Backup Ring (JIS B 2401 P・G)

Specifications

How to choose Seals

Points to check when selecting, with the values for this product (Backup Ring (JIS B 2401 P・G)).

1. 1. Select the inner diameter to suit the mating part and groove

   An O-ring must be selected with an inner diameter matched to the shaft diameter and groove dimensions it fits. Selecting by a nominal size compliant with standards such as JIS B 2401 makes it easier to align with groove design. Listed products cover inner diameters from 15 to 1055 mm, and there are application-specific series such as those for vacuum flanges.

2. 2. Check cross-section diameter and squeeze

   The cross-section diameter (wire diameter) and groove depth determine whether an appropriate squeeze (compression amount) can be achieved. An incorrect fit causes leakage, extrusion or early deterioration. O-rings for vacuum flanges come in series such as 4 mm, 6 mm and 10 mm, so select by checking against the groove dimensions.

3. 3. Select a material suited to the fluid and environment

   Material is selected based on resistance to the sealed fluid. Rubber materials differ greatly in oil resistance, weather resistance and chemical resistance depending on type, while resins such as PTFE offer excellent chemical resistance and low friction. For vacuum applications, low outgassing should also be considered. Verify against a fluid-to-material compatibility chart.

4. 4. Confirm operation is within the service temperature range

   Seal materials harden and degrade at high temperatures and lose elasticity at low temperatures, reducing sealing performance. Confirm that the maximum and minimum operating temperatures fall within the service temperature range, and if the seal is continuously exposed to high temperatures, also check the continuous service temperature. Temperature ranges may differ by grade even within the same product.

5. 5. Allow margin below the maximum pressure

   If the operating pressure exceeds the maximum pressure, the seal may extrude into the gap and fail. Check that pressure, including surge pressure (momentary pressure rise), stays within the maximum pressure. Listed products include an example with a maximum pressure of 1000 bar; at high pressures, consider gap control in the groove and the use of backup rings.

6. 6. Judge sliding applications by the limit PV value

   For dynamic seals used in reciprocating or rotating motion, wear increases sharply when the PV value, the product of pressure and speed, exceeds the limit PV value. Listed products include examples with a limit PV value of 1.5 MPa·m/s and a maximum sliding speed of 0.5 m/s. Calculate from the operating pressure and speed, and confirm that both upper limits are met.

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

About Seals and all products

Description

Backup ring made of polytetrafluoroethylene resin used to prevent extrusion of O-rings. Nominal numbers range from P3 to P400 and G25 to G300, available in three shapes: spiral, bias-cut, and endless.

FAQ

Q. What applications are JIS B 2401 P・G backup rings used for?

A. They are used to prevent extrusion of O-rings and are also used for sealing hydraulic equipment.

Q. What are the material, shapes, and nominal number range of JIS B 2401 P・G backup rings?

A. The material is polytetrafluoroethylene resin. They are available in three shapes: spiral, bias-cut, and endless, with nominal numbers from P3 to P400 and G25 to G300.

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

Source documents

• Catalog オイルシール ＆ Oリング Open page 98
  Found on: https://koyo.jtekt.co.jp/support/catalog-download/