What You Need to Know About O-Rings
Want more information on rubber o ring suppliers? Feel free to contact us.
º
F or over 200º
F (-18º
C -93º
C); otherwise, it is unlikely that temperature ratings will be much of a factor.Most applications citing specifications such as those named in #5 above already specify material type and can be purchased by vendors selling products designed to meet the same, bypassing the need for the more detailed investigation outlined below.
The First Question
Will Standard Commercial Grade Buna-n O-Rings Work?
Since it is more likely than not that you won&#;t need to look any further for a suitable material, we begin with the simple question, will Buna-n o-rings work? Not only are largely standardized Buna-n O-Rings the lowest cost and most widely available type by a wide margin across the market, it is also generally quite resistant to the kind of fluid and gas environment typically associated with o-ring seals like hydrocarbon fuels, petroleum-based fluids and lubricants, and vegetable fats. In contrast to other chemical groups of elastomers, Nitrile Rubber (or Buna-n, as more generically known), is a good quality elastomer in terms of tensile strength, elongation, and resistance to compression sets, tears and abrasion.
(By &#;good quality&#; we mean in very general terms in contrast to other common chemical groups of elastomers, not that there isn&#;t a full range of good, better, and even what might be considered sub-standard products available in the highly competitive o-ring market.)
In most cases, two more questions are all that&#;s necessary to know whether looking further at Buna-n is or investigating other options is warranted:
Buna-n rubber compounds are generally rated between -40 F and +250 F service temperatures (be sure to check particular brand ratings before buying). Application-specific testing is strongly recommended where o-rings could be subjected to extended periods of time at or near the manufacturer&#;s stated limits.
Rubber service temperature ratings are seldom ever stated as absolute, unconditional specifications. In most cases, rubber will degrade as a result of extended exposure to temperatures near or above the stated operating ranges, which can be exacerbated by the fluid and gas environment. This is a result of a breakdown in the molecular bond that gives rubber its elastic properties, so the damage is generally permanent, even if very slow in development.
On the other hand, low temperature crystallization causes rubber materials to become brittle rather than elastic, but doesn&#;t normally cause permanent damage in the same way as excessive heat. However, crystallized rubber can be damaged or broken much easier, and won&#;t exhibit any real elastic qualities in such a state. Because of this, applications involving extended exposure near, but not beyond, the actual crystallization or &#;glass&#; temperature don&#;t generate as great a risk of untimely failure as high temperature ranges.
Buna-n is known to exhibit generally good resistance to petroleum-based oils, greases and hydraulic fluids, aliphatic hydrocarbons like propane, butane, petroleum oil, mineral oil, diesel fuel and fuel oils, vegetable oils, organic fats, most silicone-based fluids and lubricants, alcohols, most HFA, HFB and HFC fluids, alkali and salt solutions, and some other chemicals. For more information, see related:
308 Chemicals that are generally COMPATIBLE with Buna-n rubber &#; These chemicals (fluids, gases) tend to have little or no affect on commercial Buna-n rubber compounds which are, therefore, very likely to perform well in both dynamic and static seals and gaskets in environments containing them.
147 Chemicals that are generally SOMEWHAT COMPATIBLE with Buna-n rubber &#; These chemicals are listed in two categories, Good and Fair, and tend to have a minor to moderate (&#;Good&#;) or moderate to severe (&#;Fair&#;) affects on commercial Buna-n rubber compounds. Buna-n is considered generally suitable for some dynamic and most static sealing applications involving the first group, while only suitable for some static sealing applications with the latter group of chemicals.
On the other hand, Buna-n rubbers generally have poor resistance to sunlight, ozone, weathering, phosphate esters, ketones, glycol-based brake fluids, high-aromatic fuels and hydrocarbons like benzene, chlorinated hydrocarbons like trichlorethylene, polar solvents like ketone, acetone, acetic acid and ethylene-ester, and strong acids. For more information, see related:
237 Chemicals that are generally INCOMPATIBLE with Buna-n rubber &#; These chemicals tend to have a severe affect on commercial Buna-n rubber compounds which are, therefore, very unlikely to perform well in sealing applications where they are present.
