A Guide to Oil Seals

Oil seals are essential for keeping lubricant and other necessary substances inside rotary shaft equipment and preventing debris from getting inside. These invaluable devices, also called rotary shaft seals, shaft seals, lips seals or elastomeric seals, protect the bearings of rotating shafts. In simple terms, oil seals form a protective barrier that separates the inside from the outside. 

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In This Article

• How Do Oil Seals Work? 
• How Is an Oil Well Sealed? 
• How Long Do Oil Seals Last? 
• How Does an Oil Seal Prevent Leakage? 
• Contact Global Elastomeric Products, Inc. for Your Oil Seal Requirements 

How Do Oil Seals Work? 

Oil seals work by forming a secure plug on shafts. All oil seals consist of three basic components: 

• Interior sealing element: This flexible lip is set firmly against rotating parts to prevent substances inside a shaft from leaking. It usually requires some form of lubricant to avoid overheating.
• Sturdy circular metal casing: The casing is mounted onto the housing to hold the seal in place. 
• Garter spring: The spring maintains pressure to hold the sealing lip against the shaft. 

How Is an Oil Well Sealed? 

When choosing an oil seal for a shaft, many factors must be considered. These include temperature, size, shaft speed, pressure, lubrication availability and environment. Each setting is unique, and the correct fit is essential to ensure that oil seals will remain in place and effectively protect the bearings. Custom-molded oil seals are usually required to provide a superior fit and increased durability. 

How Long Do Oil Seals Last? 

Although choosing quality, custom-molded oil seals can greatly prolong the device's life span, many other factors affect the longevity of parts. These include: 

• The condition of the shaft and housing chambers: Any sharp edges or burrs present will cause premature deterioration or even ruin a new seal immediately.
• The seal material: What seals are made from has a significant impact on their durability. 
• Installation and maintenance: Sufficient lubrication, fit and routine checks can increase an oil seal's life span.
• Operating conditions: Extreme temperatures, excessive pressure or exposure to chemicals can cause premature deterioration of the part. 

Due to the complexity of the factors involved, there is no accurate way to predict how long oil seals last.

How Does an Oil Seal Prevent Leakage? 

Oil seals have a flexible inner lip that presses firmly against the shaft. The garter spring maintains pressure, and the sturdy metal casing holds the unit firmly in place. When optimally fitted and in good condition, oil seals create a protective seal around the shaft that protects the inside components. 

The Global Elastomeric Products, Inc. team has been providing high-quality, custom oil seals for more than fifty years. Our in-house design engineer will work with you to choose the best oil seals for your equipment. 

Machines with many moving parts often use oil to lubricate and protect mechanical components. However, when using oil, it’s important to take steps to prevent costly and potentially hazardous leaks. Oil seals offer a simple but effective solution, closing spaces between mechanical components to prevent lubricants from escaping. As an added benefit, oil seals also prevent moisture or chemical contaminants from breaching gaps in the machinery.

MSP Seals offers a full range of oil seals to prevent oil leaks and protect sensitive machinery from damage.

What Are Oil Seals?

Oil seals, alternatively known as rotary shaft seals or lip seals, are flexible rings of elastomer that secure the boundaries between stationary and moving components in a machine. These rings are flexible but durable, resisting wear from friction and exposure to oil. These properties allow oil seals to keep lubricants in a machine while keeping contaminants out. In doing so, oil seals prolong the working life of rotating shafts and precision bearings, ensuring that moving parts retain the lubrication they need for smooth performance.

MSP’s oil seals are designed to withstand extreme working environments, offering excellent durability and low friction properties to promote long working life. Our oil seals are lightweight and have a long shelf life, so they won’t become brittle or interfere with machine operation. Compared to standard seals, they offer improved performance in a convenient and easy-to-install form, making them the perfect solution for rotary shaft sealing.

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What Is The Best Material for an Oil Seal?

Oil seals can be made from several types of polymers, but one of the most effective is polytetrafluoroethylene, or PTFE. PTFE has exceptionally low friction, allowing it to resist abrasion and retain its integrity over time. PTFE is also resistant to high temperatures and chemical solvents, and it requires minimal lubrication, making it ideal for almost any operating environment.

