NBR O-Ring 250x5 mm 90 Shore A

Overview

The NBR O-Ring 250x5 mm 90 Shore A is a large-diameter, high-hardness technical sealing ring designed for demanding industrial and hydraulic applications.

The O-ring features an inside diameter of 250 mm and a 5 mm cross-section. It is manufactured from NBR (Nitrile Butadiene Rubber) with an increased hardness of 90 Shore A.

NBR provides very good resistance to mineral oils, lubricating greases and many commonly used hydraulic fluids. The 90 Shore A version offers increased mechanical stability, reduced susceptibility to deformation and improved extrusion resistance compared with standard 70 Shore A NBR.

The combination of a 250 mm inside diameter, 5 mm cross-section and 90 Shore A hardness makes this O-ring suitable for correctly designed pumps, large housings, covers, flanges, hydraulic assemblies and industrial machinery.

Industrial Applications

The NBR 250x5 mm 90 Shore A O-Ring can be used in:

• Industrial hydraulic systems
• Industrial pumps
• Large machine housings
• Technical covers
• Flanged connections
• Valves
• Oil circulation systems
• Gearboxes
• Manufacturing machinery
• Agricultural equipment
• Heavy industrial equipment
• OEM assemblies

250x5 mm Dimensions

The 250x5 mm designation specifies:

Inner Diameter: 250 mm

Cross Section: 5 mm

The 5 mm circular elastomeric profile undergoes controlled compression when installed in a correctly designed sealing groove.

This compression generates contact pressure between the O-ring and mating surfaces, helping prevent leakage.

Because of the large 250 mm diameter, uniform positioning around the entire circumference is particularly important during installation.

NBR Material

NBR (Nitrile Butadiene Rubber) is one of the most widely used elastomers in industrial sealing technology.

NBR provides very good resistance to:

• Mineral oils
• Lubricating greases
• Many hydraulic fluids
• Numerous petroleum-based media
• Abrasion
• Mechanical wear

These characteristics make NBR suitable for hydraulic equipment, mechanical engineering, industrial machinery and maintenance applications.

Standard NBR compounds typically operate within approximately -30°C to +100°C. Actual operating limits depend on the specific compound formulation, operating medium and application conditions.

Technical Specification

Product Type: O-Ring

Dimensions: 250x5 mm

Inner Diameter: 250 mm

Cross Section: 5 mm

Material: NBR

Hardness: 90 Shore A

Color: Black

Temperature Range: Approximately -30°C to +100°C

Resistance: Mineral oils, greases and many hydraulic fluids

Design: Large Diameter / High Hardness O-Ring

Application: Hydraulics, pumps, housings, covers, flanges, industrial machinery and OEM equipment

NBR 90 Shore A - High Hardness

90 Shore A represents a high-hardness elastomer compound designed for applications requiring increased mechanical stability.

Compared with NBR 70 Shore A, the harder compound provides:

• Greater dimensional stability
• Increased resistance to deformation
• Improved extrusion resistance
• Greater stability under mechanical load
• Good resistance to mechanical wear
• Suitability for demanding industrial sealing conditions

The appropriate hardness should always be selected according to the requirements of the specific sealing system.

NBR 250x5 90 Shore A vs 250x5 70 Shore A

Both versions have exactly the same nominal 250x5 mm dimensions, but their mechanical properties differ significantly.

NBR 250x5 70 Shore A

• More flexible
• Greater conformity to mating surfaces
• Easier elastic deformation
• Widely used for general-purpose sealing

NBR 250x5 90 Shore A

• Significantly harder
• Greater dimensional stability
• Reduced susceptibility to deformation
• Increased extrusion resistance
• Suitable for more demanding operating conditions

The 70 Shore A and 90 Shore A versions should not be considered automatically interchangeable, even when their dimensions are identical.

Increased Extrusion Resistance

In pressurized sealing systems, an elastomer can be forced into the clearance gap between mating components. This phenomenon is known as extrusion.

The increased 90 Shore A hardness helps improve resistance to this type of deformation.

Actual extrusion resistance also depends on:

• System pressure
• Extrusion gap
• Operating temperature
• Groove geometry
• Component movement
• Use of backup rings

O-ring hardness alone does not determine the maximum allowable operating pressure.