If the above temperature and chemical resistance information indicates that Buna-n O-Rings likely suit your requirements, there is no need to look any further; there aren&#;t any more commonly available or lower cost options. The next step would be to compare available brands, for which we recommend the O-Rings on the Web section of our affiliate internet outlet Standard-Gasket.com as a good starting point.
However, if, based on the above, Buna-N is not a likely material for your o-ring requirements, then we&#;ll need to look a little further&#;
The Next Question
If not Buna-N, then What?
The same factors apply, but if Buna-N doesn&#;t appear to be a good option, a more broad array of materials must be considered. The next level of more or less standard materials, from the least to the most costly (in general), include Silicone, Viton® (Fluoro-elastomer), EPDM, and Kalrez® (perfluoro-elastomer). These or similar materials easily meet 90% of the remaining o-ring sealing requirements overall (after Buna-n) and are widely available through numerous sources, usually with feature-enhanced varieties as well as standard commercial grades.
As fluid and gas resistance is mostly determined by the chemical grouping of a compound, commonly published references are fairly reliable gauges of what can be expected in application, even if the information is general in nature. The following resources will usually provide sufficient information on this factor, though testing is always necessary for absolute certainty:
Complete Chart (689 chemicals) of Chemical Compatibility Ratings for Common Commercial Elastomers &#; Useful cross-compound comparisons of 14 common rubber types by 689 chemicals with four-level compatibility ratings.
Buna-n Chemical Compatibility Ratings (Efunda) &#; Includes fewer chemicals than the above (around 350), but useful utility allows easy cross-referencing of chemicals by material and, conversely, materials by chemical.
Keep in mind that temperature ranges don&#;t normally mean that the rubber won&#;t degrade by continuous subjection to the high and low ends of the stated range; usually quite the contrary. Some vendors provide standardized criteria that specifies physical property changes under defined time, temperature, and environmental conditions.
Physical properties vary greatly between material classes and the compounds within each. When stated, most of the standard commercial varieties of o-rings are made of good quality elastomers and often accompany variations designed for enhanced properties and/or chemical compatibility, though always by special quote only. In high pressure, dynamic friction, or compression applications, properties like tensile strength, elongation, compression resistance, tear resistance, and abrasion resistance can be relative to seal performance. Harder or higher durometer variations, though not &#;better&#; per se, may also improve the durability of a seal, but may also decrease the effectiveness of it, as harder rubbers will not conform to surfaces to form a seal as readily under the same compression.
If the application merits spending more for special or higher grade compounds, one way of finding one might be through various standardized specifications that have been defined by military, aerospace, ASTM, ISO, or other recognized agencies. Many of these have been formulated for specific and often demanding applications, and are available through many sources by special quotation. Having such a specification reference could make obtaining competitive and easily comparable quotations much easier, as well as lend assurance of performance and longevity.
As far as getting general bearings on what chemical class of rubber is most likely to suit your application, the following chart should be helpful:
Price Factor
Service Temperature Range
Chemical, Fluid, Gas Compatibility & Resistance
Tensile Strength
Elongation%
Tear Resistance
Abrasion Resistance
Remarks
Avg +/- % vs. Buna-N
Low F° (C°)
High F° (C°)
Resists
Attacked by
Buna-n
0%
-40°
(-40°)
+250° (+121°)
Petroleum-based oils, greases and hydraulic fluids, aliphatic hydrocarbons like propane, butane, petroleum oil, mineral oil, diesel fuel and fuel oils, vegetable oils, organic fats, most silicone-based fluids and lubricants, alcohols, most HFA, HFB and HFC fluids, alkali and salt solutions.
Sunlight, ozone, weathering, phosphate esters, ketones, glycol-based brake fluids, high-aromatic fuels and hydrocarbons like benzene, chlorinated hydrocarbons like trichlorethylene, polar solvents like ketone, acetone, acetic acid, ethylene-ester, and strong acids.
2,031 psi, G-E
250%
F-G
G
Most common o-ring material; used in hydraulic pumps, seals, carburetors, transmissions, water pumps, and, as lowest cost option, many general applications.
Silicone
+50%
-80°
(-62°)
+400°
(+204°)
Dry heat, ozone, sunlight, weathering, petroleum, animal, vegetable
Many solvents, oils, acids
870 psi min, P
150%
P
P
Rubber of choice for high temperature, medical, and food grade static seals. Complies with numerous ASTM, Military, and FDA specifications. Relatively poor tensile, tear, and abrasion resistance renders unsuitable for many dynamic sealing applications.
