O-Ring Size Chart
This table displays the actual sizes represented by the AS568 Standard O-ring “Dash” size chart. Included are 5 different Cross-Sections (0.070 through 0.275 inches), Inside-Diameters ranging from 0.029 to 18.955 inches and 20 Boss Fitting Sizes (-9XX series).
|Dash Number||I.D. (Inches)||Tol. +/-||C.S. (Inches)||Tol. +/-|
O-Ring Compound Technical Reports
Download any of these Seal Tech Stock Compound* Technical reports.
N200-70 Nitrile (Buna-N) 70 Durometer
N250-70 FDA Nitrile (Buna-N) 70 Durometer
N210-90 Nitrile (Buna-N) 90 Durometer
V500-75 FKM/Viton® 75 Durometer, Black color
V510-75 FKM/Viton® 75 Durometer, Brown color
V550-75 FDA & 3A Sanitary Grade Viton® 75 Durometer, Brown Color
V560-75 FDA FKM/Viton® 75 Durometer, Black color
S300-70 Silicone 70 Durometer, FDA Grade
E100-70 EPDM 70 Durometer, FDA Grade
*All Seal Tech compounds and formulations are manufactured and designed to meet or exceed specific ASTM requirements. Seal Tech technical reports cannot be used to determine the properties of any other manufacturer’s compounds.
Elastomer Shelf Life Recommendation
Department of Defense Rubber Products: Recommended Shelf Life (MIL-HDBK-695E) was last issued on October 20, 2011. Paragraph 1.2.2c provides the recommendation for the shelf life of O-Rings and other molded seals.
The information in the chart below is intended to be utilized by those organizations who do not already have specific recommendations for the control of elastomeric seals. It should be noted that the packaging of the elastomeric seals prior to assembly into a product is an integral part of the controlled storage procedure. It provides a positive means of product identity from the time of manufacture, to the time of assembly.
MIL-HDBK-695 does not establish limitations for storage times in assembled components, nor does it in any way provide a guideline for the operating life span of a particular compound.
|Elastomer Family||ASTM Abbreviation||Recommended Shelf Life|
|Butyl Rubber, Isobutylene Isoprene||IIR||Unlimited|
|Chloroprene (Neoprene®)||CR||15 Years|
|Ethylene Acrylic (Vamac®)||AEM||15 Years|
|Ethylene Propylene, EPDM or EP||EP||Unlimited|
|Hydrogenated Nitrile, HNBR or HSN||HNBR||15 Years|
|Nitrile (Buna-N or NBR)||NBR||15 Years|
|Polyurethane (Polyester or Polyether)||AU / EU||5 Years|
|Styrene Butadiene (Buna-S)||SBR||3 Years|
Most quality manufacturers of O-rings specify the physical properties of their product through ASTM (American Society of Testing and Materials) and/or SAE (Society of Automotive Engineers) designations. The purpose of doing so is to provide a standardized method of calling-out the required physical properties of a rubber product, based primarily on its Type (Heat Resistance) and Class (Oil Resistance). An example of an ASTM Specification for a general purpose, sulfur-cured, 70 Duro Nitrile may be:
ASTM D2000-99 M2BG714 B14 EA14 EF11 EF21 EO34 Z1
How to read this ASTM call-out?
In this case, the document date is 1999.
If the M is present, the unit of measure is expressed in Metric units. If the letter M is not present however, the unit of measure is in English units (as in psi for the tensile strength). Prior to 1980, all ASTM specifications were in English units. Beginning in 1980, the Metric unit call-outs became the standard.
The Grade Number designates instances where more extensive tests are required. Any grade other than 1 mandates additional requirements that are spelled out in Table 6 of the D2000 document.
Indicates the Heat Resistance properties of the elastomer.
Indicates the Oil Resistance properties of the elastomer.
The Shore A Durometer hardness requirement of the elastomer. In this case the 7 calls out 70 +/- 5 Durometer.
