Improvement of High Temperature Oxidation of Low Carbon Steel Exposed to Ethanol Combustion Product at 700 °C by Hot-dip Aluminizing Coating

Low carbon steel (AISI 1005) was coated by hot-dipping into a molten Al-10% Si bath at 700 °C for 18s. After hotdipping treatment, the coating layers consisted of Al, Si, FeAl3, τ5-Fe2Al8Si, and Fe2Al5. The bare steel and thealuminized steel were isothermally oxidized at 700 °C in ethanol combustion product at atmospheric pressure for 49 h. The aluminized steel shows good performance in high temperature oxidation because the formation of Al2O3 layer on the coating surface. The growth of iron oxide nodules on the surface coating was accelerated by rapid outward diffusion of Fe-ions due to the presence of H2O-vapour generated by ethanol combustion. Thus, the oxidation rate of aluminized steel increased, resulting in a substantial mass-gain as the oxidation time increased. After longer exposure, the τ1-(Al,Si)5Fe3 phase was completely transformed to the FeAl in the outer layer. The FeAl formed near the steel substrate was due to Fe-atoms diffusing into the Fe2Al5 layer when the time and temperature increased

Studi Perilaku Kegagalan Sambungan Las Tipe TConjunctions Pada Baja Karbon Rendah Dengan Pendekatan Experimen Dan Numerik

This research is conducted to investigate failure behavior of welding structure in T-conjunctions type. Welding joint failures were analyzed by both experimental and finite element analysis (2D) approach in terms of stress intensity factor mode I (KI). The stress at the welding zone was strongly influenced by specimen geometries and the ratio of L/h1. The stress intensity factor (SIF) was increased significantly. Whereas, the minimum SIF of specimen #X1 and #Y3 are 58 MPa.√m and 165 MPa.√m, respectively. Failure of welding specimen was more dominated in the zone with the highest stress concentration and also affected by material discontinuity at which the stress was not generated continuously, but localized in any certain area. Specimen without welding did not yield a maximum stress. However, plastic zone formation locally decreases the stress concentration. Discontinuity in the welding specimen does not give rise to plastic stream, thus it will raise the stress concentration at the welding extension region. Discontinuity can be observed by the Von Misses stress pattern at stress welding zone for the welding specimen whereas the specimen without welding was only occurred near the extension zone

Linguistic Features as Depicted in Tulembang Mantra

Tulembang Mantra is the oldest form of literature in South Sulawesi as an aspect of ancient cultures which is still maintained up to the present time and is still used by the traditional community such as farmers. The traditional community of Makassar uses it according to its purpose. Tulembang Mantra is the form of expressions or words believed to be able to provide occult power. The power aims to give strength to human beings in carrying out various activities. The research used the recording, interview and note taking to collect the data. The population consisted of five mantras and three informants. The samples were the same as the population. The data were analyzed using the qualitative descriptive method [3]. The research result indicates that the form is a kind of praises to something occult or something that must be assumed sacred. Tulembang Mantra exerts Basmallah “in the name of Allah” and Assalamu’alaikum “peace be upon you” in general as an opening discourse. The form of discourse is more as monolog and dialog. They are used to talk to the Almighty God and ”paddy ”. As the result, mantra tends to be free in choosing the syllables, lyrics, or rhyme. “This is clear that the mantra contains acknowledgement, hope, self-cleanliness and mind, serenity, and inner satisfaction”.   Keywords: tulembang mantra, features, occult power, textual meaning, sacre

Perbandingan Hidrodinamika Flokulator Berbentuk Setengah Lingkaran Dan Persegi Panjang Pada Proses Flokulasi Menggunakan Aliran Melaluimedia Kelereng

