Oil Seal (Lip Seal) Vs. Mechanical Seal: Pros & Cons of Each

Choosing Between Oil Seal and Mechanical Seal

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When selecting the most suitable seal for a specific application, it is essential to evaluate all relevant factors that define the operational environment and its intended use. For applications that necessitate a spring-loaded seal, both rotary shaft seals and mechanical seals can be viable options. However, in scenarios involving extreme temperatures or situations where rapid machinery movement generates intense heat, mechanical seals typically outperform oil seals.

Determining the choice between oil seals versus mechanical seals is often challenging. In certain instances, the decision is straightforward, especially when replacing a failed seal with the same type. Yet, there are cases where both types could be effective, leading to a crucial question: which one can boost efficiency and productivity the most? At Abbey Seals, we possess extensive experience across a wide variety of seal types and are eager to assist you with the specifics of your situation, recommending the best sealing solution tailored to your machinery. The choice between a rotary shaft seal and a mechanical seal involves numerous factors, and our team is ready to guide you toward the most effective option for your unique requirements.

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In machinery with numerous moving components, oil serves to lubricate and protect mechanisms. However, safeguarding against expensive and potentially dangerous leaks is vital when utilizing oil. Oil seals provide a straightforward yet efficient solution by sealing gaps between mechanical components, effectively preventing lubricants from seeping out. Additionally, they act as barriers to thwart moisture or chemical contaminants from infiltrating the machinery.

MSP Seals offers a comprehensive range of oil seals designed to avert oil leaks and safeguard sensitive machinery from harm.

What Are Oil Seals?

Known alternatively as rotary shaft seals or lip seals, oil seals are flexible elastomer rings that secure the intersections between stationary and moving machine components. These rings are not only flexible but also robust, demonstrating resistance against wear caused by friction and oil exposure. Such properties enable oil seals to retain lubricants in machinery while keeping contaminants at bay, thereby extending the operational lifespan of rotating shafts and precision bearings, which is vital for smooth functioning.

MSP's oil seals are engineered to endure demanding operational environments, featuring exceptional durability and reduced friction to support long service life. Lightweight and long-lasting, our seals remain resilient without becoming brittle, ensuring they do not interfere with machine operation. Compared to standard seals, they offer enhanced performance in a convenient, easy-to-install format, making them an optimal solution for rotary shaft sealing.

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What Is The Best Material for an Oil Seal?

Oil seals can be crafted from various polymer types, with polytetrafluoroethylene (PTFE) being one of the most effective materials. PTFE is known for its exceedingly low friction properties, making it highly resistant to abrasion while maintaining its integrity over time. Additionally, PTFE can withstand high temperatures and chemical solvents with minimal lubrication requirements, making it suitable for nearly any operational setting.

While PTFE is excellent as a general-purpose oil seal material, elastomer options such as silicone, nitrile, and EPDM can also be appropriate depending on specific application demands, including the need to resist certain chemicals. The mechanical characteristics of the rotary shaft, including shaft hardness and roughness, also influence the selection of an oil seal elastomer. For example, a softer metal rotary shaft often necessitates a softer sealing material than PTFE.

Why Does Rotary Shaft Roughness Matter for Oil Seals?

Although the seal's physical attributes are crucial, the characteristics of the rotary shaft also play a key role in performance and durability. One important aspect is rotary shaft roughness, which characterizes the unevenness of the shaft surface. Rotary shafts can vary in roughness levels based on their machining tolerances, with smoother shafts offering more consistent surfaces and finer tolerances.

Properly finished rotary shafts enhance sealing effectiveness and reduce premature wear caused by abrasion. Generally, oil seals achieve better results when paired with smooth, adequately finished rotary shafts. However, a certain amount of surface roughness is beneficial, as it allows a lubricant film to flow between the seal and the shaft, prolonging the oil seal's life.

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A shaft that is excessively smooth creates additional friction on the oil seal, inhibiting lubrication film formation. Conversely, a shaft with excessive roughness could wear down the oil seal, leading to failure and leakage.

Why Does Rotary Shaft Hardness Matter For Oil Seals?

Understanding the hardness of a rotary shaft, which refers to its resistance to indentation, is vital when specifying the elastomer for an oil seal. The seal must invariably be softer than the rotary shaft to prevent damage or wear on the metal, which could cause mechanical failure. As mentioned before, this means softer metals cannot always be paired with PTFE, as it has a higher hardness compared to other polymers. Though PTFE seals can perform exceptionally well, they might erode softer metal components.

In general, opting for harder metals is recommended for rotary shafts due to their increased durability and compatibility with seals. However, optimal hardness depends on specific application variables, including rotation speed and pressure.

Low-speed, low-pressure applications may utilize softer metal shafts, but hardness should still be a minimum of 35 on the Rockwell C scale with high lubrication. For higher speeds or pressures, ideal rotary shafts may reach hardness levels of 60 or above on the Rockwell scale, thereby influencing the selection of oil seal material.

While harder shafts present advantages, softer rotary shafts provide more options when utilizing durable oil seals. A PTFE oil seal, for instance, can polish softer metal shafts below 45 Rc hardness, improving surface finishing for superior sealing and reduced friction.

Beneath higher hardness levels, this polishing effect dissipates, leading to issues with surface roughness. Therefore, for applications requiring greater hardness, there needs to be an equal focus on achieving finer surface finishes on rotary shafts to ensure the oil seal's longevity. Even with proper finishing, seals used in conjunction with exceptionally hard rotary shafts may exhibit quicker wear due to reduced tolerance for surface imperfections.

Rotary Shafts & Oil Seals by MSP Seals

Whether your application involves harder or softer metal shafts, MSP Seals is committed to assisting you in identifying the appropriate oil seals tailored to your situation. Our dedicated customer service team collaborates with each client to understand key constraints for their application, using these factors to guide material selection.

As specialists in various rotary and shaft seals, MSP offers an extensive range of oil seals and other sealing solutions, including:

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

We provide both standard and custom configurations for all our sealing products, available in both inch (SAE, ARP) and metric (JIS, DIN) measurements.

While PTFE is our premier choice for performance oil seals, we also provide seals manufactured from a diverse array of both hard and soft materials. Our material options are extensive and 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 extensive sealing solutions encompass packaging, labeling, and inventory management, catering to clients seeking comprehensive sealing partnerships.

To discover more about MSP Seals, reach out to our team today. MSP is ISO certified. Our PTFE and sealing experts are ready to address your inquiries and support you in determining the optimal oil seals for your needs.

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