International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 04 Issue: 07 | July -2017
p-ISSN: 2395-0072
www.irjet.net
Remaining life assessment of radiant super heater in creep regime Manish Shukla1, Prof. D.D. Bhoge 2, Dr. S.S. Metan3 1Research
Scholar, Dept. of Mechanical Engineering, NKORCHID, Solapur, India
2Assistant Professor, Dept. of Mechanical Engineering, NKORCHID, Solapur, India 3Associate Professor, Dept. of Mechanical Engineering, NKORCHID, Solapur, India
NK Orchid College of Engineering and Technology, Solapur, India 413004
---------------------------------------------------------------------***-----------------------------------------------------------Abstract- Assessment of remaining life of power plant components is necessary for awareness of its health. This is beneficial in preventing failure and force shutdown while life is expended. It also helps to avoid to capital investment on premature replacement of tubes. This study investigates the condition of platen superheater of pulverized fuel fired boiler. Visual inspection and various testing like dye penetrant testing, magnetic particle testing and ultrasonic testing carried out for checking structural integrity of header and tubes. Metallographic replication carried out for both inlet and outlet header of platen superheater. Oxide scale measurement carried out for superheater tubes and remaining life of tubes calculated. Keywords—Super heater tubes; Oxide scale measurements; microstructure; creep 1. Introduction The high temperature headers include the superheater and reheater outlets which operate at temperatures in excess of 900°F. These headers experience the effects of creep under normal conditions. In addition to the material degradation resulting from creep, high temperature headers can also experience thermal and mechanical fatigue. Creep stresses combined with thermal fatigue stresses can lead to a failure much sooner than creep acting alone. [1]. As the strength reduced due to decarburization the creep mechanism transformed from long term intragranular creep to short term transgranular rupture [2]. Increased inlet temperature coupled with higher turbine rotational speeds, exposure the hot end components to faster rate of creep damage [3]. Due to combination of internal pressure loading and exposure to high temperature steam pipe experience creep damage. Seam welded steam pipes are prone to creep cracking [4]. measuring high temperature corrosion depth of boiler tubes extracted from heating surface allows assessment of the integrated impact of local operating condition metal corrosion resistance, gas environment, deposit condition and assessment of remaining life [5]. The process of creep damage leading up to crack initiation in boiler and turbine needs to be quantatively characterized in terms of material and operational parameters. The effect of environment stress state and cyclic operation on creep damage needs to be considered. The validity of life fraction rule for life assessment needs to be verified [6]. Tube forms an internal oxide layer that exhibits heat transfer through the wall and causes the tube metal temperature to rise. The thickness of this oxide can be used with unit operating data and wall thickness measurements to estimate the remaining life of a tube .At the high temperature oxide growth and diameter reduction both having simultaneous effect on tube life.[7} 2- Estimation of Remaining Life The norms developed by Neubauer and Wedel, have now table: 2.1 U. Neubauer and B. Wedel
become the industry standard as given in the following
Classification Table1. Class of assessment Class of assessment Class I Class II Class III Class IV Class V
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Damage definition Expended life fraction ( / ) Undamaged Isolated cavities Oriented cavities Linked cavities / micro cracks Macro cracks
Impact Factor value: 5.181
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.27 .46 .74 .88 1
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