Boiler Tube Failure Analysis – Steps Involved

Boiler Tube Failure Analysis – Steps Involved

As soon as tube failure is suspected in a boiler, first identify the location – roughly, take out the log data of boiler for at least eight hours before failure. If the boiler tripped due to tube failure take full first-up logs, take out the trend graphs for reference, or mark clearly the time of failure and speed of chart- it’s better to mark on all charts and take printout of trend charts from DCS.

  • Decide to run or stop boiler if unit did not trip
    • Evaluate the extent of secondary damage possibility if run
      • Water wall area lesser chances
      • Platen area- the damage can be severe and downtime and spares requirement will be high
      • LTSH and Eco- very high secondary damages possible
    • Bring down the unit at the earliest to reduce secondary damage
  • After boiler is shut down
    • Open the man hole in the suspected area of tube failure when safe, never try to enter unless temperature has come down to safe level - Near ambient
    • Try with a powerful light to find the leaky tube and mark the location on the drawing - rough elevation and tube number indicate from which side count is done
    • Any visual appearance / observation can be logged
    • Send these details with log data and trend sheets collected to designers and ask for first opinion
    • Take photos of the area of failure from outside and other areas like furnace if required
  • Ask designers
    • Tell designer that the tube samples from the failed tube is arranged
    • Any specific information other than supplied is required based on the first impression
    • Immediate checks required during shut down
    • Additional samples required from the area of failure or otherwise
  • Collecting tube sample
    • Organize to drain the boiler if required
    • Once it is safe to enter the boiler provide scaffolding and reach the area of failure
    • Make sure the location noted before is correct or need to be altered - Mark this on drawing
    • Mark about 150 to 200 mm above and below the failure area - total length of sample more than 300 mm
    • Cut the tube sample by cutting tool or hacksaw - Never cut by gas as this destroys the evidence
    • It is a good practice to cap the sample as soon as the sample is cut
  • Before repairing the failed area
    • Make sure all inspection is done- check the adjacent tubes and area for any evidence of deterioration
    • If required do open the header hand hole plates for inspection and make sure no cleaning is needed
    • If material mix-up is suspected, then it is good to replace the length from the transition point of the material
    • It is required to check the adjacent coils for any material mix-up by spark test
    • Check with the designer about the need for an expert’s visit to site before repair
  • First impression report from designer
    • Inform site about the first impression of failure- broad classification of the type of failure
    • Ask for additional details and samples if required
    • Tell about expert visit- plan immediately as owner cannot wait
    • After seeing the failed sample and noting all observations, sent it for lab analysis
      • Ask for any special test required- deposit analysis
      • Flattening test- if hydrogen damage is suspected
  • Analysis by designers
    • Review the log data and details sent from site with respect to all deviations
    • Look at the trend charts and first-up details for any inference possible
    • Look for any abrupt changes in the operating regime- log data, water chemistry, loading pattern, etc.
    • Make sure metal temperature details are reviewed
    • Correlate the findings of lab analysis- use EPRI guide lines and classification on tube failures
    • Make sure the failure is not generic in nature
  • Final evaluation and corrective action
    • The final finding can be classified for one-in-case, generic due to operational practice, design, material inadequacy, etc.
    • Make an action plan to correct the boiler in question, similar operating boilers, and similar boilers being commissioned, erected, manufactured, or designed
    • If required make out a design guide line or operational guide line
    • Inform all owners about the problem and corrective action needed- owners need to plan
    • Monitor the boiler for performance after corrective action