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Rotasi
Published by Universitas Diponegoro
ISSN : 1411027x     EISSN : 24069620     DOI : -
Core Subject : Engineering,
Mechanical Engineering
Arjuna Subject : -
Articles 676 Documents
 64   65   66   67   68 
Material characteristics and failure prediction of SA 213 Superheater Boiler tube in power plant with 315 MW capacity Nugraha, Ariyana Dwiputra; Harianto, Harianto; Suprihanto, Agus; Sulardjaka, Sulardjaka
ROTASI Vol 26, No 4 (2024): VOLUME 26, NOMOR 4, OKTOBER 2024
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.26.4.1-5

Abstract

This study was conducted at the Rembang Semarang Unit 2 power plant in Indonesia, with a capacity of 315 MW. The plant has been in operation since 2011, totaling about 13 years or over 100,000 equivalent operating hours (EOH). High-temperature operations can damage tube materials due to temperature, corrosive environment, pressure, and stress. At the end of 2022, a condenser leak at the plant necessitated an assessment of the boiler tube material. This study focuses on evaluating the SA 213 T91 (chromium (Cr) and molybdenum (Mo) alloy steel) superheater tube, a known for its excellent high-temperature mechanical and thermal properties and corrosion resistance. The research aims to assess potential failures in the boiler tube and guide future operational and maintenance plans. The analysis includes destructive testing, SEM, EDX metallography, and creep rupture testing. Results show corrosion and hard scale deposition inside the tube. Its is shown that creep strength decreases significantly at high temperatures, leading to faster material rupture.
Design and Fabrication of Jig and Fixture for Milling Operations in the Manufacturing Sector Indrawan, Rizal; Purnomo, Dhika Aditya; Bisono, Fipka; Karuniawan, Bayu Wiro; Fajardini, Ridhani Anita
ROTASI Vol 26, No 4 (2024): VOLUME 26, NOMOR 4, OKTOBER 2024
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.26.4.54-59

Abstract

Fixtures and jigs are work-holding devices used to position and support workpieces. Fixtures and jigs are important tools in production because their use determines the performance of the entire production process of a product. There are still situations in the manufacturing sector where products manufactured could be more precise. Work-holding devices that facilitate the machining process must be developed to ensure that the final products satisfy the required criteria. This study aimed to design, manufacture, and evaluate fixtures and jigs and then assess how well they worked with test specimens in rectangular shapes. The jigs and fixtures are planned based on a vacuum table that is adjusted to the machining position on the side of the material. The intention of employing a vacuum system is to simplify the process of setting up the workpiece. Fusion360 Design Software was utilized to design fixtures and jig models. Since aluminum is easy to form and has high wear resistance, it was chosen as the workpiece material. CNC machine was employed in the manufacturing process. Testing of jig and fixture tools is carried out on the side of the test specimen. According to the study's findings, jigs and fixtures accelerate the milling process on the material side. When jigs and fixtures are used, the milling process proceeds 17.47 minutes. Using this jig and fixture makes it possible to shorten the operating time, making the milling process run more quickly. Furthermore, the final product has remarkable dimensional accuracy.
Analisis Computational Fluid Dynamic (CFD) Pengaruh Overlap Ratio dan Jarak Bilah Berlapis pada Kinerja Turbin Angin Savonius Bilah Berlapis David, Jerico; Fahrudin, Fahrudin; Rhakasywi, Damora
ROTASI Vol 26, No 4 (2024): VOLUME 26, NOMOR 4, OKTOBER 2024
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.26.4.6-12

Abstract

Abstract  The demand for energy is increasing, therefore researchers are utilizing alternative energy sources such as wind energy. Savonius is a type of vertical axis wind turbine (VAWT) that is suitable for use in low wind speed conditions, making it capable of operating in urban areas. Researchers are conducting extensive studies to improve the performance of Savonius wind turbines. The Savonius wind turbine used is a Savonius wind turbine with added layered blades. This research was conducted using the computational fluid dynamics (CFD) simulation method with an existing layered Savonius wind turbine model and varied the overlap ratio and the distance between the layered blades to determine the impact of these variations on efficiency improvement using Ansys Fluent 2022 R2 software. The variations in this study included an overlap ratio of 10% with a blade distance of 33 mm and an overlap ratio of 15% with blade distances of 22 mm and 33 mm at a wind speed of 6.46 m/s. The results showed that the layered Savonius wind turbine from previous research with a configuration of a 10% overlap ratio and a blade distance of 22 mm had the best performance with a power coefficient (Cp) of 0.173 and a torque coefficient (Ct) of 0.46. The results of this study provide an understanding of the impact of increasing the value of the layered blade distance and the overlap ratio on the performance of the Savonius wind turbine, which, if not appropriate, can reduce its efficiency. Keywords: wind energy, Savonius wind turbine, layered blades, overlap ratio, distance between layered blades
The Effect Of Gear Ratio Variations And Vehicle Weight On Energy Efficiency In Electric Prototype Vehicles Of The Engineering Faculty Of Mataram University Bima, Rangga; Mara, I Made
ROTASI Vol 27, No 1 (2025): VOLUME 27, NOMOR 1, JANUARI 2025
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.27.1.23-28

