Sealing With O-Rings Permeability Testing

>O-rings are amongst the simplest and most effective, seal designs ever produced. But many have a simple flaw in their design - their vapour permeability.

Most O-rings are excellent at keeping out liquids, yet often fail by allowing vapour to pass through almost unhindered.

Our permeability meter can measure the permeability of O-rings by themselves, or from samples of the material used, or in finished applications. Many factors affect the permeability and sealing ability of O-rings, including, materials, vapour type, design and pressure.

O-rings that work well at preventing the flow of water vapour may perform very poorly in applications using hydrocarbon or solvents etc.

Our equipment can measure the permeability of O rings for an enormous range of gases including water, vapour, hydrocarbons, solvents, CO₂, N₂, O₂ and He.

Our permeability equipment provides fast and accurate measurement - usually in the parts per million range, (parts per billion with some gases). Conventional gravimetric techniques take several days or weeks, but can take as little as 30 minutes for some materials.

Common O-Ring materials and their properties
Aflas FEPM	These O-rings resist oils, lubricants and some fuels, it is suitable for use with H2S, amines, bases, hydrogen sulphide or high temperature water/steam.
Butyl IIR	Butyl IIR rings offer low gas permeability and can be used for vacuum and high pressure applications. It should not be used with mineral oils
Epichlorohydrin ECO	O-rings made from this material provides good resistance to mineral oils, fuels and ozone. Has poor compression set resistance.
Ethylene-propylene EPM/EPDM	Offers excellent O-ring resistance to weathering, ozone, water and steam.
Fluoroelastomers. Dyneon, Viton, Tecnoflon	These O-rings works well in severe chemical conditions and high temperatures.
Fluorosilicone FVMQ	This material is extensively used for static seals and O-rings in aerospace as it is highly resistant to many hydrocarbon types.
Hypalon (and other chlorosulphonated polyethylenes)	Hypalon O-rings offer excellent resistance to weathering and works well with many media for static sealing duties.
Hydrogenated nitrile, Elast-O-Lion	Offers good mechanical and chemical resistance properties for O-rings.
Kalrez FFKM	These erfluoroelastomer compounds have excellent chemical and temperature resistance (grade dependant).
Natural rubber	Strong with good abrasion resistance, it is suitable for use with ammonia, ethylene glycol, dilute acids and alkalis, though please note that synthetic rubbers provide greater resistance to heat, weathering and oils.
Neoprene	This is a general purpose elastomer and these O-rings stand up well to sunlight and atmospheric ageing.
Nitrile	Widely used with mineral oils, water and some solvents, some grades are suitable for food applications.
Polyurethane	Offers good mechanical properties as well as resistance to weathering. hydrocarbon fuels and mineral oils. Stress relaxation may occur above +50°C.
PTFE, Fluolion	Offers excellent resistance to most media and can also be used for 'O' ring back-up rings, though flow characteristics limit its use.
Silicone	Silicone based O-rings offer good heat and weathering resistance as well as having excellent electrical properties. Sealing ability is limited due to high gas permeability, low tensile strength and poor resistance to tear and abrasion.

The Permeability of O-rings

O-Rings operate across many environments and each performs differently depending on the vapours present. Most present a high permeability barrier to liquids but many are extremely poor at preventing the flow of vapours.

Click here for a press release on O-Ring permeability testing

Click here for an article on the testing the permeability of O-Rings

Click here for an article on the permeability of O-Rings on Wikipedia

Click here for sensor information for O-rings

Click here for an article on hydrocarbon permeability measurement

Contact us

Sealing With O-Rings Permeability Testing