Bonded seals are an important component in many mechanical and industrial applications. They create a tight seal between two surfaces, preventing leakage of liquids or gases. This guide will provide an overview of bonded seal design, materials, applications, and best practices.
What are Bonded Seals?
Bonded seals, also sometimes called adhesive seals, use an adhesive or glue to attach the sealing element to a substrate. The sealant material forms a barrier between the two surfaces, filling any gaps or imperfections to block leakage.
Bonded seals are typically made using materials like rubber, silicone, or urethane formed into an O-ring or gasket shape. The seal is then adhered to a smooth surface using a compatible adhesive. The adhesive cures to create a permanent, leak-proof bond.
Compared to other sealing methods, bonded seals provide high strength and durability thanks to the direct adhesive attachment. They also accommodate some flange surface imperfections better than non-adhesive seal types.
Common Applications
- Bonded seals are commonly found in:
- Gearbox and transmission seals
- Automotive engine gaskets
- Appliance seals
- Pipeline and plumbing flanges
- Bonding wear rings in pumps
- Lid seals on electronic enclosures
- Weatherstripping in doors and windows
For these applications, bonded seals prevent leakage of oils, fuels, water, refrigerants, or other process fluids. The adhesive bond withstands high pressures or temperatures while remaining flexible.
Design Considerations
Proper design is critical for bonded seals to function as intended. Key considerations include:
- Seal and substrate material compatibility – The coefficients of thermal expansion must match to avoid seal failure from temperature changes.
- Adhesive selection – The adhesive must bond strongly to both the seal material and substrate through the expected temperature range.
- Surface preparation – Surfaces must be thoroughly cleaned and textured to enable adhesive bonding.
- Compression – The seal must be compressed 15-30% to ensure intimate contact for sealing and bonding.
- Size and groove dimensions – The seal must fit the groove dimensions correctly. An oversized seal can extrude while undersized can leak.
With careful design and material selection, bonded seals kits that comes with bonded seals can maintain their seal through millions of motion cycles as well as thermal or vibration stresses.
Bonded Seal Materials
Common materials used for bonded seals include:
- Nitrile (Buna-N) – Offers good oil and temperature resistance. Nitrile is a popular general-purpose option compatible with many adhesives.
- Silicone – Withstands very high temperatures up to 500°F. Inert to most chemicals and oils.
- Neoprene – Resists fuels, oils, weather, ozone, and chemicals. Operable from -40 to 200°F.
- Viton (FKM Fluoroelastomer) – Excellent chemical resistance and high heat range of -20 to 400°F. Often used for aggressive fluids.
- PTFE (Teflon) – Inert to nearly all chemicals and temperature extremes from -450 to 500°F. Requires special bonding processes.
The seal material should be compatible with the process fluids and application temperatures. Most common elastomers can be bonded effectively using cyanoacrylates, anaerobics, or primer-based adhesives.
Bonded Seal Best Practices
To achieve reliable, leak-free seals:
- Ensure surfaces are clean, dry, and free of oil. Roughen smooth surfaces to improve adhesion.
- Apply adhesive liberally to both sealing surfaces.
- Compress seals during installation by 15-30% of their uninstalled height.
- Allow full adhesive cure time before pressurization. Cure times vary by adhesive used.
- Conduct leak testing at max pressures and temperatures to detect any flaws.
- Inspect seals periodically for damage and replace if adhesive bond fails.
With proper design, material selection, and installation, bonded seals offer a versatile sealing solution across many industrial applications. Correct use of “Bonded Seal Kits” with adhesives and compressible elastomeric seals can create durable, long-lasting seals on mechanical equipment.
