Layer 1: Raw Material Inspection
Every batch of steel plate received from mills undergoes:
Chemical composition verification via spectrometer analysis
Mechanical property testing (tensile strength, yield strength, elongation)
Ultrasonic thickness measurement
Surface defect visual inspection
Only materials meeting relevant Chinese GB/T or ASTM standards proceed to production. Non-conforming materials are quarantined and returned.
Layer 2: In-Process Quality Checks
During fabrication, QC inspectors monitor:
Plate cutting accuracy (CNC program verification)
Rolling curvature conformity (template gauges)
Weld joint preparation (bevel angle, root face dimension)
Welding parameters (current, voltage, travel speed, interpass temperature)
Welder qualification (each welder holds valid certification for the specific process and position)
Layer 3: Non-Destructive Testing (NDT)
All pressure-retaining welds undergo 100% NDT using a combination of:
Radiographic testing (RT) for internal volumetric defects
Ultrasonic testing (UT) for thickness and lamination checks
Magnetic particle testing (MT) for surface cracks in ferritic steel
Dye penetrant testing (PT) for surface flaws in non-ferrous materials
Layer 4: Final Hydrostatic and Pneumatic Testing
Each completed tank is subjected to:
Hydrostatic test at 1.3–1.5 times design pressure
Air tightness test using soap bubble method or helium leak detection
Vacuum test (for double-wall tanks) to verify interstitial space integrity
Layer 5: Documentation and Traceability
A complete quality dossier accompanies every tank, including:
Material mill certificates
Welding procedure specification (WPS) and procedure qualification records (PQR)
NDT reports and radiograph films
Hydrostatic test certificate
Dimensional inspection report
Coating inspection report
This rigorous quality system, certified to ISO 9001:2015, gives Zhongneng Huajian's customers full confidence in the reliability and compliance of every storage tank they purchase.
