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D.N. Adnyana
National Institute of Science and Technology (ISTN)

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FATIGUE FAILURE IN A LONGITUDINAL WELDED ELBOW OF A PROCESSING VESSEL D.N. Adnyana
Metalurgi Vol 36, No 3 (2021): Metalurgi Vol. 36 No. 3 Desember 2021
Publisher : National Research and Innovation Agency (BRIN)

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1282.24 KB) | DOI: 10.14203/metalurgi.v36i3.609

Abstract

A longitudinal welded elbow made of austenitic stainless steel type 316 and used as a drain line on a processing vessel had suffered damage (leakage) after it had only been in operation for a few years. Process fluid that was drained out of the vessel consists of fatty acid containing hydrogen gas at a temperature of 150°C and a pressure of 60 bar(g). Initially, the drain process was carried out only once a year, but recently due to frequent changes in the types of product being made, the frequency of drain process has increased to several times a month. This study aims to determine the type and factors that have caused leakage in the elbow. Metallurgical assessment was carried out by preparing a number of specimens from the leaking elbow. A number of laboratory examinations were performed including visual and macroscopic tests, chemical composition analysis, metallographic examination, hardness tests and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS) analysis. The results obtained indicate that the leaking elbow has experienced fatigue failure due to cyclic loadings caused by the increasing frequency of the number of drain processes carried out through the elbow. The factor causing fatigue failure at the elbow is likely due to welding defect of imperfect shape that formed on the inner wall of the elbow around the HAZ (heat-affected zone)/fusion boundary, and causing high stress concentrations in that area.
Leakage Investigation on a Fired Heater Tube of a Petroleum Refinery due to Carburization D.N. Adnyana
Metalurgi Vol 34, No 2 (2019): Metalurgi Vol. 34 No. 2 Agustus 2019
Publisher : National Research and Innovation Agency (BRIN)

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (663.408 KB) | DOI: 10.14203/metalurgi.v34i2.488

Abstract

The fired heater of a petroleum processing refinery leaks in one of the convection tubes. The tube is made of ASTM A-106 Gr.B. Process fluid in the tube is xylene with a design pressure of 15.8 kg/cm²g and design temperature of 299 °C (at the inlet) and 405 °C (at the outlet). This study aims to determine the type and causes and the mechanism of leakage in the tube. A number of tests have been carried out including visual inspection and  macroscopic analysis, chemical analysis, metallographic and hardness testing, and SEM (scanning electron microscopy) analysis which is equipped with EDS (energy dispersive spectroscopy). The results obtained showed that the leak that occurred in the convection tube was caused by carburization and metal dusting. Carburization occurs in the inner walls of the tube that experience some localized overheating due to the formation of coke deposits. AbstrakDapur pemanas pada sebuah kilang pengolahan minyak bumi mengalami kebocoran pada salah satu pipa konveksi. Pipa tersebut terbuat dari baja karbon rendah jenis ASTM A-106 Gr.B. Cairan proses di dalam pipa adalah xylene dengan tekanan desain 15,8 kg/cm²g dan suhu desain yaitu 299 °C (pada saluran masuk) dan 405 °C (pada saluran keluar). Penelitian ini bertujuan untuk menentukan jenis dan faktor penyebab serta mekanisme terjadi kebocoran pada pipa tersebut. Sejumlah pengujian telah dilakukan meliputi pemeriksaan visual dan makroskopik, analisa kimia, pengujian metalografi dan kekerasan, serta analisa SEM (scanning electron microscopy) yang dilengkapi dengan EDS (energy dispersive spectroscopy). Hasil penelitian yang diperoleh menunjukkan bahwa kebocoran yang terjadi pada pipa konveksi disebabkan oleh karburisasi dan pembentukan debu/serbuk logam. Karburisasi terjadi pada dinding bagian dalam pipa yang mengalami panas berlebih secara lokal akibat terbentuknya endapan kokas.