ISO 3669:2020 pdf download

ISO 3669:2020 pdf download.Vacuum technology – Dimensions of knife-edge flanges.
ISO 3669 is a minor revision of the second edition (ISO 3669:2017) and contains significant technical changes from the first edition (ISO 3669:1986), which defined two series of “bakeable” flanges:
— as a preferred series, the main dimensions of which ensure compatibility with already standardized non-bakeable flanges (see ISO 1609);
— a secondary series corresponding to flanges in common use.
ISO 3669 specifies only one series and is no longer dependent on the preferred number. Effectively, the preferred series has been made obsolete, thereby promoting the secondary series to be the one and only set of specified dimensions. Furthermore, several dimensions in what was formerly the secondary series, have been modified to correspond to flanges in common use. Finally, detailed dimensions for the knife-edge sealing profile have been incorporated.
It is noted, however, that the original ConFlat®1) flange dimensions and tolerances, as developed by Varian, were not available during the development stage of this specification. The intent of this document is to ensure interchangeability of flanges. It is reasonable to accept that flanges manufactured to the original Varian specifications are compatible with flanges manufactured according to this document, even though they might not fall within all tolerances.
1 Scope
ISO 3669 specifies the dimensions of fixed or rotatable bolted knife-edge flanges used in vacuum systems for pressures ranging from atmospheric to as low as 10-11 Pa.
5 Requirements
5.1 Materials
5.1.1 Flange
The selection of the material shall be compatible with the requirements for the flanges. Considerations may include service temperature, sealing capacity, corrosion resistance, magnetic permeability, type of seal gasket used and dimensions.
NOTE Austenitic stainless steel is commonly used, but it is not the intent of this document to specify or limit the choice of flange material to austenitic stainless steel.
5.1.2 Bolt holes
The flange may have either clearance or tapped bolt holes.
NOTE As a number of flanges in use currently originated in the United States, the tapped flanges often have
English tapped holes. Of increasing use are flanges with metric threads. Both are presented in this document (see
Table 1).
5.1.3 Grooves
Leak check grooves should be used. The grooves shall be arranged equidistantly between the bolt holes
5.1.4 Gasket
In general, the gasket should be softer than the flange to avoid dulling of flange knife-edge
NOTE Oxygen-free high conductivity (OFHC) copper is commonly used, but it is not the intent of this
document to specify or limit the choice of gasket material to OFHC copper.
5.2 Dimensions
Flange dimensions are shown and specified in Figures 1 to 3 and in Table 1 and Table 2. See Figure 4 for
the recommended dimensions of leak check grooves.ISO-3669-2020

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