Seals & Technical Accessories

Technical Selection Guide: How to Choose the Right Seal?

The correct selection of an O-Ring seal is based on two critical parameters: Hardness (pressure resistance) and Material (chemical and thermal resistance).

1. Pressure Resistance Based on Hardness (Shore A)

The material hardness determines the maximum pressure the seal can withstand without extrusion.

Material & Hardness	Pressure Resistance (MPa)	Pressure Resistance (Bar)
NBR 70A	14 – 16 MPa	140 – 160 bar
FKM 75A	16 – 18 MPa	160 – 180 bar
NBR 90A	18 – 20 MPa	180 – 200 bar
HNBR 90A	20 – 22 MPa	200 – 220 bar
AFLAS® 70A / 80A	16 – 20 MPa	160 – 200 bar
FKM 90A	19 – 23 MPa	190 – 230 bar
FFKM 75A / 90A	20 – 25 MPa	200 – 250 bar

💡 Technical Tip: By adding a Back-Up Ring, the pressure resistance of any of the seals above is doubled.

2. Materials Guide: Properties and Industry Applicability

🛢️ Oil & Gas Industry (Upstream & Midstream)

Material	Usage and Characteristics
NBR	Used only at the surface, for water lines, standard hydraulic oils, and fluids without associated gas.
HNBR	Excellent for medium downhole applications. Superior resistance to abrasion and H₂S. Resists Rapid Gas Decompression (RGD) phenomena.
FKM	The standard for downhole tools, injection systems, and refineries. Resists crude oil, gas condensates, and aromatic solvents.
AFLAS®	A unique solution for environments with concentrated H₂S + steam at high temperatures (up to +200°C) where FKM is chemically attacked. Used in steam injection for tertiary recovery (EOR/SAGD) and packers exposed simultaneously to H₂S and amines. No direct substitute under these combined conditions.
FFKM	The ultimate solution for HPHT conditions. Total resistance to stimulation acids, sour gas wells, and temperatures over +300°C.

🚗 Automotive and Transport Industry

Material	Usage and Characteristics
NBR	Excellent for classic fuel circuits (gasoline/diesel), engine oil, and power steering fluid at normal temperatures.
HNBR	Air conditioning systems (eco-friendly freon), wet timing belts, and high-performance engine seals.
FKM	Mandatory in high-pressure injection systems, biodiesel, and turbocharger seals (high temperatures).
AFLAS®	Exhaust systems and turbochargers exposed simultaneously to high temperatures and amine-based fluids or new-generation freon (HFO) that degrades standard FKM.
FFKM	Exclusively in motorsport (F1, rally) or high-performance exhaust systems and oxygen sensors.

🧪 Chemical and Pharmaceutical Industry

Material	Usage and Characteristics
NBR	Very limited use — only with diluted acids or weak bases at ambient temperatures.
HNBR	Improved chemical resistance compared to NBR for additive oils and some solvents. Limited in highly acidic environments.
FKM	Excellent resistance to strong mineral acids, halogenated solvents, and aliphatic hydrocarbons. Caution: destroyed by acetone, esters, and strong bases (NaOH).
AFLAS®	Superior resistance to FKM against strong bases (NaOH, KOH), amines, and oxidizing acids at high temperatures. The right choice when FKM fails in aggressive alkaline environments but FFKM is too expensive.
FFKM	Almost universal chemical resistance (1800+ substances). Compatible with concentrated acids, strong bases, ketones (including acetone), esters, and steam.

🍏 Food and Medical Industry

Material	Usage and Characteristics
NBR	Frequently used (Food-Grade variants, white/blue) for animal and vegetable fats, dairy, and diluted alcohol.
HNBR	Production processes with high-speed equipment, increased resistance to mechanical wear and thermal cleaning.
FKM	High-temperature applications (steam lines) or CIP (Cleaning-in-Place) chemical washes with acids.
FFKM	The gold standard for sterile pharma/bio-tech lines. Resists continuous SIP cycles and ultra-aggressive substances without contaminating the product.

3. Quick Summary: Which Material to Choose?

Material	Color	Main Characteristic
NBR (Nitrile)	⬛ Black	Economic, excellent for mineral oils and general medium-pressure applications.
HNBR (Hydrogenated Nitrile)	⬛ Black	Improved NBR: superior mechanical resistance, higher temperature, abrasion resistance.
FKM (Viton®)	🟫 Brown	Premium: excellent thermal resistance and high chemical compatibility with fuels and acids.
AFLAS® (TFE/P)	🟩 Green	Critical niche: the only elastomer resistant simultaneously to concentrated H₂S + steam + amines at high temperatures. No direct substitute.
FFKM (Perfluoroelastomer)	⬜ White/Grey	Absolute performance: the chemical properties of PTFE (Teflon) with the elasticity of an O-Ring. Resists where any other material fails.