Boiler tube Analysis
Boiler tube Analysis
(OP)
Can somebody volunteer information on the best practices that should be adopted for the testing of High Pressure high temprature Steam boiler ( ca 170 bar 515 C )tubes for scale accumulation & tube thickness verification.
Jimmi
Jimmi





RE: Boiler tube Analysis
As far as best practices, you need to determine test locations within the boiler pendant or platens. Usually, we test every other pendant or platen and several tubes deep, from the lead tube. What is most important is after this testing is completed you should remove several tube samples for lab analysis to compare tube wall thickness, ID oxide thickness and the condition of the tube material microstructure.
RE: Boiler tube Analysis
EPRI 1007347 (2002) Proc. Int'l Conf. on Boiler Tube Failures & HRSG Tube Failures & Inspections
EPRI CS-3272 (1983) Failures and Inspections of Fossil-Fired Boiler Tubes; 1983 Conf. & Workshop
Try websites from some of the bigger inspection companies.
RE: Boiler tube Analysis
RE: Boiler tube Analysis
You do not mention what limits are out of specification. The duration of 12 hours is significant and can result in deposits and subsequent corrosion. As a minimum, I would try to snake a borescope into one or more waterwall tubes for inspection. If deposits are found, you will need to remove a tube sample and evaluate the amount and extent of the deposits. Under deposit corrosion can be serious and result in hydrogen damage and or caustic corrosion.
RE: Boiler tube Analysis
RE: Boiler tube Analysis
RE: Boiler tube Analysis
What do you mean by the term "off spec"? Was there actual contamination of the feed-water with scale forming minerals, or were the residual treatment levels in the boiler-water out of the desired control range by 10%?
Do your operators test for either turbidity, total dissolved solids or dissolved iron as part of their normal testing routine. If so compare the results during the "off-spec" period to results when condition are within range.
If you suspect that scale deposits may have formed during this event; a remote visual internal inspection of the water wall tubes at the soonest availability would be a good place to start your assessment.
RE: Boiler tube Analysis
The off spec condition occured due to marginal transient deviation in chloride contamination in a high pressure boilers feeding to a back pressure turbine. The low pressure steam is utlised for MSF desalination.The steam condenser leaked which resulted in slight chloride contamination up from a maximum of0.1 ppm ( allowable) to .11 ppm.All other standard test values were under control.
What is the remote visual internal ispection of boiler tubes you are referring? How you do the inspection on LIVE BOILER?
RE: Boiler tube Analysis
The RVI would be during the next outage, that is why I stated soonest available opportunity. High boiler water chloride levels increase the propensity for carry-over, not scale formation; choride ions are inversely soluble. Typically at that low of a chloride level, carry-over is not a concern but without knowing the specifics of your steam generator that would be impossible for me to determine.
Do you have a in-line sodium analyzer used to monitor the steam enterning and or leaving the super-heater. A spike in this reading would be indicative of carry-over. Carry-over is more of a concern for the super-heater tubes, especially if they are made of one of the austenitic steel alloys.
RE: Boiler tube Analysis
rmw