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Kumar R K ¹, Raghavendra Naik ¹, Saravanan V ¹, Janardhana M ¹

Affiliations
1 Central Power Research Institute, Bangalore-560080, IN

Abstract

The splitter plates of coal burners in Indian thermal plants are subjected to severe erosion and erosioncorrosion conditions owing to the combined effect of abrasive nature of coal and elevated service temperature environment. During service, tilting of splitter plates is adopted to achieve the desired final steam outlet temperature which shifts the fireball location and heat release area in the combustion zone. The tilt condition gives rise to a change in the incidence angle of the coal particle as well as the change in flow profile. The erosion life of these plates is predominantly affected by the coal particle velocity, impact angle, particle size and steady state metal temperature during service. The sensitivity of burner tilt angle on the erosion life requires an understanding of primary air with coal particle flow phenomenon within the burners. The effect of burner tilt angle on the erosion of presently used SS310 grade splitter material was studied through computational fluid dynamics. The erosion sensitive velocity exponent was calculated based on the laboratory simulated erosion tests at elevated temperatures upto 700°C. The life of the splitter plates was calculated based on the predicted erosion rate intensity.

Keywords

Coal burner, high-temperature erosion, Computational Fluid Dynamics (CFD)

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Kumar R K ¹, Janardhana M ¹, Bhaskar Sharma K V ²

Affiliations
1 Joint Director, Central Power Research Institute, Bangalore -560080, IN
2 Sampoorna Rotor Dynamics Consultancy, Bangalore-560040, IN

Abstract

Blade failures in steam and gas turbines are quite a common occurrence. The last stages of steam turbines are designed to have the lowest possible fluid temperature. In view of the longest blade length in the last stages, the blades are subjected to highest bending moment forces and susceptible for erosion-corrosion phenomenon owing to the low service temperature environment. The failure analysis of last stage blade of 54 MW direct condensing type gas turbine are presented. The blade was made of martensitic grade stainless steel. Detailed analysis of the blade surface, lacing wire hole as well as the fracture morphology was analyzed using SEM-EDX. The probable reason for the failure of the blade was brought out based on the detailed investigations of the failed blade as well as the vibration signature analysis at the time of failure incidence.

Keywords

Failure Analysis, Gas Turbine Blade, Vibration Frequency, Fractography

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Arvind Kumar ¹, Malabika Roy ¹, Janardhana M ¹, Shekhar Kumar M ¹

Affiliations
1 Materials Technology Division, Central Power Research Institute, Bangalore-560 080, IN

Abstract

A power generating utility of 600 MW has reported the failure of boiler tubes after a service life of 265 hours against the design life of 25-30 years. The failure of tubes was reported in Re-heater Inlet Coil tubes which were made up of high strength material alloy of SA 213 T91 grade. These boiler tubes were operating under a high temperature and pressure. The material used for re-heater and super-heater boiler tubes should have enough creep strength to sustain at high temperature and pressure. Even though T91 grade steel has superior quality of metallurgical properties in comparison to low alloy existing material like T11, T12 and T22, T91tube was failed in a short duration. This paper describesthe investigation of the failure of high strength T91 gradereheater tubes in a coal fired thermal power plant. The failure investigation covers visual inspection, dimensional measurement, hardness mapping, oxide scale measurement, microstructural studies, and SEM and EDX analysis of the failed tubes. The analysis reveals that Tube No-3 of re-heater boiler tube failed due to short term overheating and other tubes failed due to secondary damage caused by steam impingement.

Keywords

Re-heater Boiler Tube, Visual Inspection, Grade Identification Of Alloy, Dimensional And Hardness Measurement, Oxide Scale Measurement, Microstructure Analysis

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Arvind Kumar ¹, Malabika Roy ², Janardhana M ³, Shekhar Kumar M. ³

Affiliations
1 Engineering Officer, Central Power Research Institute, Bangalore - 560 080, IN
2 JRF, Central Power Research Institute, Bangalore - 560 080, IN
3 Joint Director, Central Power Research Institute, Bangalore - 560 080, IN

Abstract

Boilers being the heart of any steam generating system, failure of its components,will lead to forced outages of the plant, resulting in heavy economic losses in terms of non–availability of plant.Periodic inspection and assessment of boiler tubes has a great impact on the generation of power and economic status. The assessment of boiler tubes minimizes the risk of forced outage of the power plant. This paper presents the assessment of water wall tubes of thermal power plant to avoid any forced outage due to failure of water wall tubes. The assessment includes non-destructive, destructive and failure analysis of failed tubes. The periodic non-destructive evaluation is performed for the boiler tubes for generation of data for assessing and deciding the integrity of the boiler tubes. Destructive and failure analysis of failed tubes gives the information and helps in identifying the ischolar_main cause of failure and to take preventive action for avoiding forced outage.

Keywords

Water Wall Tube, Forced Outage, Corrosion, Erosion, Deposited Product, Scanner, Hydrogen Damage, Microstructure and EDX Analysis

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