Waste Heat Boiler Tube Leakage
Waste Heat Boiler Tube Leakage
(OP)
We recently had to shutdown our plant due to tube leakage in our Waste Heat Boiler(WHB). Upon vessel opening we observed visible leakage from at least 01 tube as the refractory and heat shield adjacent to it was damaged. Evidence suggested that upon leakage BFW water flashed and damaged the refractory on shell and tube sheet. Thermal shock caused by the cooling effect of flashing developed cracks on adjacent tubes, ferrules and tube sheet.
Boroscopy was carried out of the leaking tube and it was observed that the source of leakage was a small hole of 1.73 mm diameter at 3’o clock position in immediate downstream (0.9” away) of the installed ferrule at hot end. Location of the leaking tubes is showing in attached tube sheet map from hot end. It is important to mention here that we did not observed any signs of thinning on either side of the hole. No damage was detected on the leaking tube on Cold End tube sheet. Equipment has been in service for nearly 6 years and no concerning observation was made during previous inspections.
In consideration of the aforementioned inspection findings, satisfactory inspection history, tube defect location and the leaking tube request your expert opinion on the possible damage mechanism responsible for this leakage.
Attached are pictures taken during our inspection as well as brief equipment introduction
Regards,
Boroscopy was carried out of the leaking tube and it was observed that the source of leakage was a small hole of 1.73 mm diameter at 3’o clock position in immediate downstream (0.9” away) of the installed ferrule at hot end. Location of the leaking tubes is showing in attached tube sheet map from hot end. It is important to mention here that we did not observed any signs of thinning on either side of the hole. No damage was detected on the leaking tube on Cold End tube sheet. Equipment has been in service for nearly 6 years and no concerning observation was made during previous inspections.
In consideration of the aforementioned inspection findings, satisfactory inspection history, tube defect location and the leaking tube request your expert opinion on the possible damage mechanism responsible for this leakage.
Attached are pictures taken during our inspection as well as brief equipment introduction
Regards,





RE: Waste Heat Boiler Tube Leakage
To determine the root cause, this tube should be removed for metallurgical analysis. Otherwise, you can speculate and it means nothing.
RE: Waste Heat Boiler Tube Leakage
Thank you for the response. Unfortunately due to time constraints we could not remove the tube itself, however based on your experience, please share besides the obvious suspicion of a manufacturing defect what possible damage mechanism could have been responsible for this defect. Does the location of defect in immediate downstream of ferrules on hot end gives us any clues to the problem?
Regards,
RE: Waste Heat Boiler Tube Leakage
"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick
RE: Waste Heat Boiler Tube Leakage
I could not open your attachment. Does the tube ID surface contain deposits or other pits? The only other possibility is under deposit corrosion caused by feedwater contaminants that plate out on the hot end of tubes.
RE: Waste Heat Boiler Tube Leakage
https://drive.google.com/file/d/0B_RKjhcx7xaDNWhCU...
Looking forward to your expert feedback.
Regards,
RE: Waste Heat Boiler Tube Leakage
Have you performed Eddy current testing to evaluate the condition of the surrounding tubes in this section of the WB?
RE: Waste Heat Boiler Tube Leakage
RE: Waste Heat Boiler Tube Leakage
And they were probably well below the level for rejection when the new tubes were tested.
The one other possibility is that during fabrication someone hit the tube with a welding rod. the arc strike would change microstructure and lead to localized attack.
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P.E. Metallurgy, Plymouth Tube
RE: Waste Heat Boiler Tube Leakage