Vacuum flange
Vacuum flanges are used as a detachable connection between vacuum containers and components. Various, partially standardized flanges are available depending on the requirements with regard to tightness, bakability , stability, corrosion resistance and diameter .
Types of flanges
Small flanges
Small flange quick connections (ISO-KF or simply KF) are available in nominal sizes 10, 16, 20, 25, 32, 40 and 50 and are the most frequently used connections in the low and medium vacuum range. The nominal sizes 10, 16, 25 and 40 are the so-called preferred sizes according to the ISO recommendation. The dimensions are specified in DIN 28403 and ISO 2861. The two small flanges to be connected have flat sealing surfaces and conical flange flanks. An O-ring with a centering ring is placed between the sealing surfaces and the flanges are pressed together using a tension chain, tension ring or quick release ring. The sealing material used is usually an elastomer such as NBR ( Perbunan) , FKM ( Viton ) or FFKM (Kalrez), more rarely also neoprene , MVQ or EPDM. Edge seals made of PTFE or aluminum can also be used for special requirements. Small flange connections with elastomer seals can be used up to high vacuum, the usually specified leak rate is 1 · 10 −9 mbar · l / s. The operating pressure range is limited by the relatively high gas permeation through the elastomer materials.
A selection of common KF flange sizes (all dimensions in mm):
| Nominal size | DN10 | DN16 | DN20 | DN25 | DN32 | DN40 | DN50 |
|---|---|---|---|---|---|---|---|
| outer diameter | 30.0 | 30.0 | 40.0 | 40.0 | 55.0 | 55.0 | 75.0 |
ISO clamp flanges and ISO fixed flanges
Clamp flange connections (ISO-K) are used in a similar way to KF connections, but here the frictional connection between the flanges and the compression of the elastomer O-ring seal is achieved using clamp screws. They are used for larger nominal widths than KF and are compatible with the ISO fixed flanges (ISO-F) if the appropriate coupling flanges are used. The ISO fixed flanges are installed using screws and nuts. The dimensions of the ISO flanges are specified in DIN 28404 and ISO 1609, flange sizes from DN63 to DN1000 are standardized.
A selection of common ISO-K flange sizes (all dimensions in mm):
| Nominal size | DN63 | DN80 | DN100 | DN160 | DN200 | DN250 |
|---|---|---|---|---|---|---|
| outer diameter | 95.0 | 110.0 | 130.0 | 180.0 | 240.0 | 290.0 |
CF flanges
CF flanges are standardized according to ISO 3669: 2017. The name originates from the registered trademark “ConFlat” of the company Varian, Inc. The flange type is meanwhile sold under the name “CF” by almost all manufacturers worldwide. They are used to connect ultra-high vacuum (UHV) components. The flanges are made of stainless steel or aluminum, the sealing material is mostly oxygen-free, high-purity copper . The flanges are provided with cutting edges which, when the connection is tightened, are pressed a little into the sealing material and thereby seal. Metallic sealing rings can only be used once due to the permanent deformation. However, elastomer seals can also be used for temporary abutments. The advantage of CF connections is that they can be heated up to 450 ° C and the extremely low leak rate of 1 · 10 −11 mbar · l / s.
A selection of common CF flange sizes (all dimensions in mm):
| Nominal size | DN10 | DN16 | DN25 | DN40 | DN50 | DN63 | DN75 | DN100 | DN125 | DN160 | DN200 | DN250 | DN275 | DN300 | DN350 | DN400 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| outer diameter | 25.0 | 33.8 | 54.0 | 69.9 | 85.7 | 114.3 | 117.4 | 152.4 | 171.5 | 203.2 | 254.0 | 304.8 | 336.6 | 368.3 | 419.1 | 469.9 |
| Typical pipe size | 12x1 | 19x1.5 | unusual | 41x1.5 | unusual | 70x2 | unusual | 104x2 | unusual | 154x2 | 204x2 | 254x2 | unusual | 306x3 | 350x3 | 400x3 |
| Flange thickness | 6.0 | 7.0 | 11.5 | 12.5 | 16.0 | 17.0 | 17.5 | 19.5 | 21.0 | 21.0 | 24.0 | 24.0 | 28.0 | 28.0 | 28.0 | 28.0 |
| Screws | 6xM3 | 6xM4 | 4xM6 | 6xM6 | 8xM8 | 8xM8 | 10xM8 | 16xM8 | 18xM8 | 20xM8 | 24xM8 | 32xM8 | 30xM8 | 32xM10 | 36xM10 | 40xM10 |
| Bolt circle | 17.5 | 27.0 | 41.3 | 58.7 | 72.4 | 92.2 | 102.3 | 130.3 | 151.6 | 181.0 | 231.8 | 284.0 | 306.3 | 338.1 | 388.9 | 437.9 |
| corresponds to an inch size
according to ASTM E2734 |
1 "OD | 1.33 "OD | 2.125 "OD | 2.75 "OD | 3,375 "OD | 4.5 "OD | 4,625 "OD | 6 "OD | 6.75 "OD | 8 "OD | 10 "OD | 12 "OD | 13.25 "OD | 14.5 "OD
(305CF) |
16.5 "OD
(not compatible) |
18.5 "OD
(405CF) |
Quick CF flanges
Quickly mountable QCF flanges combine the assembly principle of the conical KF flanges with the sealing principle of the CF flanges. You use the standardized copper flat gaskets of the CF flange system, the sealing surfaces of the flanges are also provided with cutting edges, as described in ISO 3669: 2017. The frictional connection for mounting the flanges is not created by screws, as is the case with CF flanges, but by an associated tension chain.
Bushings
A frequently used type of (blind) flange is the implementation. This is used to set up various connections required for the process or experiment, such as voltage supply, supply with gases, cooling liquids, the implementation of measurement signals from the vacuum vessel or the mechanical manipulation of structures in a vacuum.
Individual evidence
- ↑ Jobst H. Kerspe and 7 co-authors: Vacuum technology in industrial practice (= contact & studies. Vol. 204). 3rd, completely revised and expanded edition. expert verlag, Renningen 2003, ISBN 3-8169-2196-5 , p. 297.
- ↑ Jobst H. Kerspe and 7 co-authors: Vacuum technology in industrial practice (= contact & studies. Vol. 204). 3rd, completely revised and expanded edition. expert verlag, Renningen 2003, ISBN 3-8169-2196-5 , p. 299.
- ↑ International Organization for Standardization (Ed.): ISO 3669: 2017 - Vacuum technology - Bakeable flanges - Dimensions of knife-edge flanges . August 2017.