This indicates the minimum tensile strength of the elastomer. If the designation has an M after the Revision Year, then this call-out is stated in Metric units, megapascals (MPa). If no M is present, then the call-out is specifying the English unit, pounds-per-square inch (psi). In this example, the 14 is calling-out 14 MPa. The conversion to psi is: MPa x 145 = psi. Therefore, the psi Tensile Strength requirement of this designation is 14 x 145 = 2030psi.
These indicate the additional testing requirements needed to satisfy this specification call-out. Each requirement is comprised of a suffix letter, calling out the property being tested, and the suffix numbers, which call out the the test method and test temperature. Z suffix tests denote a customer added or specific test that is not necessarily covered by the D2000 document.
Chemical Compatibility for Elastomers
For complete elastomer chemical compatibility on over 600 chemicals, just follow these easy steps:
1. After clicking on the chemical compatibility link below, you’ll be taken to the international recognized Cole Parmer® Chemical Compatibility web page. There you’ll be asked to select the “chemical” you wish to research. Select one (1) chemical at a time from the scroll list.
2. After selecting the chemical, click the “submit” button. A complete listing of Elastomers and other materials will then appear, along with their compatibility to your selected chemical.
3. To return to the www.sealtechnologies.com website, click the “back” button on your browser.
Rubber Compound Profiles
Aflas® is the trade name (Asahi Glass Co.) for a non-conventional fluoroelastomer (FKM) material which has a different chemical structure than other fluoroelastomers. It is considered a “cousin” of the fluoroelastomers, but offers significant advantages over them. Aflas® exhibits excellent heat resistance; 3 months @ 446F, 30 days @ 500F and intermittent tolerance @ +572F. It also offers excellent chemical resistance to high concentrations of acids, alkali and oxidants under high temperatures. In addition, it offers exceptional electrical insulation properties, similar to those of Silicone and EPDM rubber. Aflas® is primarily used for automotive oil sealing components.
Butyl, also known as isobutylene isoprene, has exceptional resistance to gas permeation, along with excellent water and steam resistance. Butyl has a temperature range of -65F to +200F. For most Oring applications, Ethylene Propylene (EP) has replaced Butyl due to similar properties, but with better heat and compression set resistance.
Chloroprene (Neoprene®) was one of the first synthetic materials developed as an air-oil resistant substitute for Natural Rubber. It has the unusual characteristic of being resistant to both petroleum lubricants and oxygen over a temperature range of -40F to +225F. It also provides good resilience and flex resistance.
Epichlorohydrin, Hydrin® (ECO):
Hydrin® is a specialty compound, acceptable for use over a temperature range of -40F to + 275F. This compound combines good petroleum oil and fuel resistance, with good resistance to sunlight, ozone and weathering. Hydrin® has good chemical resistance, but may be corrosive to adjacent metal parts. It is frequently used for fuel and oil seals which may be exposed to weather.
Ethylene Acrylic, Vamac® (AEM):
Ethylene acrylic (Vamac®) is a specialty Dupont-Dow Elastomer offering a temperature range of -40F to +300F. It provides low temperature flexibility for automotive applications including automatic transmission seals, power steering seals and gear box seals. It also exhibits excellent resistance to weathering, ozone and air aging.
Ethylene Propylene, EPDM, or EP (EP):
EP is a copolymer of ethylene and propylene, while EPDM is a terpolymer combining ethylene, propylene and a diene monomer. EP materials offer a temperature range of -65F to +300F and offer excellent resistance to ozone, weathering, steam, water and phosphate ester type hydraulic fluids. EP can be manufactured to conform to FDA requirements, making it ideal for use with foods and medical devices.
Fluorocarbon, VITON® (FKM):
VITON® is the trade name for DuPont-Dow Elastomers Fluorocarbon or FKM material. VITON® has a temperature range of -20F to +400F, and provides excellent resistance to a wide variety of chemicals, weather and compression set requirements. The relatively high level of fluorine in VITON® materials allows for exceptional resistance to chemical attack, but with limited low temperature capabilities. Intermittent exposure to +600F can be tolerated for brief periods of time. Many industrial products are now switching to Orings made of VITON®, making it the most significant elastomer development in 50 years.
