Evaluasi Desain Sistem Venting dari Manifold Truk ke Temporary Tank di Terminal LPG Semarang

Salah satu sistem perpipaan yang terdapat di Terminal LPG Semarang adalah sistem venting. Sistem venting adalah sebuah sistem yang digunakan menampung sisa LPG berasal di manifold truk. Sisa LPG yang berasal dari manifold truk kemudian dialirkan secara gravitasi dengan memanfaatkan tekanan sisa yang berada di manifold truk sebesar 8 bar melalui pipa 1”& 2” menuju temporary tank, berupa Pipa 10” yang digunakan untuk menampung sisa LPG sementara. Kemudian setelah ditampung di temporary tank, selanjutnya di pindahkan ke storage tank melalui kompresor. Sistem venting dibangun karena pada saat proses pengisian LPG di truk masih terdapat sisa LPG di manifold truk. Sebelum terdapat sistem ini biasanya gas LPG yang tersisa di manifold truk terbuang secara percuma di atmosphere. Sistem venting terdapat 2 fungsi utama yaitu keselamatan dan ekonomi. Berdasarkan fungsi keselamtan, LPG yang sebelumnya di manifold truk langsung dibuang ke atmosphere, sehingga bisa dimungkinkan terjadi kebakaran. Dampaknya sangat berbahaya baik terhadap pekerja maupun aset yang dimiliki oleh pihak Terminal LPG Semarang. Berdasarkan fungsi ekonomi jika diasumsikan per truk mempunyai sisa LPG 0.15 liter dalam manifold dan setiap hari terdapat 150 truk yang mengisi LPG di Terminal LPG Semarang, maka setiap hari terbuang 22.5 liter, setiap bulan terbuang 562.5 liter, setiap tahunya terbuang 6750 liter. Dari beberapa keuntungan sistem venting, dalam operasioanl sehari hari masih terdapat permasalahan di sistem tersebut, yaitu ketidakmampuan aliran sisa LPG untuk memenuhi volume temporary tank. Akibatnya LPG yang tersisa di manifold truk masih ada yang terbuang di atmosphere, sehingga sangat berbahaya untuk keselamatan. Berdasarkan perhitungan ASME VIII division 1, design pressure dari temporary tank di desain dengan tekanan sebesar 55 bar, namun pada keadaan aktual saat operasi pada tekanan 2.84 bar sudah tidak mampu menampung sisa LPG. Berdasarkan simulasi CFD, hasil analisa sistem venting terkait ketidakmampuan aliran sisa LPG yang berasal dari manifold truk untuk memenuhi volume temporary tank yaitu adanya pressure drop dan check valve. Terdapat dua rekomendasi desain, pertama menggunakan pompa & kompresor otomatis dan kedua menggunakan kompresor otomatis. Berdasarkan analisa ekonomi pada sistem venting, pada desain awal memiliki CAPEX sebesar Rp.67,701,000 dan OPEX sebesar Rp.16,000,000 dengan NPV Rp.2,115,178,573 ; Net B/C 6.26, sedangkan pada rekomendasi desain 1 memiliki CAPEX sebesar Rp. 20,000,000 dan OPEX sebesar Rp. 22,450,000 dengan NPV Rp 3,049,138,214 ; Net B/C 8.17 dan pada rekomendasi desain 2 memiliki CAPEX sebesar Rp. 11,450,000 dan OPEX sebesar Rp. 24,000,000 dengan NPV Rp 2,995,314,460 ; Net B/C 6.57. ===================================================================== One of the piping systems contained in the Semarang LPG Terminal is a venting system. Venting system is a system used to hold the remaining LPG from truck manifolds. The remaining LPG from truck manifolds is then channeled by gravity by utilizing residual pressure in the truck manifold of 8 bar through 1 inch and 2 inch pipes to the temporary tank, 10 inch pipes used to accommodate temporary residual LPG. Then after being accommodated in the temporary tank, then transferred to the storage tank through the compressor. Venting system is built because at the time of LPG filling process in the truck, there is still remaining LPG gas in the truck manifold. Before this system existed, the LPG gas remaining in the truck manifold was wasted in the atmosphere. Venting system has 2 main functions namely safety and economy. Based on the safety function, LPG previously in the manifold truck directly discharged into the atmosphere, so it could allow a fire. The impact is very dangerous both on workers and assets owned by the LPG Terminal of Semarang. Based on the economic function, it is assumed that truck has 0.15 liters of LPG in the manifold every day and 150 trucks each day filled LPG at Semarang LPG Terminal, 22.5 liters per day is wasted every month, 562.5 liters per year, and each year will be wasted 6750 liters. With some advantages of this venting system, in daily operation there is still a problem in the system, that is the inability of the residual flow of LPG to meet the temporary tank volume. As a result, LPG remaining in the truck manifold is still there wasted in the atmosphere, so it is very dangerous for safety. Based on ASME VIII division 1 design pressure of temporary tank is 55 bar, but in actual condition when operation at pressure of 2.84 bar is not able to accommodate the rest of LPG. Based on CFD simulation, the result of venting system analysis related to the inability of residual flow of LPG from truck manifold to meet the temporary tank volume is pressure drop and check valve. There are two design recommendations, first using automatic pumps & compressors and second using automatic compressors. Based on economic analysis on venting system, the initial design has CAPEX of Rp.67,701,000 and OPEX of Rp.16,000,000 with NPV Rp.2,115,178,573; Net B/C 6.26, while on design recommendation 1 has CAPEX of Rp. 20,000,000 and OPEX of Rp. 22,450,000 with NPV Rp 3,049,138,214; Net B/C 8.17 and on design recommendation 2 has CAPEX of Rp. 11,450,000 and OPEX of Rp. 24,000,000 with NPV of Rp 2,995,314,460; Net B/C 6.57