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Custom O-Rings – When off-the-shelf just won’t do!

There are many reasons why a custom O-ring is used as apposed to an off-the-shelf O-rings. The O-ring may need to fit a specific design, there may not be an off-the-shelf O-ring that will fit, a special material may be required, low coefficient of friction, or a softer or harder rubber. Sometimes a part may be out of spec and using a custom O-ring would allow bringing the project to production without scrapping parts.

Custom O-ring are used in many type of products where standard O-rings are used especially if a sealing problem or other issue has surfaced. Many times a product can’t be design around a standard O-ring and using a custom O-ring is the only solution. Valve manufacturers use custom O-rings, sometimes they require a non-standard size or a special compound with low friction properties to assist the valve in operating smoothly.

O-Ring Size

When considering a custom O-ring the first criteria Satori Seal looks at is the reason a custom O-ring is needed. Is it size, material, shape? Is the customer trying to resolve a problem? And if so, what is the current problem? If the reason is size, we look at the application and retrieve specific measurements so we can design a proper O-ring that will provide a tight, long lasting seal. Sometimes a special rubber material is needed such as an internal lubed compound for low coefficient of friction or a material with increased low temperature or abrasion resistance. There are many reasons why a special material may be required and Satori Seal can assist in selecting a material that will work in the application. Once the dimensions and material are selected, Satori Seal can get samples manufactured from a prototype tool. This is a 1-2 cavity, low cost tool used to produce a few samples for testing purposes. Prototype tools are preferred in these cases because several cavities can be cut to test different size O-rings in the product before a more costly production tool is produced.

Common Material Used With Custom O-Rings

When considering a rubber material, the 5 most common are Nitrile, EPDM, Viton® (fluorocarbon), Silicone and Neoprene® (chloroprene). There are dozens of other type of rubber materials but these 5 are the most common and will work in most applications. Nitrile is a great all purpose compound that is highly resistant to oils, greases, solvents and hydraulic fluids. It has good physical properties and temperature range from -40°C [-40°F] to +100°C [+212°F]. EPDM rubber is extremely resistant to ozone, weathering, water and steam. It has a broad temperature range from -55°C [-67°F] to +125°C [+257°F] but is not compatible with petroleum oils and greases. Viton® (fluorocarbon) offers increased oil, solvent, chemical and heat resistance to over 232°C [450°F]. Viton® has a higher cost and doesn’t have quite the low temperature resistance than other elastomers. Silicone offer a high degree of resistance to ozone, heat, UV light, general weathering, ozone and compression set. It has the broadest temperature range from -65°C[-85°F] to +232°C[+450°F] with special compounds that are heat resistant to 315°C[+600°F]. Silicone is generally a weak material as shown by its low tensile strength and elongation properties and can tear or break easier making it undesirable for dynamic applications. Neoprene® (chloroprene) exhibits good abrasion, chemical, flex, heat, oil, weather and ozone resistance. It’s good in dynamic applications because of its toughness.

Along with these 5 common elastomers there are many other types of elastomers that may be better suited for your application such as perfluoroelastomer (FFKM), fluorosilicones, Aflas® (FEPM, TFE/P), styrene butadiene (SBR), and others. For a more comprehensive list, click here to view our compounds page. {https://satoriseal.com/rubber-compounds/}.

Rubber Hardness

Some applications may require a material that is softer or harder than the standard hardness, often referred to as durometer. Changing to a softer or harder rubber can significantly affect its functionality. Softer rubber compounds increase the coefficient of friction and can sometimes make it easier to install the seal in the product such as lids on cups and pool filters caps where the O-ring has to be squeezed to install. Softer materials take less force to squeeze making installation easier. Metal and plastic castings can sometimes be porous or have uneven sealing surfaces. It is easier for softer O-rings to fill in the porous, uneven surface easier creating a seal when a harder material will fail. This was the case with an automotive parts manufacture that has parts leak due to the porosity in the casting surface. By using a softer O-ring that was able to fill in the porous surface the leaking issue was resolved.

Experts in Rubber Seals

We’ve supplied custom O-rings to many industries especially automotive, medical devices, industrial uses and the consumer product industry. An automotive valve manufacturer needed a seal that would reduce the break-out (limiting) friction in their valve so it would operate correctly. We suggested an O-ring with a custom thickness that was not available off-the-shelf, and manufactured it with a rubber compound specially formulated with low friction properties. This allowed the valve to function within the specifications it was originally designed to operate. We’ve assisted in designing custom O-rings for our customer’s parts that were produced out of specification. Instead of having to scrap or rework high cost parts, we provided a custom O-rings that was significantly cheaper than scrapping or reworking the more expensive parts.

When you need a custom O-ring our engineers can help you design it. Our extensive knowledge of seals and elastomer compounds combined with our global sourcing expertise guarantees you the highest quality at a competitive price.