Fluorosilicone combine the best properties of fluorocarbons and silicones. Fluorosilicone resist solvents, fuel and oil (similar to Viton®); but also provide stability over a broad temperature range of -100F to +350F. This elastomer is frequently used in aircraft fuel systems. However, it is limited to static seal applications due to poor tear resistance.
Hydrogenated Nitrile, HNBR:
HNBR, sometimes referred to as Highly Saturated Nitrile (HSN), offers a temperature range of -25F to +350F. HNBR is often used in automotive refrigeration systems using Freon 134A, and in power steering seals using Type A Fluid. To manufacture HNBR, Nitrile is first dissolved in a solvent, then a catalyst is used and hydrogen gas hydrogenates the Nitrile. While HNBR is in the Nitrile family, it undergoes this extensive, and consequently expensive, process to become HNBR.
Nitrile, Buna-N (NBR):
Nitrile, also known as Buna-N or NBR, is a copolymer of Butadiene and Acrylonitirle. It is the most commonly used elastomer for sealing products. It has a temperature range of -40F to +250F and is exceptionally resistant to petroleum base oils and hydrocarbon fuels. Nitrile materials also exhibit excellent tensile strength and abrasion resistance properties. This material performs well with most dilute acids, silicone oils and lubricants and in water applications. It is not recommended for use with ketones, aromatic hydrocarbons and phosphate ester hydraulic fluids. Ozone resistant Nitriles are recommended where extended exposure to air and ozone are anticipated. More than 50% of the O-rings sold are Nitrile O-rings, commonly used in hydraulic/pneumatic motors, cylinders, pumps and valves.
Perfluoroelastomers combine the chemical resistance of Teflon with the elasticity of Viton to make a fully fluorinated polymer with superior chemical resistance over traditional elastomers. Saturation by Fluorine along the polymer backbone provides exceptional immunity from chemical attack and temperature range from -25F to +590F. These compounds are usually used in high temperature or caustic chemical applications where traditional elastomers degrade or show reduced product life.
Polyacrylate offers a broad temperature range of -20F to +350F. Often used in automobile transmissions and power steering seals using Type A Fluid, it has excellent resistance to petroleum fuel and oils. It also exhibits good ozone and oxidation resistance, as well as good flex cracking resistance.
Polyurethane (AU / AE):
Polyurethane compounds offer exceptional abrasion and wear resistance and are offered in two distinctively different variations. For use in oil, use a polyester type which has low volume swell, but softens dramatically when exposed to water. For water sealing applications, use the polyether type which retains its integrity in water, but swells significantly when exposed to oil. A hybrid version that is acceptable for both applications is available at a substantially higher cost.
Polytetrafluoroethylene, Teflon ® (FEP):
Polytetrafluoroethylene is a completely fluorinated polymer that is the most chemically resistant polymer available. PTFE can withstand a very wide temperature range from -300F to +500F. It is inert to most chemicals and solvents with very few substances that degrade the material (notably fluorine, chlorine trifluoride and molten alkali metal solutions) PTFE is also very slippery and repels virtually everything making it perfect for applications that require a high coefficient of friction. PTFE is not crossed-linked like a regular elastomer and therefore has poor elastic memory, can deform under constant compressive load and can be damaged during installation.
Silicone materials offer outstanding temperature resistance across a broad range, from -80F to +400F. Silicone materials provide excellent resistance to sunlight, ozone, oxygen, UV light and moisture. It’s inert qualities make it the preferred material for use with food handling and medical applications. Silicones offers poor tensile, tear and abrasion resistance, and are not recommended for use in dynamic applications.
SBR, styrene butadiene, or Buna-S, was originally developed to replace natural rubber in tires. While sometimes used for automobile brake system seals, it has been replaced in most applications by Ethylene Propylene which offers superior heat and compression set resistance.
PureSlip is Seal Tech’s proprietary internal-lubricant for Nitrile (Buna-N) and Ethylene Propylene (EP or EPDM) O-ring compounds. It was developed for use in applications where incredibly low breakout friction and low running friction are required. This specially formulated internal-lubricant provides the lowest coefficient of friction for any O-ring when compared to compounds filled with Teflon, moly-disulfide, silicone or wax. It also conforms to FDA per CFR 177.2600.