Continuity (of qualification)
Evidence that a welder has used a process within the required interval, without which a qualification lapses even though its expiry date has not passed.
Under ASME IX a welder’s qualification for a process remains in effect if they have used it within the preceding six months. Under ISO 9606-1 the coordinator confirms continuity at six-month intervals, and prolongation at the end of validity depends on production evidence from the last months of the window.
Why it is missed
It is a signature and a record, not an event. Nothing fails, nobody is notified, and the discovery usually happens when a certificate is produced for an audit — long after the window closed.