How to Choose O Ring Size and Types

Selecting the right O-ring size and type for industrial seals depends on the type of application and must be determined at the design stage. Choosing the right metric O-rings will ensure the installation of a fully functional seal suit to your application. This article outlines several easy steps to choosing O-rings and the types of materials that are best for particular applications.


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    Establish the type and nature of application. There is no universal type of seal that can be used for a variety of applications. Seals vary in the physical properties and their resistance to temperature, pressure, chemicals, environment, size O-ring, and other factors. Therefore, it is important to determine the type of application for which the seal is to be used. This will ensure that the right type of O-ring with properties to sustain temperature, pressure and the other factors described is installed in the application.
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    Select the O-ring material. O-rings are manufactured from a wide range of materials. This includes silicone, nitrile of BUNA-N, HBNR or hydrogenated nitrile, polyurethane, fluorosilicone, fluorocarbon, Teflon, and butyl, to name a few. Each compound has different physical properties and varying levels of resistance to pressure, chemicals, and temperature. Selecting the right material involves choosing a material based on various aspects of your application such as the material that needs to be sealed, variation in temperature levels, the pressure applied, and other related factors.
    • For example, polyurethane offers excellent abrasion and extrusion resistance, while AFLAS offers excellent temperature resistance in a range from -40° To 450°.
  3. Image titled Choose O Ring Size and Types Step 3
    Determine the needed O-ring size. O-ring size is an integral part of O-ring design. The dimensions of this type of seal are determined by its ID or inner diameter and CD or cross sectional diameter. Use an O-ring sizing chart that covers a range of sizes suitable for different sealing applications. There are several standard cross section diameters available in a metric O-ring chart. In dynamic, reciprocating applications the O-ring dimension chart, do not include standard O-ring sizes––this automatically narrows the choice. You will find charts with different standard and international metric O-rings online.
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    Check the O-ring seal stretch and squeeze ratio. The squeeze ratio reveals the tightness of the seal when force is applied against the hardware. It is easy to choose the right type of O-ring for your application based on the squeeze ratio. Generally, O-rings must not stretch more than 100 percent during installation. When fitted in the groove, it should not stretch beyond 5 percent to ensure there is no reduced cross section and deterioration. In most applications, an O-ring must be squeezed a minimum of 0.005 inch (0.0 cm) and a maximum of 30 percent of the cross section.
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    Consider physical factors such as temperature and pressure levels. To choose the most sustainable type of O-ring for a specific application, it is essential to consider the physical properties and resistance levels of each material to temperature and pressure. In addition to O-ring sizing chart metrics, make sure to check the material guide so that you choose O-rings that are durable and can work under the given conditions for a long period.


  • Make sure to check out the different size O-ring and uses prior to selecting any type of O-ring. Study each type with its features and recommended applications.
  • In addition to an O-ring sizing chart metric, most manufacturers provide a comprehensive list of materials suitable for different types of applications, along with their physical properties. This will reduce the risk of any leakages or damage to the hardware due to wear and tear of the O-ring.

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Categories: Jewelry and Watches