corrosion test

[metboss]

Good day,

During the SSC test of L-80 13 Cr material, the specimen was broken after 50 hrs.
“Test conditions are as follow: test method - NACE TM0177 (Method A), test duration is 720 hours”.

Now, we have received root cause analysis report from manufacturer stating that: “Tension stress + torsion stress is the cause of the failure. This failure is attributed to proof ring tester due to which specimen undergone yielding resulted from combination of tensile stress and torsion stress during loading. Torsion stress should have been avoided during loading for proper test”.

For us it is not clear that what way, torsion stress cause failure of specimen?? Moreover, manufacturer is trying to prove that that SSC failure is not attributed to poor metallurgical or mechanical properties of material.

Please advise us on the root causes of above failure.

Regards

 

[EdStainless]

They run another test, this time making sure that they don't twist the sample when they load it.
Yes the extra stress can accelerate failure, or the material may just be too sensitive.

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Plymouth Tube

 

[metengr]

The presence of torsional stress invalidates the test. Re-run another sample for results.

 

[metboss]

thanks for your input. I will ask them to go for re-test. By the way, is there any limitation on torsional stress?