EN
Weld Integrity and Non-Destructive Testing Methods
The weld is the most critical joint of pressure vessels and load-bearing structures. This guide covers welding defects, the non-destructive testing methods and the machine-inspection relation through pressure vessel and crane seams.
Weld integrity is the defining factor of pressure vessels, load-bearing steel, crane bridges and machine chassis. A seam laid with correct parameters is as strong as the base metal; porosity, crack, lack of penetration or slag inclusion silently lowers the capacity. These defects may not be visible from outside — which makes non-destructive testing (NDT) essential. On the machine side the welding machine periodic control keeps the safety line with current-earth clamp integrity. In audits the welding procedure (WPS) and welder qualification records are asked together; defect classification follows the EN ISO 5817 acceptance levels.
Common Defects
| Defect | Origin | Risk |
|---|---|---|
| Porosity | Weak gas shield-moisture | Sealing loss |
| Lack of penetration | Low current-prep | Static strength drop |
| Crater crack | Rapid cooling-hydrogen | Brittle fracture |
| Slag inclusion | Missing interpass cleaning | Fatigue crack start |
Non-Destructive Methods
- VT (visual): first step of every examination; profile, porosity, crack, dimensional fit. Cheapest, fastest.
- PT (penetrant): surface-open crack-porosity; common on vessel seams, surface cleaning is critical.
- MT (magnetic particle): ferromagnetic surface and near-surface crack; preferred for crane-girder seams.
- UT (ultrasonic): internal defect-thickness in thick section; boiler-column weld-neck scan.
- RT (radiography): volumetric defect record (film); acceptance standard for pipe-boiler seams. Safe-area plan mandatory.
Joining Control and Examination
In structural and pressure equipment the periodic inspection flags the points needing examination: wall loss, opening groove, fatigue trace. For instance a vessel after the hydrostatic proof may ask UT/MT at a suspect; a crane during lifting machine inspection may ask MT. Caught early, the repair is planned-economic-safe; caught late, the failure-accident-loss trio arrives.
Author: KYF Test Engineering Team • Last updated: September 2026