Pribadi, Wahyu (2021) Analisa Kegagalan Material L-1 Blade Low Pressure Steam Turbin Dan Pengaruh Kemampuan Daya Pembangkit Dengan Simulasi Tempo Cycle 5.1 (Studi Kasus PLTU Pangkalan Susu - Medan). Masters thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Energi listrik menjadi salah satu elemen penting untuk meningkatkan perekonomian di Indonesia. Salah satu teknologi yang dipakai untuk membangkitkan energi listrik adalah Pembangkit Listrik Tenaga Uap. Uap bertekanan yang diproduksi oleh boiler digunakan untuk memutar turbin yang dikopel menjadi satu dengan Generator sehingga menghasilkan energi listrik. Kehandalan turbin uap saat operasi sangat penting sehingga kegagalan turbin saat beroperasi sangat dihindari.
Turbin blade yang terbuat dari stainless steel AISI 422 pada low pressure turbin stage L-1 pada PLTU Pangkalan Susu unit 1, Medan, Sumatera Utara mengalami retak pada sisi leading edge di sisi governor dan generator. Lokasi retakan tersebut berjarak 317 mm – 379 mm dari root blade turbin dan terjadi pada baris stage L-1. Kegagalan ini terjadi saat usia turbin masih muda yaitu 3 tahun (26.376 OH) semenjak Comercial Operation Date (COD) pada tahun 2015, padahal turbin di desain untuk beroperasi selama 30 tahun. Pengujian visual, metalografi dan Scanning Electron Microscope (SEM) dilakukan untuk melihat fraktografi dan struktur mikro. Pengujian hardness dilakukan untuk mengetahui perubahan sifat mekanik pada baja yang mengalami retakan. Spectrometry pada material ditujukan untuk mengetahui komposisi kimia dan kaitannya dengan persyaratan standar material blade. Analisa termodinamika dibantu dengan simulasi tempo cycle 5.1 diharapkan dapat membantu menganalisa perubahan beban pembangkit optimal yang diijinkan.
Hasil pengujian nondestructive testing magnetic particle dan liquid penetran test menunjukkan adanya pola retakan di area leading edge disertai bintik erosi. Inisiasi awal retakan terdeteksi pada sisi leading edge yang merambat tegak lurus sampai 21 mm dari lebar blade 100 mm. Pengujian kekerasan menunjukkan adanya sedikit kenaikan kekerasan sampai 358,7–385 HB pada sisi leading edge dekat retakan bila dibanding dengan kekerasan dari standar material dengan angka kekerasan sebesar 293 - 341 HB. Dari pengamatan visual, metalografi dapat ditelusuri bahwa kegagalan retakan pada L-1 turbine blade terjadi awalnya karena adanya direct contact akibat aliran fluida yang mengenai blade sisi leading edge. Hal ini menyebabkan terjadinya perubahan sifat material yaitu naiknya kekerasan sehingga menjadi lebih getas. Keretakan blade ini terjadi pada 4,75.109 cycle yang merupakan kegagalan jenis high cycle fatigue akibat pembebanan rendah, temperature rendah dan terjadi di daerah deformasi elastis. Hasil Scanning Electron Microskop (SEM) tidak ditemukan adanya unsur impurities yang bersifat korosif. Pemotongan turbine blade baris L-1 sisi generator dan sisi governor untuk menjaga kehandalan unit bisa beroperasi. Dampak pemotongan blade baris L-1 dianalisa dengan termodinamika menggunakan software Tempo Cycle versi 5.1 menunjukkan terjadinya penurunan beban pembangkit 85,71% pada maximum continuous rating (MCR) dari desain pembangkit sehingga daya maksimun nett yang mampu dihasilkan menjadi 173,48 MW.
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Electrical energy is one of the important elements to improve the economy in Indonesia. One of the technologies used to generate electrical energy is the Steam Power Plant. The pressurized steam produced by the boiler is used to turn the turbine which is coupled with the generator to produce electrical energy. The reliability of the steam turbine during operation is very important so that failure of the turbine while operating is avoided. The turbine blade made of stainless steel AISI 422 on the low pressure turbine stage L-1 at PLTU Pangkalan Susu unit 1, Medan, North Sumatra experienced cracks on the leading edge on the governor and generator side. The location of the crack is 317 mm – 379 mm from the turbine blade root and occurs in the L-1 stage row. This failure occurred when the turbine was still young, namely 3 years (26,376 OH) since the Commercial Operation Date (COD) in 2015, even though the turbine was designed to operate for 30 years. Visual, metallographic and Scanning Electron Microscope (SEM) tests were carried out to see the fractography and microstructure. Hardness testing is carried out to determine changes in the mechanical properties of cracked steel. Spectrometry on the material is intended to determine the chemical composition and its relation to the standard requirements of blade materials. Thermodynamic analysis assisted by tempo cycle 5.1 simulation is expected to help analyze the changes in the allowable optimal generator load. The results of the non-destructive testing of magnetic particle and liquid penetrant tests showed a crack pattern in the leading edge area with erosion spots. The initial crack initiation is detected on the leading edge which propagates perpendicular to 21 mm from the blade width of 100 mm. The hardness test showed a slight increase in hardness up to 358.7–385 HB on the leading edge near the crack when compared to the hardness of the standard material with a hardness number of 293 - 341 HB. From visual observation, metallography can be traced that the failure of cracks in the L-1 turbine blade occurred initially due to direct contact due to fluid flow hitting the blade on the leading edge. This causes changes in material properties, namely increasing hardness so that it becomes more brittle. This blade crack occurs at 4,75,109 cycles, which is a type of high cycle fatigue failure due to low loading, low temperature and occurs in the elastic deformation area. The results of the Scanning Electron Microscope (SEM) did not find any corrosive impurities. Cutting the turbine blade of the L-1 row of the generator side and the governor side to maintain reliable operation of the unit. The impact of cutting the blade of the L-1 row, which was analyzed by thermodynamics using Tempo Cycle software version 5.1, showed a decrease in generating load of 85.71% at the maximum continuous rating (MCR) of the generator design so that the maximum net power that could be generated was 173.48 MW.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | Kegagalan, Retak, Low Pressure Turbine, Turbine Blade, High Cycle Fatigue, Tempo cycle 5.1,Failure, Crack, Low Pressure Turbine, Turbine Blade, High Cycle Fatigue, Tempo cycle 5.1 |
| Subjects: | T Technology > T Technology (General) > T57.62 Simulation T Technology > T Technology (General) > TA404 Materials--Biodegradation T Technology > TJ Mechanical engineering and machinery > TJ164 Power plants--Design and construction T Technology > TJ Mechanical engineering and machinery > TJ266 Turbines. Turbomachines (General) |
| Divisions: | Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21101-(S2) Master Thesis |
| Depositing User: | Mr Wahyu Pribadi |
| Date Deposited: | 25 Aug 2021 06:59 |
| Last Modified: | 17 Sep 2024 09:31 |
| URI: | http://repository.its.ac.id/id/eprint/90343 |
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