O-Rings and Backup Rings

Specifications

How to choose O-Rings

Points to check when selecting, with the values for this product (O-Rings and Backup Rings).

1. 1. Specify dimensions by standard and size number

   For series such as JIS B 2401 P and G, JASO F 404, and AS 568, the inner diameter, cross-section diameter, and recommended groove dimensions are defined for each size number. Confirm which standard series the equipment groove is designed to, and select a size number from the same series to avoid dimensional mismatch with the groove.

2. 2. Select an inner diameter that suits the groove and shaft diameter

   Select the inner diameter d1 to match the diameter of the shaft or groove bottom it fits onto. For applications sealing the outer periphery, the O-ring is generally installed with slight stretch over the shaft; for applications sealing the inner periphery, it is generally fitted along the bore side. Excessive stretch thins the cross-section and reduces squeeze.

3. 3. Check the cross-section diameter against groove depth

   The relationship between cross-section diameter d2 (wire diameter) and groove depth determines the squeeze. Even with the same inner diameter, some series have different cross-section diameters, so select a wire diameter that suits the groove depth and width. The cross-section diameters of the listed products range from 1.02 to 10 mm.

4. 4. Select a material suited to the fluid and temperature

   NBR is suitable for mineral-oil-based hydraulic fluids; FKM for heat and chemical resistance; and EPDM for water, steam, and brake fluid, but it is not suitable for mineral oils. VMQ (silicone) can be used from low to high temperatures, but its mechanical strength is lower. Confirm the fluid type and operating temperature range together.

5. 5. Select hardness according to pressure

   Hardness (Durometer A) is generally around 70 as standard; at higher pressures, selecting a harder material helps suppress extrusion into the gap. However, a harder material requires greater force to compress and slightly reduces sealing performance at low pressure.

6. 6. Use backup rings under high pressure

   In high-pressure or dynamic applications, the O-ring may extrude into the gap and be damaged. Prevent this by installing backup rings, such as those made of PTFE, on the side opposite the pressurized side. Use one for single-side pressure, or two when pressure acts from both sides, and widen the groove width to accommodate their thickness.

This guide was written by AI based on the listed products' documents and specification items.

About O-Rings and all products

Description

Presents the material types, physical properties, media compatibility, cross-section selection and gland design considerations for O-rings conforming to JIS, JASO, AS568, ISO and other standards. Backup rings are available in three types: spiral, bias-cut and endless.

FAQ

Q. What types of materials are available for O-rings and backup rings?

A. You can select from materials including NBR, FKM, EPDM and VMQ. Selection should consider oil resistance, heat resistance, chemical resistance and other requirements of the application.

Q. What is the operating temperature range and the typical squeeze rate for O-rings and backup rings?

A. The operating temperature range is -30 to 100 ℃. The squeeze rate is approximately 8 to 30 %.

Q. What applications can O-rings and backup rings be used for?

A. They can be used for sealing in hydraulic and pneumatic equipment, and for sealing in automobiles and aircraft.

Q. Which standards do O-rings and backup rings conform to?

A. The O-rings conform to JIS, JASO, AS568, ISO and other standards.

Q. What types of backup rings are available for O-rings and backup rings?

A. Backup rings are available in three types: spiral, bias-cut and endless. The material is PTFE.

Written by AI based on the content of the source documents.

Source documents

• Catalog オイルシール ＆ Oリング
  Found on: https://koyo.jtekt.co.jp/support/catalog-download/