O-Ring 7.65x1.78 NBR 70 ShA

O-Ring 7.65x1.78 NBR 70 ShA - 100 pcs is a pack of elastomeric sealing rings with a 7.65 mm inside diameter and 1.78 mm cross-section, manufactured from NBR nitrile rubber with a nominal hardness of 70 Shore A. This size is intended for appropriately designed static and dynamic sealing systems. NBR is widely used with many mineral oils and lubricating greases, making these O-rings suitable for hydraulic systems, pneumatics, industrial machinery, maintenance and technical sealing applications.

Technical Specifications

Product Type: O-Ring / sealing ring
Material: NBR - Nitrile Butadiene Rubber / Buna-N
Hardness: 70 ShA / 70 Shore A
Inside Diameter: 7.65 mm
Cross-Section: 1.78 mm
Nominal Outside Diameter: approximately 11.21 mm
Color: Black
Typical Temperature Range: approximately -30 to +100°C for standard NBR compounds
Chemical Resistance: Many mineral oils, greases and compatible technical fluids
Packaging: 100 pcs

The exact temperature and chemical resistance depend on the specific NBR compound, operating medium and service conditions.

Why Choose NBR 70 ShA?

NBR 70 Shore A is one of the most widely used material and hardness combinations in industrial O-ring sealing.

A hardness of approximately 70 Shore A provides a practical balance between elasticity, sealing capability and resistance to deformation.

NBR is commonly selected for applications involving compatible:

• mineral oils
• lubricating greases
• hydraulic fluids
• technical lubricants
• industrial machinery fluids

NBR should not be considered universally resistant to every chemical or high-temperature environment. Compatibility should always be checked for the actual operating medium.

7.65x1.78 mm O-Ring Dimensions

The two principal dimensions are:

Inside Diameter: 7.65 mm
Cross-Section: 1.78 mm

The nominal outside diameter can be calculated as:

7.65 + 1.78 + 1.78 = 11.21 mm

Therefore, the nominal outside diameter is approximately 11.21 mm.

For replacement purposes, both the inside diameter and cross-section should be verified.

Industrial Applications

The 7.65x1.78 NBR 70 ShA O-ring can be used in appropriately designed:

• hydraulic systems
• pneumatic systems
• valves
• pumps
• fittings
• industrial machinery
• technical equipment
• maintenance assemblies
• mechanical components
• static sealing joints
• selected dynamic sealing applications

The groove geometry, operating pressure, temperature, fluid and required O-ring compression should always be considered before installation.

Hydraulic Sealing

NBR O-rings are widely used in hydraulic equipment due to their compatibility with many commonly used mineral oil based hydraulic fluids.

In a properly designed hydraulic groove, the O-ring is compressed between mating surfaces to create a sealing barrier.

Performance depends on factors including pressure, extrusion gap, groove dimensions, material hardness and temperature.

For high-pressure applications, additional supporting elements such as backup rings may be required depending on the system design.

Pneumatic Applications

The 7.65x1.78 mm NBR O-ring can also be used in appropriately designed pneumatic systems.

Typical applications can include valves, fittings, connectors and pneumatic components.

In dynamic pneumatic applications, friction, lubrication, surface finish and operating speed become particularly important because the O-ring moves relative to the mating surface.

Static Sealing Applications

In static sealing arrangements, there is no intended relative movement between the sealing surfaces during normal operation.

The O-ring is compressed within a correctly dimensioned groove, producing sealing contact against the mating surfaces.

Static O-ring performance depends on:

• correct groove dimensions
• appropriate compression
• surface condition
• pressure
• temperature
• fluid compatibility

Correct installation helps prevent twisting, cutting or pinching of the O-ring.

Dynamic Sealing Applications

NBR 70 ShA O-rings can also be used in certain dynamic sealing systems.

Dynamic applications require additional consideration because relative movement produces friction and wear.

Important factors include:

• operating speed
• lubrication
• surface finish
• pressure
• temperature
• friction
• wear resistance
• groove geometry

An O-ring arrangement designed for static operation should not automatically be considered suitable for dynamic service.

Resistance to Oils and Greases

One of the principal reasons for using NBR nitrile rubber is its resistance to many mineral oils and lubricating greases.

