✅ What NBR Hardness Is Best for Oil Systems?

? Introduction

Choosing the right O-ring or shaft seal made from Nitrile Butadiene Rubber (NBR) is crucial for the performance and durability of hydraulic, pneumatic, and lubrication systems. One of the most important technical parameters is the hardness, expressed in Shore A (ShA).

So, which NBR hardness works best for oil-based systems? Here's everything you need to know.

⚙️ What Is NBR Hardness?

Shore A hardness measures the flexibility and compression resistance of a rubber compound.

• Lower values mean softer, more flexible materials.

• Higher values mean harder, more pressure-resistant materials.

Most common NBR hardness grades:

✅ Why Is 70 ShA the Best for Oil Applications?

✔️ Balanced performance
70 ShA offers the ideal balance between elasticity and mechanical strength. It fits sealing grooves well, resists deformation, and maintains reliable contact pressure.

✔️ Chemical resistance
NBR 70 is resistant to mineral oils, lubricants, fuels, and most standard fluids used in hydraulic and oil systems.

✔️ Widely available
Most catalog seals and O-rings are manufactured in 70 ShA, ensuring easy replacement and consistent stock availability.

⚠️ When to Use Other Hardness Grades?

• 60 ShA – For uneven or damaged surfaces, where a softer compound ensures better conformity.

• 80–90 ShA – In high-pressure applications (>20 bar) or dynamic movements, such as piston rods and moving shafts.

?️ Practical Tips from simmering.pl

• ✔️ Always check groove tolerances and shaft diameters before choosing the seal.

• ✔️ For standard static sealing in oil, NBR 70 ShA is the most recommended option.

• ✔️ For extreme temperatures or aggressive fluids, consider alternative materials like FKM (Viton®).

? Summary: Best NBR Hardness for Oil Systems

For the vast majority of oil, hydraulic, and lubrication systems, the best NBR rubber hardness is:

✅ 70 ShA – Durable, flexible, chemically resistant, and reliable.

It provides excellent sealing performance in normal operating conditions.

? Need NBR 70 ShA O-rings or Oil Seals?

Find the full range of standard and custom dimensions on:

? simmering.pl – your trusted source for industrial sealing products.

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