Summary

• Oil seals comprise three core components – the sealing element (or lip), the metal case, and the optional garter spring, each contributing to the seal’s functionality and effectiveness.
• Choosing an oil seal involves evaluating multiple factors, including design, application needs, shaft diameter, bore diameter, sealing material, and environmental considerations.
• Regular maintenance, including proper lubrication, routine inspections, and scheduled replacements, ensures the longevity and reliability of oil seals, enhancing overall machine efficiency.

Introduction

In the mechanical world, where machinery and equipment make the earth move and gears rotate, the oil seal is an important component. Oil seals, or shaft seals, are a crucial part of various industrial equipment and applications, ensuring that lubricants don’t escape and contaminants don’t enter. While they may seem simple, their construction, design, and application are anything but. This in-depth guide aims to help you understand the essential role of oil seals, their construction, the various designs available, and key factors to consider when selecting one for your application.

Purpose of an Oil Seal

An oil seal serves three crucial purposes within any machinery. First, it prevents the leakage of lubricants or fluids outside the seal, even under high pressure. This function ensures the effective operation of equipment, as sufficient lubrication is a key requirement for the smooth functioning of machinery. Second, it retains the lubricating oil within the machinery. This retention function reduces the need for constant maintenance or re-lubrication, saving time and resources. Third, the oil seal acts as a barrier against contaminants. It prevents dirt, dust, and other potential contaminants from entering the machinery, protecting sensitive parts from damage or wear.

Construction of an Oil Seal

The construction of an oil seal is a testament to meticulous engineering. Each oil seal primarily comprises two core components: the sealing element and the metal case. The collaboration of these parts brings about the seal’s functionality and effectiveness. A garter spring may also be included as an available feature, providing an extra layer of operational support.

Sealing Element

The sealing element, also known as the sealing lip, forms the interior of the oil seal. Various materials can make up the lip depending on the application’s specific needs. Below are some commonly used materials:

• Nitrile Rubber (NBR): This is the most frequently used material for sealing elements, boasting good heat resistance properties and resistance to salt solutions, oils, hydraulic oils, and gasoline. Its recommended operating temperature range is from -40 to 248°F (-40 to 120°C). Nitrile functions adequately in a dry environment but only for intermittent periods.
• Polyacrylate Rubber (PA): PA is a go-to material for high surface speed environments as it has better heat resistance than nitrile. It performs optimally within a temperature range of -4 to 302°F (-20 to 150°C). It is incompatible with water or temperatures below -4°F (20°C).
• Silicone Rubber (SI): A popular choice for its resistance to low and high temperatures (-58 to 356°F, or -50 to 180°C). Silicone rubber has high lubricant absorbency, which reduces friction and wear, making it ideal for crankshaft seals. However, it is unsuitable for oxidized or hypnoid oils due to its poor resistance to hydrolysis.
• Fluorocarbon Rubber (FKM): Also known as Viton®, this material offers excellent resistance to chemicals and performance at high temperatures. It’s highly esteemed for its exceptional durability and heat resistance.

Metal Case

The metal case serves as the oil seal’s exterior or frame, providing rigidity and strength to the seal. The case material selection depends on the environment in which the seal will operate. Often, the same rubber material used in the seal element covers the case to help seal the exterior of the oil seal in the housing bore.

• Carbon Steel:  The most common material for oil seal cases, suitable for use with standard lubricants.
• Stainless Steel: Ideal for water, chemicals, or corrosion resistance applications. Stainless steel cases are also suitable for many FDA applications.

Oil seals with outer metal cases may include finishes or treatments applied to the outer edge to aid in rust protection, identification, and sealing of scratches or imperfections in the housing bore. Common finishes applied to the outside edge of metal O.D. oil seals include plain (a bonding agent of usually a yellowish-green color), a color-painted edge, and a grinded-polished edge.

Garter Spring

When included, the garter spring applies pressure to the sealing lip against the shaft, ensuring a tight seal. The choice of material, like that of the case, largely depends on the environment of use.

Garter springs are generally used when the lubricant is oil, as it provides the necessary downward force to maintain a tight seal. However, when grease is the lubricant, garter springs can often be eliminated. Due to its low viscosity, grease doesn’t require as much downward force to maintain an effective seal.

Standard Sealing Lip Designs

Oil seals come with various lip designs, each serving a unique purpose and suitable for different applications. Let’s discuss the most common industry-standard lip designs:

• Single Lip: This design features a garter spring and primarily seals against internal media in low-pressure applications. It’s not ideal for environments with dirt or contaminants.
• Double Lip: Like the single lip design, this design uses a garter spring with a primary lip that seals against internal media in low-pressure applications. The secondary (or auxiliary) lip offers extra protection from dust and dirt.
• Dual or Twin Lip: This design features two identical primary lips and a garter spring, typically used to separate two liquids. Lubricating the space between the lips with a grease or similar substance is essential for this lip design.
• Single Lip, No Spring: This lip design, which does not include a spring, is mainly used for sealing a non-pressure medium, such as grease, or protecting against dirt.
• Double Lip, No Spring: This design is also springless and is generally used to seal non-pressure media like grease. It protects against both internal and external media.

