O-Ring 12.42x1.78 mm NBR 90 ShA

O-ring 12.42x1.78 mm NBR 90 ShA

O-ring 12.42x1.78 mm NBR 90 ShA is a technical sealing ring manufactured from NBR nitrile rubber with a high nominal hardness of 90 Shore A. It has a 12.42 mm inside diameter and a 1.78 mm cross-section. The harder 90 ShA compound is intended for appropriately designed sealing systems where greater resistance to deformation is required compared with commonly used 70 ShA O-rings.

O-ring NBR 12.42x1.78 mm 90 ShA - Technical Data

The nominal outside diameter is calculated from the basic dimensions:

12.42 + 2 x 1.78 = 15.98 mm

What Does O-ring Size 12.42x1.78 mm Mean?

The standard O-ring dimension format specifies the inside diameter and cross-section.

For this product:

12.42 mm - inside diameter ID

1.78 mm - cross-section CS

The nominal outside diameter is approximately:

15.98 mm

Both dimensions must be considered when selecting an O-ring. A sealing ring with a 12.42 mm inside diameter but a different cross-section is not automatically interchangeable with a 12.42x1.78 mm O-ring.

Even a small difference in cross-section can change the compression of the O-ring within the groove and affect the performance of the complete sealing system.

NBR - Nitrile Rubber

This O-ring is manufactured from NBR, or acrylonitrile-butadiene rubber, commonly known as nitrile rubber.

NBR is one of the most widely used elastomers in technical sealing applications. It is commonly selected for appropriately designed applications involving many oils, greases and technical fluids.

NBR O-rings are widely used in:

hydraulic systems

pneumatic systems

industrial machinery

pumps

valves

cylinders

technical fittings

lubrication systems

automotive applications

machine manufacturing

maintenance operations

technical service and repair

Exact chemical and temperature resistance depends on the specific NBR compound. The designation NBR 90 ShA alone does not define every operating parameter of the product.

NBR 90 ShA - What Does 90 Shore A Mean?

The nominal hardness of this O-ring is 90 ShA.

Compared with the widely used NBR 70 ShA grade, 90 ShA represents a significantly harder elastomer.

Higher hardness generally means that the elastomer is less susceptible to deformation under load. This can be advantageous in appropriately designed sealing systems where a harder sealing element is required.

However, this does not mean that a 90 ShA O-ring is always better than a 70 ShA O-ring.

The required hardness must match the design and operating conditions of the specific sealing system.

NBR 70 ShA vs NBR 90 ShA O-ring

O-rings with identical 12.42x1.78 mm dimensions but different hardness ratings of 70 ShA and 90 ShA should not automatically be considered interchangeable.

NBR 70 ShA is more flexible and is one of the most commonly used hardness classes for standard technical O-rings.

NBR 90 ShA is harder and less susceptible to deformation.

In certain sealing arrangements, higher hardness can help reduce the tendency of the elastomer to extrude into a clearance gap. However, actual extrusion resistance also depends on system pressure, clearance gap, temperature, groove geometry and the use of backup rings.

Therefore, a 70 ShA O-ring should not be replaced by a 90 ShA version, or vice versa, without checking the requirements of the specific sealing system.

O-ring 12.42x1.78 NBR 90 - Applications

This O-ring can be used as a sealing element in appropriately designed technical assemblies.

Typical application areas for O-rings include:

hydraulic systems

pneumatic systems

industrial machines and equipment

pumps and valves

cylinders

control valves

industrial fittings

technical connections

machine components

lubrication systems

industrial production and assembly

maintenance operations

Suitability for a particular application depends not only on dimensions and hardness but also on the operating medium, temperature, pressure, type of movement and groove geometry.

NBR 90 ShA O-ring for Hydraulic Applications

Harder NBR O-rings can be used in appropriately designed hydraulic sealing systems.

Under higher pressure loads, an important phenomenon is extrusion, where the elastomer can be forced into the clearance gap between mating components.

Higher elastomer hardness can reduce susceptibility to this type of deformation, but a universal maximum working pressure cannot be assigned to this O-ring based solely on its 90 ShA hardness.

Permissible pressure depends on factors including:

clearance gap

groove geometry

temperature

operating medium

type of movement

mating materials

use of backup rings

For this reason, an exact maximum pressure rating should not be stated without technical data for the complete sealing arrangement.

Why Is the 1.78 mm Cross-Section Important?

The 1.78 mm cross-section is one of the two primary dimensions identifying this O-ring.

An O-ring works through controlled compression of its elastomeric cross-section inside a correctly designed groove.

Changing the cross-section changes groove fill and sealing compression.

Therefore, an O-ring measuring:

12.42x1.78 mm

should not automatically be replaced by:

12.42x2 mm

12.42x1.5 mm

or another similar size.

Similar dimensions do not automatically mean technical interchangeability.

Outside Diameter of O-ring 12.42x1.78 mm

The nominal outside diameter can be calculated using:

OD = ID + 2 x CS

For this O-ring:

ID = 12.42 mm

CS = 1.78 mm

therefore:

OD = 12.42 + 2 x 1.78 = 15.98 mm

The nominal outside diameter is therefore approximately 15.98 mm.

