T23 Boiler Tube - Curious Fracture 7

[Guest102023]

T23 Reheater Tube Fracture in Weld -- Anyone seen this fracture morphology before?


Several T23 reheater tubes failed in a similar manner after less than 6 months and ~250 cycles from commissioning of the HRSG. The circ. fracture originates in the weld, at the front (where you would expect bending force to be greater) then moves into the base metal as it propagates around to the back side. Meanwhile, a ~4" long tear happened on the front side. It seems like there is more than one thing wrong here.

Unfortunately I did not see the header side of the story (another case of repair first, ask questions later), so it is hard to confirm the lack of penetration that me and the repair contractor suspected.

Particulars: 2" T23, welded to P22 header with manual TIG, ER9018-B3, PWHT. Unknown tube origin, but they are significantly older than the plant. All zones appear to have normal microstructure (no ferrite at least). The correct filler was used. Weld hardness is 285HV1, HAZ up to 335HV1, base ~192HV1. I have found both tube surfaces decarburized. Scattered corrosion pits up to 3 mils deep on outer surface. A few very short secondary cracks and sometimes oxide along prior austenite GBs.

Any thoughts or suggestions? The hardness seems on the high side for a PWHT joint. I thought about reheat cracking, but did not think that can affect the weld also(?)

I am a newbie here so I hope this gets posted correctly ...

 

[unclesyd]

As I don't have your layout suggesting any different approach like Infrared thermography or Optical Pyrometry to help locate your thermocouples is iffy.

You might want to give these people a call about their
Acoustical Pyrometry

http://www.enertechnix.com/

 

[Guest102023]

I found a long article by Anderson & Dooley looking at 11 power plants - it was invaluable; I am locating as many of their references as possible.

 

[davefitz]

I think they are both scheduled to be at the 19-21 EPRI HRSG tube failure conference in Baltimore, maryland, USA- more info can be otained at that venue.

 

[davefitz]

the date I omitted is 19-21 April 2010 at Baltimore

 

[Guest102023]

I would LOVE to attend but unfortunately it is beyond my means at the moment. Hopefully EPRI will publish proceedings, but there's no substitute for meeting top experts in person.


[This is the kind of professional development my previous employer should have paid for, but the manager spent the money on new office furniture instead ]

 

[unclesyd]

Been there and done that, only mine was for a $1.500,000 spiral staircase.

 

[Guest102023]

I am typing this at a $50 particle board + plastic veneer desk, but - I am manager-free