1. Full Plate Ultrasonic Testing (UT) for Thickness ≥ 15mm
ABS Requirement:
100% automated UT scanning is mandatory for steel plates ≥15mm thick used in hull structures, decks, and high-stress zones.
Key Specifications:
Scanning method: Shear-wave UT (45°-70° probe angles) for subsurface flaw detection.
Calibration standards: Use IIW or DSC blocks with side-drilled holes (SDH) for sensitivity adjustment.
Defect acceptance criteria:
No linear indications >50mm in length.
No cluster defects (>3 indications within 100mm²).
Reporting: UT records must include scan maps, defect logs, and operator certifications.
Why Critical?
Prevents lamination defects that could lead to catastrophic failure in heavy plates.
2. Weld Inspection: UT + RT for Full Penetration Joints
ABS Requirement:
Butt welds in primary structures (e.g., hull seams, bulkheads) require:
100% UT for thickness ≥10mm.
10% random RT (radiographic testing) as a cross-verification.
Acceptance Standards:
UT defects rejected if:
Cracks or lack of fusion >6mm in length.
Porosity clusters >4mm in diameter.
RT defects rejected if:
Slag inclusions >4% of weld thickness.
Internal cracks of any size.
Technique Requirements:
Phased-array UT (PAUT) preferred for complex geometries.
Film or digital radiography (DR) allowed for RT.
3. Post-Weld Heat Treatment (PWHT) Verification via Hardness Testing
ABS Requirement:
Hardness testing (HV10) is mandatory after PWHT for thickness >50mm to prevent hydrogen cracking.
Testing Protocol:
Vickers hardness limits:
≤350 HV10 for carbon-manganese steels.
≤380 HV10 for high-strength low-alloy (HSLA) steels.
Sampling frequency: 1 test per 10m of weld length.
Associated NDT:
Dye penetrant testing (PT) if hardness exceeds limits.
Why Critical?
Ensures weld HAZ toughness and prevents stress corrosion cracking (SCC).
4. Thickness Measurement & Corrosion Mapping for In-Service Ships
ABS Requirement:
Ultrasonic thickness gauging (UTG) is required during special periodic surveys (5-year renewal).
Inspection Zones:
Ballast tanks, cargo holds, and seawater pipelines.
Critical structural members (e.g., web frames, longitudinal girders).
Acceptance Criteria:
Minimum remaining thickness = 75% of original (or as per ABS SafeHull limits).
Corrosion rate >0.3mm/year triggers enhanced monitoring.
Reporting:
Digital thickness mapping must be submitted to ABS for review.
5. Additional NDT for Special Applications (Ice-Class, LNG Carriers)
ABS Requirement:
Magnetic particle testing (MT) for ice-class vessels (e.g., ABS A5, PC3).
Liquid penetrant testing (PT) for stainless steel LNG containment systems.
Special Cases:
100% MT for fillet welds in ice belt zones.
Cryogenic impact testing for LNG tank materials.