Abstract

Electric vehicles are vehicles that are driven by electric motors using electrical energy derived from battery energy sources. Like most other electric vehicles, electric prototype vehicles are also controlled using throttle pedals on the steering wheel and also the braking system. This study also aims to determine how much electrical energy consumption is used in the vehicle, by varying the gear ratio and vehicle weight. The test method was carried out by releasing the throttle when the vehicle reached maximum speed, with the aim of being able to produce a lower level of energy consumption with higher efficiency. Gear ratio variations used were 6.43; 7.56; 8.57; 9.08 and 10.20 and vehicle weight variations used were 120.5 kg; 130.5 kg and 140.5 kg. The results of the test show that if the smaller the gear ratio used and the heavier the load from the vehicle, the greater the energy required. The results of this study indicate that, vehicles with lighter weight and with the use of larger gear ratio variations can reduce the consumption of electrical energy used. And can increase higher energy efficiency, so as to increase the maximum mileage range of the vehicle. The findings from this study can also provide additional information and valuable insights in the development of more efficient electric vehicles in the future.
Analisis Perbandingan Kontak Mekanik pada Permukaan Sinusoidal dengan Variasi Kondisi Pelumasan Menggunakan Metode Elemen Hingga Anwar, Syaiful; Lamura, M. Danny Pratama; Jamari, Jamari; Bayuseno, Athanasius Priharyoto
ROTASI Vol 27, No 1 (2025): VOLUME 27, NOMOR 1, JANUARI 2025
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.27.1.1-7

Abstract

Studi tentang kontak antara dua permukaan sangat menarik untuk dipelajari karena berhubungan dengan gesekan, pelumasan, dan keausan. Mekanika kontak berperan sangat penting dalam bidang tribologi. Penelitian ini bertujuan untuk mengetahui fenomena-fenomena yang terjadi pada pemodelan entrapped oil dalam kondisi kontak kering dan kontak berpelumas pada geometri sinusoidal. Proses simulasi dilakukan menggunakan Finite Element Method (FEM) dengan bantuan software Abaqus CAE 2020. Bentuk geometri dimodelkan sebagai axisymmetric 2D dengan ukuran elemen 0,01 untuk plat kaku dan 0,0005 untuk model geometri. Penelitian dilakukan pada model dengan ketinggian 2 mm dan memiliki kedalaman cavity 0,02 mm yang diberikan tekanan (0,5 MPa - 640 MPa) dari bawah model. Penelitian ini meninjau hasil von Mises stress, contact area, dan deformasi pada setiap kondisi variasi. Hasil penelitian menunjukkan bahwa model sinusoidal pada kontak berpelumas menghasilkan nilai von Mises stress, contact area, dan deformasi yang lebih kecil dibandingkan model sinusoidal pada kontak kering. Pada parameter tegangan von Mises, variasi kondisi pelumasan yang diterapkan menghasilkan perbedaan sebesar 28,41%. Sementara itu, untuk parameter area kontak dan deformasi, perbedaan kondisi pelumasan memberikan perbedaan hasil masing-masing sebesar 42,79% dan 16,46%. Analisis ini sangat penting bagi para peneliti untuk memahami pengaruh signifikan pelumas dalam kontak mekanik.
Pengembangan Under Water Remotely Operated Vehicle (UWROV) untuk Eksplorasi Lingkungan Bawah Air Kedalaman Rendah Christiand, Christiand; Caesko, Hulio; Arbiyani, Filian
ROTASI Vol 27, No 1 (2025): VOLUME 27, NOMOR 1, JANUARI 2025
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.27.1.8-14