Viton®
+300%
-20°
(-29°)
If you want to learn more, please visit our website custom o ring.
+400° (+204°)
excellent against abrasion, oils, and does well against the ozone, weather, and flame.
1,450 psi min, G-E
150%
F
G
EPDM
+325%
-65°
(-57°)
+300°
(+149°)
animal / vegetable oils, strong oxidizing chemicals, weathering, and ozone.
/ psi
200/310%
G-E
G-E
Known as the smallest gaskets, O-rings are donut-like, round gaskets that seal off space between both static and moving parts. Their goal is to prevent leaks and create a strong seal between two joined parts.
O-Rings Known as the smallest gaskets, O-rings are donut-like, round gaskets that seal off space between both static and moving parts. Their goal is to prevent leaks and create a strong seal between two joined parts.
O-Rings Known as the smallest gaskets, O-rings are donut-like, round gaskets that seal off space between both static and moving parts. Their goal is to prevent leaks and create a strong seal between two joined parts.
Known as the smallest gaskets, O-rings are donut-like, round gaskets that seal off space between both static and moving parts. Their goal is to prevent leaks and create a strong seal between two joined parts. O-rings are fairly inexpensive to manufacture and quite effective, making them very popular in a variety of applications. Read More&#;
Rocket Seals Corporation is a leading provider of o-rings, rubber o-rings and o-ring kits. Our o-rings are available in a variety of materials, including Nitrile, Fluorocarbon, Silicone, Teflon® and Ethylene Propylene. Call one of our qualified customer service representatives today for more information.
Here at Global O-Ring and Seal, LLC we are committed to providing out customers with outstanding o-rings. These products can be manufactured from all of the major compounds such as Silicone, Viton, Buna, Teflon, Aflas and much more. Our experts work hard to adhere to your every specification and we have experience in a number of industries including: Oil & Gas, Industrial, Automotive, Food &...
RD Rubber Technology Corp is an ISO : / AS: certified and ITAR registered company. We offer compression, transfer, injection and Liquid Injection molding, rubber to metal bonding, engineering support, tooling design, machining and more. Our customers rely on us to give them the best possible production o-rings. From aerospace to medical, food processing to military applications we ...
A leading o-ring manufacturer of quality metric seals for industries worldwide, defines Allied Metrics Seals & Fasteners. We offer FDA-approved elastomers, Teflon® seals, o-rings & much more. Choose from o-ring sizes, metal & plastic o-rings, o-ring kits, o-ring seals, silicone o-rings, EPDM o-rings, static o-rings, etc. Call/visit our website for more information about our products & services!
Since , we have been an o-ring distributor. We offer commercial, FDA, military, metric o-rings, caps, plugs, gaskets & more. Custom, rubber o-rings, metal o-rings, diaphragms, face seals and non-standard o-rings are also offered.
Overall, O-rings serve pneumatic, hydraulic and vacuum flow applications, such as: rotating pump shafts, hydraulic cylinder pistons, gas caps, water bottle lids, engine turbines and brake systems. They are important to industries including: the medical field, aerospace, aviation, chemical processing, petrochemical and oil, water treatment and even, occasionally, jewelry making.
The first O-ring patent was issued in Sweden on May 12, , to a man named J.O. Lundberg. However, in the United States, the first O-ring patent wasn&#;t issued until . At that time, it was awarded to a Danish-American citizen named Niels Christensen. Unfortunately, his patent was not honored by large, money hungry corporations, who passed his intellectual property around, with it eventually ending up in the hands of Westinghouse. During World War II, the US government took advantage of this and took the patent for itself, citing the war effort. They then gave the right to manufacture O-rings to many different organizations, so that they could manufacture rubber seals for military airplane hydraulic systems. Afterwards, Christensen received a lump sum payment of $75,000. In , after litigation, his heirs were awarded another $100,000.
O-Rings &#; Arizona Sealing Devices, Inc.
In the s and s, engineers applied Christensen&#;s rubber seal gasket to their designs in industrial hydraulics, automotive manufacturing and agricultural tech manufacturing. Between the &#;50s and &#;70s, scientists and engineers created a wide variety of synthetic rubbers and polymers, which were and continue to be very useful in O-ring fabrication.
