Analisis Kegagalan Pada High Temperature Tubing Superheater Dengan Material 12CrMoVG Pada Boiler Pembangkit Listrik 65 MW Tipe Pulverized Coal

Iswahyudi, Yanuar (2026) Analisis Kegagalan Pada High Temperature Tubing Superheater Dengan Material 12CrMoVG Pada Boiler Pembangkit Listrik 65 MW Tipe Pulverized Coal. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Kegagalan high temperature superheater (HT SH) tube merupakan salah satu penyebab menurunnya keandalan dan ketersediaan pembangkit listrik tenaga uap (PLTU) berbahan bakar batubara. Penelitian ini menganalisis mekanisme kegagalan tube HT SH berbahan 12Cr1MoVG pada pulverized coal boiler berkapasitas 65 MW yang telah beroperasi sekitar 96.000 jam dan mengalami rupture hingga menyebabkan forced outage selama 18 hari. Investigasi dilakukan melalui inspeksi makro dan fraktografi, pemetaan ketebalan, metalografi, pengujian kekerasan dan tarik, perhitungan hoop stress, analisis komposisi kimia menggunakan OES, karakterisasi deposit dan oksida menggunakan SEM-EDS, serta evaluasi data operasional DCS. Hasil pemeriksaan menunjukkan rupture berbentuk fish-mouth dengan ketebalan minimum 4,26 mm dari ketebalan nominal 5 mm. Metalografi pada tube gagal menunjukkan carbide spheroidization, elongasi butir, dan kavitasi intergranular yang mengindikasikan degradasi akibat long-term overheating dan kerusakan creep. Kondisi tersebut didukung oleh penurunan kekerasan sebesar 11,0% dan kuat luluh sebesar 11,7% dibandingkan material referensi. Hoop stress pada lokasi rupture sebesar 38,1 MPa menunjukkan bahwa kegagalan tidak dipicu oleh peningkatan beban tekanan secara langsung. SEM-EDS mengidentifikasi oxide scale yang disertai deposit abu aluminosilikat pada permukaan tube. Data DCS menunjukkan distribusi temperatur yang tidak seragam, dengan temperatur metal di sekitar lokasi kegagalan mengalami overheating excursion hingga 623 °C, sedangkan area yang lebih jauh tidak melampaui 580 °C. Estimasi Larson–Miller menunjukkan penurunan umur creep yang signifikan seiring peningkatan temperatur. Berdasarkan keseluruhan hasil investigasi, kegagalan diawali oleh long-term overheating yang menyebabkan degradasi mikrostruktur dan penurunan kekuatan material. Pembentukan oxide scale dan deposit yang tebal meningkatkan hambatan termal serta berpotensi menimbulkan ketidakseragaman pemuaian. Pada material yang telah terdegradasi, overheating excursion menjadi kondisi yang mempercepat kerusakan creep dan menurunkan kemampuan tube menahan tegangan akibat tekanan internal hingga akhirnya terjadi rupture.
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Failure of high-temperature superheater (HT SH) tubes is a major contributor to reduced reliability and availability of coal-fired power plants. This study investigates the failure mechanism of a 12Cr1MoVG HT SH tube in a 65 MW pulverized-coal boiler after approximately 96,000 h of service. The tube rupture resulted in an 18-day forced outage. The investigation comprised macroscopic and fractographic examinations, wall-thickness mapping, metallography, hardness and tensile testing, hoop-stress calculation, chemical composition analysis by optical emission spectroscopy (OES), characterization of oxide and deposits by SEM-EDS, and evaluation of operational data from the distributed control system (DCS). The failed tube exhibited a fish-mouth rupture with a minimum wall thickness of 4.26 mm, compared with the nominal thickness of 5 mm. Metallographic examination revealed carbide spheroidization, grain elongation, and intergranular cavities, indicating microstructural degradation associated with long-term overheating and creep damage. These findings were supported by reductions in hardness and yield strength of 11.0% and 11.7%, respectively, relative to the reference material. The calculated hoop stress at the rupture location was 38.1 MPa, indicating that the failure was not directly initiated by overload mechanism. SEM-EDS analysis identified an oxide scale covered by aluminosilicate-rich ash deposits. DCS data revealed a non-uniform temperature distribution, with the tube metal temperature near the failure location experiencing an overheating excursion up to 623 °C, while the far region remained below 580 °C. Larson–Miller analysis demonstrated a substantial reduction in creep life with increasing temperature. The overall findings indicate that long-term overheating progressively degraded the microstructure and mechanical strength of the tube. The development of thick oxide scale and deposits increased thermal resistance and potentially introduced differential thermal expansion. In the already degraded material, the subsequent overheating excursion accelerating creep damage and reducing the tube strength under internal pressure, ultimately leading to rupture.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	tube superheater, 12Cr1MoVG, creep, slagging, overheating, analisis kegagalan, failure analysis
Subjects:	T Technology > TJ Mechanical engineering and machinery T Technology > TJ Mechanical engineering and machinery > TJ174 Maintenance and repair of machinery T Technology > TJ Mechanical engineering and machinery > TJ263.5 Boilers (general)
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21101-(S2) Master Thesis
Depositing User:	Yanuar Iswahyudi
Date Deposited:	01 Aug 2026 01:36
Last Modified:	01 Aug 2026 01:36
URI:	http://repository.its.ac.id/id/eprint/139998

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