What is a skeleton oil seal and how does it work?

Are you dealing with oil leakage, contamination, or frequent seal failure? You might be using the wrong type of oil seal. Let’s uncover how a skeleton oil seal could be the answer.

A skeleton oil seal is a reinforced shaft seal with an internal metal frame, designed to retain oil and block contaminants under dynamic conditions. It offers high stability, long life, and reliable performance.

In this guide, I’ll break down everything from what it is, to where it’s used, the types available, and how to choose the right one. If you’re a maintenance engineer, importer, or industrial OEM, this article is made for you.

What is a skeleton oil seal?

Are all oil seals created equal? Why do some fail while others last?

A skeleton oil seal includes a steel-reinforced inner frame (the “skeleton”) that provides added rigidity, helping the sealing lip maintain optimal contact with the rotating shaft—even under pressure, misalignment, and high speed.

Skeleton seals are typically made from rubber (NBR or FKM) molded around this metal insert. The metal ensures that the seal doesn’t deform or collapse during operation. This makes them ideal for rotating applications like electric motors, pumps, gearboxes, and compressors.

They’re also referred to as radial shaft seals or shaft oil seals in different regions or industries.

What are the common types of skeleton oil seals?

It can be confusing—TG4, TC, K-type… What’s the difference?

Here are the most common types of skeleton oil seals we manufacture at Hengoseal:

Each type has a unique structure tailored to different sealing environments. For example, our TG4 oil seal in NBR is ideal for standard rotating shafts, while TC oil seal in FKM offers better resistance in high-temperature gearboxes.

What materials are used in skeleton oil seals?

Rubber is just rubber, right? Not quite.

Skeleton oil seals are typically made from two core materials:

💡 Pro tip: If you’re sealing in high-speed, high-temperature environments, go with FKM. For standard machinery, NBR is often sufficient and cost-effective.

Where are skeleton oil seals used?

Skeleton oil seals are everywhere—you just don’t notice them.

Typical applications include:

• Electric motors and generators
• Hydraulic pumps
• Gear reducers and gearboxes
• Automotive components
• Compressors and fans

Because of their strength and longevity, they’re widely used in both OEM manufacturing and after-sales repair & maintenance.

If you’re looking for skeleton oil seals for gearboxes, industrial pumps, or automotive crankshafts, we have the right type in stock or ready to customize.

How do I choose the right skeleton oil seal?

The wrong seal size or material can lead to disaster. So how do I choose correctly?

Here’s a simple checklist to help:

For complex selections, contact us directly.

Want to find the right replacement oil seal?

If you already know your old oil seal’s part number—or you’re trying to match National or SKF seals—you’ll love our Oil Seal Cross Reference Chart.
Use it to quickly find Hengoseal equivalents and get instant support.

Conclusion

Skeleton oil seals provide superior durability and sealing performance due to their internal metal structure. Choosing the right type and material is key to preventing leakage and extending equipment life.

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Ready to upgrade your oil seals? We manufacture TG4, TC, and custom designs in both NBR and FKM.
📧 Email: [email protected]
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