|
Return to
Failure Analysis Case Histories
|
Chloride Induced Stress Corrosion Cracking of Stainless Steel Water Still
|
|
ENVIRONMENT:
|
Humid Utility Room |
|
MATERIAL: |
Distilled Water Still -
Approximately 48" diameter |
|
SERVICE TIME:
|
10 years |
|
FAILURE:
|
Chloride induced Stress
Corrosion Cracking |
|
|
|
A water still failed
due to water leaks in the shell. These leaks were below the water line in an area
heated by an internal steam coil. A weld repair was attempted by the maintenance
personnel on site. After welding, several other cracks in the same general area
opened up.
|
|
The still was
disassembled and the outer insulation was stripped off for examination. Several
rust stains were observed on the inside of the shell below the tube sheet in the
area of the weld repair.
|
|
A dye penetrant test
performed on the outside revealed several other cracks. All of these cracks were
below the tube sheet. Some of these cracks penetrated through to the inside as
evidenced by red penetrant seeping through to the inside of the still. In no
instance was a crack found on the inside that was not a through wall
penetration. Several cracks were found on the outside with no indication of
through wall penetration (Figure 1). The cracks had initiated from the outside
to the inside.
|
