The flange connection is a friction-locked, separable pipe connection comprising two flange halves and a seal. The tightening torque of the fastening screws generates the necessary sealing force. Flange connections are used preferably for pipe diameters >38 mm or in connections subject to high loads instead of pipe fittings. The most important shapes for hydraulics are shown in (Figure F 20):
- Split flange with four fastening screws and O-ring seal according to ISO 6162. The two arc-shaped half flanges are placed around the collar (mostly welded on pipes, crimped on hoses) on the end of the line during mounting and bolted in place. Two series are standardised: Nominal diameters DN 13 to 127 for operating pressures from 25 to 350 bar and nominal diameters DN 13 to 51 for 400 bar operating pressure.
The port dimensions correspond to the SAE flange according to SAEj 518, however for new designs metric screws are to be used. Flanges with this layout are very common in hydraulics and are used in suction and pressure lines. They are very space-saving to install.
- Square flange with four fastening screws with metric thread and O-ring seal according to ISO 6184. Two series are standardised: Nominal diameters DN 10 to 63 for 250 bar operating pressure and nominal diameters DN 10 to 80 for 400 bar operating pressure. This flange shape comes from heavy machinery manufacture and is particularly suitable for systems subjected to high loads.
- DIN flanges (welding neck flanges) according to DIN 2632 (nominal pressure PN 10) and DIN 2633 (nominal pressure PN 16) with O-ring seal are used in particular for low pressure lines (suction lines, return filters).