CRACK IN STEAM DRUM BAFFLE 2

[hyl]

Hello members
We have crack in steam drum baffle can any one give us advice how to repair that crack.
thank you very much and god bless.

jamil a alshahed nama
hartha power station

 

[unclesyd]

Can you comeback with a better description of the crack and the material of construction?

 

[hyl]

Hello
Thank you MR unclesyd for you reply .The material of the baffle is carbon steel (ss41) and the crack is radial hair crack with alonge of 5cm .The thickness of the material is 4.5mm .thank you very much and god bless .

jamil a alshahed nama
hartha power station

 

[davefitz]

Not clear of the overall geomtrey, but a 5cm crack is not likely to leak a lot of 2-phase mixture into the water space, so to avoid issues with weld damage to a brittle drum shell, try drilling a small hole at the edge of the leading crack to act as a crack arrestor .

If you are still concerned with the possibility of affect of steam leaking into a downcomer, conduct a downcomer "loss of head" test during operations.

 

[metengr]

hyl;
Based on your description, locally grind the crack until removed. Verify defect removal using Liquid PT or wet MT. Apply a local preheat, and weld restore the excavation using 7018 filler metal (low hydrogen). After welding is completed, perform a final NDT (wet MT or Liquid PT).

If this boiler steam drum is outside of the US, you need to follow the requirements of your local authority that regulates boilers. If you have no local authority requirements and you are on your own, use a contractor that has qualified welding procedures to ASME Section IX, or use the boiler OEM for repair as I described above.

 

[BillBirch]

metengr,
The boiler is in Basra, Iraq! I think they have more pressing issues than boiler certification.
Regards,
Bill

 

[metengr]

BillBirch;
Read my second paragraph in the second post!

 

[davefitz]

If you decide to weld repair, the material in the weld zone would need to be "passivated" to remove caustic deposits prior to welding. Otherwise, caustic deposits will lead to increased brittleness and a rapid re-cracking.

The drum girth baffle plate may be very thin , perhaps 1/4" thk or less, and thus it can change metal temperature much faster than the drum metal ( 6" thk) to which it is welded. If you quickly change drum water temp by over 150 F ( as during a shutdown and fast depressurization) , then the girth baffle will schrink relative to the drum metal, which is the probably driving mechanism for the cracking. In my opinion, if the crack re-appears, then use a drilled hole at the leading edge of the crack as a crack arrestor.

 

[athomas236]

Is there any reason why the crack could not be sealed by a bolted cover plate. The plate could be firmly bolted on one side of the crack and bolted into slotted holes on the other to allow some thermal movement.

regards

athomas236