API 510

5.6 INSPECTION OF PARTS

c. Examine the surfaces of all manways, nozzles, and other
openings for distortion, cracks, and other defects, paying particular
attention to the welding used to attach the parts and
their reinforcements. Normally, weep holes in reinforcing
plates should remain open to provide visual evidence of leakage
as well as to prevent pressure build-up in the cavity.
Examine accessible flange faces for distortion and determine
the condition of gasket-seating surfaces.

Some flange faces may be inaccessible due to blinding equipment meant to isolate the vessel.  All Accessible flange faces should be inspected as Ariel DC points out.