3.3.2.3 ISO-K/ISO-F flange

ISO-K clamping flange components and ISO-F fixed flange components are described in DIN 28404 and ISO 1609 in nominal diameters DN 10 to DN 630 for ISO-K flanges and to DN 1000 for ISO-F flanges.The connections are suitable for pressures up to 1 · 10^-8 hPa and can be used for overpressures up to 1,500 hPa. With metal seals, the pressure range can be extended to less than 1 · 10^-9 hPa. Metal seals require significantly higher contact forces. Screwed flange connections provide that. If clamp screws are used, their number must be increased if necessary.

An ISO-K and ISO-F compound consists of two symmetrical flanges and one O-ring seal, which is positioned and supported with an inner centering ring and also supported by an outer ring. The required contact pressure for sealing, is created with double claw clamps (Figure 3.9) or screws (Figure 3-13).

Figure 3.9: ISO-K connection with centering ring and double claw clamps

With ISO-K flanges, a circumferential outer ridge on the back of the flanges prevents slippage by the clamp screws. The flanges can be aligned around the main axis in any direction. Claw clamps are used for mounting an ISO K flange on a base plate. Depending on whether a centering ring is resting on the base plate (Figure 3.10) or an O-ring lies in base plate (Figure 3.11), claw clamps of different heights are used. Alternatively, the ISO-K flange can be screwed with a bolt ring onto the base plate (Figure 3.12).

Figure 3.10: ISO-K flange mounted on base plate with centering ring and claw clamps

Figure 3.11: ISO-K flange mounted on base plate with O-ring nut and claw clamps for base plate with sealing groove

Figure 3.12: ISO-K flange mounted on base plate with centering ring, bolt ring and screws

The ISO-F flange has a fixed bolt hole circle that is dependent on the nominal diameter. The flanges can be aligned with a hole spacing around the main hole axis. An ISO-F flange can be bolted onto a base plate. As a seal, a centering ring can be used or an O-ring with a sealing groove in the base plate.

Figure 3.13: ISO-F connection with centering ring and screws

Mounting an ISO-K flange on to an ISO-F flange can be done with a bolt ring (Figure 3.14). To install the bolt ring, it is slipped over the ISO-K flange and then a circlip is put into the outer circumferential groove of the ISO-K flange. The flanges can be aligned around the main axis in any direction.

Figure 3.14: ISO-K flange with bolt ring mounted on ISO-F flange with centering ring and screws