Tabla de medidas de juntas tóricas: estándares y aplicaciones

O-ring size chart: standards and applications

O -rings are circular rings made of flexible materials such as nitrile, Viton, or EPDM. Their main function is to act as sealing elements, preventing liquids or gases from leaking between mechanical components.

They are a key resource in different industries, as we will see later, due to their versatility, resistance and effectiveness, both in static (fixed) and dynamic (with movement) systems.

Thanks to their simple design and ability to withstand high pressures and temperatures, O-rings are used in industries such as automotive, hydraulics, the food industry, and more.

Having an O-ring size chart makes it easier to select them based on system needs, avoiding sealing problems.

Main advantages of O-rings

O-rings are a widely used resource due to their many advantages. Their low maintenance and effectiveness make them an indispensable solution in any industry.

  • Versatility : they adapt to any system, whether hydraulic, pneumatic or mechanical.
  • High resistance : they withstand extreme temperatures, chemicals and constant pressure without losing their properties.
  • Low cost : They are economical, easy to install and long-lasting if selected correctly.
  • Efficient sealing : they provide total tightness, preventing fluid or gas leaks.

How O-rings are measured

To ensure a proper seal, it's essential to know the exact O-ring measurements. These measurements are:

  • Inside diameter (d1) : measures the distance between the inner edges of the gasket.
  • Outer diameter (d2) : is the total distance between the external edges.
  • Cross section (C) : corresponds to the thickness of the ring.

Tools for measuring O-rings

  • Vernier caliper : ideal for precise measurements.
  • Measuring cones : allow identification of small joints.
  • Reference tables : simplify the selection of standard measurements without the need for tools.

International standards of measurement

O -rings follow international standards to ensure compatibility in different industries:

AS568 Regulation

It's the most widely used American standard and measures in inches. It's common in the automotive and heavy machinery industries.

ISO 3601 Standard

This international standard defines dimensions in millimeters and is the most widely used in Europe.

DIN 3771 standard

It is the German reference, very precise and with tight tolerances, ideal for demanding industrial applications.

The most common standard sizes of O-rings are as follows:

  • Inner diameter of 5 mm with a cross section of 1.5 mm, resulting in an outer diameter of 8 mm.
  • Inner diameter of 10 mm with a cross section of 2.0 mm, resulting in an outer diameter of 14 mm.
  • Inner diameter of 20 mm with a cross section of 2.5 mm, obtaining an outer diameter of 25 mm.
  • Inner diameter of 50 mm with a cross section of 3.0 mm, resulting in an outer diameter of 56 mm.

O-ring size chart

Since a picture is often worth a thousand words, we've prepared a table of O-ring sizes for European, English, and American sizes:



Inner Diameter (mm)

Cross Section (mm)

Outer Diameter (mm)

Inside Diameter (inches)

Cross Section (inches)

American Standard (AS568)

5

1.5

8

0.197

0.059

AS568-001

10

2.0

14

0.394

0.078

AS568-010

20

2.5

25

0.787

0.098

AS568-018

50

3.0

56

1.969

0.118

AS568-032

75

3.5

82

2.953

0.138

AS568-041

100

4.0

108

3.937

0.157

AS568-050


Types of materials used in O-rings

The O-ring material determines its strength and applications. The most common are:

Nitrile (NBR)

  • Use : ideal for oils and fuels.
  • Resistance : temperatures between -40 ºC and 120 ºC.

Viton (FKM)

  • Use : withstands aggressive chemicals and high temperatures.
  • Resistance : up to 200 ºC.

EPDM

  • Use : applications with water and steam.
  • Resistance : temperatures up to 150 ºC.

Silicone (VMQ)

  • Use : ideal for the food and pharmaceutical industries.
  • Resistance : -60 ºC to 230 ºC.

PTFE (Teflon)

  • Use : chemical and high-demand applications.
  • Resistance : up to 260 ºC.

Comparison of materials according to application

When choosing the right material, you need to consider:

  • Temperature : Viton and PTFE withstand extreme temperatures.
  • Chemical compatibility : PTFE is ideal for aggressive products.
  • Cost : Nitrile is the most economical and flexible option.

Main function of O-rings in industry

The main function of O-rings is to ensure a hermetic seal, preventing leaks of liquids or gases in mechanical systems.

  • Static sealing : used on fixed connections, such as pipes or flanges.
  • Dynamic sealing : applied in moving systems, such as pistons or rotating shafts.

Applications in the automotive industry

In the automotive sector, O-rings are essential:

  • Engine sealing : prevents leaks in combustion and cooling systems.
  • Fuel systems: maintain tightness in lines and pumps.
  • Refrigeration and air conditioning : ensure the correct operation of refrigeration circuits.

Use of O-rings in the hydraulic and pneumatic industry

O-rings are key in hydraulic and pneumatic systems due to their strength:

  • Hydraulic pumps and cylinders : withstand high pressures and prevent fluid loss.
  • Pneumatic systems : maintain air pressure in compressors and valves.

Applications in the food and pharmaceutical industries

In these sectors, O-rings must comply with health regulations:

  • Packaging machinery : ensures a secure seal on production equipment.
  • Fluid systems : Silicone or PTFE seals ensure compatibility with food and medical products.

Use of O-rings in industrial equipment

O-rings also play an important role in industrial machinery:

  • Air conditioning systems : prevent leaks in air ducts and refrigerant fluids.
  • Heavy machinery : guarantees effective sealing under high pressure and temperature conditions.
Back to blog