Teori Camp & Stein menyebutkan bahwa untuk mendapatkan hasil flokulasi yang baik harus memenuhi nilai Gtd tertentu. Tetapi dalam flokulasi melalui media berbutir dengan nilai Gtd yang relatif lebih rendah dari yang disyaratkan telah didapatkan hasil flokulasi yang baik. Berdasarkan hal tersebut maka diduga ada faktor lain yang berpengaruh pada proses flokulasi menggunakan aliran melalui media berbutir selain Gtd.Penelitian ini bertujuan untuk mengetahui kinerja dari dua buah flokulator dengan media kelereng dalam aplikasinya sebagai flokulator dan mengetahui aspek hidrodinamika yang berpengaruh dalam flokulasi. Flokulator yang digunakan adalah flokulator saluran terbuka berbentuk setengah lingkaran dan flokulator saluran terbuka berbentuk persegi panjang. Variasi debit yang digunakan adalah 1 liter/menit, 1,5 liter/menit, 1,7 liter/menit, 2 liter/menit, dan 2,2 liter/menit. Metode analisis hasil penelitian yang digunakan adalah berupa analisis laboratorium dan analisis perhitungan.Penurunan kekeruhan dengan air baku buatan mencapai lebih dari 98%, dan 94,49% untuk air baku alami. Penurunan kadar organik mencapai 65,23% dan 38,10% untuk penurunan TSS. Angka kehilangan tekan yang terjadi pada flokulator berbentuk setengah lingkaran berkisar antara 0,20 hingga 6,95 cm, dan 0,60 hingga 7,85 cm untuk flokulator berbentuk persegi panjang. Nilai G berkisar antara 33,035 hingga 166,751/detik dan nilai Gtd berkisar antara 306,464 hingga 25304,741. Bilangan Reynolds yang diperoleh berkisar antara 245,392 hingga 708,225. Nilai bilangan Froude untuk kedua flokulator berkisar antara 0,030 hingga 0,064. Angka kecepatan gerusan pada flokulator berbentuk setengah lingkaran berkisar antara 0,026 hingga 0,033 cm/detik, dan antara 0,020 hingga 0,025 cm/detik untuk flokulator berbentuk persegi panjang. Waktu detensi aktual untuk kedua flokulator lebih kecil jika dibandingkan dengan waktu detensi teoritisnya

PENILAIAN KONDISI TRANSFORMATOR DAYA PADA PT.X

Transformator daya merupakan peralatan yang vital dalam penyaluran energi listrik dari unit pembangkit menuju sistem jaringan saluran tegangan. Kehandalan transformator daya sangat penting untuk keberhasilan operasi dari sistem tenaga listrik. Untuk itu dilakukan pendekatan sistematis dengan cara mengetahui kondisi peralatan komponen utama dari transformator daya tersebut. Transformator secara ideal memiliki useful life sesuai dengan design life yang direkomendasikan yaitu 30 tahun. Sedangkan transformator daya PT X sudah tidak berada dalam range useful life, dimana transformator daya tersebut diproduksi oleh Takaoka Electric pada tahun 1976. Oleh karena factor usia transformator yang sudah berumur maka diperlukan inspeksi khusus secara mendalamsebagai pendukung untuk membuat keputusan pembatasan operasi atau keputusan investasi pembangkit secara tepat dan tidak merugikan unit pembangkit itu sendiri. Untuk itu penulis melakukan serangkaian pengujian dan analisa penilaian kondisi transformator daya PT X untuk memperoleh nilai kondisi dengan mengacu  pada referensi penilaian HAP (Hydro Power Advancement Project). Hasil penilaian kondisi diharapkan nantinya akan digunakan sebagai bahan pendukung tindak lanjut pengambilan keputusan oleh PT. X

Efek Shot Peening Terhadap Korosi Retak Tegang (SCC) Baja Karbon Rendah Dalam Lingkungan Air Laut

The aim of this study is to investigate the effect of shot peening on stress corrosion cracking of a low carbon steel in ocean water environment. The dimension of specimens were prepared in accordance with the ASTM G39. The hardness testing was carried out using microvickers with 0,25 kgf load in the longitudinal direction. The corrosion cracking test was immersed into artificial sea water for about 7 months. The test shows that the pitting corrosion is dominantly nucleated at the metal film interface. The biggest pitting corrosion was occurred under the static loading of 70 for the specimens unpeened. The presence of pitting corrosion promotes stress corrosion cracking. The cracking has a intergranular branched morphology which is typical for the chloride cracking of low carbon stee