O-ring seals - in perfect shape, part 2

Planning and designing

In the second part of our series ‘O-ring seals – in perfect shape’ we show you what to consider when planning and designing the O-ring seal groove.

Axial installation - circular pocket or ring groove?

The circular pocket offers the easiest and most space-efficient way to introduce an O-ring seal. However, the disadvantage is that the O-ring seal is always in direct contact with the medium (e.g. water or oil). This reduces the service life and shortens the maintenance cycles.

O-ring seal in a circular pocket: space-saving

O-ring seal in a circular pocket: more security

Advantage:

• Space-saving
  

Disadvantages:

• Contact with medium
• Abrasion
• Dirt build-up

The ring groove, on the other hand, completely separates the O-ring seal from the medium and thus offers maximum service life and long maintenance cycles. For optimal introduction, we recommend using an O-ring countersink, but it may also be carried out using a milling cutter.

O-ring seal in ring groove

Advantages:

• O-ring seal protected
• Long service life
• Concentric grooves when using countersink for O-ring

Disadvantage:

• Requires more installation
  

WZB 12112 WZB 32112

Specifications for the groove dimensions

The groove depth T1 is designed so that the cord size of the O-ring is pretensioned by 15-30%. The groove width B must guarantee that the cross section of the O-ring fills the groove to a maximum of 85% in order to provide reserves for swelling or thermal expansion. When pressure is applied from the inside, the O-ring seal should be in contact with the outside diameter, whereas when vacuum or pressure is applied from the outside, it should be in contact with the inner diameter.

Groove dimension for circular pocket

Groove dimension for ring groove

Tip: The outside diameter D2 can be 1% to 3% smaller than the outside diameter d2 of the O-ring seal, so that the seal is tightly fitted and will not fall out.

In our groove recommendations, you will find the finished groove dimensions and the matching O-ring seals coordinated to the O-ring countersinks clearly displayed. This covers ≈ 90% of cases, saves time when searching and provides safety during use.
For your own groove design, you will find the recommended dimensions t1 and b on the respective O-ring seal catalogue pages E 2130 or E 21311.

E 2130 E 21311 O-Ring seal groove recommendations

Radial installation

For radial installation, we recommend a lead-in chamfer with 20°. You will find the appropriate dimensions B and T2 on the O-ring seal catalogue page. When drilling crosswise to the installation hole, the edges must be rounded. The O-ring seal may be stretched up to 6% when installed. For installation, the O-ring seal can be stretched up to 20% for a short time.

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