O-ring 270x8 NBR 70 ShA - Sealing Ring

Technical Specifications

The nominal outside diameter of 286 mm is calculated from the specified dimensions:

270 mm + 2 x 8 mm = 286 mm.

This calculated value does not represent a separately verified manufacturing inspection dimension.

What Does O-ring 270x8 NBR 70 ShA Mean?

The designation 270x8 identifies the nominal dimensions of the sealing ring.

It does not automatically establish a specific manufacturing tolerance class or compliance with a particular dimensional standard.

Dimensional tolerances and surface quality requirements must be verified against the applicable product documentation.

Construction and Operating Principle

O-ring 270x8 NBR 70 ShA is a continuous elastomeric ring with a circular cross-section.

When installed in a correctly designed sealing groove, the ring undergoes controlled elastic deformation.

This deformation generates contact pressure between the O-ring and the mating surfaces, restricting the passage of the working medium through the sealing interface.

Sealing performance depends on several factors:

• Groove dimensions and installation geometry.

• Compression of the 8 mm cross-section.

• Circumferential stretching or compression of the ring.

• Surface roughness and condition 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.

The relatively large inside diameter of 270 mm makes uniform groove geometry and consistent compression around the entire circumference particularly important.

NBR 70 Shore A - Material Properties

NBR, or nitrile butadiene rubber, is an elastomer widely used in industrial sealing applications.

Suitable NBR compounds generally provide resistance to many mineral oils, lubricating greases, and mineral oil-based hydraulic fluids.

The nominal hardness of 70 Shore A is commonly selected where a balance between elastic deformation and mechanical resistance is required.

Important material considerations include:

• Chemical resistance depends on the specific NBR compound.

• Not all NBR formulations are suitable for fuels containing alcohol.

• Standard NBR compounds generally have limited resistance to ozone and prolonged outdoor weathering.

• Compatibility with esters, ketones, and aggressive chemicals requires separate verification.

• Operating temperature limits depend on the compound formulation and service conditions.

The designation NBR 70 ShA alone does not establish an exact temperature range, chemical resistance classification, or material approval.

Such properties must be confirmed through the manufacturer's material documentation.

O-ring 270x8 NBR 70 ShA vs Other Materials and Hardness Grades

These variants are presented for technical comparison only. Their availability and interchangeability have not been confirmed.

Identical dimensions of 270x8 mm do not guarantee interchangeability.

Material composition and hardness must be compatible with the working medium, pressure, temperature, and sealing groove design.

O-ring Selection and Interchangeability

Before selecting O-ring 270x8 NBR 70 ShA, verify the requirements of the sealing application.

Important selection criteria include:

• Inside diameter: 270 mm.

• Cross-section diameter: 8 mm.

• Material: NBR.

• Hardness: 70 Shore A.

• Groove dimensions and manufacturing tolerances.

• Required cross-section compression.

• Permissible stretching during installation.

• Operating pressure and pressure direction.

• Operating temperature.

• Chemical composition of the working medium.

• Static or dynamic sealing conditions.

• Required dimensional tolerance class.

When selecting an alternative O-ring, compare not only the nominal dimensions but also the properties of the elastomer compound.

An O-ring with identical dimensions but a different material or hardness may behave differently under operating conditions.

Applications of O-ring 270x8 NBR 70 ShA

O-ring 270x8 NBR 70 ShA may be considered for appropriately designed static sealing arrangements in:

• Covers and housings of industrial equipment.

• Flanged mechanical connections.

• Hydraulic assemblies operating with compatible fluids.

• Mechanical housings and enclosures.

• Large-diameter static sealing connections.

These are typical application categories for NBR O-rings, not confirmed applications of this specific product in a particular machine.

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

The dimensions and material designation alone do not establish suitability for dynamic operation.

Alternative Designations and Reference Formats

Natural descriptive formats include:

• O-ring 270x8 NBR 70 ShA

• O-ring NBR 270x8 70 Shore A

• O-ring 270x8 NBR 70

• NBR O-ring 270x8 mm

• Nitrile Rubber O-ring 270x8 70 ShA

• O-ring Seal 270x8 NBR 70 Shore A

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

The primary product designation remains O-ring 270x8 NBR 70 ShA.

Installation, Handling and Storage

Before installation, clean the sealing groove and all mating surfaces.

Inspect the O-ring for cuts, cracks, permanent deformation, contamination, or other visible defects.

During installation:

• Avoid contact with sharp edges.

• Prevent twisting of the ring inside the groove.

• Do not stretch the O-ring beyond what is necessary for correct installation.

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

• Ensure uniform positioning around the entire circumference.

• Verify correct compression after assembling the connection.

For large-diameter O-rings, particular attention should be paid to avoiding local stretching and uneven positioning.

Store the sealing rings in clean conditions, away from direct sunlight, ozone sources, excessive heat, and chemicals that may affect the elastomer.

Frequently Asked Questions - FAQ

What are the dimensions of O-ring 270x8 NBR 70 ShA?

The inside diameter is 270 mm, and the cross-section diameter is 8 mm. The calculated nominal outside diameter is 286 mm.

What does NBR mean?

NBR stands for nitrile butadiene rubber, an elastomer commonly used in technical sealing applications, including applications involving compatible mineral oils.

What does 70 ShA mean?

70 ShA indicates a nominal elastomer hardness of 70 units on the Shore A hardness scale.

Is O-ring 270x8 NBR resistant to hydraulic oil?

Suitable NBR compounds are generally compatible with many mineral oil-based hydraulic fluids. Compatibility must be verified for the specific fluid and operating conditions.

Can O-ring 270x8 NBR 70 ShA be replaced with a 90 ShA version?

Not automatically. Higher hardness changes the deformation characteristics of the seal and may require different groove geometry and compression conditions.

Is O-ring 270x8 suitable for dynamic sealing?

Suitability for dynamic sealing must be evaluated separately. The nominal dimensions and material designation alone do not confirm compatibility with dynamic operation.

What is the operating temperature range of O-ring 270x8 NBR?

The exact operating temperature range depends on the NBR compound formulation and must be confirmed through the manufacturer's material specifications.

Is the outside diameter of O-ring 270x8 equal to 286 mm?

Yes. The calculated nominal outside diameter is 286 mm, based on the 270 mm inside diameter and the 8 mm cross-section. Actual manufactured dimensions are subject to tolerances.

O-ring 270x8 NBR 70 ShA - Key Technical Information

O-ring 270x8 NBR 70 ShA is a nitrile rubber sealing ring with a 270 mm inside diameter, an 8 mm cross-section, and nominal hardness of 70 Shore A. It is primarily intended for appropriately designed static sealing applications. Correct selection requires verification of groove geometry, working medium compatibility, operating pressure, and temperature.

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.