PENENTUAN UKURAN CONTROL VALVE PADA UNIT PENGOLAHAN AIR BEBAS MINERAL IRADIATOR GAMMA PRFN

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ABSTRAK

PENENTUAN UKURAN CONTROL VALVE PADA UNIT PENGOLAHAN AIR BEBAS MINERAL IRADIATOR GAMMA PRFN. Instalasi air bebas mineral (demineralized water) berfungsi untuk mengolah air baku menjadi air bebas mineral menggunakan resin ion exchange, yang digunakan untuk keperluan pendingin dan perisai radiasi gamma. Air tersebut akan dialirkan pada kolam Iradiator melalui beberapa peralatan yang salah satunya adalah control valve yang berfungsi sebagai final control element. Air dalam kolam iradiator harus tetap terjaga levelnya, dimana low levelnya tidak boleh lebih rendah dari 30 cm. Untuk menentukan control valve yang sesuai dengan proses tersebut maka dilakukan penentuan ukuran (sizing) terlebih dahulu yaitu mengetahui nilai Cv (Coefisient valve) pada Control Valve. Untuk melakukan perhitungan/sizing pada control valve harus mengacu pada standart ISA: S75.01-1985 “Flow Equations for Sizing Control Valves”. Dari hasil perhitungan secara analitis berdasarkan persamaan pada standart ISA tersebut, dan dari perhitungan secara numerik menggunakan software first vue (fsm) diperoleh nilai Cv sebesar 6.31 pada kondisi normal operasi dengan ukuran valve 1 inci. Nilai Cv tersebut menunjukan pada kondisi normal, control valve bekerja pada bukaan katup sebesar 63%. Tipe control valve yang digunakan adalah globe valve, karakteristik alirannya equal percentage, prinsip kerjanya air to open. Dari hasil tersebut penggunaan control valve ukuran 1 inch telah sesuai karena tidak menimbulkan efek kavitasi ataupun flashing pada control valve yang dapat menimbulkan pemilihan material khusus dan berefek pada nilai ekonomis.

Kata kunci: iradiator gamma, kolam iradiator, tangki penampungan, pengolahan air bebas mineral, control valve.

ABSTRACT

SIZING CONTROL VALVE ON DEMINERALISED WATER PROCESS FOR GAMMA IRRADIATOR PLANT OF PRFN. Installation of demineralized water is used to process the raw water into demineralized water using ion exchange resins which is used as coolant and gamma radiation shielding. The water will flow into the irradiator’s pool through several equipment in which one of them is a control valve which serves as the final control element. Water level of irradiator’s pool should be maintained, where the low level of water irradiator pool should not be lower than 30 cm. To select the control valve in accordance with the system, the first step is the determination of the size (sizing) which is to determine the value of Cv (Coefisient valve) on the Control Valve. For sizing the calculation of the control valve, it should refer to the standard ISA: S75.01-1985 "Flow Equations for Sizing Control Valves". From the result of analytical calculations according to the equation in standard ISA and the numerical calculation using the software first vue (FSM) is obtained Cv value of 6.31 on condition normal operation with a valve size is 1 inch. The Cv value indicates at normal condition in which the Control Valve working is at valve opening 63%. The type of control valve used is a Globe valve, flow characteristic is equal percentage, and working principle is air to open. From the calculation of Cv Control Valve for this application using Control Valve with size 1 inch is already suitable because it does not have the appropriate effect cavitation or flashing on Control Valve which can lead to the selection of specific materials and affect on its economic value.

Keywords: gamma irradiator, irradiator’s pool, reservoir tank, demineralized water process, control valve