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Abstrak :
[Jaringan pipa adalah salah satu sarana transportasi minyak dan gas yang paling aman dan ekonomis sehingga pipa tidak boleh mengalami kegagalan saat beroperasi. Pipa sambungan dalam suatu pipeline adalah pipa dengan geometri yang paling sering dijumpai. Jalur pipa transmisi biasanya ditanam didalam tanah (underground) sehingga rentan terhadap korosi eksternal. Oleh karena itu perlu dilakukan analisis keandalan, terutama pada geometri sambungan. Pengujian keandalan dilakukan dengan menggunakan simulasi Monte Carlo. Untuk mengetahui pengaruh tanah terhadap laju korosi pipa maka dilakukan pengukuran pH , resistivitas tanah dan laju korosi pipa pada setiap segmen. Hasil dari pengukuran laju korosi pipa sambungan kemudian dibandingkan dengan laju korosi pipa sambungan. Pengamatan mikrostruktur dilakukan untuk mengetahui penyebab perbedaan laju korosi kedua jenis pipa tersebut. Nilai resistivitas tanah pada segmen I berada pada level very corrosive 􀀋􀀟􀀘􀀓􀀓􀈍-cm), segmen II berada pada level corrosive (500-􀀔􀀓􀀓􀀓􀀃 􀈍-cm), dan segmen II berada pada level moderately corrosive (1000-􀀕􀀓􀀓􀀓􀀃􀈍-cm). Nilai pH berada pada rentang 5-7 untuk semua segmen. Laju korosi pipa sambungan meningkat seiring penurunan nilai resistivitas tanah, dengan range nilai antara 0.03-0.75 mm / year. Keandalan pipa sambungan pada segmen adalah 34,53%, segmen II adalah 64,04%, dan segmen III adalah 99,78%, Pipeline is one mean of oil and gas transportation which is the most safe and economical so that the pipe should not fail during operation. Tee pipe in the pipeline is a pipe which geometry is the most frequently encountered. Transmission pipelines are usually planted in the ground (underground) so that it is susceptible to external corrosion. Therefore it is necessary to perform the reliability analysis, especially in a tee geometry. Reliability testing was done using Monte Carlo simulations. To determine the influence of soil on the rate of corrosion of pipes, the measurements of pH, soil resistivity and corrosion rate of pipes on each segment were carried out. Results of tee pipe corrosion rate measurements were then compared with the corrosion rate of the straight pipe. Microstructural observations was performed to determine the cause of differences in the corrosion rate of the two types of pipe. Soil resistivity values in the segment I was at the very corrosive level 􀀋􀀟􀀘􀀓􀀓􀈍-cm), segment II at the corrosive level (500-􀀔􀀓􀀓􀀓􀀃 􀈍-cm), and segment II at the moderately corrosive level (1000-2000 􀈍-cm). pH value was in the range 5-7 for all segments. Tee pipe corrosion rate increases with the decreasing of soil resistivity values, ranging between 0.03-0.75 mm / year. Reliability tee pipe segment was 34,53%, segment II was 64,04%, and segment III was 99,78%]

Abstrak :
Pipa elbow biasanya digunakan sebagai sambungan (fitting) ketika terjadi perubahan orientasi yang cukup ekstrim pada jalur pipa transmisi. Jalur pipa transmisi biasanya ditanam didalam tanah (underground) yang rentan terhadap korosi eksternal sehingga perlu dilakukan analisis keandalan. Analisis keandalan dilakukan dengan menggunakan simulasi Monte Carlo dengan terlebih dahulu mengukur pH, resistivitas tanah dan menghitung laju korosi eksternal. Keandalan pipa elbow pada segmen I adalah 39.56%, segmen II adalah 75.68%, dan segmen III adalah 99.99% Nilai resistivitas tanah pada segmen I berada pada level very corrosive (<500Ω-cm), segmen II berada pada level corrosive (500-1000 Ω-cm), dan segmen III berada pada level moderately corrosive (1000-2000 Ω-cm). Nilai pH berada pada rentang 5-7 untuk semua segmen. Laju korosi pipa elbow berkisar antara 0.029-0.765 mm/year, dan meningkat seiring penurunan nilai resistivitas tanah. Pengamatan struktur mikro menunjukkan ukuran butir pipa elbow adalah sebesar 16,5 µm. Hasil permodelan Autodesk Inventor memperlihatkan bahwa terjadi konsentrasi tegangan pada pipa sebesar 160 MPa , sementara itu hasil permodelan Caesar II.5.1 menunjukkan bahwa bending stress pada pipa elbowmerupakan stress paling tinggi (666-679 kg./sq. cm) pada saat kondisi operasi. ......Elbow pipe is commonly used as fitting when pipeline shows an extreme change on its direction. Generally, transmission pipeline is buried underground which severe to external corrosion, thus reliability analysis is required. Reliability analysis was performed by using Monte Carlo simulation by first measured pH, soil resistivy and external corrosion rate. Reliability of elbow pipe at segment I was 39.56%, segment II was 75.68%, and segment III was 99.99%. Soil resistivity value at segment I was on very corrosive level (<500Ω-cm), while segement II was on corrosive level (500-1000 Ω-cm), and segment III was on moderately corrosive level (1000-2000 Ω-cm). pH value ranged from 5-7 for all segments. Corrosion rates ranged from 0.029-0.765 mm/year, and increased gradually as decreased of its soil resistivity value. Microstructure examination showed that grain size on elbow pipe was 16,5 µm. Autodesk Inventor modelling revealed that stress concentration was occured on innert side of elbow pipe as much as 160 MPa , while Caesar II.5.1 modelling showed that bending stress was the highest stress (666-679 kg./sq. cm) in operating condition.