O-Ring 91x5.5 NBR 90 ShA - High Hardness Nitrile Seal

Technical Specs & Applications of the O-Ring 91x5.5 NBR 90 ShA

The O-Ring 91x5.5 NBR 90 ShA is a precision sealing ring with an inner diameter of 91 mm and a cross-sectional thickness of 5.5 mm, made from nitrile rubber (NBR) at 90 Shore A hardness. This configuration is engineered for use in demanding environments where pressure resistance, mechanical stability, and durability are essential.

Key Features & Benefits

• Material: NBR (nitrile rubber) — excellent compatibility with oils, greases, fuels, and many hydraulic media

• Hardness: 90 Shore A — high rigidity and minimal elastic deformation under load

• Dimensions: 91 x 5.5 mm — precise fit in grooves and sealing cavities

• Temperature resistance — typical service range from about −30 °C up to +100 °C (varies by compound)

• Pressure capability — suitable for static sealing under moderate to high pressure; for dynamic or very high-pressure use, back-up rings or anti-extrusion support is recommended

• Chemical resistance — good resistance to mineral oils, fuels, lubricants; limited resistance to ozone, UV, strong acids or solvents

• Long mechanical life — enhanced wear and fatigue resistance due to higher hardness and structural stability

Common Applications

This O-ring is well suited for hydraulic systems, pneumatic cylinders, pumps, valves, industrial machinery, piston seals, cylinder heads, and mechanical couplings where a robust and dependable sealing element is needed.

Installation & Operational Recommendations

• Design sealing grooves (cord grooves) with proper clearances, entry radii, and tolerances

• In systems with higher pressure or movement, use back-up rings or anti-extrusion rings to prevent material extrusion

• Lubricate the O-ring with a lubricant compatible with NBR (e.g., silicone grease or NBR-safe oil) prior to installation

• Avoid exposure to ozone, direct UV light, or aggressive chemicals that degrade NBR

• Inspect periodically in cyclic load applications; hardness helps reduce deformation but wear over time may occur

FAQ - Frequently Asked Questions

Q1: What does “NBR 90 ShA” mean?
It refers to nitrile rubber (NBR) with a hardness of 90 Shore A, indicating a relatively stiff elastomer with high mechanical strength.

Q2: Can this O-ring be used for dynamic sealing (moving parts)?
Yes, but in high-pressure or reciprocating applications, use of back-up rings is advised to protect against extrusion and prolong service life.

Q3: What temperature range is typical for this O-ring?
Normal working range for NBR 90 is approximately -30 °C to +100 °C (some formulations may extend up to +120 °C depending on additives).

Q4: Which fluids is it compatible with?
It has good compatibility with mineral oils, hydraulic fluids, fuels, and lubricants. It has limited resistance to ozone, UV, strong acids, and aggressive solvents.

Q5: How fast is the delivery?
We maintain stock in Lublin and offer 24h shipping - fast and efficient order processing for global customers (depending on delivery location).