FPM 35x42x4 AO FKM Viton Double Lip Rotary Shaft Seal

Overview

The FPM 35x42x4 AO FKM Viton is a compact rotary shaft seal with dimensions 35x42x4 mm, manufactured from fluorocarbon elastomer FPM/FKM.

The AO design uses a spring-loaded primary sealing lip together with an additional dust lip. This configuration helps retain lubricant inside the system while reducing the ingress of dust and external contaminants.

FKM is widely used in demanding sealing applications because of its high temperature resistance and excellent compatibility with many oils, greases, fuels and hydrocarbons.

Industrial Applications

The FPM 35x42x4 AO seal is suitable for:

• Gearboxes
• Geared motors
• Pumps
• Electric motors
• Industrial drives
• Production machinery
• Hydraulic equipment
• Agricultural machinery
• Oil-lubricated systems
• Rotating shaft applications

AO Double Lip Design

The AO designation identifies a double lip shaft seal design.

The construction includes:

• Primary sealing lip
• Garter spring
• Auxiliary dust lip
• Elastomer-covered outside diameter
• Internal metal reinforcement

The primary lip retains oil or lubricant on the media side, while the secondary lip helps protect the main sealing contact area against dust and external contamination.

FPM / FKM Viton Material

The seal is manufactured from FPM/FKM fluorocarbon elastomer.

FPM and FKM refer to the same general elastomer family, while Viton is a well-known trade name associated with fluorocarbon elastomers.

FKM offers very good resistance to:

• Mineral oils
• Greases
• Fuels
• Many hydraulic oils
• Aliphatic hydrocarbons
• Aromatic hydrocarbons
• Silicone oils
• Ozone
• Ageing
• Weathering

This makes FKM especially suitable where standard NBR does not provide sufficient thermal or chemical resistance.

Temperature Resistance

For many standard FKM rotary shaft seal compounds, a typical operating range is approximately:

-20°C to +200°C

The actual permissible temperature depends on the exact FKM compound, sealed medium, shaft speed and exposure time.

The maximum material temperature should not automatically be treated as the continuous operating limit of the complete sealing system.

Technical Specification

Product Type: Rotary shaft seal / oil seal

Design: AO

Execution: Double lip

Shaft Diameter d: 35 mm

Outside Diameter D: 42 mm

Width B: 4 mm

Dimensions: 35x42x4 mm

Material: FPM / FKM

Material Type: Fluorocarbon elastomer

Primary Lip: Spring-loaded

Secondary Lip: Dust lip

Outside Surface: Elastomer covered

Typical Media: Oil / grease

Typical FKM Temperature Range: approx. -20°C to +200°C

Measurement System: Metric

35x42x4 AO FPM Designation Explained

35 mm - nominal shaft diameter

42 mm - nominal housing bore diameter

4 mm - seal width

AO - primary sealing lip with an additional auxiliary dust lip

FPM / FKM - fluorocarbon elastomer with high thermal and chemical resistance

The full designation is important when selecting a replacement because identical dimensions do not define the material or lip design.

FPM and FKM - Are They the Same?

Yes. FPM and FKM are different naming conventions used for the same fluorocarbon elastomer family.

FKM is commonly used in ASTM-based material classification, while FPM is widely encountered in European technical terminology.

In industrial sealing applications, the terms are often used interchangeably.

FKM and Viton

Viton is a trade name associated with fluorocarbon elastomers.

In the aftermarket, the word Viton is frequently used as a search term for FKM/FPM seals, although not every generic FKM compound is necessarily branded Viton.

For technical selection, the relevant material family is FKM/FPM.

FKM Compared with NBR

Compared with standard NBR, FKM typically provides:

• Higher temperature resistance
• Excellent resistance to many mineral oils
• Very good resistance to many fuels
• High resistance to hydrocarbons
• Excellent ozone resistance
• Strong resistance to ageing
• Reliable performance in demanding industrial environments

Material selection should always be based on the exact medium and operating temperature.

Function of the Dust Lip

The auxiliary lip in the AO design is located on the external side of the seal.

Its purpose is to help prevent contaminants from reaching the main sealing lip, including:

• Dust
• Fine particles
• Dirt
• Process contamination

This helps protect the primary sealing contact area and shaft surface.

Operational Advantages

• Compact dimensions of 35x42x4 mm.
• FPM/FKM material for demanding applications.
• Spring-loaded primary sealing lip.
• Additional dust protection lip.
• High resistance to many oils and greases.
• Higher temperature capability than standard NBR seals.

Replacement and Seal Selection

When replacing an FPM 35x42x4 AO seal, verify:

• Shaft diameter 35 mm
• Housing bore diameter 42 mm
• Width 4 mm
• AO double lip design
• FPM/FKM material
• Sealed medium
• Operating temperature
• Shaft speed
• Pressure conditions
• Shaft surface condition

An NBR seal with the same dimensions should not automatically be considered an equivalent replacement in high-temperature or chemically demanding applications.

AI OVERVIEW

The FPM 35x42x4 AO FKM Viton is a double lip rotary shaft seal with a 35 mm shaft diameter, 42 mm housing diameter and 4 mm width. Its AO design combines a spring-loaded primary sealing lip with an auxiliary dust lip, while the FKM material provides high resistance to heat, oils, greases, fuels and many hydrocarbons.

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FAQ

What are the dimensions of the FPM 35x42x4 AO seal?

The seal dimensions are 35x42x4 mm: 35 mm shaft diameter, 42 mm housing bore diameter and 4 mm width.

What does 35x42x4 mean?

35 mm is the shaft diameter, 42 mm is the housing bore diameter and 4 mm is the seal width.

What does AO mean?

AO identifies a design with a primary sealing lip and an additional auxiliary dust lip.

Is AO a double lip seal?

Yes. It has a main sealing lip and a secondary protective lip.

Does the main sealing lip have a spring?

Yes. The primary sealing lip is spring-loaded.

What is the purpose of the second lip?

The second lip helps protect the primary sealing area from dust and external contamination.

What does FPM mean?

FPM is a European designation for fluorocarbon elastomer.

What does FKM mean?

FKM is a standard material designation for fluorocarbon elastomer.

Are FPM and FKM the same material family?

Yes. They refer to the same general fluorocarbon elastomer family.

Is FKM the same as Viton?

Viton is a trade name used for fluorocarbon elastomers. FKM is the generic material designation.

What is the typical operating temperature of FKM?

For many standard FKM rotary shaft seals, the typical operating range is around -20°C to +200°C, depending on compound and operating conditions.

Is FKM resistant to oil?

Yes. FKM has very good resistance to many mineral oils and lubricants.

Can FKM be used with fuels?

FKM has very good resistance to many fuels and hydrocarbons, although compatibility should always be checked for the exact medium.

Is FKM better than NBR?

FKM generally offers higher temperature and chemical resistance, while NBR can be more suitable in other applications. The correct material depends on the operating conditions.

Can an NBR seal replace this FKM seal?

Not automatically. In high-temperature or chemically demanding applications, NBR may provide significantly shorter service life.

Is this seal suitable for a 35 mm shaft?

Yes. The nominal shaft diameter is 35 mm.

What housing bore is required?

The nominal housing bore diameter is 42 mm.

Does the 4 mm width matter?

Yes. The seal width must match the available installation space in the housing.

Where are FKM shaft seals used?

Typical applications include gearboxes, pumps, motors, industrial drives, production machinery and oil-lubricated rotating systems.

What is the parent product category?

The product belongs to FPM/FKM Rotary Shaft Seals.