However, the standard method of identifying the O-ring remains its inside diameter and cross-section: 12.42x1.78 mm.

How to Select an NBR 12.42x1.78 mm 90 ShA O-ring

Before selecting this O-ring, verify:

• inside diameter 12.42 mm,
• cross-section 1.78 mm,
• NBR elastomer material,
• required hardness of 90 ShA,
• groove dimensions and geometry,
• required compression,
• operating medium,
• operating temperature,
• pressure,
• clearance gap,
• static or dynamic operating conditions,
• equipment manufacturer's requirements.

When replacing an existing O-ring, the machine or component manufacturer's technical documentation should be used whenever possible.

Measuring a used O-ring can produce inaccurate results because the elastomer may have become worn, stretched or permanently deformed during service.

Is NBR Resistant to Oils and Greases?

NBR is widely used in sealing applications involving many technical oils and greases.

However, this does not mean that NBR is universally resistant to every oil, fuel, solvent or other chemical substance.

Compatibility depends on the specific NBR compound, composition of the operating medium, temperature and duration of exposure.

For unusual or aggressive media, the sealing material should be selected using chemical compatibility information for the specific elastomer compound.

Industrial and B2B Applications

O-ring NBR 12.42x1.78 mm 90 ShA is intended for professional use in appropriately designed sealing systems.

It may be used by:

industrial plants

maintenance departments

machine manufacturers

equipment manufacturers

hydraulic service companies

pneumatic service companies

technical workshops

industrial repair companies

technical distributors

OEM customers

B2B customers

simmering.pl supplies O-rings and technical sealing solutions for industry, maintenance departments, service companies, machine manufacturers and professional B2B customers.

Alternative Designations and Search Terms

The product may also be searched as:

O-ring 12.42x1.78 NBR 90 ShA

O-ring NBR 12.42x1.78 90 ShA

O-ring NBR 12.42x1.78 90 Shore A

O-ring 12.42x1.78 NBR 90

NBR 90 O-ring 12.42x1.78

NBR 90A O-ring 12.42x1.78

O-ring 12.42x1.78 90 Shore

O-ring 12.42x1.78 NBR 90A

NBR seal 12.42x1.78

nitrile O-ring 12.42x1.78

hard NBR O-ring 90 ShA

hydraulic O-ring 12.42x1.78

12.42 mm ID O-ring

1.78 mm cross-section O-ring

15.98 mm OD O-ring

For international product listings, 12.42x1.78 mm is the preferred dimension format.

Installation of NBR 90 ShA O-ring

Before installation, clean the groove and all mating surfaces.

Check the installation path for sharp edges, burrs or exposed threads that could cut or damage the elastomer.

Avoid twisting or excessively stretching the O-ring during installation.

Because 90 ShA NBR is less flexible than a typical 70 ShA O-ring, correct groove dimensions and proper installation technique are particularly important.

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

After installation, verify that the O-ring is correctly seated and is not twisted within the groove.

FAQ - O-ring 12.42x1.78 NBR 90 ShA

What are the dimensions of this O-ring?

The inside diameter is 12.42 mm and the cross-section is 1.78 mm.

What is the outside diameter?

The nominal outside diameter is approximately 15.98 mm.

What material is this O-ring made from?

It is manufactured from NBR, also known as nitrile rubber or acrylonitrile-butadiene rubber.

What is the hardness of this O-ring?

The nominal hardness is 90 ShA (Shore A).

What is the difference between NBR 90 ShA and NBR 70 ShA?

NBR 90 ShA is harder and less susceptible to deformation than NBR 70 ShA. However, this does not mean it can automatically replace a 70 ShA O-ring. The required hardness depends on the sealing system design.

Is an NBR 90 ShA O-ring suitable for hydraulic systems?

It can be used in appropriately designed hydraulic systems when its dimensions, material, hardness and other characteristics meet the requirements of the specific sealing arrangement.

Is NBR 90 ShA suitable for high-pressure applications?

Higher hardness can reduce the elastomer's susceptibility to extrusion, but permissible pressure cannot be determined from O-ring hardness alone. Clearance, groove geometry, temperature, medium and overall system design must also be considered.

Can I replace a 12.42x1.78 NBR 70 ShA O-ring with a 90 ShA version?

Automatic interchangeability should not be assumed. Although the dimensions are identical, different hardness affects how the O-ring behaves and compresses within the groove. The hardness specified for the particular application should be used.

O-ring 12.42x1.78 NBR 90 ShA - Key Information

O-ring 12.42x1.78 NBR 90 ShA is a technical sealing ring with a 12.42 mm inside diameter, 1.78 mm cross-section and nominal outside diameter of approximately 15.98 mm. It is manufactured from NBR nitrile rubber with a high nominal hardness of 90 Shore A and is intended for appropriately designed industrial, hydraulic, pneumatic and machinery sealing applications.

Available from simmering.pl, stock in Poland with worldwide shipping.

Warehouse and Store: Lublin, Smoluchowskiego 1 Street, Building 4, Poland.

simmering.pl supplies O-rings and technical seals for industry, maintenance departments, technical service companies, machine manufacturers and B2B customers.