminants are effectively kept out. This not only helps to maintain the integrity of the equipment but also reduces the risk of downtime, maintenance, and associated costs.
2. High-Quality Materials: We utilize only the finest quality materials in the construction of our oil seals, providing excellent durability and resistance to wear, temperature variations, and chemical exposures. Our seals are manufactured from premium elastomers, such as nitrile rubber, fluoroelastomer (Viton®), silicone, PTFE, or a combination of materials, depending on the specific requirements of the application.
3. Optimal Design: Our oil seals are intricately designed to meet the precise needs of different industries and applications. With a variety of configurations, sizes, and lip profiles available, we ensure an optimal fit and sealing solution for your specific machinery. Whether you require a single lip, double lip, or specialized designs such as cassette seals or mechanical face seals, we have you covered.
4. Easy Installation: Our oil seals are designed for easy installation, reducing the time and effort required to replace or fit seals within existing systems. They come with a flexible lip that can be easily pushed onto or around the shaft, providing a secure and reliable seal.
5. Wide Range of Applications: Our oil seals are suitable for numerous applications, including automotive engines, power transmission systems, hydraulic and pneumatic cylinders, gearboxes, pumps, electric motors, agricultural equipment, and more. From small assemblies to heavy-duty machinery, our seals effectively address various sealing requirements across industries.
6. Custom Solutions: We understand that every application comes with unique demands. Therefore, we offer custom-engineered oil seals tailored to your specific requirements. Our highly skilled engineering team can work closely with you to develop a solution that perfectly matches your application's needs, optimizing efficiency and durability.
How do you choose an oil seal?
1. Understanding the Basics of Oil Seals: Oil seals consist of an elastomeric lip bonded to a metal housing, usually made of steel or stainless steel. The lip contacts the rotating shaft, forming a dynamic seal that prevents fluid or oil from leaking. The metal housing ensures stability and provides a mechanical barrier against external forces. These seals are available in various designs, such as radial lip seals, axial seals, and rotary shaft seals, each tailored for specific applications.
2. Identifying Key Factors for Selection: To choose the ideal oil seal, several factors should be considered:
a) Shaft Diameter and System Pressure: Match the inner diameter of the oil seal to the shaft diameter for a secure fit. System pressure is another critical factor, as higher pressures may require seals with additional reinforcement or alternative materials.
b) Operating Conditions: Consider the environment where the oil seal will be used. Extreme temperatures, chemicals, fluids, or abrasive conditions necessitate the selection of specialized materials offering resistance to these factors.
c) Speed and RPM: High-speed applications require oil seals with lower friction to minimize heat generation and ensure smooth rotation. Understanding the required operating RPM of the shaft will help determine the appropriate lip design and material.
d) Seal Performance: Evaluate the expected lifespan and seal efficiency. Look for seals with high wear-resistant properties to enhance their durability and ensure long-term reliability.
e) Seal Type: Different applications require specific seal types. Radial lip seals are commonly used for rotating shafts, axial seals are suitable for linear motion applications, and rotary shaft seals are versatile options for various applications.
3. Choosing the Right Material: The material selection plays a crucial role in the performance and longevity of oil seals. Commonly used materials include:
a) Nitrile (NBR): Ideal for general-purpose applications, nitrile provides excellent resistance to oil, water, and some chemicals. It has good temperature resistance but may not be suitable for extreme conditions.
b) Fluorocarbon (FKM / Viton®): These materials offer superior resistance to high temperatures, chemicals, and fuels. Fluorocarbon seals excel in harsh environments and are often chosen for applications involving extreme temperature fluctuations.
c) Silicone (VMQ): Silicones are resistant to temperature extremes and have good low-temperature flexibility, making them suitable for food-grade applications and environments with high heat or low-temperature requirements.
d) Polyacrylate (ACM): ACM seals are known for their resistance to petroleum-based oils and lubricants. They perform well in applications with moderate temperature ranges.
4. Consulting Experts and Industry Standards: When in doubt, consult industry experts or manufacturers who specialize in oil seals. They possess in-depth knowledge and can guide you in choosing the most suitable oil seal for your specific requirements. Additionally, consider ISO and ASTM standards that outline quality criteria, physical properties, and performance benchmarks for oil seals.
Choosing the right oil seal is critical to ensuring smooth operations, minimizing leaks, and maximizing the lifespan of equipment or machinery. By considering factors such as shaft diameter, operating conditions, speed, seal type, and material, you can confidently select a high-quality oil seal tailored to your needs. Partnering with reputable suppliers and adhering to industry standards will further guarantee optimal performance and reliable sealing solutions.
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