Three technologies, three different economies
Moulded O-ring
Extruded toric cord, cut and joined
Joined toric cord (small-section O-ring cord)
Quick technology comparison
| Technology | Typical diameters | Minimum viable run | Tolerance | Sealing quality | Unit cost |
|---|---|---|---|---|---|
| Moulded O-ring | 3 – 400 mm | Medium-high (>500 pcs) | ISO 3601-3 | Optimal (no joint) | Low in series, high if new tooling |
| Extruded cord joined (vulcanised) | 50 mm – several metres | Single unit | ISO 3302-1 | Very good if vulcanised joint | Medium, no tooling |
| Extruded cord joined (bonded) | 50 mm – several metres | Single unit | ISO 3302-1 | Good in static, limited in dynamic | Low, no tooling |
| Joined toric cord | 20 – 500 mm (small section) | Single unit | ISO 3302-1 | Depends on user joint | Very low |
Material selection
VMQ Silicone
FKM Fluoroelastomer (Viton®, FPM)
EPDM
NBR (Nitrile) and HNBR
FVMQ Fluorosilicone
Neoprene (CR)
Fluid selection matrix
| Service fluid | Recommended material | Alternative |
|---|---|---|
| Cold / potable water | EPDM, silicone | NBR (if oil contact) |
| Hot water and steam < 150 °C | EPDM, VMQ silicone | — |
| Continuous saturated steam | EPDM | — |
| Mineral oils, hydraulic fluids | NBR, FKM | HNBR |
| Fuels, petrols | FKM, HNBR | FVMQ |
| Dilute mineral acids | FKM, EPDM | — |
| Aromatic solvents | FKM | — |
| Polar solvents (ketones, esters) | EPDM | — |
| FDA / EC food contact | Platinum silicone, EPDM FDA | FKM FDA |
| USP VI pharmaceutical contact | Platinum biocompatible silicone | FKM USP VI |
| Ozone / UV environments | EPDM, silicone, FKM | Neoprene |
| Cryogenic service (< -40 °C) | Silicone, FVMQ | — |
| High temperatures (> 200 °C) | HT silicone, special FKM | FFKM |
View product
Silicone O-Rings
Silicone VMQ O-Rings molded by compression or injection. Static or dynamic sealing in critical applications. Hardness 30–90 Shore A. Certified materia...
View product →Shore A hardness selection
| Hardness | Typical application | Behaviour |
|---|---|---|
| 40 – 50 Shore A | Dynamic seals with low pressure, medical equipment, easy assembly | Maximum adaptability, higher compression set, extrusion risk if gap present |
| 60 – 70 Shore A | General static and dynamic use, the default hardness | Balance between sealing and stability. Covers >80% of applications |
| 75 – 80 Shore A | Seals with medium-high pressure, moderate gaps | Less extrusion, requires greater compression to seal |
| 85 – 90 Shore A | High pressure, large gaps, open grooves | Lower adaptability, demands precision-machined grooves |
Surface finish and special versions
Quick decision tree
- Is the dimension standardised (AS568 / BS1806 / DIN 3771) and does the series justify tooling or do we use existing moulds? → Moulded O-ring.
- Is the dimension non-standard or the diameter > 400 mm and the runs are short? → Extruded cord cut and joined (vulcanised if sealing is critical, bonded if not).
- Does the repair or prototype require an immediate solution without tooling? → Joined toric cord, with the joint made in the workshop.
- Material: apply the fluid matrix above.
- Hardness: 70 Shore A by default; increase if there is significant gap, decrease if the groove geometry requires high adaptability.
- Finish / special version: detectable if certified food industry, polished surface if dynamic, colour if plant coding applies.
Minimum specification for tender
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