How to Control Boiler Tube Leakage (BTL) in coal fired power stations. Best twenty (20) practices to control Boiler Tube Failure-An Engineering Case Study..

Best practices in coal fired power stations to arrest Boiler tube leaks or Measures to control Boiler tube leaks. An Engineering Case Study by Mechwix Technology.

 

Mechwix

Having work experience of more than fifteen (15) years in operation & maintenance (O&M) department along with relevant exercise in maintenance planning, we have summarize the best Twenty (20) measures to control Boiler Tube Failure. Perhaps it may be the perfect operation & maintenance guide lines for Boiler operation engineer (BOE) and along with maintenance engineer. Above all it will help for cost effective green power generation.

 1. Boiler tubes are the most important parts of the thermal power generating unit. Failure of boiler tube components statistically contribute over all six percent (6%) availability loss in the power plant units. It requires close monitoring by the performance group of power plant engineering section. The formation of performance optimization group comprises of Operation, O&E, BMD, C&I, CHEMISTRY and CHP (O&E), guides the measures to be taken to Boiler tube leakage (BTL).

2. Thermal efficiency depends on the steam temperature. Higher temperature gives higher thermal efficiency. Boiler tube has the metallurgical limitation of temperature withstanding. So it needs to maintain & control the tube metal temps within design value by sacrificing the steam temperatures (Responsible department Process/Operation).

3. Boiler is designed in such a way that the maximum combustion occurs in the first pass of the furnace. This position of fire ball is centered by the combustion air pressure. Hence it needs to maintain the wind box(WB) to furnace differential pressure(DP) as per design value (Responsible department Process/Operation).

4. It requires the periodic checking of secondary air damper control (SADC) position. It is one of the main constitute in metal excursions (Responsible department Process/Operation).

5. Periodic long retractable shoot blower (LRSB) operation is highly useful to avoid over heating of the tube metal as it removes the deposited shoots on the tube elements (Responsible department Process/Operation).

6. Wall blowers impinges steam on the water wall of the furnace. So higher pressure of the impinge steam impacts the tube erosion. Hence the pressure needs to set once in every six months (Responsible department Process/Operation).

7. Protection shields over top banks of Economiser and low temperature super heater (LTSH) area, vertical hanging tubes of rear walls are required (Responsible department BMD).

8. Damages of coal burner nozzles disturbs the fire ball in the furnace resulting in secondary combustion So all the coal burners need to repair in every overhaul (Responsible department BMD).

9. Tube thickness survey by ultrasonic thickness gauge needs to perform in every overhaul (Responsible department BMD).

10. It requires to maintain chemistry parameters of feed water, condensate water and steam. Close monitoring of parameters to avoid water corrosion in case of sea water usages (Responsible department CHEM). C&I loops are required to be very accurate; especially drum level controller and metal temp (Responsible department C&I).

11. Periodic checking of mill fineness is required to avoid secondary combustion & overheating of boiler tube at the low temperature zone (Responsible department O&E, RM).

12. If the recurrent failure occurs in the reheater & super heater zone, it is recommended to change the tube metal with high grade metals as Stainless Steel and T91 alloy materials (Responsible department BMD).

13. It is suggested or recommended to maintain bottom ash hopper level around 450mm down to normal value to avoid splashing of sea or river water on bottom side of water walls (Responsible department AHM, BMD).

14. It needs to control the excess air to avoid high velocity and high flue gas exit temp (Responsible department Process/Operation).

15. During commission stage, flushing and chemical cleanings plays important role to clear any blockages in the circuit. Otherwise, these blockages will lead to tube failure (Overheating) (Responsible department Process/Operation).

 

16. The soot blower must be ensured to it's home position other wise it continuous steam impinging erodes the tube elements (Responsible department Process/Operation).

17. Thermal drain in soot blower steam line needs to be opened before it operates as it impacts with thermal quenching of tube elements (Responsible department C&I).

 

18. Shoot blower steam sources need to be fully isolated to avoid continuous steam passing through the blower (Responsible department Process/Operation).

 

19. Acoustic steam leak detector (ASLD) needs to be installed to monitor frequently & rectify the minor tube failure to avoid major tube failure (Responsible department Process/Operation).

 

20. Burner Swaying mechanism is recommended either in horizontal or downward position to minimize secondary combustion that enhances the tube overheating (Responsible department Process/Operation).

 Author & Engineer: Md Kamaluddin

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