When the flanges are to be used on a piping system, then they must carry their own Canadian Registration Number (CRN). Even if they are built to a recognized standard such as ASME B16.5, they still need to be registered. One the other hand, if they are used on a pressure vessel, then they are covered by that vessel’s CRN.
Of course, if the piping system requires registration, then not only the flanges, but all the elbows, pressure gauges, pressure safety valves, bellows, weldolets, instruments, etc., need to carry their own CRN as well. Excluded from this is the pipe itself, that doesn’t need to be registered.