When standard O-rings can’t seal large diameters or irregular shapes, what’s the alternative? That’s where spliced O-rings come in.
A spliced O-ring is a custom-sized seal made by cutting rubber cord to length and bonding the ends together to form a continuous loop. It’s ideal for large or non-standard groove applications.
I’ve helped clients from Europe who needed 2-meter-long O-rings for industrial filters or tank covers. There’s no off-the-shelf O-ring that big—spliced O-rings were the only answer. They’re not perfect, but they solve sealing problems when other options can’t.
When do you need a spliced O-ring?
Some applications simply don’t fit into standard O-ring catalogs.
Spliced O-rings are used when the required diameter is too large for molded parts, or when rapid turnaround and flexibility are more important than absolute uniformity.
When a customer needs 20 different diameters in small quantities, I recommend spliced O-rings1. They’re especially useful for:
✅ Common Applications for Spliced O-Rings
| Industry | Typical Use Case |
|---|---|
| Filtration | Sealing tank lids and housings |
| Hydraulics | Large equipment access covers |
| HVAC | Large round duct seals |
| Marine | Hatch seals, manholes |
| Pharmaceutical | Large vessels and reactors |
✅ A Dutch customer once sent me a sketch for a round 1.2m door gasket. We cut EPDM cord2 and used a cold vulcanization method3 to create a seamless seal that passed their vacuum test.
What materials are used for spliced O-rings?
Picking the right rubber ensures the splice doesn’t become the weakest link.
Spliced O-rings can be made from EPDM, NBR, silicone, FKM, or neoprene cords. The key is matching the base material to the working environment and bonding method.
I always verify the material before splicing. Silicone is easy to bond, but NBR needs careful surface prep. For harsh chemicals, we usually choose FKM with specialized adhesives.
🛠️ Material Options for Spliced O-Rings
| Material | Temperature Range | Key Properties | Best For |
|---|---|---|---|
| NBR4 | -30°C to 100°C | Oil and fuel resistance | Hydraulic and fuel applications |
| EPDM5 | -40°C to 130°C | Weather, steam, ozone resistance | HVAC, outdoor equipment |
| FKM (Viton) | -20°C to 200°C | Chemicals, solvents, heat | Industrial, chemical sealing |
| Silicone6 | -50°C to 200°C | Food-safe, flexible | Food, medical, cleanrooms |
| Neoprene | -40°C to 120°C | Moderate oil/chemical resistance | Marine, refrigeration |
✅ For one HVAC ducting project in Germany, we supplied grey EPDM spliced rings in 1.5m diameter with Shore A60—perfect for outdoor weather and duct vibration sealing.
How are spliced O-rings manufactured?
Every splice needs to be strong, clean, and dimensionally accurate. That’s not easy.
Spliced O-rings are made by cutting rubber cord to a precise length, preparing the ends, bonding them using adhesive or vulcanization, and inspecting the joint for seal integrity.
At Julong Rubber, we follow a step-by-step method:
✅ Splicing Process7
- Cord Cutting – We calculate and cut the rubber cord to the exact length using the formula:
Length = π × Diameter – Splice allowance - End Preparation – We angle or butt-cut the ends, then clean with solvent.
- Bonding – Using vulcanizing adhesive8 or heat + pressure for permanent join.
- Curing – We allow the bond to set (some up to 24 hours depending on method).
- Inspection – Every O-ring9 is visually and manually checked for bond strength.
✅ We use both hot vulcanizing (press + heat) and cold bonding depending on quantity, material, and urgency.
What are the pros and cons of spliced O-rings?
Spliced O-rings are convenient—but they’re not always the best option.
The main benefit of spliced O-rings is flexibility in size and fast delivery. But the splice can be weaker than molded joints, so not suitable for extreme conditions.
If a customer needs 1,000 pcs of the same large-size O-ring for critical sealing10, I suggest investing in a custom mold11. But for small or emergency orders, spliced is the smart choice.
✅ Pros and Cons Table
| Pros | Cons |
|---|---|
| Custom sizes, no mold required | Splice joint may be a weak point |
| Fast production for prototyping | Not suitable for extreme pressure/vacuum |
| Cost-effective for small batches | Appearance less uniform than molded |
| Can be made from various cord types | Needs careful bonding and QC |
✅ I always inform Andreas when we quote spliced rings12—it’s about transparency. If the application allows, we go for it. If not, we quote molded.
Conclusion
Spliced O-rings offer a practical sealing solution for oversized or non-standard applications. When done right, they deliver excellent performance at lower cost and lead time.
Need custom-sized O-rings for large filters, tanks, or HVAC ducts?
Contact Julong Rubber or Request a Quote for NBR, EPDM, or FKM spliced O-ring solutions.
Or message us directly on WhatsApp:
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Explore the advantages of spliced O-rings for diverse applications, enhancing your understanding of their utility. ↩
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This link will help you understand the benefits and limitations of spliced rings, crucial for making informed decisions in sealing solutions. ↩
