O-Ring Material Selection Guide
Verified by Rachel Mayfield, Supply Chain Analyst - April 2026
What Are the Common Mistakes in O-Ring Material Selection?
Many engineers pick materials based on cost alone, ignoring critical factors like chemical resistance and temperature range. O-Ring Material Selection Guide This can lead to premature failure and costly downtime.
Nitrile (NBR) is a popular choice for oil-based applications but fails at higher temperatures or with aggressive chemicals. Viton (FKM), while more expensive, offers superior performance in high-temperature environments and with acids. EPDM is ideal for water and steam systems, but it's not suitable for petroleum products.
Nitrile (NBR) O-Ring Material
Nitrile works best between -40°C and +120°C. It's resistant to oils, fuels, and lubricants but isn't suited for acids or ketones. Its hardness ranges from 50-90 Shore A. Common applications include automotive parts, hydraulic systems, and pneumatic seals.
Hardness Range
Nitrile rubber typically comes in hardness grades of 70-80 Shore A for most industrial uses, ensuring durability without excessive stiffness.Viton (FKM) O-Ring Material
Viton excels from -20°C to +200°C. It's highly resistant to acids, fuels, and oils but isn't compatible with ketones or esters. Its hardness ranges from 50-80 Shore A. Common applications include aerospace seals, automotive parts, and chemical processing.
Chemical Compatibility
Viton is particularly effective in environments exposed to aggressive chemicals like hydrochloric acid and aromatic hydrocarbons.EPDM O-Ring Material
EPDM operates between -50°C and +150°C. It's resistant to water, steam, alkalis, and ozone but isn't suited for oils or solvents. Its hardness ranges from 40-80 Shore A. Common applications include automotive coolant systems, HVAC equipment, and food processing.
Temperature Range
EPDM's wide operating temperature range makes it ideal for seasonal changes in industrial environments.Silicone (VMQ) O-Ring Material
Silicone works well from -60°C to +200°C. It's resistant to high temperatures, ozone, and weathering but isn't suitable for fuels or oils. Its hardness ranges from 40-75 Shore A. Common applications include automotive underhood parts, food processing equipment, and medical devices.
Food-Grade Applications
Silicone materials that meet FDA/EU 1935/2004 are preferred in the food industry due to their inertness and high-temperature stability.PTFE O-Ring Material
PTFE operates between -200°C and +260°C. It's resistant to virtually all chemicals but isn't ideal for use with steam or hot water above 150°C. Its hardness is typically very low, around Shore A 90-100.
Pressure Resistance
PTFE can handle extreme pressures up to 34 MPa (5000 psi), making it suitable for high-pressure applications like hydraulic systems and chemical processing equipment.Neoprene (CR) O-Ring Material
Neoprene works effectively from -40°C to +120°C. It's resistant to weather, oils, fuels, and ozone but isn't compatible with ketones or chlorinated hydrocarbons. Its hardness ranges from 50-90 Shore A.
UV Resistance
Neoprene's high resistance to ultraviolet light makes it a good choice for outdoor applications where exposure is inevitable.O-Ring Sizing Standards
O-rings are sized according to international standards: BS 1806 in the UK, AS568 internationally, and metric measurements. These standards define dimensions based on cross-sectional diameter (CSD) and bore diameter.
Metric vs Imperial
In metric sizing, O-rings are specified by their outer diameter plus two times the CSD. For example, a 20 mm ID x 3 mm CSD ring is a 26 mm O-ring according to BS 1806.Cross-Section vs Bore Diameter Selection
Selecting the correct cross-section (CSD) and bore diameter involves ensuring that the O-ring fits snugly in the gland without excessive compression, which can cause extrusion or leakage. At O-Ring Material Selection Guide, the standard BS ISO 3601 provides guidelines for proper sizing.
Gland Fit
A properly fitted O-ring should have a squeeze of about 20% on its cross-section and at least 50% engagement into the gland's axial length to ensure reliable sealing.Decision Flowchart
To select an appropriate material, first identify the media (oil, water, steam) the seal will encounter. Next, determine the operating temperature range. Finally, assess the pressure requirements.
Material Recommendation
If dealing with oils and fuels at moderate temperatures, choose Nitrile (NBR). For high-temperature environments exposed to acids or aggressive chemicals, opt for Viton (FKM).Conclusion
Correct material selection is important for reliable O-ring performance. Considering factors like temperature range, chemical compatibility, hardness, and application specifics helps avoid costly failures and downtime.
Final Tip
Always consult with a qualified engineer or supplier when selecting materials for critical applications to ensure compliance with industry standards and regulations.References
Frequently Asked Questions
What does this guide cover?
This guide covers o-ring material selection guide with practical selection criteria, real specifications, and references to ISO and BS standards. Written for UK engineers and procurement professionals.
What is the O-Ring Material Selection Guide?
The O-Ring Material Selection Guide provides engineers with detailed information on selecting appropriate materials for O-rings based on application requirements such as temperature and chemical exposure. It covers common mistakes to avoid when choosing between materials like Nitrile (NBR) and Viton (FKM).
What are the main types of O-ring material variants covered in the guide?
The guide includes detailed information on various material variants, including Nitrile (NBR), which is suitable for oil-based applications up to +120°C, and Viton (FKM), which offers superior performance at temperatures up to +200°C with resistance to acids and fuels.
How does the O-Ring Material Selection Guide help in choosing between different hardness grades?
The guide advises that Nitrile rubber typically comes in hardness grades of 70-80 Shore A for most industrial uses, ensuring durability without excessive stiffness. For Viton (FKM), the hardness range is from 50-80 Shore A, offering flexibility across a wide temperature range.
What are some relevant standards mentioned in the O-Ring Material Selection Guide?
The guide references AS568 for standard sizes and dimensions of O-rings. It also highlights ISO 3672 as an important standard for fluorocarbon rubber (FKM), which is important for ensuring material quality and compatibility.
Where can UK engineers find reliable suppliers listed in the O-Ring Material Selection Guide?
The guide suggests contacting reputable UK suppliers like Parker Hannifin, Trelleborg Sealing Solutions, and Freudenberg Sealing Technologies. These companies offer a wide range of O-rings with detailed material specifications to meet various industrial needs.
What are the key considerations when selecting an O-Ring material according to the O-Ring Material Selection Guide?
The guide emphasizes considering factors like chemical resistance, temperature range, and application requirements. For instance, Nitrile (NBR) is suitable for oil-based applications within -40°C to +120°C but fails with acids or ketones.
Which types of O-Ring materials are recommended in the O-Ring Material Selection Guide for high-temperature environments?
The guide recommends Viton (FKM) for its superior performance from -20°C to +200°C, making it ideal for applications involving acids and fuels. However, it's not compatible with ketones or esters.
How does the O-Ring Material Selection Guide assist engineers in choosing between Nitrile (NBR) and Viton (FKM)?
The guide advises selecting Nitrile (NBR) for its cost-effectiveness and resistance to oils and fuels, but it's limited by temperature and chemical compatibility. For harsher conditions, the guide suggests using Viton (FKM) due to its broader temperature range and superior chemical resistance.
What UK-based suppliers are mentioned in the O-Ring Material Selection Guide for sourcing high-quality O-rings?
The guide references reputable UK suppliers like MLC Rubber Seals Ltd., which provide a wide range of O-rings conforming to international standards such as ISO 3601-1. These suppliers offer competitive pricing and fast delivery options.