This makes NBR a common sealing material in industrial machinery, hydraulic equipment and mechanical systems containing oil-based lubricants.

Chemical compatibility should nevertheless be confirmed whenever the O-ring will contact unusual fluids, aggressive additives or elevated temperatures.

100 pcs Pack for Maintenance and Service

The 100 pcs package provides a practical stock quantity for maintenance departments, workshops, repair services and industrial users requiring repeated access to the same O-ring size.

It is particularly suitable for:

• machine maintenance
• workshop stock
• equipment servicing
• repair operations
• spare parts inventory
• recurring assembly work

The 100 pcs variant provides a convenient service quantity without positioning the product as a large industrial bulk pack.

Storage of NBR O-Rings

O-rings should be stored under conditions that help limit premature elastomer ageing.

Recommended storage practices include:

• keeping seals dry
• avoiding direct sunlight
• protecting against UV exposure
• keeping away from excessive heat
• avoiding unnecessary stretching
• protecting against ozone sources
• keeping away from incompatible chemicals

O-rings should preferably remain in suitable packaging until required for installation.

Installation Guidelines

Before installation, inspect the groove and mating surfaces for contamination, burrs and sharp edges.

The O-ring should not be cut, twisted or excessively stretched during assembly.

Where an installation lubricant is required, it should be chemically compatible with both NBR and the operating medium.

Extra care should be taken when passing an O-ring over threads, splines, keyways or sharp shoulders.

How to Select a 7.65x1.78 O-Ring

Before selecting a replacement, verify:

Inside Diameter: 7.65 mm
Cross-Section: 1.78 mm
Material: NBR
Hardness: 70 ShA
Operating Medium: Compatible with NBR
Temperature: Suitable for the specific compound
Pressure: Suitable for the sealing arrangement
Application: Static or dynamic
Groove Dimensions: Appropriate for the O-ring

Dimensions alone are not sufficient to determine suitability for every sealing application.

Operational Advantages

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

1.78 mm cross-section: suitable for compact sealing grooves designed for this specific cross-section.

Oil resistance: NBR is compatible with many mineral oils and lubricating greases.

Versatile application: suitable for many hydraulic, pneumatic and mechanical sealing systems.

100 pcs packaging: practical quantity for maintenance, service and workshop inventory.

Defined 7.65x1.78 mm size: supports precise identification during technical purchasing and replacement.

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FAQ - O-Ring 7.65x1.78 NBR 70 ShA

What are the dimensions of this O-ring?
The O-ring has a 7.65 mm inside diameter and 1.78 mm cross-section.

What is the outside diameter of a 7.65x1.78 O-ring?
The nominal outside diameter is approximately 11.21 mm.

How many O-rings are included in the package?
The package contains 100 O-rings of the same size and specification.

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

Is this NBR O-ring resistant to oil?
NBR provides good resistance to many mineral oils and lubricating greases. Compatibility should still be checked for the specific fluid and temperature.

Can this O-ring be used in hydraulic systems?
Yes, provided that NBR is compatible with the hydraulic fluid and the groove, pressure and operating conditions are suitable.

Can it be used in pneumatic equipment?
Yes. NBR 70 ShA O-rings are widely used in appropriately designed pneumatic sealing systems.

Frequently Asked Questions by Engineers

Is the 7.65x1.78 mm size alone sufficient to select the correct O-ring?
No. Material, hardness, operating fluid, temperature, pressure and groove geometry should also be considered.

Can NBR 70 ShA be used for dynamic sealing?
Yes, in appropriately designed applications. Dynamic operation requires additional consideration of friction, lubrication, speed, surface finish and wear.

Should an O-ring be lubricated before installation?
A compatible assembly lubricant can reduce installation damage and friction, but it must be suitable for both the NBR material and the operating medium.

Can this O-ring be used at high pressure?
Pressure capability cannot be determined from O-ring size alone. Groove geometry, extrusion gap, hardness, temperature and the possible use of backup rings must also be considered.

Why is 70 Shore A commonly used for NBR O-rings?
It provides a useful balance between elastomer flexibility, sealing contact and resistance to deformation for many general industrial applications.