NDE method 2

[Corgas]

Result from a failure analysis on water tube (floor) from a packaged type boiler (type D) indicates cracking occur due to thermal fatigue.

What NDE method will be best to confirm or ruled out thermal fatigue damage in rest of tubes?

Thanks,

Corgas

 

[rustbuster]

MPI and or Eddy Current surface scan would find OD cracking. If you suspect ID craking, shear wave UT would be my choices.

I would have the failure and material analysed by a metallurist, you may be at or near end of life.

Good Luck

 

[metengr]

Well.. my first question back without shooting from the hip is does this package boiler have a refractory floor? If this boiler floor covered with refractory, I would recommend remote field eddy current testing if you can access the tube ID surface. A company called Tes Tex outside of Pittsburg, PA does a decent job.

Is the thermal fatigue OD initiated damage?

 

[Corgas]

rustbuster :

Brand new boiler, only three years old. Failure analysis was done by qualified lab.

What's MPI?

If tubes are connected by "welded web" (membrane type), can we still apply shear wave UT?

Thanks,
Corgas

 

[metengr]

MPI - magnetic particle inspection. The only problem with the above two mentioned NDE methods is that you need to get your hands on the OD surface of the floor tubes - gas side surfaces.

 

[Corgas]

metengr :

Cracking comes from ID and it is transgranular. Tubes are not covered by refractory but, section that failed (close to mud drum) it is supposed to be covered by refractory.

thanks,

corgas

 

[metengr]

Corgas;
What about a borescope? If you can access from the lower supply drum you can visually check for cracks on the ID surface. The remote field ECT will also provide the same results.

 

[Corgas]

metengr :

Some of them were checked by boroscope but not all. This mud drum is pretty small and narrow.

ECT means eddy current testing??

Thanks,

Corgas

 

[metengr]

Yes. For visual inspections of waterwall and riser tubing we have used a company called VIT. I believe they are now owned by GE. They have a wide range of articulating probes for borescopes and small cameras (with crawlers) that can access tight spots for detailed visual inspection.

Is the thermal fatigue damage circumferential or axial in the floor tubes?

 

[Corgas]

metengr:

Circumferential!!! You'd expect cracking around 6 o clock position but it actually showed at 12 o clock position.

Corgas,

 

[eyec]

i have used Everest VIT in my past life, they are an excellent inspection outfit, but they were short on analysis of their inspection results.

another outfit i had worked with was Tordonato Energy Consultants. they have a complete metalurgical lab and some of their people were extremely knowlegable in failure analysis.



Steven C
Senior Member
ThirdPartyInspections.com

 

[TVP]

Sebastian Tordonato and Fred Ellis from TEC are well known for metallurgical analysis in this area. Take a look at their website and click on the Field Services button:

http://www.tordonatoenergy.com/

 

[metengr]

eyec;
Not to commercialize any one vendor here, I know TEC and have worked with others below on various projects in the Power Generation sector. All are equally good.

http://www.structint.com/

http://www.mmengineering.com/

http://www.thielsch.com/

 

[eyec]

not trying to commercialize either just offering opinions from personal experiences.

you're right, Thielsch is another good one i am aware of.

Steven C
Senior Member
ThirdPartyInspections.com

 

[SMF1964]

6:00 vs 12:00 position - so the cracking is on the cold side of the tube?

 

[unclesyd]

What is the size of the drum?

What is the size of the access?

How many tubes would need to be inspected?
If say you inspect 4 on each end and all have have problems you should seriously look at replacing all as you probably have a design problem. I would suspect that the call for insulation in this area was based on experience.

A comment on the location of the failure.
I've been involved in similar failures on a D tube boiler where the root cause was attributed to "steam blanketing" that allowed periodic heating and quenching of failure area. Our problem was attributed to rapid rate changes mainly due to implication of different instruments and a new control scheme.