FEP/PFA Encapsulated Hollow-Core Silicone O-rings

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FEP/PFA Encapsulated Hollow-Core Silicone O-Rings

High-Performance Sealing for Extreme Chemical Environments

FEP/PFA encapsulated hollow-core silicone O-rings combine the outstanding chemical resistance of fluoropolymers with the flexibility and resilience of silicone elastomers. Designed for critical sealing applications, these O-rings deliver superior performance in environments where traditional elastomers fail.

Applications for Hollow-Core FEP/PFA O-Rings

Hollow-core encapsulated O-rings are particularly well-suited for dynamic sealing applications where low friction, flexibility, and chemical resistance are critical. Their reduced compression force and smooth fluoropolymer surface make them a preferred choice over solid-core alternatives in moving systems.

Reciprocating Seals (Linear Motion Systems)

Used in pumps, valves, and cylinders where components move back and forth, hollow-core O-rings provide:

  • Lower friction during motion
  • Reduced wear on mating surfaces
  • Consistent sealing with minimal force

Rotary Seals (Slow-Speed Applications)

In slow rotational systems such as mixers, agitators, and rotary unions:

  • The non-stick FEP/PFA surface minimizes drag
  • Hollow-core flexibility improves contact without excessive squeeze
  • Helps extend seal life under light dynamic loads

Valve Stem Sealing

Ideal for control valves and dosing systems:

  • Smooth surface prevents sticking or “stiction”
  • Ensures precise movement and control
  • Maintains sealing integrity with frequent cycling

Pump Applications (Low to Moderate Pressure)

Common in chemical and pharmaceutical pumps:

  • Performs well in corrosive media
  • Reduces frictional heat buildup
  • Suitable for frequent start-stop operations

Semiconductor Wet Processing Equipment

In highly sensitive and clean environments:

  • Chemically inert surface prevents contamination
  • Low particle generation during motion
  • Maintains seal integrity in aggressive fluids

Food & Pharmaceutical Processing Equipment

Used in dynamic joints and moving assemblies:

  • Non-contaminating and easy-to-clean surface
  • Performs reliably under repeated motion cycles
  • Compatible with hygienic design requirements

Why Hollow-Core Excels in Dynamic Use

Compared to solid-core O-rings, hollow-core designs offer:

  • Lower breakaway friction (reduced stick-slip effect)
  • Better sealing under low compression loads
  • Improved adaptability to movement and misalignment
  • Easier installation in dynamic assemblies

Engineering Limits for Dynamic Applications

While hollow-core FEP/PFA encapsulated O-rings perform well in dynamic conditions, they are best suited for controlled operating ranges. Exceeding these limits can lead to premature wear, deformation, or seal failure.

Surface Speed (Rotary Applications)

  • Recommended: Up to 0.5 m/s
  • Intermittent operation: Up to 1.0 m/s (with lubrication)

Higher speeds may increase frictional heat and accelerate wear of the fluoropolymer jacket.

Reciprocating Speed (Linear Motion)

  • Recommended: Up to 0.3 m/s
  • Short-stroke / intermittent: Up to 0.5 m/s

Lower speeds help maintain seal integrity and minimize abrasion of the encapsulation.

System Pressure

  • Recommended operating pressure: Up to 10 bar
  • Maximum (static or low dynamic load): Up to 15 bar

Hollow-core designs are not intended for high-pressure sealing due to reduced structural support compared to solid-core O-rings.

PV Value (Pressure × Velocity)

  • Recommended limit: ≤ 1.5 MPa·m/s

PV values above this range can result in:

  • Excessive heat buildup
  • Accelerated wear
  • Potential deformation of the hollow core

Temperature Limits

  • FEP encapsulated: -60°C to +205°C
  • PFA encapsulated: -60°C to +260°C

Note: At higher temperatures, allowable speed and pressure should be reduced.

Compression (Squeeze)

  • Recommended squeeze: 10% – 20% of cross-section
  • Avoid excessive compression, which can:
    • Collapse the hollow core
    • Increase friction
    • Reduce service life

Important Design Considerations

To maximize performance in dynamic systems:

  • Avoid sharp edges or rough sealing surfaces
  • Ensure proper gland design and tolerances
  • Minimize eccentricity and misalignment
  • Use backup rings if extrusion risk exists
  • Prefer slow-speed, low-load applications

When Not to Use Hollow-Core O-Rings

Hollow-core FEP/PFA O-rings are not recommended for:

  • High-speed rotary sealing
  • High-pressure hydraulic systems
  • Heavy dynamic loads or shock conditions
  • Applications requiring high extrusion resistance
  • Prefer slow-speed, low-load applications

In such cases, spring-energized seals or solid-core alternatives may be more suitable.

For expert guidance on selecting the right O-rings and seals for your application, our team is on hand to help you match the ideal encapsulation type to your operating conditions and industry standards.

What Are Encapsulated Hollow-Core O-Rings?

Encapsulated O-rings feature a seamless outer jacket made from FEP (Fluorinated Ethylene Propylene) or PFA (Perfluoroalkoxy) that fully encloses a hollow-core silicone elastomer. The hollow-core design provides:

  • Lower compression force
  • Enhanced flexibility
  • Improved sealing at lower loads