Visual Inspection (VT)

Visual inspection (VT) is the first and most-used NDT method: a trained inspector examines a weld and its surroundings with the eye, aided by gauges, a mirror, and adequate light, to find surface cracks, undercut, overlap, porosity, profile errors, and arc strikes before any volumetric test. ISO 17637 sets the conditions, illumination at least 350 lux, viewing within 600 mm and at no less than 30 degrees, and weld gauges measure throat, leg, and reinforcement against the acceptance limits. VT is performed before, during, and after welding, and a weld that fails VT is rejected without further testing. It is mandatory on 100 percent of structural welds and screens which joints get UT or RT.