Although PTFE is an excellent general-purpose oil seal material, using elastomers can also be appropriate, including silicone, nitrile, and EPDM. Materials are often chosen based on specific application requirements, such as the need to withstand specific chemicals. The mechanical properties of the rotary shaft, including shaft hardness and roughness, can also impact the selection of an oil seal elastomer. For instance, a softer metal shaft often requires a softer seal material than PTFE.

The company is the world’s best Custom Oil Seal supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Why Does Rotary Shaft Roughness Matter for Oil Seals?

Although the physical properties of the seal are important, the properties of the rotary shaft can also affect performance and longevity. One primary consideration in this respect is rotary shaft roughness, which refers to the surface unevenness of the shaft. Rotary shafts can have different degrees of roughness based on their machined tolerance. Smoother shafts have more even surfaces with finer machined tolerances.

Rotary shafts with the appropriate surface finish promote even sealing and limit premature wear due to abrasion. Generally, oil seals perform better when they are paired with smooth, properly finished rotary shafts. However, some surface roughness is desirable as it allows a film of lubricant to flow between the seal and the shaft, extending the longevity of the oil seal.

A rotary shaft that is too smooth exerts extra friction on the oil seal since this lubricant film cannot form. By contrast, a rotary shaft that is too rough can abrade an oil seal, causing it to fail and leak oil.

Why Does Rotary Shaft Hardness Matter For Oil Seals?

Rotary shaft hardness refers to the shaft’s resistance to indentation, which is important to consider when selecting an oil seal elastomer. The seal must always be softer than the rotary shaft to avoid damaging or wearing down the metal, leading to mechanical failure. As mentioned above, this means that softer metals are not always compatible with PTFE, which has a higher hardness relative to other polymers. PTFE seals can erode softer metal components, despite their otherwise favorable performance characteristics.

In general, harder metals are preferable for rotary shafts than softer metals, since increased hardness usually corresponds to more durable shafts and seals. However, the ideal hardness depends on a number of application-specific variables like rotation speed and pressure.

The lowest speed and lowest pressure applications can handle softer metal shafts, but hardness should still be at least 35 on the Rockwell C scale with high lubrication. When speeds or pressures are higher, the ideal rotary shafts might have hardness levels of 60 or 70+ Rc. The ideal oil seal material changes accordingly.

Despite the overall performance advantages of hard shafts, one benefit of softer rotary shafts is that they offer more leeway when working with durable oil seals. A PTFE oil seal polishes underlying metals that have hardness levels below 45 Rc, refining the surface finish for a better seal and less friction.

At higher hardness levels, this polishing effect disappears, so excess surface roughness can be more problematic. Thus, the higher the hardness required for the application, the smoother the rotary shaft needs to be to protect the working life of the oil seal. Even with proper surface finishing, seals used with very hard rotary shafts may wear out faster simply because there is less room for imperfections in the surface finish.

Rotary Shafts & Oil Seals by MSP Seals

Whether your application uses harder metal shafts or softer ones, MSP Seals can help you identify the most appropriate oil seals for your application. Our personalized customer service team works with each client to determine your application’s key constraints, using these factors as a guide for material selection.

As experts in all manner of rotary and shaft seals, MSP offers a diverse range of oil seals and other sealing solutions, including:

• Grease Seals
• Shaft Seals
• Mechanical Seals
• V-Seals
• Braided Packing

We offer both standard and custom configurations for all of our sealing products, with standard and custom sizes measured in inches (SAE, ARP) and metric (JIS, DIN).

While PTFE is our preferred material for performance oil seals, we also offer seals from a wide variety of hard and soft materials. Some of our material capabilities include:

• Carbon
• Ceramic
• Nitrile Butadiene Rubber (NBR, Buna-N)
• EPDM (EP)
• Butyl Rubber (IIR)
• Fluorocarbon (V, FKM, FPM, FFKM, FFPM)
• Neoprene / Chloroprene (CR)
• Fluorosilicone (FSi)
• Polyacrylate (ACM)
• Silicone (Si)
• Polyurethane Rubber (AU, EU)
• PTFE
• Stainless Steel (304, 316, 316L, etc)
• Carbon Steel
• Brass
• Bronze

Our comprehensive sealing offerings include packaging, and labeling, as well as inventory and total cost management for clients seeking full-service sealing partners.

To learn more about MSP Seals, contact our team today. MSP is certified to ISO : and ISO :. Our PTFE and sealing specialists are on hand to answer your questions and help you identify the best oil seals for your application.

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