Waterwall damage by fast internal oxidation of boiler tubes

Anu Lokkiluoto, Juha Viuhko, Pertti Auerkari, Sanni Yli-Olli

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

Abstract

Recurring waterwall leaks have been observed in a coal-fired boiler where subsequent inspections have shown through-wall internal oxidation, mostly at butt welds of 16Mo3 boiler tubes. In several cases the oxide had retained a thick pit plug even after local penetration of the tube wall. The original initiation site is no longer visible as it was removed by oxidation, but away from the most severe damage the internal oxidation appears to have initiated immediately downstream after a protruding weld root. This location, estimated oxidation rate and oxide appearance suggest that the mechanism is related to locally intensive heating in addition to flow turbulence. In the damage history of the same boiler wall, the first comparable leaks were recorded at shop welds with strongly protruding root shape, presumably inducing particularly strongly turbulent flow, and even then only after long term service. The most recent failures, however, occurred at normal repair welds or even within parent material, and after much shorter time in service. The characteristic features and causative factors of the tube failures are discussed in the paper, based on the available evidence and experience from operation and maintenance.
Original languageEnglish
Title of host publicationBaltica X
Subtitle of host publicationInternational Conference on Life Management and Maintenance for Power Plants
EditorsPertti Auerkari
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages9
ISBN (Electronic)978-951-38-8436-9, 978-951-38-8435-2
Publication statusPublished - 2016
MoE publication typeA4 Article in a conference publication
EventBALTICA X - International Conference on Life Management and Maintenance for Power Plants - Cruise, Helsinki-Stockholm, Finland
Duration: 7 Jun 20169 Jun 2016

Publication series

SeriesVTT Technology
Volume261
ISSN2242-1211

Conference

ConferenceBALTICA X - International Conference on Life Management and Maintenance for Power Plants
Abbreviated titleBaltica X
CountryFinland
CityHelsinki-Stockholm
Period7/06/169/06/16

Fingerprint

oxidation
damage
oxide
parent material
turbulent flow
repair
penetration
turbulence
coal
heating
boiler
history
services
shop
inspection
rate

Cite this

Lokkiluoto, A., Viuhko, J., Auerkari, P., & Yli-Olli, S. (2016). Waterwall damage by fast internal oxidation of boiler tubes. In P. Auerkari (Ed.), Baltica X: International Conference on Life Management and Maintenance for Power Plants Espoo: VTT Technical Research Centre of Finland. VTT Technology, Vol.. 261
Lokkiluoto, Anu ; Viuhko, Juha ; Auerkari, Pertti ; Yli-Olli, Sanni. / Waterwall damage by fast internal oxidation of boiler tubes. Baltica X: International Conference on Life Management and Maintenance for Power Plants. editor / Pertti Auerkari. Espoo : VTT Technical Research Centre of Finland, 2016. (VTT Technology, Vol. 261).
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title = "Waterwall damage by fast internal oxidation of boiler tubes",
abstract = "Recurring waterwall leaks have been observed in a coal-fired boiler where subsequent inspections have shown through-wall internal oxidation, mostly at butt welds of 16Mo3 boiler tubes. In several cases the oxide had retained a thick pit plug even after local penetration of the tube wall. The original initiation site is no longer visible as it was removed by oxidation, but away from the most severe damage the internal oxidation appears to have initiated immediately downstream after a protruding weld root. This location, estimated oxidation rate and oxide appearance suggest that the mechanism is related to locally intensive heating in addition to flow turbulence. In the damage history of the same boiler wall, the first comparable leaks were recorded at shop welds with strongly protruding root shape, presumably inducing particularly strongly turbulent flow, and even then only after long term service. The most recent failures, however, occurred at normal repair welds or even within parent material, and after much shorter time in service. The characteristic features and causative factors of the tube failures are discussed in the paper, based on the available evidence and experience from operation and maintenance.",
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Lokkiluoto, A, Viuhko, J, Auerkari, P & Yli-Olli, S 2016, Waterwall damage by fast internal oxidation of boiler tubes. in P Auerkari (ed.), Baltica X: International Conference on Life Management and Maintenance for Power Plants. VTT Technical Research Centre of Finland, Espoo, VTT Technology, vol. 261, BALTICA X - International Conference on Life Management and Maintenance for Power Plants, Helsinki-Stockholm, Finland, 7/06/16.

Waterwall damage by fast internal oxidation of boiler tubes. / Lokkiluoto, Anu; Viuhko, Juha; Auerkari, Pertti; Yli-Olli, Sanni.

Baltica X: International Conference on Life Management and Maintenance for Power Plants. ed. / Pertti Auerkari. Espoo : VTT Technical Research Centre of Finland, 2016. (VTT Technology, Vol. 261).

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

TY - GEN

T1 - Waterwall damage by fast internal oxidation of boiler tubes

AU - Lokkiluoto, Anu

AU - Viuhko, Juha

AU - Auerkari, Pertti

AU - Yli-Olli, Sanni

PY - 2016

Y1 - 2016

N2 - Recurring waterwall leaks have been observed in a coal-fired boiler where subsequent inspections have shown through-wall internal oxidation, mostly at butt welds of 16Mo3 boiler tubes. In several cases the oxide had retained a thick pit plug even after local penetration of the tube wall. The original initiation site is no longer visible as it was removed by oxidation, but away from the most severe damage the internal oxidation appears to have initiated immediately downstream after a protruding weld root. This location, estimated oxidation rate and oxide appearance suggest that the mechanism is related to locally intensive heating in addition to flow turbulence. In the damage history of the same boiler wall, the first comparable leaks were recorded at shop welds with strongly protruding root shape, presumably inducing particularly strongly turbulent flow, and even then only after long term service. The most recent failures, however, occurred at normal repair welds or even within parent material, and after much shorter time in service. The characteristic features and causative factors of the tube failures are discussed in the paper, based on the available evidence and experience from operation and maintenance.

AB - Recurring waterwall leaks have been observed in a coal-fired boiler where subsequent inspections have shown through-wall internal oxidation, mostly at butt welds of 16Mo3 boiler tubes. In several cases the oxide had retained a thick pit plug even after local penetration of the tube wall. The original initiation site is no longer visible as it was removed by oxidation, but away from the most severe damage the internal oxidation appears to have initiated immediately downstream after a protruding weld root. This location, estimated oxidation rate and oxide appearance suggest that the mechanism is related to locally intensive heating in addition to flow turbulence. In the damage history of the same boiler wall, the first comparable leaks were recorded at shop welds with strongly protruding root shape, presumably inducing particularly strongly turbulent flow, and even then only after long term service. The most recent failures, however, occurred at normal repair welds or even within parent material, and after much shorter time in service. The characteristic features and causative factors of the tube failures are discussed in the paper, based on the available evidence and experience from operation and maintenance.

M3 - Conference article in proceedings

T3 - VTT Technology

BT - Baltica X

A2 - Auerkari, Pertti

PB - VTT Technical Research Centre of Finland

CY - Espoo

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Lokkiluoto A, Viuhko J, Auerkari P, Yli-Olli S. Waterwall damage by fast internal oxidation of boiler tubes. In Auerkari P, editor, Baltica X: International Conference on Life Management and Maintenance for Power Plants. Espoo: VTT Technical Research Centre of Finland. 2016. (VTT Technology, Vol. 261).