O-Ring 145x3.5 NBR 70 ShA - Large Diameter Industrial Sealing Ring

O-Ring 145x3.5 NBR 70 ShA is a large-diameter elastomeric sealing ring with a 145 mm inside diameter and 3.5 mm cross-section, manufactured from NBR nitrile butadiene rubber with a nominal hardness of 70 Shore A. The combination of a large 145 mm diameter and relatively compact 3.5 mm section makes this O-ring suitable for appropriately designed housings, covers, flanges, pumps, hydraulic components and industrial machinery requiring reliable sealing against compatible oils, greases and technical fluids.

Technical Specifications

Product Type: O-Ring / sealing ring
Material: NBR - Nitrile Butadiene Rubber / Buna-N
Hardness: 70 ShA / 70 Shore A
Inside Diameter: 145 mm
Cross-Section: 3.5 mm
Nominal Outside Diameter: 152 mm
Color: Black
Typical Temperature Range: approximately -30 to +100°C for standard NBR compounds
Chemical Resistance: Many mineral oils, lubricating greases and compatible technical fluids
Application: Industrial sealing, machinery, hydraulics, pumps, covers and mechanical assemblies

Exact temperature and chemical resistance depend on the specific NBR compound, medium and operating conditions.

145x3.5 mm O-Ring Dimensions

The principal dimensions are:

Inside Diameter: 145 mm
Cross-Section: 3.5 mm
Nominal Outside Diameter: 152 mm

The nominal outside diameter is calculated as:

145 + 3.5 + 3.5 = 152 mm

O-rings are normally identified using the inside diameter and cross-section, making 145x3.5 mm the primary dimensional specification.

Large 145 mm Inside Diameter

The 145 mm inside diameter makes this O-ring particularly relevant to larger mechanical components and sealing interfaces.

Unlike smaller O-rings commonly used in fittings and compact valves, this size can be used in larger housings, covers and machine assemblies where a continuous elastomeric sealing ring is required.

Correct groove geometry becomes particularly important with a large-diameter O-ring to prevent twisting, uneven stretching or incorrect positioning during assembly.

Why NBR 70 ShA?

NBR is one of the most widely used elastomers in industrial sealing technology.

It provides useful resistance to many:

• mineral oils
• lubricating greases
• compatible hydraulic fluids
• machine lubricants
• oil-based technical media

The 70 Shore A hardness provides a practical balance between flexibility, sealing contact and resistance to deformation.

For this reason, NBR 70 ShA is widely used in machine building, maintenance, hydraulics and general industrial sealing.

Industrial Applications

The 145x3.5 NBR O-ring can be used in appropriately designed:

• industrial machinery
• pumps
• hydraulic equipment
• gearboxes
• mechanical housings
• covers
• flanges
• drive assemblies
• machine components
• maintenance applications
• static sealing connections

The actual application should always be evaluated according to groove dimensions, medium, pressure, temperature and operating conditions.

Static Sealing of Housings and Covers

The large diameter makes this O-ring particularly useful for appropriately designed static sealing arrangements.

Typical examples include interfaces between a housing and cover or between two mechanical components.

When the assembly is tightened, the O-ring is compressed within its groove and creates a sealing barrier between the mating surfaces.

Reliable operation requires correct compression and sufficient groove volume to accommodate the elastomer.

Hydraulic Applications

NBR 70 ShA is widely used in hydraulic systems operating with compatible mineral oil based hydraulic fluids.

A 145x3.5 mm O-ring may therefore be suitable for larger hydraulic components, covers and assemblies where this specific sealing geometry is required.

Pressure capability cannot be determined from the O-ring dimensions alone. Groove design, extrusion clearance and pressure conditions must also be considered.

Pumps and Industrial Equipment

Large-diameter O-rings are frequently required in equipment containing removable covers, housings or other circular sealing interfaces.

The 145 mm inside diameter can be relevant to pump assemblies and other industrial equipment where a replaceable elastomeric seal is required between mating components.

Compatibility with the actual fluid should always be confirmed before installation.

Resistance to Oils and Greases

NBR is particularly useful in industrial applications involving many conventional mineral oils and lubricating greases.

This makes the material suitable for numerous mechanical and maintenance applications.

