O-Rings: Material Selection
O-rings are round, ring-shaped molded rubber sealing devices, which are
critical for creating seals between connecting pieces in machines
belonging to nearly every industry. Named for their O shape, the
function of o-rings are both extremely simple and extremely important.
O-rings function similarly to the way gaskets do in connecting valves,
tubes, vacuums and hydraulic flow applications, with an impermeable seal
between two joints.
Known as the smallest gaskets, o-rings are employed in a
wide range of fields for a variety of sealing applications, both static as well
as dynamic. These small elastomer loops are one of the most widely used seals
for machine design as they are simple to produce, economical, and reliable. Available
in a variety of sizes and materials, o-rings can be found in dynamic
applications such as hydraulic cylinder pistons and rotating pump shafts as
well as in static applications such as water bottle lids and gas caps.
Obviously, the size and type of material will depend on the
intended application for the o-ring. The material to be used, for instance,
will vary depending on chemical compatibility, sealing pressure, temperature,
and lubrication requirements as well as others. The materials to choose from include synthetic
rubbers such as butyl rubber, fluoroelastomer, nitril rubber, saniflour, and
silicone rubber among others; thermoplastic options include polyurethane,
polyamides, melt processible rubber and more. As a practical example, vacuum
applications where system is submerged in liquid nitrogen, indium o-rings
should be used as rubber would become brittle at such low temperatures.
A majority of materials will fail at extreme temperature,
either by becoming brittle and failing to seal in extremely low temperature or
burning and decomposing at very high temperatures. However some o-ring
materials are suited to withstand temperatures ranging from -200°C and up to
250+ °C. But even elastomers that can
withstand extreme temperatures may not hold up against factors such as ionizing
radiation. Usually o-rings are protected from exposure to ultraviolet and soft
x-rays, but neutrons could cause very fast decomposition. In cases where
penetrating radiation may occur, soft metal seals are usually used. This is why
it is so important to understand all aspects of a system before deciding on the
best material for the job.
All standard o-rings have round profiles, doughnut like and thin, although the applications a certain o-ring is designed for affects its thickness. However, some gasket styles that perform exactly the same functions as o-rings have flat or square profiles. O-rings are manufactured by a relatively cost-effective process, making them a simple, fairly cost-effective solution for machinery and equipment manufacturers who require seals between parts where leaks are likely to occur. O-rings are made in a wide range of synthetic and natural elastomers, each of which carries different application-specific properties. The most common types of rubber o-rings include viton o-rings, teflon o-rings, neoprene o-rings, silicone o-rings and nitrile o-rings. Some of these plastic materials create clear o-rings, particularly the silicone base. The food and medical fields use the clear o-rings often. Metal o-rings are also widely available. O-rings are made according to non-metric measurements or as metric o-rings, and o-ring suppliers often supply bulk o-rings of assorted sizes, including large o-rings in o-ring kits to manufacturers who use o-rings commonly in manufacturing.
Hydraulic, pneumatic and vacuum flow applications, whether they involve static parts or moving joints, use o-rings of all sizes and materials to create seals where tubes or other equipment join together. Aerospace and aviation industries in particular rely on o-rings in critical applications, such as engine turbines and brake systems. O-rings used in aerospace applications require extremely high resistance to extreme temperatures and include materials such as silicone, EPDM, perfluoroelastomer and fluorosilicone. Petro-chemical hydraulic applications in oil refineries, chemical processing and water treatment facilities use o-ring seals with high chemical and fuel-resistance made from materials such as teflon, nitrile, viton and perfluoroelastomer. Silicone o-rings are especially resistant to UV weathering, dry heat and wide temperature swings, while neoprene is often used to seal refrigerants such as freon in liquid chiller systems and heat exchangers. Due to o-rings' low manufacturing cost, some rubber o-rings and silicone o-rings are used in jewelry accessories as necklace strings and around ear plugs. The range of o-ring sizes manufactured and distributed is another positive characteristic that makes o-rings popular.
Viewed at a cross-section, o-rings are disc-shaped; when placed within a groove between two joints and pressure is applied to the o-ring, the disc-shaped cross-section deforms. This compression deformation is what causes o-rings to create a seal, and as more pressure is applied either within or without the seal, the o-ring deforms even more within the groove as it is pressed up against one side, further reinforcing the seal. O-rings' sealing capabilities are based on their resilience, or their ability to retain their original shape long after deformation. Static o-rings, used to seal two rigid, nonmoving parts, will remain stationary and therefore do not require any lubricants. O-rings joining joints with motion typically require o-ring lubricant to reduce wear; lubricants are often made from elastomers such as silicone or neoprene, but manufacturers must be careful never to use o-ring lubricant with an o-ring made from the same materials, which can cause erosion of the o-ring. Besides the use of a lubricant, o-rings may also be covered or encapsulated within Teflon, which protects the weaker o-ring materials from natural deterioration as well as protecting it from harmful chemicals. Teflon is the toughest of the synthetic rubber materials used for o-ring construction, although they are not as flexible as other substances and therefore are used only in certain applications.
