News

Ultrasonic testing (UT) of crane hooks is a key non-destructive testing technology for detecting internal defects (such as cracks, pores, inclusions), which can effectively prevent safety accidents caused by material fatigue or damage. The following is a detailed application guide for this technology:

1. Application scenarios of ultrasonic flaw detection

1. Regular testing

   • According to TSG Q7015-2016, hooks in high-risk environments (such as metallurgy and port cranes) must be tested by UT every 6 months.

2. Manufacturing and acceptance stage

   • New hooks must undergo 100% ultrasonic testing before leaving the factory, in compliance with GB/T 10051-2010 standards.

3. After an accident or overloading

   • The hook needs to be inspected immediately after experiencing collision, overload or abnormal vibration.

2. Key testing areas

3. Ultrasonic flaw detection technology solution

1. Equipment and parameter selection

• Probe Type :

  • Straight probe (longitudinal wave) : detect internal pores and interlayers (frequency 2.5MHz~5MHz).

  • Angle probe (shear wave) : detect surface cracks (commonly used 45° or 60° refraction angle).

• Couplant : Glycerin or special ultrasonic couplant to ensure effective transmission of sound waves.

• Calibration test block : Use CSK-IA or RB-2 test block to calibrate sensitivity and sound velocity.

2. Detection steps

1. Surface treatment :

   • Grind the inspection area to Ra≤6.3μm and remove paint and rust.

2. Probe Calibration :

   • Adjust the gain on the test block so that the reference reflected wave is as high as 80% of the screen height.

3. Scanning method :

   • Zigzag scanning : covers the entire inspection area (step ≤ 50% of the probe diameter).

   • Dynamic scanning : The probe moves at a constant speed (speed ≤ 150 mm/s).

4. Defect determination :

   • Crack : The waveform is a steep echo, and the peak changes rapidly when the probe is moved.

   • Air hole : isolated echo with low amplitude and no directionality.

3. Defect Recording and Evaluation

• Record contents : defect location, depth, length, amplitude (dB value).

• Acceptance criteria :

  • Crack defects : Any size will be considered as scrap (according to GB/T 10051).

  • Non-crack defects : single defect size ≤ 2mm, dense defect area ≤ 10mm².

4. Technical advantages and limitations

5. Comparison with other detection technologies

Recommendation : For key areas of the hook (such as the hook neck) , UT+MT can be combined to detect both internal and surface defects.

6. Operational safety precautions

1. Environmental requirements :

   • During inspection, the crane must be powered off and the hook must be unloaded and secured.

2. Personnel protection :

   • Avoid contact of coupling agent with skin and wear insulating gloves (if using a conductivity tester).

3. Data Archiving :

   • Save the test images and reports, and the archiving period shall be ≥5 years.

7. Case Application

• Analysis of a port gantry crane hook fracture accident :
  UT detection found an 8mm fatigue crack inside the hook neck. The cause of the accident was long-term overload that led to crack expansion.

• Preventive measures :
  Increase the frequency of UT inspections to once every three months and install a load monitoring system.

8. Future Technology Development

• Phased Array Ultrasonic Wave (PAUT) : Multi-angle scanning improves the efficiency of complex structure inspection.

• AI-assisted interpretation : Automatically identify defect waveforms and reduce human errors.

Conclusion
Ultrasonic flaw detection is the core means to ensure the safety of hooks. It must be operated strictly according to standard procedures and combined with other detection methods to form multiple protections. Regular training of detection personnel and updating of equipment technology can significantly reduce the risks of lifting operations.