Indication — Definition & NDT Use
A signal or response detected by NDT equipment that may or may not represent an actual defect. Not all indications are defects; some are from surface conditions, geometry, or material property variations. Indications must be evaluated to determine if they meet acceptance criteria and constitute rejectable flaws. Proper characterization distinguishes between relevant indications (actual defects) and irrelevant indications (false signals or acceptable conditions).
From the inspector's bench, Indication is run as a defined sequence: equipment verification on a known reference, scan setup against the procedure, scanning the part, and writing the indications into the report. Procedure writing, inspector qualification, and the reference block establish the chain that lets a remote engineer trust an indication called a kilometre away from the office.
Indication is selected when the failure mode the engineer cares about — surface crack, internal void, wall loss, lack of fusion — lines up with what the technique is physically capable of detecting.
The most expensive mistake with Indication is treating it as a yes/no test rather than a characterisation — an indication called without a sizing strategy forces a repair where a fitness-for-service review might have left the part in service.
What does "Indication" mean in NDT?
A signal or response detected by NDT equipment that may or may not represent an actual defect. Not all indications are defects; some are from surface conditions, geometry, or material property variations
Which standards govern the use of Indication?
Indication is most often referenced under ASME Section V together with the relevant ASTM practice or the matching ISO standard for the method; the contract or purchase order will name the controlling document and edition for any specific job.
What other NDT concepts should I read alongside Indication?
The most directly related entries in this glossary are "defect", "flaw", "relevant indication"; reading those together gives you the surrounding vocabulary used in inspection reports and procedures.