Waste heat boiler economizer tubes
Waste heat boiler economizer tubes
(OP)
We have a waste heat boiler in our plant. The economizer tubes are heavily leaking & boiler needs shut down for the same reason.
We are suspecting leak at the joints but it could also be in the tube itself
There are two questions -
1) Economizer tubes are CS A192 while there are u bends which is P5 (2 1/4Cr Mo ). Does it require PWHT for these joints? We referred ASME code & it says it is not mandatory.
Also can we replace a part of tube as a repair option or is it advisable to replace complete portion of the tube? Is there any repair code for such applications?
2) Now the economizer is bypassed & the flue gas temperature at its inlet is around 300 degC but there is no heat transfer as there is no water inside. Will it affect the life of tube?
Your valuable inputs are highly appreciated.
We are suspecting leak at the joints but it could also be in the tube itself
There are two questions -
1) Economizer tubes are CS A192 while there are u bends which is P5 (2 1/4Cr Mo ). Does it require PWHT for these joints? We referred ASME code & it says it is not mandatory.
Also can we replace a part of tube as a repair option or is it advisable to replace complete portion of the tube? Is there any repair code for such applications?
2) Now the economizer is bypassed & the flue gas temperature at its inlet is around 300 degC but there is no heat transfer as there is no water inside. Will it affect the life of tube?
Your valuable inputs are highly appreciated.





RE: Waste heat boiler economizer tubes
Where do the leaks originate?
The 300 C stack will cause trouble with the stack CEMS , stack paint, workers exposure, etc.
RE: Waste heat boiler economizer tubes
Yes the return bends are 180 deg.
But i need to know, after welding do the joints need stress relieving as the code is not giving it a mandatory requirement.
Usually the leaks are observed on the return bend joints, but mostly due to corrosion & not cracks. This is what the history/ records show.
RE: Waste heat boiler economizer tubes
RE: Waste heat boiler economizer tubes
No. Regarding the tubing you are not above the temperature for time dependent properties (creep deformation or stress rupture). Locations of tube support and terminal tube attachment welds could be subjected to high than design bending stresses caused by higher than anticipated thermal stresses. Do not remain by-passed any longer than necessary.
RE: Waste heat boiler economizer tubes
RE: Waste heat boiler economizer tubes
On larger boiler systems with bent tube designs we typically will repair the leaking section only. This is normally done due to access and the amount of effort to tear done a unit to have access for a full replacement. Keep in mind that with replacing a section only you will typically have to due some window welding
Hope this helps