Pre-service Storage Tank Weld Inspection

Above ground storage tanks are manufactured with welded plates and radiography continues to be used for the inspection of the butt welded joints. Many issues exist with this approach. Technicians are exposed to high doses of radiation. The manufacturer needs to shut down certain operations and wait at least 12 hours to get inspection results. Today, API 650 Appendix U provides detailed rules of ultrasonic storage tank weld inspections in place of radiography eliminating those issues and safety concerns.

Inspection Challenges

For this type of inspection, it is critical that the full volume of the weld is inspected. The position of the probes on each side of the weld must be carefully calculated and monitored during the inspection. Should the scanner drift, the full volume of the weld is not inspected as requested by codes and there is a high probability that the operator isn’t aware of that issue.

Recommended Solution & Advantages:

An integrated TOFD and Phased Array system is the optimal solution for this type of application delivering significant advantages including:
Improved productivity

• • Faster than radiography (single face access with direct imaging capability)
  • No need to use external computers for setup and data transfer
  • Fast and automatic report generation
  • Cut weld re-scan costs
    – live video stream during acquisition allows operator to immediately correct scanner trajectory

– 16 bit digitation allowing offline gain adjustment without losing linearity

Better probability of detection

• Onboard calculator ensures the full volume of the weld is covered

Optimized analysis

• Real time corrected view
• Ability to merge groups

Complete traceability

• Files can be inspected without data converters
• Probe position is recorded at the same time as ultrasound data

Zetec Products:

TOPAZ32 Phased Array Ultrasonic Instrument
Integrated TOFD and Phased Array weld inspection solution

• Inspection preparation: Onboard calculator enables the operator to calculate the probe’s position ensuring optimal probability of detection
• Proposed set-up: Includes specific thickness/materials and diameters covering the majority of weld configurations in storage tanks
• Data acquisition: Create a C Scan related to a radiograph image. 2GB file size enables 100% vertical joint coverage with multiple groups in one scan
• Onboard analysis: Real time volume corrected views. Merge different groups for optimal analysis conditions
• Onboard reporting: Detailed report generation including weld sketches that automatically map the indications listed in the analysis table

Vision Kit
Prevents rescan by enabling the operator to verify probe positions around the weld

• Two micro cameras stream live view during scanning for immediate trajectory correction when drifting
• Streamed images from micro cameras recorded for post analysis and data validation
• Virtual laser overlay displays a software reticule on the image emulating a laser pointer

Weld Crawler Scanner
Robust design for quick and accurate probe positioning

• Dialog encoder – automatically recognizes when connected to a TOPAZ32; Setup is adapted to the scanner
• Two optional micro motors can automatically compensate for accidental misalignment from obstacles
• Adjust scanner direction directly from the TOPAZ32 touch screen