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6.3 Detachable joints<br />
The individual components of a vacuum system, e.g. pumps, valves, measurement instruments,<br />
vacuum chambers, etc., are connected with one another either directly or by means<br />
of hoses or piping. The joints between these components must be vacuum-tight and<br />
detachable. In configuring a vacuum system, however, as few detachable joints as possible<br />
should be used, as they represent a significantly more frequent source of potential leakage<br />
than non-detachable joints.<br />
Piping and piping components made of aluminum, plain steel and stainless steel are used<br />
as connection elements. Metal hoses made of stainless steel are preferable to thick-walled<br />
rubber or thermoplastics for flexible joints, and they are a strict necessity from the lower<br />
medium vacuum range onward. To reduce the wide variety of existing dimensions and<br />
shapes, internationally valid series of nominal diameters have been specified. The series<br />
of nominal diameters that originated with the PNEUROP manufacturers’ association and<br />
which were later adopted by the ISO is:<br />
10 - 16 - 25 - 40 - 63 - 100 - 160 - 250 - 400 - 630 - 1000 and is supplemented by the<br />
auxiliary series 20 - 32 - 50 - 80 - 125 - 200 - 320 - 500 - 800<br />
Small flanges<br />
The small flange connection (ISO-KF in accordance with ISO 2861 / I / DIN 28403), consisting<br />
of two flat flanges having tapered rear sides, a centering ring, a sealing ring and a circlip<br />
(clamp), is available in nominal diameters of DN 10, 16, 25, 40 and 50 ISO-KF, whereby<br />
DN 50 ISO-KF comes from the auxiliary series and is being used more and more rarely today.<br />
An adaptation of components with one of the old nominal widths, 20 and 32, can be adapted<br />
by means of a reducing centering ring, or by means of an old DN 25 / 20 ISO-KF or<br />
DN 40 / 32 ISO-KF outside centering ring. Small flanges can also be held against flat<br />
surfaces by means of claws (Figure 6.5).<br />
1) Small flange with pipe stub<br />
2) Clamping ring<br />
3) Centering ring with o-ring<br />
4) Claw<br />
1<br />
2<br />
Figure 6.5: Small flange connection<br />
3<br />
7.5<br />
4<br />
3<br />
1<br />
Page 127<br />
<strong>Vacuum</strong><br />
<strong>Technology</strong>
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