O-rings have been the center of many important technological advances in the last several decades, specifically since the disaster of the space shuttle Challenger takeoff in 1986, which was traced back to a faulty o-ring. Due to below freezing temperatures the morning of the launch, the o-rings in the Challenger's solid rocket boosters had deformed permanently, failing to decompress and create an effective seal. Extreme temperature endurance had not been taken into account during the o-rings' engineering, and as a result the Challenger exploded during liftoff, killing all seven of its crewmembers. Since the Challenger disaster, the o-ring and gasketing industries have made extensive investigations into material properties and endurance under harsh conditions. Regulations have been made regarding o-ring packaging and labeling, expiration dating and quality control. O-rings used in critical applications, such as aerospace or aviation, are examined under UV lights before distribution for any stresses or fractures that might cause sealing failure. These safety precautions exemplify the care and precision that quality products require of manufacturers, which is true of the manufacturers and suppliers of o-rings.
O-Rings Manufacturers - Arizona Sealing Devices, Inc.
O-Rings Manufacturers - Allied Metrics Seals & Fasteners, Inc.
O-Rings Suppliers - Arizona Sealing Devices, Inc.
O-Rings Suppliers - Global O-Ring and Seal, LLC
O-Rings Manufacturers - Global O-Ring and Seal, LLC.
O-Rings Manufacturers - Arizona Sealing Devices, Inc.
- Clear O-rings are made of materials that are semi-clear, though not totally transparent in natural form. Certain additives are able to produce ultra-clear silicone. Clear O-rings are generally transparent in both UV light and visible light.
- are extremely resistant to polar solvents such as alcohols,
acetone and MEK. However, EPDM o-rings are not a good choice for applications
that involve petroleum oils and greases.
are commonly used in conjunction with power steering liquids, transmission
fluids and engine oils. Compared to polyacrylate o-rings, these have
a better low temperature performance but do tend to swell up more.
- Flat O-rings, also called lathe cut and square rings, are sealing rings with square or rectangle profiles that are used as alternatives to the standard O-ring shape.
have excellent heat stability as well as great oil and fuel resistance,
but they should not be used in dynamic applications due to their poor
have similar properties to standard nitrile
rubber, but are ozone resistant. Some popular uses include automotive
refrigerants and high temperature hydraulics.
are made of an advanced material that is being implemented more and
more on a daily basis. Kalrez resists over 1,800 different chemicals
and is stable in temperatures up to 620 °F; it is also used in aggressive
chemical processing, oil and gas recovery and in aerospace and petroleum
- Large O-rings are the biggest sized O-rings available for sale. Some are offered through sizing charts and mass produced, while others must be custom made to fit certain dimensions.
- Metal O-rings are round, disc shaped devices used predominantly for sealing applications, though they are also manufactured to suit a variety of alternative industrial purposes. While elastomers continue to be a common choice for o-ring production, metals offer better temperature, pressure and corrosion resistant capabilities.
- Metric O-rings are o-rings whose measurements are specified in metric units.
- are made of a material that was the first synthetic rubber.
During WWII, it served as the primary seal material, but today it is
mostly used in refrigerant applications.
- Nitrile O-rings are by far the most popular type of seal material used in the world.
Nitrile o-rings are carbon triple-bonded to nitrogen, which provides
good resistance to oils and fuels.
- O-ring kits are sets
of o-rings that are designed to replace faulty o-rings.
- O-Ring seals are the air and water tight connections made between two pieces of machinery when an o-ring is compresses between the two components preventing the loss of fluid or gas.
are extremely resistant to petroleum oils, ozone and oxygen. However,
polyacrylate o-rings have relatively poor water resistance and low temperature
- Rubber O-rings are made of rubber and synthetic rubber materials.
- Silicone O-rings are made of a material that is commonly used in hot air applications
as well as devices in the medical field. The silicon-oxygen structure
gives silicone o-rings good thermal stability.
- are gaskets used in static joints.
- Teflon O-rings are made from a hard, rigid plastic with high temperature and outdoor element resistance.
- Viton O-rings are made of a material that is one of the most commonly used for seals.
Its popularity can be attributed to its good chemical resistance and
extreme upper temperature limit.
- When a material undergoes
physical changes over time.
- A hard ring
that is placed in the gland between the o-ring and the groove walls in
order to prevent extrusion.
- The resulting product
from a mixing operation.
- A small cavity that is
surrounded either completely or partially by walls.
- Any of the various
materials that are elastic and resemble rubber. Elastomers can be used
instead of springs as energizers.
- A device used in
some o-rings that acts to retain the ring's natural shape. Often,
either a spring or an elastomer serve as the energizer at the core of
- The resistance to
motion when two or more surfaces rub against one another.
- Cavity into which an
o-ring is installed, which also has the groove and mating surface of the
- The size measured
from any inner point of an o-ring to the inner location on the direct
opposite side, creating a straight line.
- The slippery, lubricated
qualities an o-ring material has.
- A material's
tendency to resume its original shape after deformation.
- O-rings that meet
and/or surpass standards of the United States military.
- When a mold is misaligned and causes an out-of-round
cross section of an o-ring.
- The size
measured from an outside point of an o-ring to that same point on the
direct opposite side, creating a straight line.
- A groove around
the mold cavity of an o-ring that is used to accept excess material from
the cavity in order to create a better fit.
- A line outside
of o-rings that is left-over from when the two mold plates met.
- Any of various
resins that vary in flexibility and are used in chemical resistant coatings,
foams and adhesives.
- Cross-section compression
of an o-ring gland assembly that shows between the surface of the groove
bottom and surface of the mating metal part.
- Improved strength,
lubricity and resiliency by combining sulfur and/or other additives with
both heat and pressure.
- The bulging or
increased size of an o-ring due to water intake.
When materials stick or cling to one another.