The ASME Standards have progressively been converted to metric. The millimetre is now the primary unit of measure. This process started in 2003 and applies to flanges, fittings, valves etc. For example an ASME B16.5, 4"NB 150LB flange had a metric outside diameter of 228.6mm (9in). In the latest standard the diameter is now 230mm. This is typical for all non-critical diameter and face to face dimensions. The flanges remain generally interchangeable with those manufactured to the earlier dimensions.
Inch dimensions (U.S. Customary units) are still included as an appendix to the standards; these too have changed and are no longer derivatives of the fractional inch format but decimal and generally to two decimal places.
Zeataline's electronic pipe specifications, component tables and parametric code reflect these changes and Pipedata-Pro is kept in line and up to date.