Metallurgical Aspects of Boiler Tube Failures – A Few Case Studies

B.G.SettySr. Manager R&D Centre, Noida

Metallurgical analysis

– Failure analysis– Health/ Condition Assessment – Residual Life Assessment– Indegenisation / Material Development

Components

– Boiler tubes– Turbine components– High Energy Piping– CHP Components– Grinding elements– Gas Turbine Components

Failure Mechanisms(Water Touched Tubes)

Corrosion FatigueFlyash ErosionHydrogen DamageAcid Phosphate corrosionCaustic GougingFireside CorrosionThermal FatigueErosion CorrosionSootblower Erosion

Short Term Overheating Low Temperature CreepChemical Cleaning DamageFatigue PittingCoal Particle ErosionFalling Slag DamageAcid Dew Point Corrosion

Failure Mechanisms(Steam Touched Tubes)

Long Term Overheating / CreepFire Side CorrosionDissimilar Metal Weld Short Term OverheatingStress Corrosion CrackingSH/RH Sootblower Erosion

FatigueRubbing Tubes / FrettingPittingGraphitisationSH /RH Chemical Cleaning

Stages in Failure Analysis

Visual Examination.Collection of background data.Identification of sampling locations.Laboratory investigationsAnalysis of data

Visual examination of damaged parts is the first and most critical step in failure investigation

Case Studies in Failure Investigation

Singarauli STPS

Boiler No.3Date of Failure: 05/04/2004Zone: Economiser Lower BankLocation: Coil No.02Material: SA210 A1R&D Ref: 2210

Kahalgaon STPS

Boiler No.2Date of Failure: 28/03/2004Zone: Convection Pass Wall (RHS)Location: Front Tube-01 (from RHS)Material: C20R&D Ref: 2209

Ramagundam STPS

Boiler No.1Date of Failure: 01/03/2004Zone: Economiser LHS wallLocation: Bank no.03 (from rear)Material: SA210 A1R&D Ref: 2198

Corrosion Fatigue

Ramagundam STPS

Boiler No.2Date of Failure: 27/02/2004Zone: ReheaterLocation: Bank-05, Coil-22, Tube-07Material: SA213 T22R&D Ref: 2199

Korba STPS

Boiler No.1Date of Failure: 09/01/2004Zone: ReheaterLocation: Panel-31, 3rd Bend, 2nd BunchMaterial: SA213 T11R&D Ref: 2132

Long Term Overheating

Talcher #2, Stage –I

S-Panel Water Wall Tube Failure

Dated 09/01/2004

Report: R&D/MET/2130

Pinhole on weld

Vindhyachal #8

S-Panel Water Wall Tube Failure

Dated 06/12/2003

Report No R&D/MET/2073

2073

Origin of Leak

Origin of Leak

NCPP Dadri #2

S-Panel Water Wall Tube Failure

Dated 05/11/2003

Report No. R&D/MET/R-2118

TANDA Unit #2

Hydrogen Damage Failure in Water Wall

NCPP Dadri Unit #2

Weld Porosity in Economiser Tube

Talcher Thermal Unit #6

Weld Defects in Economiser Tube

Water wall Tube (near Man hole)Material: SA210 GrA1

Thermal Fatigue

Hydrogen Damage

Usefulness of Failure Analysis

Establishing the main reason of failureEstablishing the main reason of failureTaking remedial action to prevent further Taking remedial action to prevent further

failuresfailuresReduces forced outagesReduces forced outagesHelps in taking decisions for making design Helps in taking decisions for making design

modifications, if necessarymodifications, if necessary

Water wall (Rear Side- tube no. 139 - S-Panel bend)Water wall (Rear Side- tube no. 139 - S-Panel bend)

Short Term Overheating