DO Floating Seal: Working Principle, Applications, and Selection Guide

A DO floating seal—also called a duo-cone seal or metal face seal—is a heavy-duty sealing assembly designed to keep lubricant inside rotating equipment while limiting the entry of water, dust, mud, and other contaminants. It typically uses two precision-finished metal rings, one in each housing half, with elastomer rings that support and seal the metal rings. The metal faces meet to form the primary seal, while the elastomers provide secondary sealing and help accommodate movement. To select one correctly, match its dimensions, materials, and operating conditions to the equipment rather than choosing by name or appearance alone.

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Key Takeaways

• A DO floating seal seals at the contact between two metal faces; elastomer rings support the assembly and seal against the housing.
• It is commonly considered for demanding rotating equipment exposed to abrasive contamination, including track rollers, final drives, and gearboxes.
• Correct selection depends on the housing geometry, speed, pressure, temperature, lubricant, contamination, and installation requirements.
• Share equipment details and a drawing with a supplier to confirm fit and identify material or design requirements before ordering.

Who This Guide Is For

This guide is for equipment manufacturers, maintenance teams, distributors, and procurement professionals sourcing a DO floating seal for new machinery or replacement work. It explains how the seal functions, where it is used, and what information to gather before requesting a quotation. It is not a substitute for the machine manufacturer’s specifications or an engineering review of a particular application. Where application limits are not established, confirm them with the seal supplier and equipment designer.

How a DO Floating Seal Works

Metal faces form the primary seal

A typical assembly has two metal rings arranged face-to-face, with one ring fitted into each side of the seal housing. Their carefully finished contact faces form the primary sealing interface. As the equipment rotates, the rings rotate with their respective components while the faces remain in controlled contact. The seal’s behavior depends on face geometry, surface condition, installation, lubrication, and operating conditions.

Elastomer rings support and seal the assembly

Elastomer toric rings sit between the metal rings and their housings. They help center and support the metal rings, provide a secondary seal against the housing, and allow a degree of movement as components shift in service. The elastomer also transfers rotation to the metal ring in many designs. The exact geometry and installation method vary, so follow the instructions for the specific seal rather than assuming all assemblies fit identically.

The interface should not be treated as a simple static gasket. Face contact, lubricant conditions, heat, pressure, and contamination all affect performance. Poor alignment, damage during installation, incorrect compression, or unsuitable materials can compromise the assembly. For that reason, identifying the seal’s operating environment is as important as measuring its basic dimensions.

Types, Materials, and Application Fit

Common material considerations

Metal ring materials may include wear-resistant cast iron or steel-based options, depending on the design and intended service. Elastomer choices may include compounds such as NBR, HNBR, or FKM, but no compound should be selected solely by its name. Compatibility depends on the actual lubricant or process fluid, temperature range, exposure time, and other chemicals present. Confirm the proposed material combination against the service conditions and supplier documentation.

Where floating seals are used

DO floating seals are commonly associated with rotating machinery that must operate around abrasive or wet contamination. Typical application areas include construction and earthmoving equipment, mining machinery, agricultural equipment, track rollers, wheel hubs, final drives, and some gearboxes. Suitability still depends on the specific equipment design; a seal used in one machine should not automatically be assumed interchangeable with a similar-looking assembly elsewhere.

These seals may be a poor fit where the housing cannot maintain the required geometry, where the specified operating conditions exceed the design limits, or where the application requires a different sealing arrangement. If the equipment has unusual movement, a nonstandard fluid, or limited installation access, provide those details during supplier review. A technically compatible material cannot compensate for an incorrect fit or unsuitable mounting arrangement.

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DO Floating Seal Selection Framework

1. Identify the seal and its housing dimensions

Start with the equipment model, assembly location, existing part number, and any drawings or maintenance records. Record the relevant housing and ring dimensions using the drawing or measurement method specified by the equipment manufacturer. Do not rely on visual similarity alone: small differences in geometry or seating can change the way the assembly fits and operates. If the old seal is damaged, use machine documentation where possible instead of treating its worn condition as the original specification.

2. Describe the operating conditions

Document rotational speed, temperature, pressure or pressure differential, lubricant, and expected contamination. State whether the equipment experiences water exposure, mud, fine dust, abrasive particles, or frequent starts and stops. As an example of how to communicate operating data, a duty record might list 1,500 rpm, 80 °C, and a pressure differential of 0.05 MPa. These are illustrative values only—not recommended operating limits or specifications for a particular DO seal.

3. Confirm materials and installation requirements

Ask the supplier to confirm the proposed metal and elastomer materials for the fluid and temperature conditions. Verify how the seal is oriented, seated, lubricated, and installed, and whether any special tools or cleanliness precautions are required. Keep the mating surfaces protected from scratches, grit, and impact during handling. If the seal is being used as a replacement, confirm that the proposed design corresponds to the original application rather than assuming dimensional resemblance is sufficient.

4. Review the complete application, not just the part

Before release, compare the supplier’s proposed seal information with the equipment drawing and service requirements. Resolve differences in dimensions, material, operating limits, or installation instructions before placing a production or maintenance order. For a new design, involve the equipment engineer and seal supplier early enough to review housing design and assembly access. This reduces the risk of choosing a seal that matches a catalog description but not the real duty.

Pricing, MOQ, and Lead Time

Pricing and lead time depend on factors such as seal dimensions, material selection, design availability, order quantity, and whether the requirement is for a standard item or a specially specified assembly. Minimum order quantities may also vary by product and supplier. We recommend requesting a quotation with the part number, quantity, destination, required delivery date, and any packaging or documentation needs. If the application requires a nonstandard specification, include drawings and operating details so the supplier can assess the request before confirming price or timing.

Supplier Evaluation Checklist

• Application review: Can the supplier review the operating environment and clarify missing technical details?
• Product identification: Can they confirm the proposed seal against a drawing, part number, or equipment reference?
• Material information: Can they identify the proposed metal and elastomer materials and discuss fluid compatibility?
• Order terms: Are quotation validity, MOQ, packaging, lead time, and delivery terms stated clearly?
• Technical communication: Can they explain installation requirements and flag conditions that need engineering confirmation?

For a B2B purchase, clear product identification and traceable order details are useful safeguards. Ask what product and material information will appear on the quotation and shipping documents, and confirm how revisions to drawings or specifications will be handled. Do not treat a supplier’s general product description as proof that a seal meets a specific equipment requirement. Request confirmation against your application data.

Common Selection Mistakes to Avoid

One common mistake is ordering by outside dimensions alone while overlooking the seal cross-section, housing arrangement, or material. Another is specifying a material based only on a broad label such as “oil resistant” without checking the actual fluid and temperature. Buyers may also omit pressure, speed, contamination, or installation details, leaving the supplier unable to assess the full duty. Finally, a seal can be damaged by improper handling or installation even when the selected part is otherwise suitable.

Conclusion and Next Steps

A DO floating seal works through a pair of contacting metal faces supported and sealed by elastomer rings. It is often considered for rotating equipment that needs protection against lubricant loss and external contamination, but correct selection depends on the exact housing, materials, and service conditions. Start with the equipment reference or drawing, record the operating data, and confirm installation and material requirements with the supplier before ordering. At ZHONO, we can review your DO floating seal inquiry as part of our mechanical components supply work; send the application details, quantity, and available drawings so we can discuss the appropriate specification and quotation.

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