Abstract

Aktifitas observasi pada lingkungan bawah air selain dapat dilakukan secara langsung dengan penyelaman manusia, dapat juga dilakukan dengan sebuah kendaraan yang disebut sebagai under water remotely operated vehicle (UWROV). Kendaraan tersebut dapat dikendalikan dari jarak jauh dan dilengkapi dengan berbagai sensor dan mekanisme untuk menggantikan fungsi manusia pada kegiatan eksplorasi. Kerja penelitian yang dipaparkan pada artikel ini telah mengembangkan sebuah UWROV yang ditujukan untuk lingkungan bawah air yang tidak terlalu besar, seperti danau air tawar dengan kedalaman rendah serta danau-danau buatan pada area tertentu. UWROV yang telah dikembangkan berukuran kecil dan mengutamakan pemilihan material yang mudah didapat di pasaran sehingga berbiaya murah. Pada eksperimen yang telah dilakukan, UWROV dapat melakukan maneuver dengan kecepatan 0.2 m/detik untuk gerak linear dan 1.2 rad/detik untuk gerak putar atau berbelok. UWROV juga mampu mempertahankan posisi diam melayang dengan deviasi posisi sebesar 0.015 meter pada sumbu-z (vertikal) ruang kerja. 
Evaluation of Motorcycle Fueled with Blends of Gasoline and Pyrolytic Oil from Plastic‒Palm Kernel Shell Co-Pyrolysis Thoharudin, Thoharudin; Santosa, Tito Hadji Agung; Iswandi, Iswandi
ROTASI Vol 27, No 1 (2025): VOLUME 27, NOMOR 1, JANUARI 2025
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.27.1.15-22

Abstract

This study explores the co-pyrolysis of plastic grocery bags and palm kernel shells (PKS) as a sustainable solution for addressing plastic waste and producing renewable energy. A stainless-steel batch reactor operating at 500oC produced pyrolytic oil, char, and non-condensable gases, with a product yield of 48.3%, 26.7%, and 25.0%, respectively. Pyrolytic oil was characterized by higher viscosity, density, and oxygen content but a lower heating value compared to gasoline (pertalite). Various blends of pyrolytic oil (0–30%) with pertalite were tested in a 108 cc motorcycle engine. While pure pertalite offered better torque and power at low speeds, pertalite with 10% and 20% pyrolytic oil showed comparable engine performance at low to medium rotational speeds and better performance at high rotational speeds. In addition, blends with higher pyrolytic oil concentrations improved fuel efficiency, with the 30% blend achieving the best fuel economy at 33.3 km/L. The study concludes that pyrolytic oil can be a viable alternative fuel for motorcycles, particularly in carburetor systems, but requires further refinement to address particulate content and enhance compatibility with fuel injection systems.
Distribusi Udara dan Panas, Pengering Rumah Kaca, Rak Susun, CFD Ismail, Ismail; Purwanto, Agus
ROTASI Vol 27, No 1 (2025): VOLUME 27, NOMOR 1, JANUARI 2025
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.27.1.44-51

Abstract

Penelitian ini menganalisis distribusi udara dan panas yang terjadi pada pengering surya tipe rumah kaca dan rak susun. Analisis dilakukan dengan metode simulasi menggunakan software Computational Fluid Dynamics (CFD) dan dilanjutkan dengan eksperimen. Simulasi dilakukan pada kedua jenis pengering dengan memvariasikan temperatur udara masuk, kecepatan hisap kipas, posisi serta ukuran inlet dan outlet, suhu yang diambil sebagai variabel pengamatan pada simulasi penelitian ini adalah 30oC dan dengan 3 variasi kecepatan aliran udara pada kedua pengering (1, 3, dan 5 m/s). Hasil dari simulasi ini digunakan sebagai basis untuk melakukan eksperimen pengeringan irisan tomat dan kentang. Alat pengering dibuat dengan ukuran masing-masing 95 x 48 x 68 cm untuk rumah kaca dan 95 x 48 x 48 cm untuk rak susun, dengan ukuran inlet dan outlet sama pada keduanya, yaitu 11,5 x 11,5 cm untuk outlet dan 40 x 6 cm untuk bagian inlet. Berat sampel yang akan diuji dengan menggunakan 2 alat pengering ini masing-masing 1 kg tomat dan kentang. Hasil eksperimen yang telah dilakukan didapatkan data pengeringan dengan menggunakan rak susun lebih unggul sekitar 1,8% - 2,97% dalam hal pengurangan massa, dan 0,01 - 0,23oC untuk suhu, serta 0,46 - 0,61% untuk humidity, dibandingkan dengan pengering rumah kaca.
Back Matter Rotasi Vol. 26 No. 4 Oktober 2024 Sari, Ika Ayu Wulan
ROTASI Vol 26, No 4 (2024): VOLUME 26, NOMOR 4, OKTOBER 2024
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.26.4.App. 1-4

Abstract

Front Matter Rotasi Vol. 26 No. 4 Oktober 2024 Sari, Ika Ayu Wulan
ROTASI Vol 26, No 4 (2024): VOLUME 26, NOMOR 4, OKTOBER 2024
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.26.4.i-v

Abstract

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