Makalah ini mengkaji besarnya tegangan yang terjadi pada sistem perpipaan, beban pada nosel pompa dan tegangan lokal pada evaporator. Kajian bersifat statik tersebut dilakukan karena adanya kesalahan instalasi penempatan evaporator yang tidak sesuai perencanaan. Analisa tegangan yang dilakukan mencakup tegangan akibat beban sustain dan tegangan akibat beban ekspansi thermal. Analisa tegangan sistem perpipaan mengacu pada ketentuan ASME B31.3, analisa beban nosel pompa mengacu pada ketentuan API 610, dan analisa tegangan lokal pada evaporator mengacu pada ketentuan WRC 107. Dari hasil analisa tegangan diperoleh bahwa besarnya tegangan akibat beban sustain dan ekspansi thermal masih memenuhi kriteria tegangan ijin. Dari hasil analisa beban nosel pada pompa diketahui nilai yang melebihi ketentuan ijin, dan dari hasil analisa tegangan lokal diketahui besarnya tegangan lokal nosel evaporator masih memenuhi besarnya tegangan ijin. Sehingga dapat dikatakan bahwa efek pergeseran posisi evaporator saat instalasi menyebabkan besarnya beban nosel pompa berlebih, namun dari sisi tegangan sistem perpipaan tidak megalami perubahan siknifikan.

Thepiping system is a medium used to convey, distribute, mix, separate, discharge, meter, control or snub fluid flows, and transmit a fluid pressure. The piping system design will have stresses due to thermal and pressure effect. The thermal effect induce pipe expansion. The pipe expansion affect to pipe flexibility, so it is necessary to design an expansion loop. Expansion loop is a method used to increase flexibility in piping systems. This article aims to analyze symmetrical and non-symmetrical in vertical expansion loops whether it can increase flexibility and reduce pipe stress. This article conducts an expansion loop design with 3 trials, namely trial 1 (Vertical Expansion Loop), trial 2 (Nonsymmetrical Vertical Expansion Loop 1), and trial 3 (Nonsymmetrical Vertical Expansion Loop 2). The three trials were compared for flexibility and stress values based on ASME B31.3 requirements. The study results show that all trial 1, trial 2, and trial 3 have good flexibility with a value of 0.00016 because not exceed the requirements of ASME B31.3. The highest design code stress value in trial 1 is 5955 psi (Node A07F), trial 2 is 5906 psi (Node A05F), and trial 3 is 5906 psi (Node A06N). All trials have a code stress not exceeding the allowable stress (20000 psi). So that the symmetrical or nonsymmetrical design of the vertical expansion loop can both increase flexibility and reduce pipe stress.

The berthing and unberthing process of a shuttle tanker on the FSO unit has its difficulties if the FSO unit is between several mooring lines. This is an early study to simulate the berthing and unberthing of a 5000 DWT shuttle tanker at the FSO unit without going through the mooring ropes and still comply with the requirements of PIANC berthing speed. The manoeuvring simulation was based on a mathematical manoeuvring group model that used the effects of the propeller and rudder. The model simulated the percentage and direction of force and moment of tugboats to perform the manoeuvring properly. The model assumed the environmental disturbances of wind, current, and wave as the constant values and applied three scenarios of the current direction. As a case study, the berthing and unberthing manoeuvre of a 50000 DWT export tanker need two tugboats with the capacity of at least 2x42 tons bollard pull, exceptional for unberthing in scenario-2.

AbstrakPenelitian ini mengkaji respons getaran torsional model turbin arus laut sumbu vertikal terhadap pola eksitasi momen puntir yang acak akibat variasi kecepatan arus laut. Model turbin terdiri atas 3 buah blade alumunium jenis NACA 0018 yang masing-masing terhubung pada poros, dengan dimensi chord 10 cm, chamber 1,8 cm dan span 100 cm. Variasi kecepatan arus laut yang digunakan adalah 0,5 m/s, 1,0 m/s, 1,5 m/s, 2,0 m/s, 2,5 m/s dan 3,5 m/s. Model mempunyai 2 derajat kebebasan yang digambarkan dengan 2 persamaan diferensial orde-2. Penyelesaian eigenvalue menghasilkan nilai frekuensi natural model, yaitu 201,38 rad/s dan 457,91 rad/s. Deret Fourier digunakan untuk mendefinisikan persamaan momen puntir eksitasi, sedangkan penyelesaian persamaan getaran menggunakan transformasi Laplace. Hasil analisis menyatakan bahwa tidak terjadi resonansi karena nilai frekuensi natural model tidak sama dengan nilai frekuensi eksitasinya. Model mengalami puntiran statis dahulu sebelum bergetar. Respons yang terjadi diawali dengan respons transien, kemudian respon tunak (steady). Semakin besar eksitasi momen puntir menyebabkan semakin besarnya simpangan sudut dan amplitudonya. Abstract Shaft Torsional Vibration Response of Vertical Axis Ocean Current Turbine Model Due to Torque Excitation.The current research aimed to study the torsional vibration response of Vertical Axis Ocean Current Turbine due to randomly torque excitation pattern, owing to the variety of ocean current velocity. The turbine model is composed of 3 aluminum blades of NACA 0018 connected to steel shaft. Turbine dimensions are 10 cm of chord, 1.8 cm of chamber and 100 cm of span. The variation of ocean current velocity is 0.5 m/s, 1.0 m/s, 1.5 m/s, 2.0 m/s, 2.5 m/s and 3.0 m/s. The Model has 2 degree of freedom which is described into two 2 nd order differential equations. The eigenvalue solution yields the model's natural frequencies; 201,38 rad/s and 457.91 rad/s. Fourier series is used to define the equation of torsional excitation, whilst the vibration equation is solved using Laplace Transform. According to analysis, there is no resonance occur. That because of the system's natural frequencies is diverse to the magnitude of excitation frequencies. Model will be statically twisted first before vibrated. The response will be transient first then constantly steady. Furthermore, the bigger torque excitation will cause the bigger angular displacement as well the amplitude.

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