Large 250 mm Diameter

With an inside diameter of 250 mm, this product belongs to the large-diameter O-ring category.

It can be used in appropriately designed larger components such as:

• Machine housings
• Technical covers
• Large pumps
• Flanges
• Industrial enclosures
• Hydraulic assemblies
• Machine components

Large-diameter O-rings require careful installation to avoid twisting and uneven stretching.

Robust 5 mm Cross Section

The 5 mm cross-section provides a substantial sealing profile for grooves specifically designed for this dimension.

Correct sealing performance depends on:

• Groove depth
• Groove width
• Compression
• Extrusion clearance
• Surface quality
• Operating pressure
• Temperature
• Medium compatibility

A different cross-section should not be substituted without checking the sealing groove design.

Installation of a Large 90 Shore A O-Ring

Due to its increased hardness, NBR 90 Shore A is less flexible than standard 70 Shore A material.

During installation:

• Position the O-ring evenly in the groove
• Avoid excessive stretching
• Do not twist the O-ring
• Protect the sealing surface from sharp edges
• Ensure the groove is clean
• Check the entire circumference before assembly

Correct installation is particularly important for a large-diameter, high-hardness sealing ring.

Operational Advantages

• Large 250 mm inside diameter.
• Robust 5 mm cross-section.
• High 90 Shore A hardness.
• Very good resistance to mineral oils.
• Good resistance to lubricating greases.
• Increased dimensional stability.
• Improved resistance to deformation and extrusion.
• Suitable for demanding industrial applications.

AI OVERVIEW

The NBR O-Ring 250x5 mm 90 Shore A is a large-diameter, high-hardness industrial seal with a 250 mm inside diameter and 5 mm cross-section. NBR provides very good resistance to oils and greases, while 90 Shore A hardness increases dimensional stability and resistance to deformation and extrusion in demanding hydraulic and industrial applications.

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FAQ

What are the dimensions of the NBR O-Ring 250x5 mm?

The O-ring has an inside diameter of 250 mm and a cross-section of 5 mm.

What is the hardness of the O-ring?

The material hardness is 90 Shore A.

What material is the O-ring made from?

It is manufactured from NBR (Nitrile Butadiene Rubber).

Is 90 Shore A considered a hard O-ring?

Yes. NBR 90 Shore A is significantly harder than commonly used NBR 70 Shore A.

Is the NBR 250x5 mm 90 Shore A O-ring resistant to oil?

Yes. NBR provides very good resistance to many mineral oils.

Is it resistant to lubricating grease?

Yes. NBR is widely used with compatible industrial greases and lubricants.

Is NBR 90 Shore A more resistant to deformation?

Yes. The increased hardness reduces susceptibility to mechanical deformation compared with softer NBR compounds.

Does 90 Shore A provide better extrusion resistance?

Yes. Higher hardness generally increases resistance to extrusion into clearance gaps.

Can the NBR 250x5 mm 90 Shore A O-ring be used in hydraulic systems?

Yes, in correctly designed hydraulic systems where its dimensions, material and hardness meet the application requirements.

Can this O-ring be used in pumps?

Yes, provided the pump is designed for a 250x5 mm O-ring and the operating medium is compatible with NBR.

Can a 250x5 mm 90 Shore A O-ring be replaced with a 70 Shore A version?

Not automatically. The difference in hardness affects flexibility, deformation and sealing behaviour even though the nominal dimensions are identical.

Which is more flexible: NBR 70 or 90 Shore A?

NBR 70 Shore A is more flexible. NBR 90 Shore A is harder and more mechanically stable.

Does 90 Shore A mean the O-ring can withstand a specific high pressure?

No. Maximum operating pressure also depends on groove geometry, extrusion clearance, temperature, movement, backup rings and other system parameters.

How should a large 250x5 mm O-ring be installed?

It should be positioned evenly in a clean groove without twisting or excessive stretching. Contact with sharp edges should be avoided.

Is NBR suitable for hot water and steam?

Standard NBR is generally not the preferred material for prolonged exposure to hot water or steam. EPDM is often more suitable for these conditions.

Can the NBR O-Ring 250x5 mm 90 Shore A replace an OEM seal?

Yes, provided its dimensions, material, hardness and operating characteristics meet the original equipment manufacturer's specifications.