TOLERANCES

The actual as produced seal diameter shall be as close as possible to the groove diameter.

By compressing the seal in the groove, the seal outside diameter for internal pressure seals will try to grow and the seal inside diameter for external pressure will try to shrink.

This phenomena is covered by the DC or diametrical clearance. The DC will give allowance for this increase or decrease of the seal diameter.

The seal tolerance and also groove tolerance shall be kept as small as possible. It is better for the seal performance to keep the DC in compressed condition as small as possible.

Ideally, once compressed the seal outer diameter should slightly touch the groove outer diameter or for an external pressure seal the inner seal diameter should slightly touch the groove ID.

Internal Pressure Groove OD Tolerance
Type
-----
Cross section

O Ring

C Ring
&
Oysterseal
CS Ring
0.79 + 0.05 + 0.05 ---
0.89 + 0.10 + 0.05 ---
1.19 + 0.10 + 0.08 ---
1.57 + 0.10 + 0.08 + 0.10
2.39 + 0.15 + 0.10 + 0.10
3.18 + 0.15 + 0.10 + 0.13
3.96 + 0.15 + 0.13 + 0.15
4.78 + 0.20 + 0.15 + 0.15
6.35 + 0.20 + 0.20 + 0.20
7.9 + 0.20 + 0.20 + 0.20
9.53 + 0.25 + 0.25 + 0.25
12.7 + 0.25 + 0.25 + 0.25

Groove tolerances for face type seals

External Pressure Groove OD Tolerance
Type
-----
Cross section

O Ring

C Ring
&
Oysterseal
CS Ring
0.79 - 0.05 - 0.05 ---
0.89 - 0.10 - 0.05 ---
1.19 - 0.10 - 0.08 ---
1.57 - 0.10 - 0.08 - 0.10
2.39 - 0.15 - 0.10 - 0.10
3.18 - 0.15 - 0.10 - 0.13
3.96 - 0.15 - 0.13 - 0.15
4.78 - 0.20 - 0.15 - 0.15
6.35 - 0.20 - 0.20 - 0.20
7.9 - 0.20 - 0.20 - 0.20
9.53 - 0.25 -0.25 - 0.25
12.7 - 0.25 -0.25 - 0.25

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