What Is a Floating Seal and Where Is It Used?

1. What Is a Floating Seal?

A floating seal is a rotary sealing unit intended for preventing the lubricant from escaping and minimizing the intrusion of foreign materials. In terms of heavy-duty machines, a floating seal generally means a mechanical face seal or, as it is also called, a Duo-Cone seal, toric seal, or heavy-duty face seal.

As opposed to the traditional radial lip seal where the sealing is performed by the lip made from elastomer contacting the shaft or other rotating parts, in case of floating seal, the sealing effect is achieved by two opposing high precision finishing metal rings.

In addition to supporting the metal rings, the elastomeric elements perform secondary sealing to the housing and also maintain the axial load to ensure that the main sealing surfaces remain in constant contact.The unit proves especially effective in situations where the rotating part has to retain the oil or grease when being exposed to the environments with the presence of abrasive dirt, mud, water, or other contaminants.

The exact cross-section, elastomer profile, metal alloy, and housing requirements vary by design. Buyers should verify the required seal type and dimensions against the equipment drawing or original part specification.

2. How Does a Floating Seal Work?

Working of an ordinary floating seal is achieved through controlled axial load, metal face contact, secondary sealing with elastomer, and proper lubrication. Each component serves a separate role in sealing efficiency.

An elastohydrodynamic film can be created between the two facing surfaces under certain working conditions. This is an effective way to handle friction and wear, but it is affected by many factors such as surface finish, face loads, speeds, lubrication, temperatures, and many more.

These elastomers are not rubber lips in contact with the shaft. In a conventional mechanical face seal, the rubber lips act as secondary seals and the metal rings as primary seals.

3. Where Are Floating Seals Commonly Used?

The floating seal is best suited for the rotary assembly when the normal seals are subjected to extreme dirt, abrasion, impacts, and other difficult conditions. Here are the most typical applications, but the final selection should be made according to specific equipment requirements.

Floating seals do not necessarily offer the optimum option in all cases of pumps, fans, compressors, and gearboxes. The speed at which the system operates, fluid compatibility, cavity design, lubrication, and the type of relative motion need to be considered.

4. What Are the Advantages and Limitations of Floating Seals?

Advantages

• Resistance to foreign contaminants: The seal configuration is intended to protect against the penetration of mud, dust, water, and other abrasive materials into the sealed area.
• Durable metallic sealing surfaces: Metallic sealing surfaces that have been accurately finished may be used in demanding rotating applications in which the lip seals would wear out quickly.
• Retention of lubricants: The seal is helpful in retaining oil or grease inside compatible components, thereby lubricating the bearings and gears.
• Compatibility with heavy machinery: Certain seal designs can work under harsh environmental conditions and slight misalignments and movements.

Limitations and Selection Risks

• Sensitivity of installation: Faces with contamination, twisted elastomers, improper compression, or faulty housing can affect the function.
• Housing considerations: The sealing system needs appropriate geometry and dimensions of the housing along with proper alignment.
• Operating conditions: Inappropriate speed, lubrication, temperature, and materials could be responsible for early wear and leakage.
• Application-specific cost: The use of precise metal rings along with installation requirements might not be economical for applications requiring simpler seals.

5. Floating Seal vs. Conventional Rotary Lip Seal

Although both the floating seal and the rotary lip seal prevent leakage in rotating machines, they vary when it comes to the nature of the sealing surface and applications. It is important to note that there are distinct differences between the two design concepts.

The traditional lip type seal might be the best choice for most shaft seals for general use purposes. However, a floating seal will have to be considered where there is heavy-duty work and contamination where a metal face seal would be better.

6. How to Select and Install the Right Floating Seal

There must be an initial starting point for choosing a reliable floating seal. The seal itself can fit according to its physical dimensions but may not match up because of the difference in the metal ring profile and geometry of the housing.

Confirm the Operating Conditions

Rotating speed, temperature of operation, lubricating oil used, contamination present externally, pressures involved, vibration, and environment of usage need to be considered while deciding on the suitability of floating seal and materials used for it.

Verify Dimensions and Housing Geometry

Check the seal's inside diameter, outside diameter, axial height, ring profile, elastomer section, and installation arrangement against the equipment drawing or original part number. The housing's dimensions and surface condition can affect elastomer compression and metal-face loading.

Evaluate Metal and Elastomer Materials

The material of the metal ring must be appropriate for the intended wear, loading, and environment. The elastomer must also be compatible with the intended lubrication as well as the temperature level. There are several possible elastomers like NBR, HNBR, and FKM, but the right choice depends on the particular compound and environment.

Control Installation Quality

• Clean the metal sealing faces, elastomers, and housing surfaces before installation.
• Inspect the mating faces for scratches, chips, corrosion, or other damage.
• Ensure the elastomeric elements are seated correctly and are not twisted or pinched.
• Use the installation procedure, tools, and approved assembly lubricant specified for the seal design.
• Follow the equipment manufacturer's instructions for assembly, lubrication, and commissioning.

Incorrect installation can compromise a correctly manufactured seal. For this reason, purchasing teams should consider the availability of installation instructions, dimensional documentation, and appropriate technical support when evaluating suppliers.

For related sealing requirements, you can also explore FOREVER SEALS oil seal products and custom rubber sealing solutions. Confirm the availability and suitability of a specific floating seal configuration directly with the supplier.

Frequently Asked Questions

Answers to common questions about floating seal construction, applications, maintenance, and selection.

Conclusion: Choose a Floating Seal for the Right Operating Conditions

Floating seals are an exceptional solution for applications where there is a need to maintain adequate lubrication and avoid contamination in challenging working conditions. Their efficiency relies on the metal face design, elastic backing, housing design, lubricant, and installation quality.

As far as selection for OEMs, distributors, and maintenance crews is concerned, the most optimal approach would start from the application needs and equipment specifications. Verification of the seal type, size, materials compatibility, and proper installation technique would help avoid mistakes.