Analisis Kegagalan Water Wall Tube Boiler PLTU Ditinjau dari Aspek Metalurgi

Conita, Isnata Conita (2023) Analisis Kegagalan Water Wall Tube Boiler PLTU Ditinjau dari Aspek Metalurgi. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Ketel uap atau boiler memiliki peran sebagai tempat mengubah air dari liquid menjadi uap. Salah satu komponen penting dari boiler adalah water wall tube. Pada water wall tube boiler ditemukan kegagalan berupa kebocoran dengan bentuk patahan berdinding tebal pada fireside tube. Kebocoran tersebut menghambat proses produksi listrik karena diperlukan shut down untuk perbaikan. Penelitian ini dilakukan untuk mengetahui penyebab dan mekanisme terjadinya kebocoran water wall tube boiler. Pada penelitian ini pengujian diawali dengan melakukan pengamatan makroskopis dan pengukuran pada spesimen uji. Kemudian spesimen dipotong menjadi beberapa sample untuk dilakukan pengujian. Pengujian yang dilakukan yaitu pengujian metalografi dan Scanning Electron Microscope (SEM) untuk mengetahui perubahan struktur mikro, pengujian Energy Dispersive X-Ray Spectroscopy (EDS) dan X-ray Diffraction (XRD) untuk mengetahui karakteristik dari lapisan oxide pada inner maupun outer tube, pengujian Optical Emission Spectroscopy (OES) untuk mengetahui komposisi kimia tube, dan pengujian Vickers Hardness untuk mengetahui perubahan nilai kekerasan tube. Lapisan oxide yang tebal pada inner dan outer tube hingga mencapai 446 μm dan 377 μm menyebabkan adanya pemanasan lokal atau hot spot formation pada tube. Berdasarkan data operasi didapatkan bahwa tube beroperasi pada lingkungan dengan temperatur yang melebihi batas temperatur desain dari tube dan adanya kegagalan fuel oil supply nozzle yang menyebabkan pelebaran sudut api burner hingga mengenai water wall tube boiler. Kondisi operasi dan hot spot formation menyebabkan tube mengalami speroidisasi, tebentuknya grafit dan elongated grain pada struktur mikro tube. Hal ini berdampak pada nilai kekerasan tube yang menurun hingga 110,6 HV pada titik kebocoran (sample 2). Adanya void yang membentuk intergranular crack mengindikasikan tube mengalami creep dan menyebabkan terbentuknya tonjolan (bulging) pada titik kebocoran. Berdasarkan analisis hasil pengujian dan data yang diperoleh kebocoran water wall tube boiler disebabkan oleh adanya patahan berdinding tebal (thick-lip rapture) dan mengalami mode kegagalan long-term overheating.
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The steam boiler has a role as a place to convert water from liquid into steam. One important component of the boiler is the water wall tube. In the boiler water wall tube, a failure was found in the form of a leak in the form of a thick-walled fault on the fireside tube. The leak hampered the electricity production process because it required a shut down for repairs. This study was conducted to determine the causes and mechanisms of boiler water wall tube leaks. In this study, testing begins with macroscopic observations and measurements on test specimens. Then the specimen is cut into several samples for testing. The tests carried out are metallographic testing and Scanning Electron Microscope (SEM) to determine changes in microstructure, Energy Dispersive X-Ray Spectroscopy (EDS) and X-ray Diffraction (XRD) testing to determine the characteristics of the oxide layer on the inner and outer tubes, Optical Emission Spectroscopy (OES) testing to determine the chemical composition of the tube, and Vickers Hardness testing to determine changes in tube hardness values. The thick oxide layer on the inner and outer tubes up to 446 μm and 377 μm causes local heating or hot spot formation on the tube. Based on the operating data, it is found that the tube operates in an environment with a temperature that exceeds the design temperature limit of the tube and the failure of the fuel oil supply nozzle which causes the widening of the burner flame angle to hit the boiler tube water wall. The operating conditions and hot spot formation cause the tube to experience speroidization, graphite formation and elongated grain in the tube microstructure. This has an impact on the hardness value of the tube which decreases to 110.6 HV at the leak point (sample 2). The presence of voids that form intergranular cracks indicates that the tube is experiencing creep and causes the formation of bulging at the leakage point. Based on the analysis of test results and data obtained, the leakage of the boiler water wall tube is caused by a thick-walled fracture (thick-lip rapture) and experiences a long-term overheating failure mode.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	water wall tube, kebocoran, long term overheating water wall tube, leak, long term overheating
Subjects:	T Technology > TJ Mechanical engineering and machinery T Technology > TJ Mechanical engineering and machinery > TJ263.5 Boilers (general)
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User:	Isnata Prayarsni Conita
Date Deposited:	04 Aug 2023 08:07
Last Modified:	04 Aug 2023 08:07
URI:	http://repository.its.ac.id/id/eprint/101493

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