Though manufacturers have seen many great successes with the advent of O-rings, they have also been witnessing the sobering consequences of poor construction. No example is more sobering than that of the Challenger disaster of , when the Challenger space shuttle exploded during lift off and took with it the lives of all seven crew members. This tragedy has been traced back to a faulty O-ring. Because it was so cold the morning of the launch, the O-rings attached to the solid rocket boosters deformed properly, but did not decompress as they were meant to, failing to create an effective seal. If the engineers had taken into account the possibility of extreme temperatures, perhaps this tragedy could have been avoided.
With this in mind, O-ring engineers and manufacturers went on to extensively test material characteristics, particularly temperature resistance, so that this would not happen again. They also rapidly developed comprehensive regulations related to: quality control, packaging, labeling and expiration dating. To test O-rings for critical application use, for example, manufacturers examine them under UV lights, looking for any fractures or stresses that could cause seal failure. If they find such imperfections, they will not distribute the O-ring.
Production Process
Manufacturers produce O-rings using one of two processes: injection molding or compression molding. Of the two, injection molding is most popular. This is because, using injection molding, O-ring manufacturers can fabricate high volumes of O-ring products in a relatively short amount of time. Compression molding, on the other hand, is time consuming and can only really be used with low volume requests.
Materials
O-rings may be made with any of a broad range of natural and synthetic elastomers. The choice of which depends on the properties a manufacturer seeks and a material&#;s reaction to that which it seals, such as: sealing pressure, chemical compatibility, temperature and lubrication requirements.
Popular O-ring materials include: rubber materials, like Teflon, viton, silicone, neoprene, nitrile, EPDM, perfluoroelastomer, fluorosilicone, etc. Other options include polyamides, indium, melt processible rubber, Sani flour, clear plastic and various metals.
Since aerospace applications like brake systems and engine turbines require extremely strong and resilient O-rings, theirs are usually made from materials like EPDM, perfluoroelastomer and fluorosilicone. Petro-chemical hydraulic applications, which include oil refining, water treatment and chemical processing, use viton, nitrile, perfluoroelastomer, Teflon and the like because they are highly resistant to fuels and chemicals.
Design and Customization Considerations
During design and customization, manufacturers must map out specifics like: material, material durability, material hardness, cross-section diameter, inner diameter, O-ring seal capacity, O-ring shape and O-ring size. They make these choices based on application specifications like: required sealing pressure, required chemical compatibility, required temperature resistance and lubrication requirements. Depending on where the O-ring will be used, they also choose between metric and nonmetric measurements. While round or donut-shaped O-rings are most common, manufacturers can also fabricate O-rings with custom profiles, including flat, square, rectangle or irregular.
At their cross-section, most O-rings are disc-shape. Users place the O-ring within a groove between two joints, where, when pressured, its disc-shaped cross-section is compressed and deforms. When this happens, the O-ring creates a seal. The more pressure is applied inside or outside the O-ring, the stronger the seal becomes. The sealing capabilities of an O-ring, however, are not based on how well it deforms. Rather, they are based on its resilience, which is measured by its ability to hold its original shape after deformation.
Silicone O-Ring
Silicone lends its support to applications that require a material high in resistance to fast, wide temperature swings, extreme dry heat and UV weathering. Typically, they&#;re used in the heating and medical industries. However, because silicone is so expensive, silicone O-rings are also sometimes used around earplugs and as necklace strings.
EPDM O-Ring
O-ring EPDM types are extremely resistant to alcohol, acetone and polar solvents like MEK. However, they do have poor resistance to petroleum oils and greases. Most often, they are used with solvents.
Neoprene O-Ring
Heat exchangers and chiller systems rely on neoprene O-rings to seal refrigerants, like Freon, inside.
Viton O-Ring
Viton O-rings are useful in processes similar to other rubber O-rings, such as oil refining and chemical processing, because they are chemical resistant and have an extremely high process temperature limit.
Nitrile O-Ring
Of all the standard O-ring products, nitrile O-rings are the most popular. They are regarded for their oil and fuel resistance.
Clear O-Ring
Clear plastic O-rings are used routinely in hospitals and medical care centers, for IVs and other clear tubing. They are also common in food and beverage processing. Typically made from Teflon, polyurethane or silicone, they can be ultra-clear or semi-clear, depending on your needs.