Standard Sealing Case Designs

Beyond the variety of lip designs, oil seals also come in various case designs, each serving a unique role. Here are some of the most common ones:

• Type A: An outer metal case with a reinforced plate for structural rigidity. It’s ideal for shafts when the diameters exceed 150mm, smaller shafts that need extra strength, or when used with special rubber compounds.
• Type B: An outer metal case generally used on shafts with diameters under 150mm and bore housing materials made of steel or cast iron. It provides a firm and accurate seal in the housing but may limit the static sealing on the outer diameter (O.D.).
• Type C: A rubber-covered metal case that can be useful on any size shaft. The rubber prevents rust & corrosion and shields against damage during assembly. This design is suitable for soft alloy, plastic housing materials, or replacement in environments with minor damage to the housing surface.

Factors in Oil Seal Selection

Selecting the right oil seal involves comprehensively evaluating your application’s needs and conditions. Below are the key factors to consider when choosing an oil seal:

1. Type: The combination of lip design and case type you select will determine the overall design of the oil seal.
2. Shaft Diameter: The outside diameter of the shaft where the seal will operate (sometimes referred to as the I.D. of the oil seal)
3. Bore Diameter: The inside diameter of the bore housing where the seal will operate (sometimes referred to as the O.D. of the oil seal)
4. Width: The thickness or width of the oil seal is another critical dimension that impacts the fit and functionality of the oil seal.
5. Sealing Material: The material used in the seal lip should be resistant to the operating temperature range, chemicals, lubricants, and pressures in your application.
6. Environmental Factors: Consider external factors such as exposure to dirt, water, and other contaminants, temperature fluctuations, chemical exposure, and shaft speed. For example, oil seals that must withstand high-speed rotational motion, high-pressure conditions, or extreme temperatures require more durable and resilient materials.
7. Lubrication: The lubrication used in the application will affect the choice of sealing material. The material must be compatible with the lubricant to prevent degradation and ensure the seal’s longevity.
8. Spring Material: The choice of garter spring material is also crucial as it must resist environmental factors such as exposure to water, chemicals, etc.
9. Application Requirements: The specific requirements of your application are critical to making the right choice. For example, if the seal is for a food processing machine, it must meet FDA standards.

Failure Modes of Oil Seals

It is crucial to understand that oil seals, like any other mechanical component, are subject to failure over time. The key to minimizing downtime and enhancing operational efficiency is recognizing the signs of oil seal failure and understanding its reasons. Here are some common failure modes:

• Excessive Wear: This is often a sign of regular friction between the seal lip and the shaft, usually resulting from inadequate lubrication or a rough shaft surface finish.
• Hardening or Cracking: Exposing oil seals to high temperatures for extended periods may cause the sealing material to harden or crack. This breakdown compromises the seal’s effectiveness and can lead to leakage.
• Chemical Erosion: If the seal material is incompatible with the chemicals or lubricants used in the machinery, it can degrade over time, leading to seal failure.
• Improper Installation: Incorrect oil seal fitting can cause immediate or premature failure. This improper fit can be due to many reasons, such as damage during installation, misalignment, or using the incorrect size.
• Excessive Pressure: Exposing an oil seal to pressure beyond its design parameters can result in seal deformation.

Maintenance and Inspection of Oil Seals

Proper maintenance and regular inspection are vital for prolonging the service life of oil seals and preventing unplanned downtime. Here are some tips:

• Regular Lubrication: Ensuring adequate lubrication will minimize friction and prevent wear and tear on the seal. Use only compatible lubricants as per the seal material to avoid chemical erosion.
• Routine Inspections: Schedule regular inspections of the oil seals to spot any signs of failure, such as leakage, hardening, or visible wear. Catching issues early can prevent minor problems from escalating into significant failures.
• Proper Cleaning: Dirt, grime, and debris can damage the sealing surface, leading to leaks. Regular cleaning of the seal and surrounding areas can help prevent this.
• Monitor Operating Conditions: Keep track of pressure levels, temperatures, and shaft speed. Excessive fluctuations can signal something wrong and potentially harm the oil seal.
• Replacement: Even with impeccable maintenance, oil seals won’t last forever. Understanding the typical lifespan of the oil seal type and material used in your machinery will help you plan for timely replacements.

Conclusion

Oil seals are integral components in a range of machinery and equipment, playing a vital role in keeping lubricants in, contaminants out, and machinery operating efficiently. Understanding the design, materials, and selection factors of oil seals can help you make an informed choice regarding your industrial needs. The reliability, longevity, and efficiency the right oil seal can bring to your machinery is priceless.

Global O-Ring and Seal offers over 50,000 unique oil seals with 215,000 cross-referenced part numbers for OEMs and Manufacturers. To find a part you need, search for the OEM/Manufacturer part number alone, and the oil seal matching the part number will be displayed. If you don’t have a part number, visit our online store and use the filter options to find the oil seal you are interested in. If you are unsure which oil seal is right for your application, please contact us and speak with a sales representative to discuss your best options.

