What Is a Floating Seal?
[2025-11-22] | By Xiamen Jinshun Sealing Technology Co., Ltd. Annie Xu
Introduction
Floating seals-also called mechanical face seals, Duo-Cone seals, or heavy-duty rotating oil seals-are highly durable sealing components engineered for equipment operating in extreme environments, such as mud, sand, water, gravel, and abrasive dust.
They protect critical components like bearings and gearboxes by preventing external contamination and retaining lubrication even under high load, oscillation, shock vibration, and severe wear.
This guide explains:
- What floating seals are
- How they are structured
- How they work
- Installation precautions
- Real-world applications
- Why they are essential for heavy machinery
Table of Contents
- What Is a Floating Seal?
- Structure & Components
- How a Floating Seal Works
- Why Floating Seals Are Used in Heavy-Duty Equipment
- Technical Specifications (Table)
- Installation Notes
- FAQs
- Contact Jinshun Sealing (CTA)
A floating seal is a type of mechanical face seal designed specifically for rotary equipment used in harsh operating conditions. Also known as Duo Cone seals or metal face seals, they combine:
- A floating metal sealing ring
- A secondary elastomer element (O-ring or toric ring)
- A semi-floating structure that compensates for wear and misalignment
These seals rely on a thin oil film between two precision-ground metal faces to create a tight, wear-resistant seal that prevents leakage while blocking contaminants like:
- Mud
- Sand
- Water
- Rock dust
- Slurry
Floating seals are widely used in construction machinery, agricultural equipment, mining equipment, tunnel boring machines, and any rotating system exposed to heavy contamination.
A standard floating seal set consists of:
- 2 precision-machined metal seal rings
- 2 elastomer elements (O-rings or toric rings)
There are two main types:
• Type DO:
Uses an O-ring as the secondary sealing element.
• Type DF:
Uses a diamond-shaped toric elastomer ring, providing better stability in high-vibration environments.
Both designs work the same way:
- One metal ring stays stationary, and the other rotates with the shaft, forming a floating, self-compensating, lubricated sealing surface.
The sealing function comes from the axial compression of the elastomer ring. This creates a constant pressure between the two metal sealing faces.
Here's how it works step-by-step:
- The O-ring or toric ring compresses axially.
- Compression generates an elastic preload on the metal sealing faces.
- A micro-thin lubricating oil film forms between the faces.
- This oil film reduces friction, prevents wear, and provides sealing.
- Even as the metal faces wear over time, the elastomer pushes forward, automatically compensating, keeping the seal tight.
Most floating seals achieve a service life of 4,000+ operating hours, depending on lubrication and working conditions.
Floating seals are ideal for equipment operating in severe environments. Common applications include:
Construction Machinery
- Excavators
- Bulldozers
- Track rollers & idlers
- Swing drives
- Final drives
Mining & Tunneling
- Mining trucks
- Drilling rigs
- Tunnel boring machines
Agricultural Machinery
- Tractors
- Harvesters
Industrial Equipment
- Mixers
- Agitators
- Gearboxes
- Wind power systems
Wherever bearings and lubricated parts need protection from abrasive contaminants, floating seals and heavy-duty oil seals are the go-to solution.
| Parameter | Description |
|---|---|
| Metal Material | High-alloy cast iron / high-carbon steel |
| Hardness | 58–62 HRC (typical) |
| Surface Roughness | Ra 0.2–0.4 μm |
| Seal Type | DO type (O-ring) / DF type (toric ring) |
| Operating Temperature | –40°C to +200°C (depending on elastomer) |
| Service Life | 4,000–8,000 hours |
| Pressure Capacity | Up to 2 MPa |
| Typical Applications | Track rollers, travel motors, mining equipment |
✔ 1. Check the contact surface
Ensure the shaft and housing surface:
- Are smooth
- Have no axial scratches
- Have no burrs or corrosion
If there is severe wear or scarring, re-machine the surface to the specified dimensions.
✔ 2. Inspect the seal before installation
Replace the seal if:
- The elastomer is cracked
- There is deformation
- There is oil contamination or aging
✔ 3. Use proper tools
Avoid stretching or scratching the elastomer.
A simple method (if tools are unavailable):
- Wrap the shaft with a thin plastic film
- Apply light oil
- Slide the seal smoothly into position
Never reverse the lip direction-the lip must face the lubricating oil side.
✔ 4. Keep everything clean
Dirt on the sealing surface can immediately reduce the lifespan of a floating seal.
Ensure:
- Clean hands
- Clean tools
- Clean lubricating oil
- Correct positioning of the preload spring (if applicable)
Q1: What is the purpose of a floating seal?
To protect lubrication and prevent contaminants from entering rotating components in harsh environments.
Q2: How long does a floating seal typically last?
Typically 4,000–8,000 hours, depending on load, lubrication, and environmental conditions.
Q3: What is the difference between DO and DF type seals?
DO uses an O-ring.
DF uses a diamond-shaped toric elastomer ring for better vibration stability.
Q4: Are floating seals the same as Duo Cone seals?
Yes-they are two names for the same type of mechanical face seal.
Q5: Does Jinshun Sealing provide custom floating seals?
Yes, we provide standard and custom OEM/ODM floating seals, oil seals, hydraulic seals, PTFE seals, and more.
Looking for a reliable floating seal or oil seal manufacturer in China?
Xiamen Jinshun Sealing Technology Co., Ltd. supplies OEM & ODM seals for global machinery brands, offering stable quality, competitive pricing, and fast delivery.
📩 Get a quote or request samples:
https://www.jinshunsealing.com/
Our engineering team can help you design custom seals for your machinery project.