| Industry: |
Chemical |
| Specimen Description: |
Failed Scaffold Clip |
| Material: |
Carbon Steel |
| Environment: |
Atmosphere |
| Background: |
Welds attaching a scaffold clip to a scaffold failed causing the scaffold
boards to fall to the bottom of a API 650 tank. |
| Time in Service: |
~ Less than a week. |
| Findings: |
The as-received scaffold clips were
made by fillet welding one side of
a bent bar onto the I.D. of the tank wall with approximately one-inch of
weld. On one sample, the clip still remained. On the other sample both
welds attaching the bar to the tank wall had failed. Visual observation
of the fillet welds showed that they had been made with the SMAW process
and apparently without removing rust, etc. from the tank wall or the bar.
The weld fracture appeared dendritic and contained significant voids. SEM
examination of a fractured weld revealed significant unfused areas amongst
areas of ductile overload. A polished and etched profile of the unfailed
clip showed that the weld contained large interdendritic cracks and a large
untempered weld heat-affected zone. The weld microstructure contained many
interdentric cracks suggestive of hot tear cracks. |