Metal O-Ring
Rubber O-rings are not universally temperature resistant without additives, which is why manufacturers sometimes also use metal O-rings or metal alloyed O-rings. Metal O-rings are generally stronger and more resistant to other stresses as well, like corrosion. They are used with applications that have a wider range process range, temperature range and/or corrosion range.
Metric O-Ring
Metric O-rings are O-rings with measurements specified using the metric system. Most O-rings outside of the US, including global O-rings, use metric O-ring measurements.
O-Ring Cord
O-ring cord is an O-ring product sold by the foot. With it, you can slice the material yourself, creating any O-ring size for a quick seal whenever you need it. They work best with large diameter, static applications.
Oil Seal Gasket
An oil seal O-ring gasket is designed to do three main things: 1) keep contaminants from seeping into any static or dynamic machinery 2) keep lubricant inside the equipment 3) keep fluids, like oil and water, from mixing
O-rings offer their users quite a few advantages over other seal types. These include: flexibility, superior sealing, a wider range of uses, a wider range of sizes, low manufacturing costs and reusability.
What we mean by flexibility is that, even if the two surfaces it&#;s joining are uneven or imperfectly matched, the O-rings can seal them. In addition, the seal they create, no matter the surface, is airtight. This is because O-rings on the shape of the cavity in which it resides, creating a vacuum.
As we mentioned, O-rings have a much wider range of use than other gasket seals. This is because they have a wider temperature range, a greater pressure tolerance (sometimes upwards of 100 bar), and because they can be made into an extremely wide range of sizes. Also, they do not generate critical torque under high pressure, meaning they put neither themselves nor their application at risk for structural damage.
Though they are superior to other gaskets, they are not more expensive than them. Instead, they are relatively cost-effective, thanks to the reasonably priced processes used to make them. On top of that, because they are usually made from rubber, metal or polymer materials, they can be used over and over again. This saves you money and puts less stress on the environment.
Typical O-ring accessories include: assembly greases and lubricants, O-ring kits, extraction tools and measuring cones. To find out what might benefit you most, talk to your manufacturer.
1. Lightly coat your O-ring with a compatible lubricant (unless your manufacturer has told you that your O-ring does not require a lubricant).
2. If required, cover any surface sharp edges that have the potential to cut or otherwise compromise your O-ring seal.
3. Position your O-ring between the joining parts.
4. Make sure that the O-ring is uniformly stretched, not just stretched on one side.
5. Check that the installation stretch is less than 50%.
6. Ensure that the seal is not twisted in the gland or groove.
O-rings are durable as long as they are properly maintained. For the best results, consider getting your O-ring encapsulated or covered with Teflon. Doing so will shield weaker O-ring materials from exposure to harmful chemicals and/or natural deterioration. Another way to protect your O-ring is by using a supportive coating, like a lubricant. Make sure to never use a lubricant that features the same materials as your O-ring itself, as this may cause erosion. Finally, we recommend you purchase a set of spare O-rings, so that if something happens to your primary set, you will not be caught off guard.
Inferior O-ring construction can be very dangerous. So, governments and industry organizations alike require adherence to strict O-ring standards. Common standard requirements include those put out by ISO (International Standards Organization) and SAE International, which publishes the Aerospace Standard. For the best advice on the standard certifications your O-ring should have, talk to both your manufacturer and your industry leaders.
To help you cut through all the riff raff and avoid shady manufacturers, we&#;ve put together a list of some of the industry leaders we most trust. You&#;ll find their names and profiles sandwiched in between all of this information. Before checking out what they offer, we recommend you put together a list of specifications and questions you want to ask, including your:
&#; Required pressure and temperature tolerance, O-ring size, O-ring shape and your order quantity
&#; Standard requirements&#;Can they meet them?
&#; Customization requirements
&#; Timeline
&#; Budget
&#; Delivery preferences&#;Can they deliver to you?
Once you&#;ve compile your list, you&#;re ready to start looking. Check out the manufacturers we have listed above, and pick out three or four that appear to best fit your needs. Then, reach out to each of them, relay your requirements and ask your questions. Compare and contrast their answers. When you&#;ve determined which one can best assist you, reach out again and get started.
The company is the world’s best tc oil seal supplier supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.