A silent threat in a pressurized recirculation line.
Inspection is not a snapshot.
Sometimes, you read the life story of a weld… and uncover a ticking time bomb.
This case involves a WB36 pipe (⌀ 298.6 × 23 mm), operating at 375 °C and 346 kgf/cm².
During a routine inspection, I detected a subtle MT indication in one of the welds.
Further investigation revealed:
A transgranular crack propagating from the inside, initiated at a notch in the root pass.
Causes & Findings
- Crack initiated at a sharp angle caused by excessive root penetration
- Partially filled with oxides, likely formed during or shortly after welding
- No anomalies in hardness or microstructure (200 HV10, compliant with WB36)
- Mechanism: Thermal stress, not pressure-induced
Lesson:
Even with properly stress-relieved weld metal, geometric stress concentrations combined with thermal cycling can initiate critical cracking.
Inspection means understanding.
It’s not just about what you see — but what it’s becoming.
🔎 Your Turn
In your experience, which geometries deserve special attention in weld design or inspection?
Copyright © Farid Farnia 2025
Alle rechten voorbehouden.
Delen van publicaties is toegestaan met bronvermelding.
Kopiëren of overnemen van inhoud is niet toegestaan zonder voorafgaande toestemming en duidelijke naamsvermelding.