We often take the maintenance of oil seals and their accessory tools lightly. But a slightly defective seal or a dented shaft can cause a lot of damage and even fail the whole equipment process. A failed oil seal means wastage of money, time and even loss of company reputation.

The reasons behind a failed oil seal are several. Here you can find some of the ways to avert seal failure and maximize its performance rapidly.

1. Protecting from dirt and impurities

Dust, dirt and debris are often the primary reasons for the failure of a seal. When a TTO Oil Seal is used in high pressure equipment, even the smallest particle can make a gap in between the seal and the equipment. This results in the access of impurity or the leakage of fluid or gas. So the best way to ensure that no dust particle pollutes the oil seal is to store it in a container or a sealed bag and keep it away from a place where dust and impurities exist.

2. Keeping the surface clean

While taking the oil seals and DOOSAN SEAL KIT from a storage bag, make sure that they do not get dirty. The surface where the seal will come into contact must be cleaned properly. Some oil seals that have greasy features are very vulnerable to dust. So, what you can do is separate the seals from other products and clean surfaces of bins, tables, conveyors, etc separately to minimize the chances of the oil seals getting dusty.

3. Protecting the shaft

Keep the shaft of the end application dust-free and protect it from any kind of damage. This will increase the performance of oil seals as well as the equipment where the former will fit into. If there is the slightest dent or chip in the shaft, the seal will work not function properly and the contaminants will infiltrate into the equipment. To fix this problem, it is required to wrap the shafts in mesh rubber screen or any other protective material and keep them in their own compartments.

4. Maintaining oil accessories

The accessories used with TCK Oil Seals are to be protected as much as the former. Installation tools, grease container, etc. are to be stored in a sealed container when they are not in use. This will lower the chances of infiltration of impurities. Also, make sure that the installation tools have no dented edge because this can affect the oil seal at the time of the installation process.

Top 8 Installation Tips for Oil Seals

Rubber oil seals play a significant role in preventing contamination and leakage in various applications, from automotive engines to industrial machinery. Although widely used seals, many users fail to get the results as expected mainly due to improper installation in applications. Understanding what rubber oil seals are and how to install them correctly is essential for ensuring the efficient and reliable operation of these systems. Would you like to get a clear clarity about oil seals and how to install them correctly in your applications? If yes, continue reading this post.

What are Rubber Oil Seals?

Rubber oil seals, also known as oil seals, are popularly used components in various industrial applications especially to prevent the leakage of fluids, such as oils or lubricants, from machinery or equipment. Made to fit tightly around rotating or moving shafts, these industrial oil seals, efficaciously create a barrier between the inner workings of the machine and the external environment.


As they are made from synthetic rubber materials, such as nitrile rubber, these seals offer excellent sealing properties, along with resistance to oil and other fluids. The rubber material is molded into a ring shape, often with a metal casing or reinforcement to provide structural support and ensure durability.

Steps to Install Rubber Oil Seals Properly

Following the steps below leads to a proper installation of industrial rubber seals when used in your applications.

1. Prepare the Surface: Take out the oil seals from their packaging only just before installation. Before installing the rubber oil seal, make sure the surface where it will be installed is clean and free of any debris or contaminants. Wipe the surface with a clean cloth or use a solvent if necessary to remove any grease or oil.
2. Inspect the Rubber Oil Seal: Before blindly installing the seal, have a thorough check and inspect the rubber oil seal for any damage or defects. Ensure to use a seal of the correct size and type for your application.
3. Apply lubrication: Apply a thin layer of lubricant to the industrial oil seal. This will help the seal slide into place smoothly and prevent any damage during installation.
4. Position the seal: Now carefully position the rubber oil seal on the designated area. Ensure that the seal is aligned correctly and evenly with the surface. Avoid stretching or distorting the seal during this step.
5. Use a seal installation tool: To securely install the seal, it is advisable to use a seal installation tool. This tool is specifically designed to prevent any damage to the seal and ensure a proper fit. If you need advice on the right tool, get in touch with the oil seal manufacturer.
6. Apply consistent pressure: When installing the seal, ensure to apply consistent and even pressure around its circumference. You can gradually push the seal into its housing with a gentle, tapping motion. Applying excessive force can deform or damage the seal.
7. Check the seal: Once done with the installation, double-check that it is seated correctly and evenly. Ensure that the seal is flush with the surface and there are no gaps or misalignments.
8. Test for leaks: Testing the rubber oil seal for leaks is the last and crucial step. Apply appropriate fluid or pressure to the sealed area and carefully observe for any signs of leakage. You may make necessary adjustments or repairs to ensure proper sealing.

If you are still confused and have more doubts about rubber seals and their installation, get in touch with trusted oil seal manufacturers such as SSP Seals. With their expertise and experience, they can provide you with comprehensive information and guidance to ensure the successful use and installation of these seals.

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