O-ring FKM 125x3 FPM Viton

O-ring FKM 125x3 mm FPM Viton

O-ring FKM 125x3 mm is a sealing ring made from fluoroelastomer, internationally designated as FKM and also commonly referred to as FPM. The O-ring has a nominal inside diameter of 125 mm and a circular cross-section of 3 mm. Viton is a well-known trade name associated with fluoroelastomer materials and is frequently used when searching for FKM/FPM seals.

Technical data

The nominal outside diameter of approximately 131 mm is geometrically derived from the O-ring dimensions: 125 mm + 2 x 3 mm.

Unconfirmed Shore A hardness, exact operating temperature range, specific FKM compound and material certifications are intentionally not stated.

What does O-ring FKM 125x3 mm mean?

The dimensions 125x3 mm indicate:

125 mm - nominal inside diameter (ID)

3 mm - nominal circular cross-section (CS)

The resulting nominal outside diameter is approximately:

125 + 2 x 3 = 131 mm

O-ring dimensions should therefore be interpreted as inside diameter x cross-section, not outside diameter x thickness.

FKM, FPM and Viton - what do they mean?

FKM is the internationally recognised designation for a family of fluoroelastomers used in technical sealing applications.

FPM is another designation for fluoroelastomer commonly encountered in European technical terminology.

Viton is a trade name associated with specific fluoroelastomer materials. In the sealing market, the term "Viton O-ring" is also widely used when searching for FKM/FPM seals.

However, not every O-ring made from FKM should automatically be described as being manufactured from genuine Viton branded material. If a specific branded compound or material certification is required, this must be confirmed separately.

Properties of FKM/FPM

FKM fluoroelastomer is used for sealing applications where properties different from those of standard NBR are required.

FKM is commonly selected for characteristics including:

• resistance to many oils

• resistance to many fuels

• resistance to a broad range of chemicals

• good ageing resistance

• good ozone resistance

• suitability for applications where standard NBR may not provide the required performance

Exact chemical and temperature resistance depends on the specific FKM compound.

Compatibility should therefore not be determined solely from the FKM designation. The actual medium, temperature and operating conditions must also be considered.

Construction of the 125x3 mm O-ring

An O-ring is a closed elastomeric sealing ring with a circular cross-section.

In its uninstalled state, this O-ring has:

• 125 mm nominal inside diameter

• 3 mm nominal cross-section

• approximately 131 mm nominal outside diameter

When installed in a correctly designed groove, the O-ring is compressed between the mating surfaces. Controlled deformation of the elastomer creates the sealing interface.

Correct operation depends not only on O-ring dimensions but also on groove geometry, compression, stretch, pressure, medium, temperature and the condition of the mating surfaces.

FKM 125x3 vs NBR 125x3

FKM and NBR O-rings may have identical dimensions of 125x3 mm, but they are not technically identical products.

FKM/FPM - fluoroelastomer with chemical and thermal characteristics typical of fluorinated elastomers.

NBR - nitrile rubber widely used in standard oil and general technical sealing applications.

Material selection should take into account:

• sealed medium

• operating temperature

• pressure

• static or dynamic operation

• required chemical resistance

• environmental conditions

An FKM O-ring should not be replaced with an NBR O-ring solely because both have the same 125x3 mm dimensions.

Alternative designations and search references

Natural product reference formats include:

• O-ring FKM 125x3 mm

• O-ring FPM 125x3 mm

• O-ring Viton 125x3 mm

• FKM O-ring 125x3

• FPM O-ring 125x3

• Viton O-ring 125x3

• FKM 125x3 O-ring

• FPM 125x3 O-ring

• 125x3 FKM O-ring

• 125x3 FPM O-ring

• 125x3 Viton O-ring

• fluoroelastomer O-ring 125x3

The primary dimensional specification remains 125x3 mm, meaning a 125 mm inside diameter and 3 mm cross-section.

How to select an FKM 125x3 O-ring

Before purchasing or replacing the O-ring, verify:

• inside diameter 125 mm

• cross-section 3 mm

• required FKM/FPM material

• sealed medium

• operating temperature

• pressure

• static or dynamic operating conditions

• groove geometry

• required compression

• required O-ring stretch

• condition of mating surfaces

• required elastomer hardness, if specified by the application

A specific Shore A hardness should not be assumed when it has not been provided in the product designation or technical documentation.

Applications

The FKM/FPM 125x3 mm O-ring is designed to create a seal between appropriately designed mating surfaces.

It can be used in static sealing arrangements and, where the system design and operating conditions permit, in suitable dynamic sealing arrangements.

The designation 125x3 FKM alone does not confirm suitability for a specific vehicle, pump, valve, hydraulic system, machine or other equipment.

Selection should be based on dimensions, material compatibility and actual operating conditions.

Installation

Before installation, make sure the groove and mating surfaces are clean.

The O-ring should not be pulled across sharp edges, threads or burrs without suitable protection.

During installation, avoid:

• cutting the elastomer

• twisting the O-ring

• excessive stretching

• damaging the sealing surface

• contaminating the sealing area

If an assembly lubricant is used, it must be compatible with both FKM and the medium being sealed.

FAQ

What are the dimensions of the FKM 125x3 O-ring?

The O-ring has a nominal inside diameter of 125 mm and a cross-section of 3 mm.

What is the outside diameter of a 125x3 O-ring?

The nominal outside diameter is approximately 131 mm. This is geometrically calculated as 125 mm + 2 x 3 mm.

What does FKM mean?

FKM is the international designation for a family of fluoroelastomers widely used in technical sealing applications.

What does FPM mean?

FPM is another designation for fluoroelastomer commonly encountered in European technical terminology.

Are FKM and Viton exactly the same?

Not exactly. FKM describes a class of fluoroelastomer materials, while Viton is a trade name associated with specific fluoroelastomers. An FKM O-ring should not automatically be claimed to use genuine Viton branded material without confirmation.

Can an FKM 125x3 O-ring be replaced with an NBR 125x3 O-ring?

Not automatically. Although the dimensions are identical, FKM and NBR have different material properties. Medium, temperature and other operating conditions must be checked before substitution.

What is the hardness of this O-ring?

Hardness is not specified in the product designation, so a Shore A value should not be assumed without documentation for the specific compound.

Is the 125x3 FKM O-ring sold individually?

Yes. This size is sold individually as 1 pc.

O-ring FKM 125x3 mm FPM Viton - key information

O-ring FKM 125x3 mm is a fluoroelastomer sealing ring with a nominal inside diameter of 125 mm and a 3 mm cross-section. Its calculated nominal outside diameter is approximately 131 mm. FKM/FPM identifies the fluoroelastomer material family, while Viton is a recognised trade name associated with specific fluoroelastomer materials.

O-ring FKM 125x3 mm is available from the specialist industrial supplier simmering.pl, with stock in Poland and worldwide shipping. Assistance with O-ring identification and technical seal selection is also available.