1,720,960 research outputs found
Analisa Kegagalan Pipa Udara A312 Tipe 304H Pada Line A-1011-14” (25P2J) Unit Amonia PT. Petrokimia Gresik
No full textLine A-1011-14”(25P2J) menggunakan pipa tahan karat TP304H berdiameter 14 inch. Pipa mengalami pecah saat beroperasi pada temperatur 800oC (overheating) dan crack ditemukan pada hampir semua sambungan las. Kegagalan pipa dievaluasi dengan metode RCFA (root cause failure analysis) didukung pengujian Metalografi, SEM-EDX, dan OES. Metode ini digunakan untuk mengetahui akar penyebab kegagalan pipa udara TP304H pada line A-1011-14”(25P2J). Hasil analisa didapat adanya pre-existing crack mengakibatkan tegangan pipa 12978.55 psi masih di bawah tensile strength material TP304H pada temperatur 800oC yaitu 18000 psi. Hasil pengujian SEM dan metalografi menyatakan bahwa, kegagalan yang terjadi pada las longitudinal diakibatkan adanya IGSCC (intergranular stress corrosion cracking) yang mengakibatkan batas butir mengalami sliding, dan terjadi penurunan kekuatan pada material. Adanya sensitisasi dibuktikan dengan pengujian EDX yang menunjukkan kenaikan persentase unsur krom dan karbon pada batas butir yaitu 1.4% dan 21.64%. Untuk menghindari kegagalan yang sama, maka material TP304H welded pipe perlu diganti TP304H seamless pipe. Crack yang terjadi pada las circumferential diakibatkan adanya IP (incomplete penetration) yang menyebabkan tumbuhnya crack yang menjalar dari ujung IP menuju fusion zone, untuk mencegah hal tersebut maka setiap proses pengelasan yang dilakukan harus disesuaikan dengan prosedur.</p
Analisa Kegagalan Poros Pompa Centrifugal Multistage (GA101A) Sub Unit Sintesa Urea PT. Petrokimia Gresik
No full textAmonia Feed Pump GA101A merupakan pompa jenis centrifugal multistage dan merupakan salah satu critical equipment pada pabrik urea PT. Petrokimia Gresik. Kegagalan yang terjadi pada pompa GA101A adalah patahnya poros. Patah poros pompa dianalisa dengan melalui beberapa tahapan, yaitu pengamatan makroskopis, melakukan pemodelan CAD, kemudian melakukan analisa Finite Element. Analisa thermal expansion yang dilakukan yakni dengan membandingkan material ring sebelum dan sesudah modifikasi serta mengetahui thermal expansion yang terjadi pada poros. Dari analisa didapatkan mekanisme yang menyebabkan poros pompa GA101A patah, yaitu vibrasi tinggi pada pompa yang menyebabkan gesekan dan kenaikan temperatur melebihi temperatur kerja pompa. Temperatur akibat gesekan menyebabkan ekspansi material kedua komponen, sehingga ring mengunci poros hingga akhirnya patah. Langkah preventif dari hasil analisa adalah memperbesar clearance poros-ring sebesar 0.40mm tanpa mengganti jenis material, yakni Stainless Steel 304, sedangkan jika dengan material Stainless Steel 410 clearance minimal yang dibutuhkan adalah sebesar 0.35mm
Studi Quenching Media pada proses Hardening Material Baja Paduan SKJ Mod
Full text linkSalah satu faktor yang dapat mempengaruhi nilai kerasan material pada Hardening adalah
kemampuan cooling rate dari Quenching Media. Paper ini akan mencoba melakukan studi
Quenching Media alternatif dengan harga relatif murah dan memiliki karakteristilc minimal
mendekati Quenching Media standard seperti Issodur 220. Quenching Media alternatifyang dipilih
adalah oli Mesin baru. Oli Mesin bekas. oli Gardan Baru dan bekas. Pada tahap awol dilakukan
pengamatan lcecepatan pendinginan Quenching media alternaitf terse but. kemudian dibandingkan
dengan Quenching Media bermerek yaitu Issodur 220. Hasil percobaan diperoleh data bahwa
cooling rate keempat Quenching Media alternatif dan sebuah Quenching Media Issodur 220 adalah
sebagai berikut: oli mesin bekas memiliki kecepatan pendinginan 48.6° per detik, oli bekas gardan
mampu mendinginkan material uji dengan Ieece paton pendinginan 44'C per detik. Sedangkan jika
dibanding dengan kemampuan pendinginan Quenching Media Issodur 220 yaitu 56 per detik, maka
oli mesin bekas diperkirakan memiliki kemampuan sebagai Quenching Media. Tahap berikutnya
adalah menguji kemampuan Quanching media dalam mengeraskan material uji. oli Mesin bekas
mampu mengeraskan Baja SKJ Mod sampai dengan 60 HRC. sedangkan tiga oli quenching yang
lain hanya dapat menghasilkan dibawah 58 HRC. Jika dibanding dengan lssodur 220. dimana
dalam penggunaannya dapal menghasilkan kekerasan material 62 HRC. maka oli Mesin bekas
dapat menjadi Quenching media alternatif dengan capaian kemampaun mengeraskan mendekati
Issodur 220
Optimasi Temperatur Pemanasan Dan Holding Time Serta Media Pencelupan Terhadap Kekerasan Material SK3 Mod Dengan Metode Respon Surface
Full text linkHeating temperature(Quenching temperature), holding time and cooling rate(cooling rate)is an important process parameter in the hardening processes, to obtain maximum hardness number of materials.To determine the optimum parameters influenced by the type of material, process conditions and quenching media. Different process conditions, then the process parameters should also be defined with different process parameters.Thus experiments on the process of hardening steel materials Mod SK3 is done to get the setting parameters of the optimum quenching temperature and holding time. Optimization of process parameters using Response Surface methode. The experimental results: if the cooling media (cooling fluid) used "engine oil", the optimal parameter is "quencing temperature -828.9 °C, holding time - 40.12198 minutes (40 minutes 8 seconds).If the cooling media used lssodur 2.20, the optimal process parameters are "quencing temperature" - 832.88 °C, holding time - 39 818 minutes (39 minutes SO seconds). Kekerasaan maximum material that can be achieved is 59.7 HRC (quenching media:"engine oil") and 62.2 HRC (quenching media:"ussodur 220")
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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