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Pressure Sealing

  
   Technical Information
     O-Rings, Kits & Cord
     Static Applications
     Dynamic Applications
     Running Surface
     Installation Instructions
     Compound Hardness
     Pressure Sealing
     O-Ring Materials
     BS 0 Series Size Charts
     BS 1 Series Size Charts
     BS 2 Series Size Charts
     BS 3 Series Size Charts
     BS 4 Series Size Charts
High Pressure Applications
oring6-1
When pressures exceed 100 kg/cm2 it is advisable (with the exception of flange connections) to install backup rings that protect the O-Ring from being forced into the clearance. Backup rings are especially required when hard O-Rings cannot be used or when the tolerances are not close enough to prevent extrusion.

Backup Rings
oring6-2
The width of the backup ring is identical to the groove depth and the width of the groove should be increased once or twice the back up ring thickness depending on the quantity used in the application. In theory it is sufficient to install back up rings on the side where extrusion can occur, however it is usual to install the rings on both sides.

Vacuum Applications
oring6-3
When constructing O-Ring grooves for sealing a vacuum, it is important that the groove is filled by the O-Ring as much as possible, because when rubber is exposed to vacuum, it will shrink to a certain extent. O-Ring must be prevented from sliding or rolling. The surfaces to be sealed must be machined as smooth as possible.

Cross Section Groove Depth E Groove Width F
1.78 1.27-1.32 2.11-2.24
2.62 1.88-1.98 3.00-3.12
3.53 2.57-2.62 3.99-4.14
5.33 3.86-3.94 5.99-6.12
7.00 5.11-5.18 7.75-7.87

The figures in the table represent the cross section according to AS 568A for vacuum sealing. Dimensions are in millimetres.

In the case of high-vacuum sealing, gas permeability and degassing properties of the O-Rings play an important part. These properties vary widely among the various elastomers and are also highly dependent on temperature and medium handled. In the majority of cases butyl, and particularly VITON®, are the compounds to be preferred for sealing against vacuum. In the case of a vacuum and/or elevated temperatures, KALREZ® will give the best results.
 

Table of Groove Dimensions for Dynamic and Static Sealing
Cross Section Groove Dimensions Groove Radius
R
Dynamic Application Static Application
Depth
E
+0.00
-0.05		 Width Flange Seal Other Static Parts
Recipro-
cating
F
+0.10
-0.00		 Rotary
F
+0.10
-0.00		 Groove Depth
E
+0.00		 Groove Width
F
±0.10		 Groove Depth
E
+0.00		 Groove Width
F
±0.10
1.00 to 1.02
1.20
1.25 to 1.27
1.30
1.42
1.50 to 1.52		 0.81
1.00
1.04
1.10
1.16
1.24		 1.57
1.80
1.85
1.90
2.08
2.16		 1.20
1.40
1.45
1.50
1.60
1.70		 0.68
0.82
0.85
0.88
0.96
1.02		 1.57
1.80
1.85
1.90
2.08
2.16		 0.73
0.88
0.92
0.95
1.03
1.10		 11.30
1.60
1.70
1.80
2.00
2.20		 0.2
1.60 to 1.63
1.78
1.83
1.98 to 2.00
2.08
2.21
2.40
2.46
2.50
2.62
2.75
2.95 to 3.00
3.15		 1.30
1.45
1.50
1.60
1.70
1.80
2.10
2.15
2.20
2.30
2.45
2.65
2.85		 2.20
2.40
2.45
2.70
2.75
3.00
3.25
3.30
3.40
3.60
3.70
4.05
4.25		 2.10
2.30
2.35
2.50
2.50
2.55
2.70
2.75
2.80
2.90
3.10
3.35
3.50		 1.10
1.20
1.20
1.50
1.60
1.70
1.90
1.95
2.00
2.10
2.20
2.40
2.50		 2.20
2.40
2.45
2.70
2.75
3.00
3.25
3.30
3.40
3.60
3.70
4.05
4.25		 1.15
1.30
1.30
1.55
1.65
1.75
2.00
2.00
2.05
2.20
2.30
2.50
2.60		 2.20
2.30
2.40
2.40
2.50
2.70
2.90
3.00
3.10
3.20
3.40
3.70
3.90		 0.5
3.50 to 3.53
4.00
4.50
5.00
5.33
5.50
5.70
6.00
6.30 to 6.35		 3.10
3.55
4.00
4.40
4.80
4.95
5.15
5.40
5.55		 4.80
5.50
6.20
6.80
7.20
7.50
7.80
8.20
8.60		 3.90
4.35
4.90
5.50
5.80
6.30
6.35
6.70
7.00		 2.80
3.30
3.70
4.10
4.40
4.55
4.70
4.95
5.20		 4.80
5.50
6.20
6.80
7.20
7.50
7.80
8.20
8.60		 2.90
3.50
3.90
4.30
4.60
4.70
4.80
5.20
5.30		 4.30
4.60
5.20
5.70
6.10
6.30
6.50
6.90
7.10		 1.0
7.00
8.00
8.40
10.00
12.00		 6.10
7.20
7.55
9.00
10.40		 9.50
10.80
11.40
13.70
16.40		 7.80
8.90
9.40
11.20
13.40		 5.80
6.70
7.00
8.30
10.00		 9.50
10.80
11.40
13.70
16.40		 5.90
6.80
7.20
8.50
10.20		 8.00
9.30
9.60
11.40
13.70		 1.5

Sizes in accordance with AS 568A should be preferred.
N.B. When sealing against a vacuum or using PTFE O-Rings, groove dimensions are different.