However, NBR is not universally compatible with every fluid or chemical.

For aggressive chemicals, unusual fuels, high temperatures or other demanding media, the required elastomer should be verified before installation.

Installation of a Large Diameter O-Ring

Large O-rings require careful installation because the ring can be unintentionally twisted or unevenly stretched while being positioned in the groove.

Before assembly:

• clean the groove
• inspect mating surfaces
• remove dirt and particles
• check for sharp edges
• avoid twisting the O-ring
• distribute any required stretching evenly
• ensure the complete circumference is correctly seated

If an assembly lubricant is required, it must be compatible with both NBR and the operating medium.

Groove and Compression Considerations

The groove must be designed for a 3.5 mm cross-section.

An excessively shallow groove can over-compress the O-ring, increasing deformation and assembly forces.

An excessively deep groove may provide insufficient compression and reduce sealing effectiveness.

For large-diameter seals, groove dimensions and tolerances should therefore be verified against the technical requirements of the application.

Storage of NBR O-Rings

NBR sealing rings should be stored in conditions that minimize premature elastomer ageing.

Protect the O-ring against:

• direct sunlight
• UV radiation
• ozone
• excessive heat
• aggressive chemicals
• permanent deformation
• unnecessary stretching

A large O-ring should not be stored hanging from a small point or under continuous tension, as this can produce unwanted deformation.

How to Select a 145x3.5 O-Ring

Before ordering or installing the seal, verify:

Inside Diameter: 145 mm
Cross-Section: 3.5 mm
Material: NBR
Hardness: 70 ShA
Nominal Outside Diameter: 152 mm
Operating Medium: Compatible with NBR
Temperature: Suitable for the NBR compound
Pressure: Suitable for the sealing arrangement
Groove Geometry: Designed for a 3.5 mm section
Application: Static or appropriately designed dynamic sealing

The dimensions alone do not determine complete suitability for a specific machine.

Operational Advantages

145 mm inside diameter: suitable for larger industrial sealing interfaces and mechanical assemblies.

3.5 mm cross-section: provides a defined sealing section for appropriately dimensioned grooves.

NBR 70 ShA: widely used material and hardness combination for technical sealing.

Oil resistance: suitable for contact with many mineral oils and lubricating greases.

Continuous sealing ring: provides circumferential sealing without a joint in the O-ring.

Industrial versatility: applicable to appropriately designed pumps, housings, covers, hydraulic equipment and machinery.

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FAQ - O-Ring 145x3.5 NBR 70 ShA

What are the dimensions of the 145x3.5 NBR O-ring?
It has a 145 mm inside diameter and 3.5 mm cross-section.

What is the outside diameter of a 145x3.5 O-ring?
The nominal outside diameter is 152 mm.

What material is this O-ring made from?
It is manufactured from NBR nitrile butadiene rubber, also known as Buna-N.

What does 70 ShA mean?
70 ShA indicates the nominal hardness of the elastomer measured on the Shore A scale.

Can a 145x3.5 NBR O-ring be used with oil?
NBR is compatible with many mineral oils and lubricating greases. Compatibility should be verified for the specific fluid and operating temperature.

Where can a large 145 mm O-ring be used?
Depending on the groove and operating conditions, it can be used in industrial housings, covers, pumps, hydraulic equipment, machinery and other large sealing interfaces.

Frequently Asked Questions by Engineers

Does 145x3.5 mean inside diameter and cross-section?
Yes. 145 mm is the nominal inside diameter and 3.5 mm is the cross-sectional thickness.

Why is installation important with a 145 mm O-ring?
A large-diameter O-ring can be twisted or stretched unevenly during assembly. It should be positioned uniformly around the entire groove circumference.

Can a 145x3.5 O-ring be replaced with a 145x4 O-ring?
Not automatically. Increasing the cross-section changes groove filling and compression and can prevent correct assembly or sealing.

Can NBR 70 ShA be used in hydraulic equipment?
Yes, provided the hydraulic fluid is compatible with NBR and the groove, pressure and temperature conditions are appropriate.

Is this O-ring suitable for static flange sealing?
It can be suitable for an appropriately designed flange or cover groove. The groove dimensions and required compression must correspond to the 3.5 mm cross-section.