Chloride Cracking in 316L grade S/S

[honeywellinspector]

Does anyone have a suggestion for finding Chloride Stress Corrosion Cracking in 3/8" 316L grade S/S. Leaning towards ACFM or the ID/OD Creeping Wave method.
Background:
Presently have a 316L grade 3/8" thick pressure vessel that has shown SCC with leakage at a lifting lug. After removal of this section of column(4'in lenght x entire circumference)it was discovered that various areas showed cracking but only about .5mm in depth. These areas were discovered during the failure analysis. PT of the areas show inconclussive results.

Since these cracks are small and tight I am having difficulty finding a technique that would detect other areas on this column. Doeas anyone have any sugestions.

 

[unclesyd]

Well, here we go.
SCC at times is hard to detect and qualify as you describe to being small and tight. It has been my experience that most external SCC on SS equipment starts life as very small rusty pits with virtually no cracking. This makes any area of apparent rust and or pitting a suspect area.

This is going to upset a few people but here are several approaches to detecting hidden SCC.

If there is any indication that there has been a process leak or water under insulation and there is s suspect look area use a small side grinder and litely brush the area and immediately hit the worked area with a lite coat of Developer. This will let any material in the cracking act as the penetrant.

Take a small side grinder and very lightly go over a small area, 12"x12" and immediately flood the area with penetrant, wait a least 15 minutes and immediately clean the area and use the developer, light coat. immediately watch for any indication.

If the cracking is very tight all the indications you see see is a few dots in line.

In either of the above cases the application of a little heat to area will not hurt.

What I've had to do several times to convince people that there is SCC is do a Navy Welding Test if environmental conditions permit. This is welding a single SMAW bead in a 1" diameter circle and doing penetrant test as soon as the weld area is touchable.

 

[rustbuster]

You can try Phased Array UT or eddy current methods.