Flare Tip - Softening of SS310

[SCinspector]

Recently removed a flare tip from service (refinery) after 8 years in operation. Flare tip body is constructed of SS310 and is severely distorted.
DPI shows scattered surface porosity and also some cracking (photos).
Hardness test reported 100-120HV, which seems alot softer than original mill cert - 220HV.
Wondering repair methodology for cracking - replacement, or grind out cracks and pad weld.
What does the softening mean? Carburisation? Service is mostly methane/ethane, sour.
Any input appreciated

 

[SCinspector]

Another photo - crack

 

[SCinspector]

Photos

 

[SJones]

Eight years is not bad going for a flare tip considering the abuse that they get. They are subject to a whole raft of degradation mechanisms, possibly including carburisation. However, this mechanism generally produces an increase in hardness. The specific grade and composition of 310 used, and the filler metal employed for the welds, may help in guiding you to a mechanism, or mechanisms, that could be confirmed through more formal analysis.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.