This International Standard specifies size designations
for industrial fans and specifies dimensions for the circular
and rectangular flanges of general purpose industrial
fans as defined in 3.1 .I. It does not apply to
cross-flow fans, or fan appliances used for household
or similar applications.
For circular flanges, this International Standard provides
two different flange series, one for standard
casing thicknesses and a second for heavy duty fans
as used on board sea-going vessels or in heavy industry.
In order not to restrict fan designs unduly, only the
pitch diameter, hole numbers and hole diameters are
standardized. Flange thickness as well as internal and
external flange diameters can be chosen freely within
the limits of good engineering practice.