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.
Best Oil Seal Guide
Table of Contents
1. What is an oil seal and why does it matter?
2. Parts for Oil Seals
3. How does an oil seal work?
4. Types of Oil Seals
5. What are the functions of the oil seal?
6. How to Choose the Right Oil Seal?
7. Oil Seal Materials and Specifications
8. Oil seal installation and maintenance considerations
9. Conclusion
Oil leaks look bad, right? This is mainly due to worn oil seals.These seals may seem small, but they are vital to mechanical systems. They prevent fluid leaks that often lead to equipment failure.
This article explains the function of oil seals and explores the various types of seals. Follow our step-by-step installation guide and get expert maintenance tips.
What is an Oil Seals and Why Does it Matter?
Oil seals are simple components that prevent lubricating oil from leaking out of machinery and equipment. They work by sealing the space between the fixed and moving parts of the machine. At the same time, the seals prevent foreign matter such as dust from entering the machine.
Lubrication is essential for the smooth operation of machinery, machines or car engines. Oil seals keep the lubricant in the machine. If the fluid leaks out due to a broken seal, the machine will suffer extreme wear.
In addition, various types of oil seals are widely used in car engines, transmissions and pumps, as well as in all hydraulic machinery and mechanical systems that require fluid to operate.
Parts for Oil Seals
Oil seals are not very complex components. Let’s explore the different parts of the seal. We will learn more about their functions on this basis.
Shell
The enclosure is designed to provide a secure fit. It is made of metal to strengthen the seal. Other types of oil seals also have rubber-coated housings for added durability.
Seal lip
The sealing lip consists of two parts: the main lip and the dust lip. Each part has a different function, but both are crucial. The main lip is in direct contact with the rotating portion to provide a sealing effect. It prevents liquid leakage under high-pressure conditions. The sealing main lip can be made of rubber, elastomer, or PTFE. The choice of material depends on the need, as these materials vary in performance.
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Spring
The garter spring supports the seal lip to ensure contact with the rotating part. It exerts continuous pressure on the sealing lip to achieve a tight seal. The springs are made of stainless steel to maintain durability and long life. It also reduces wear and tear on the main lip.
How Does an Oil Seals Work?
The diameter of the oil seal is smaller than the shaft to surround it tightly. When the seal is installed on the rotating shaft, it forms a barrier that prevents the lubricating oil from leaking and blocks contaminants.
The spring ensures continuous contact with the shaft by applying a radial force, resulting in a strong sealing effect. The springs are adapted to different operating conditions. For example, during high-performance operation, the pressure on the seal rises.
Types of Oil Seals
1. Lip Seal (Single and Double Lips)
These seals are mounted directly on the shaft. They produce a suction seal effect to prevent leakage and contamination. The spring is wound around the seal, applying maximum pressure to enhance the sealing effect.
2. Rotary Shaft Seal
Rotary shaft seals are designed for low-pressure and high-speed applications. They provide relatively little friction and are ideal for motors and pumps. Seals prevent water, oil, and other fluids from leaking while maintaining the required pressure.
The rotary shaft is encapsulated in hub bearings, differential gears, engine crankshafts, fuel pumps, and water pumps. They keep the fluid within the system for seamless operation.
3. Radial Oil Seals
Radial oil seals have special applications on rotating shafts, crankshafts, and camshafts. They prevent oil leakage by sealing the gap between the rotating shaft and the machine housing.The seal is mounted on the shaft. The inner rubber portion of the seal is wrapped around the shaft.
4. U Cup and V Ring
U-cups are U-shaped seals for hydraulic and pneumatic applications. They provide a leak-proof seal to hold fluid in high-pressure systems, and their flexible design helps avoid wear and misalignment.
The V-ring is a rotating seal attached to the shaft. These seals can rotate in two directions depending on the movement of the shaft. Designed for high-speed applications due to flexible design adaptability. They provide effective pollution protection.
What are the Functions of the Oil Seals?
