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Abstract

One of the key issues in the pipeline design is wall thickness calculation. This paper highlights a comparison of wall thickness calculation methods of submarine gas pipeline based on Norwegian Standard (DNV-OS-F101), Indonesian Standard SNI 3474 which refers to American Standard (ASME B31.8), and Russian Standard (VN39-1.9-005-98). A calculation of wall thickness for a submarine gas pipeline in Indonesia (pressure 12 MPa, external diameter 668 mm) gives the results of 18.2 mm (VN39-1.9-005-98), 16 mm (ASME B31.8), and 13.5 mm (DNV-OS-F101).The design formula of hoop stress due to internal pressure is interpreted in different ways for every standard. Only Norwegian Standard requires calculating hoop stresses in the inner surface, which leads to a decreased value of the wall thickness. Furthermore, the calculation of collapse factor due to external pressure is only regulated in American and Norwegian Standards while Russian Standard uses that factor as an intermediate parameter in calculating local buckling. For propagation buckling, either Russian or American Standard explains empirical formula of critical hydrostatics pressure as the input in propagation buckling calculation. This formula is almost similar to the empirical formula of Norwegian Standard. From the comparison of these standards, DNV OS-F101 gives more stringent requirements than others.

Bahasa Abstract

Perbandingan Standar Perancangan Amerika, Norwegia, dan Rusia dalam Menghitung Ketebalan Dinding Pipa Gas Bawah Laut. Salah satu parameter utama dalam perancangan jaringan pipa adalah perhitungan ketebalan dinding pipa. Studi ini membahas perbandingan metode perhitungan ketebalan dinding pipa untuk pipa gas bawah laut berdasarkan standar perancangan Norwegia (DNV-OS-F101), standar perancangan Indonesia (SNI 3474) yang mengacu pada standar Amerika (ASME B31.8), dan standar perancangan Rusia (VN39-1.9-005-98). Berdasarkan perhitungan terhadap pipa gas bawah laut di Indonesia (tekanan 12 Mpa, diameter eksternal 668 mm) didapatkan hasil ketebalan dinding pipa sebesar 18.2 mm (VN39-1.9-005-98), 16 mm (ASME B31.8), dan 13.5 mm (DNV-OS-F101). Untuk setiap standar, formula untuk hoop stress diintrepretasikan dengan metode yang berbeda. Hanya standar Norwegia yang menghitung hoop stress dari permukaan dalam pipa sehingga menghasilkan nilai ketebalan dinding pipa yang lebih kecil. Untuk perhitungan faktor collapse akibat tekanan luar, hanya standar Amerika dan Norwegia yang memperhitungkan faktor tersebut sedangkan standar Rusia hanya menggunakan faktor tersebut sebagai parameter antara untuk menghitung local buckling. Untuk propagation buckling, baik standar Rusia maupun Amerika menerapkan formula empiris tekanan hidrostatis kritis sebagai input dalam menghitung propagation buckling. Formula empiris ini hampir sama dengan formula empiris yang diterapkan pada standar Norwegia. Dari ketiga standar yang dibandingkan tersebut, standar Norwegia memberikan persyaratan desain yang lebih ketat dibandingkan yang lainnya.

References

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M. Braestrup, J.B. Andersen, L.W. Andersen, M.B. Bryndum, N-J. Nielsen, Design and Installation of Marine Pipelines, Blackwell Science, Oxford, 2005, p.384.

Det Norske Veritas.Submarine Pipeline Systems DNV OS-F101, Det Norske Veritas, Oslo, 2007, p.240.

American Society of Mechanical Engineers. Gas Transmission and Distribution Piping Systems B31.8. The American Society of Mechanical Engineers, New York, 2003, p.200.

Gazprom, Нормы проектирования и строительства морского газопровода ВН39-1.9-005-98 (Standards Design and Construction of Submarine Gas Pipeline VN 39-1.9-005-98), Moscow, 1998, p.32.

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