O-ring 79x2.5 NBR 70 ShA

Technical Specifications

The nominal outside diameter is calculated as follows:

79 mm + 2 x 2.5 mm = 84 mm.

This is a geometrically calculated nominal dimension based on the inside diameter and cross-section, not a separately verified manufacturing inspection dimension.

What Does O-ring 79x2.5 NBR 70 ShA Mean?

The designation 70 ShA describes the hardness of the elastomer, not its pressure resistance or operating temperature capability.

Exact mechanical and chemical properties depend on the specific NBR compound.

Construction and Operating Principle

O-ring 79x2.5 NBR 70 ShA is a continuous elastomeric sealing ring with a circular cross-section of 2.5 mm.

When installed in a correctly designed sealing groove, the ring undergoes controlled compression. The resulting contact pressure between the elastomer and mating surfaces restricts the passage of the working medium through the sealing interface.

Sealing performance depends on:

• Sealing groove dimensions and tolerances.

• Compression of the 2.5 mm cross-section.

• Stretching of the ring during installation.

• Surface condition and roughness of mating components.

• Operating pressure and extrusion gap.

• Operating temperature.

• Chemical compatibility between NBR and the working medium.

• Compression set of the elastomer during service.

A hardness of 70 Shore A is commonly used in sealing technology, but this property alone does not establish suitability for a particular operating pressure.

NBR 70 Shore A - Material Properties

NBR is a synthetic rubber produced from acrylonitrile and butadiene. It is widely used in sealing ring manufacturing because of its mechanical characteristics and resistance to many oil-based media.

Appropriately selected NBR compounds may provide:

• Resistance to many mineral oils.

• Resistance to selected greases and mineral oil-based hydraulic fluids.

• Good elasticity within the specified operating range.

• Compound-dependent abrasion resistance.

• Suitable mechanical properties for common sealing applications.

However, NBR does not provide universal chemical resistance.

It may be unsuitable for contact with ketones, certain solvents, ozone, and media requiring specialised elastomers.

A specific operating temperature range should not be assigned to this product without confirmed material documentation.

O-ring 79x2.5 NBR 70 ShA vs Other Materials

Material selection must consider the working medium, temperature, pressure, and sealing arrangement.

Identical dimensions of 79x2.5 mm do not automatically guarantee interchangeability between NBR, FKM, EPDM, and VMQ sealing rings.

O-ring Selection and Interchangeability

Before selecting O-ring 79x2.5 NBR 70 ShA, verify the requirements of the sealing application.

Important selection criteria include:

• Inside diameter: 79 mm.

• Cross-section diameter: 2.5 mm.

• Material: NBR.

• Nominal hardness: 70 Shore A.

• Dimensional tolerances of the sealing ring.

• Sealing groove dimensions and tolerances.

• Required compression and permissible stretching.

• Operating pressure and extrusion gap.

• Operating temperature.

• Chemical compatibility with the working medium.

• Static or dynamic sealing conditions.

Replacing a 2.5 mm cross-section O-ring with a different cross-section requires verification of the sealing groove geometry.

Changing the hardness from 70 Shore A to 90 Shore A also requires evaluation of the operating conditions.

Applications of O-ring 79x2.5 NBR 70 ShA

O-ring 79x2.5 NBR 70 ShA may be considered for appropriately designed sealing arrangements in:

• Industrial equipment housings and covers.

• Flanged mechanical connections.

• Oil systems operating with compatible fluids.

• Selected hydraulic systems.

• Mechanical assemblies requiring a 2.5 mm sealing cross-section.

These are potential application categories based on the O-ring geometry and general properties of NBR, not confirmed OEM applications for this particular product.

Dynamic sealing applications require additional evaluation of friction, lubrication, operating speed, and sealing groove geometry.

Alternative Designations and Reference Formats

Natural descriptive formats include:

• O-ring 79x2.5 NBR 70 ShA

• O-ring 79x2.5 NBR

• O-ring NBR 79x2.5 70 Shore A

• NBR O-ring 79x2.5

• Nitrile Rubber O-ring 79x2.5

These are descriptive reference formats, not confirmed manufacturer catalogue numbers or OEM part numbers.

The primary product designation remains O-ring 79x2.5 NBR 70 ShA.

Installation, Handling and Storage

Before installation, clean the sealing groove and mating surfaces and inspect the condition of the sealing ring.

During installation:

• Protect the O-ring from sharp edges.

• Avoid excessive stretching.

• Prevent twisting of the cross-section.

• Ensure uniform positioning inside the groove.

• Use only assembly lubricants compatible with NBR and the working medium.

• Verify correct seating before closing the assembly.

NBR sealing rings should be stored in clean conditions, protected from excessive heat, ozone, direct sunlight, and chemicals that may damage the elastomer.

Frequently Asked Questions - FAQ

What are the dimensions of O-ring 79x2.5 NBR 70 ShA?

The inside diameter is 79 mm, and the cross-section diameter is 2.5 mm. The geometrically calculated nominal outside diameter is 84 mm.

What does NBR 70 ShA mean?

NBR stands for nitrile butadiene rubber, while 70 ShA indicates the nominal material hardness on the Shore A scale.

Is O-ring 79x2.5 NBR 70 ShA resistant to oils?

Appropriately selected NBR compounds offer resistance to many mineral oils and greases. Compatibility must be confirmed for the specific working medium and operating temperature.

Can an NBR 70 ShA O-ring be replaced with an FKM O-ring?

Not automatically. Material properties, hardness, dimensional tolerances, and operating conditions must be compared before substitution.

Can O-ring 79x2.5 be replaced with O-ring 79x3?

Not without verifying the sealing groove design. The difference in cross-section affects compression and sealing performance.

What is the operating temperature range of O-ring 79x2.5 NBR 70 ShA?

The exact operating temperature range has not been confirmed. It depends on the specific NBR compound and operating conditions.

Does 70 Shore A hardness indicate high-pressure resistance?

No. Hardness is only one parameter affecting sealing performance. Permissible pressure also depends on groove geometry, extrusion gap, temperature, and material properties.

Is the nominal outside diameter 84 mm?

Yes. It is calculated from the 79 mm inside diameter and 2.5 mm cross-section. Actual manufactured dimensions depend on production tolerances.

O-ring 79x2.5 NBR 70 ShA - Key Technical Information

O-ring 79x2.5 NBR 70 ShA is a nitrile rubber sealing ring with a 79 mm inside diameter, a 2.5 mm cross-section, and a nominal hardness of 70 Shore A. Its calculated nominal outside diameter is 84 mm. NBR is used in sealing systems containing compatible oils and greases. Correct selection requires verification of the working medium, temperature, and sealing groove geometry.

NBR O-rings at simmering.pl

NBR O-rings, industrial sealing components, rolling bearings, and mechanical accessories are available through simmering.pl, a specialist B2B trading platform serving industrial companies, engineers, maintenance departments, and technical purchasing teams.

Our warehouse and order processing facilities are located in Lublin, Poland. We provide worldwide shipping from stock in Poland.

Technical product identification and selection assistance is available based on sealing dimensions, elastomer material, hardness, and application requirements.