Scuba Diving O-Rings
Characteristics of Viton® O-Rings, Seals & Gaskets
Temperature range: -20°F to 400°F (-29°C to 204°C)
Standard hardness: 70-75 Shore A
Hardness range: 50-95
Standard colors: black, brown
The materials commonly used in SCUBA applications
|NBR, Nitrile||Acrylonitrile-butadiene rubber||Perbunan||Most O-rings used in SCUBA are made from Nitrile, a hydrocarbon-based synthetic rubber. Nitrile offers excellent resistance to many oils and acids and has good physical properties. However, Nitrile is not a very oxygen resistant material and is not considered oxygen compatible. Nitrile is also often referred to as Buna-N.|
|FKM||Fluoro rubber||Viton®||O-rings made of FKM Viton® have been the preferred choice for oxygen and nitrox compatibility in SCUBA diving applications. FKM Viton® is an elastomer with excellent oil and oxygen resistance at high and low temperatures, very good chemical resistance. Even for use with ordinary air, most experts agree that FKM Viton® O-rings outperform common Nitrile O-rings.|
O-ring is made of Polyurethane. Polyurethane is very abrasion-resistant, but it is sensitive to UV light (sunlight). Good hydraulic oil and gasoline resistance. Resistant to pure aliphatic hydrocarbons (propane, butane, fuel).Resistance to mineral and silicone oils and greases.Resistant to water, oxygen, ozone, and aging. Excellent tear and abrasion resistance
|EPDM||Ethylene propylene diene rubber||Nordel®||EPDM materials generally have a high resistance to hot water, steam, aging, and chemicals, and are suitable for a wide range of temperature applications. EPDM has good resistance to hot water and steam, detergents, caustic potash solutions, sodium hydroxide solutions, silicone oil and greases, many polar solvents, many diluted acids, and chemicals. Special qualities are recommended for glycol-based brake fluids. EPDM materials are totally unsuitable for use with all mineral oil products (lubricants, fuels). They can be used between –45°C and +130°C (peroxide-cured –50°C to +150°C).|
The Difference between FKM and Viton®?
- FKM is the short form for the fluoroelastomer category according to the American standard ASTM.
- Viton® is the registered trademark of DuPont Performance Elastomers.
Viton o-rings are commonly available in 75 & 90 Shore Hardness. These compounds are normally stocked in Black although other colors can be manufactured in Brown / Green / White
Black FKM VITON ® better properties over brown or green material.
Five Common Reasons why Scuba O-Ring Fail
O-Ring Failure Description: The seal exhibits blisters, pits, or pocks on its surface.
Absorption of gas at high pressure and the subsequent rapid decrease in pressure.
The absorbed gas blisters and ruptures the elastomer surface as the pressure is rapidly removed.
Contributing Factors: Rapid pressure changes. Low-modulus/hardness elastomer.
O-Ring Failure Description: The seal or parts of the seal may exhibit small cuts, nicks, or gashes.
Contributing Factors: Sharp edges on glands or components. Improper sizing of elastomer.
Low-modulus/hardness elastomer. Elastomer surface contamination.
Spiral Twisting Failure
O-Ring Failure Description: The seal exhibits cuts or marks which spiral around its circumference.
Contributing Factors: Difficult or tight installation (static). Slow reciprocating speed.
Low-modulus/hardness elastomer. Irregular O-ring surface finish (including excessive parting line).
Excessive gland width. Irregular or rough gland surface finish. Inadequate lubrication.
Abrasion - Friction
O-Ring Failure Description: The seal or parts of the seal exhibit a flat surface parallel to the direction
or motion. Loose particles and scrapes may be found on the sealing surface.
Contributing Factors: Rough sealing surfaces. Excessive temperature. Process environment containing
abrasive particles. Dynamic motion. Poor elastomer surface finish.
O-Ring Failure Description: The seal exhibits a flat-sided cross-section,
the flat sides corresponding to the mating seal surfaces.
Contributing Factors: Excessive compression. Excessive temperature. Incompletely cured elastomer.
Elastomer with a high compression set. Excessive volume swells in chemicals.
The information has been gained from manufacturing partners.