UT Inspection Acceptance Criteria for Tank Plates

Inspection Equipment and Personnel Requirements:
UT testing requires the use of 2-5MHz high-frequency probes, with instrument sound velocity error ≤ ±0.5%, and calibration must be performed quarterly. Operators must hold Level II or higher qualification certificates, with a misjudgment rate 40% lower than that of unqualified personnel. The surface roughness of the inspection area must be below Ra12.5μm to avoid interference from welding slag.

Defect Acceptance Criteria:
Cracks, lack of fusion, and defects with a reflected wave amplitude > DAC-4dB are prohibited in primary welds. Secondary welds are allowed to have single pores ≤ 2mm, with a dense area ratio ≤ 5%. Butt welds with a thickness ≥ 8mm must detect equivalent defects of Φ2mm flat-bottom holes.

Reporting and Re-inspection Specifications:
The report must include defect location data (lateral error ±5mm, longitudinal ±10mm). After repair, the re-inspection range needs to be expanded by 2 times the defect range, and cooled to below 150℃. A 98% detection rate verification is required for high-risk scenarios such as nuclear power.