Analisa response transient cascade control temperature dan pressure pada furnace PT. Z menggunakan metode direct synthesis

Furnace pada PT. Z adalah furnace yang berfungsi untuk memanaskan heavy naptha hingga mencapai temperature 513℃ sebelum masuk ke rekator. Pada furnace menggunakan sistem pengendalian cascade temperature dan pressure untuk menjaga temperature outlet furnace dengan mengatur besarnya tekanan fuel gas untuk proses pembakaran yang masuk ke furnace. Temperatur Indicator Controller berperan sebagai master control yang memiliki aksi direct dengan mode controller Proportional Integral Derivative (PID) yang dalam kondisi operasinya mempunyai nilai Kp=75, τi=375, τd=2. Sedangkan Pressure Indikator Controller berperan sebagai sleve control yang memiliki aksi direct dengan mode controller Proportional Integral Derivative (PID) yang dalam konsisi operasinya mempunyai nilai Kp=1000, τi=1500, τd=0. Dari hasil simulasi menggunakan kondisi aktual diperoleh delay time 16,302s, settling time 2,8288s, rise time 0,2686s serta terdapat overshoot 19,880% dan undershoot 1,725%. Sedangkan hasil simulasi menggunakan metode direct synthesis diperoleh delay time 33,445s, settling time 10,5639s, rise time 5,557s, overshoot 0,0054% dan tidak terdapat undershoot. Berdasarkan perbandingan antara kondisi aktual dan metode direct synthesis dilihat bahwa walaupun terdapat keterlambatan untuk mencapai kondisi steady state namun dengan metode direct synthesis ini, dapat menghilangkan keadaan overshoot dan undershoot yang muncul pada kondisi aktual yang dianggap dapat mengurangi kinerja sistem. Oleh karena itu metode direct synthesis bisa dikatakan mempunyai respon sistem yang baik. ABSTRACT Furnace at PT. Z is a furnace whose function is to heat heavy naptha to a temperature of 513℃ before entering the reactor. The furnace uses a cascade temperature and pressure control system to maintain the furnace outlet temperature by regulating the amount of fuel gas pressure for the combustion process that enters the furnace. The Temperature Indicator Controller acts as a master control which has direct action with Proportional Integral Derivative (PID) controller mode which in operating conditions has values Kp=75, τi=375, τd=2. Meanwhile, the Pressure Indicator Controller acts as a control arm which has direct action with Proportional Integral Derivative (PID) controller mode which in its operating conditions has the values Kp=1000, τi=1500, τd=0. From the simulation results using actual conditions, the delay time was 16.302s, settling time was 2.8288s, rise time was 0.2686s and there was an overshoot of 19.880% and an undershoot of 1.725%. Meanwhile, the simulation results using the direct synthesis method obtained a delay time of 33.445s, settling time of 10.5639s, rise time of 5.557s, overshoot of 0.0054% and no undershoot. Based on a comparison between actual conditions and the direct synthesis method, it can be seen that although there is a delay in reaching steady state conditions, the direct synthesis method can eliminate overshoot and undershoot conditions that appear in actual conditions which are considered to reduce system performance. Therefore, the direct synthesis method can be said to have a good system response.