These seals primarily prevent fluid leakage at high pressures but have other functions as well. Let us explore the function of these seals in detail:
- Seal to prevent contaminants
Fast-moving parts, such as shafts and pistons, are sensitive to dust, foreign objects, and debris. Seals protect these critical components by limiting the flow of contaminants in the system. It uses rubber elements to form a barrier to block the entry of impurities.
During high-pressure operation, lubricants may leach out of the system. The seal is used to maintain the pressure required to hold the lubricant. They also fill in the space where the lubricant can leak.
- Heat and pressure resistance
The seals are manufactured according to ISO and DIN standards. The type of oil seal varies depending on the application.The correct seal and material are selected based on the fluid to be sealed and the expected temperature and pressure levels. It ensures that the seal can withstand high temperatures, pressures, and chemical exposure.
Leaks are catastrophic for moving parts in machinery. Any difference in the optimal fluid level results in high friction, which affects performance. The seal can close the gap between the stationary housing and the moving shaft to prevent leakage.
How to Choose the Right Oil Seals?
When looking for the perfect seal, pay attention to the type, oil seal size, and material. Where will you install the oil seals? It answers which type best suits your needs. Next, determine the desired size and select the appropriate seal. You must measure the shaft diameter, slot diameter, and slot width.
The choice of oil seal material depends on its specific application. You should check the maximum pressure and temperature level expected for the seal. For example, PTFE is suitable for low-pressure applications.
Oil Seal Materials and Specifications
Depending on the use, all parts of the seal have specific material requirements.
The housing is mounted on the shaft and undergoes certain resistance under high pressure. Therefore, it uses carbon steel for reinforcement and resistance.
After the outer case, the seal lip is the most critical part of the seal. The material selection depends on the fluid type and shaft speed. Seals commonly use rubber materials like nitrile rubber, fluorine rubber, and polytetrafluoroethylene.
The spring helps to ensure continuous contact with the moving parts. Preventing leaks in the machine is essential. Carbon steel springs are usually used because they do not deform quickly.
Oil Seal Installation and Maintenance Considerations
Are you looking for help installing an oil seal? Follow our step-by-step guide and install the seals like a pro. Don’t forget to check maintenance tips to ensure the durability and longevity of the seals.
Installation Steps:
Here’s a DIY installation guide. Follow each step to ensure proper installation and avoid any errors.
1. Prepare for installation
You must ensure that the seals, shafts, and holes are clean. In addition, surfaces and seals should be checked for damage or wear to prevent leaks. Apply lubricating grease to the shaft to facilitate the installation of O-rings and to avoid bouncing.
2. Proper alignment
The seal needs to be mounted vertically on the shaft and hole. If misplaced, the seal can experience high pressure, leading to leakage or failure.
3. Tools and materials required
Now that you know the initial steps, here are some essential tools for installing seals:
- Lubricating oil to make the seal slip.
- Gloves to grip firmly to prevent damage.
- Bearing Mounting Kit or Seal Drive for Mounting
4. Install oil seals
When installing seals, ensure proper alignment. Drive the seal into the hole using the bearing mounting tool.Choose the right tool to set the seal perfectly so that it does not have any skew or damage. If the seal does not fit, avoid hammering or forcing it. Realign the process appropriately.
5. Common mistakes to avoid
- Cleaning the installation area is necessary because any debris in the seal can cause a leak.
- Checking the alignment helps ensure the fit.
- Improper tool use or forced insertion can damage the seal.
Maintenance Precautions:
Proper maintenance keeps seals intact for longer and ensures efficient operation.
- Arrange an inspection in time to check for damage, especially the seal lip.
- If the seal shows signs of damage such as cracking, hardening, or liquid oozing, you should replace it.
- Lubrication is necessary for the smooth operation of the seal. Use compatible lubricants for best results.
- Dust, debris, and other impurities can build up around the seal. Cleaning them prevents contamination and reduces wear and tear.
Conclusion
From exploring the correct oil seal function to choosing the right seal. Now you can get the perfect seal according to your needs. Finally, the professional installation guide will play an important role when you get started.
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