Penurunan Tekanan pada Pompa Air Laut pada Mesin Induk Kapal

Tujuan penelitian ini untuk mengetahui penyebab menurunya tekanan pompa pendingin air laut pada mesin induk di kapal. Metode penelitian menggunakan analisis kuantitaif deskriptif yaitu dengan melakukan pengamatan tentang menurunnya tekanan pompa air laut pendingin mesin induk kapal. Waktu yang digunakan dalam melaksanakan penelitian dan pengumpulan data-data yang diperlukan adalah 12 bulan lebih 10 hari. Hasil pengamatan diperoleh kurangnya daya hisap dan tekanan pompa air laut disebabkan saringan isap tertutup kotoran saat kapal masuk ke perairan dangkal baik pantai maupun sungai yang terdapat kotoran terutama sampah plastik dan lumpur, kotoran tersebut akan menghalangi aliran isap dari pompa pendingin. Menurunnya kinerja impeller pada pompa disebabkan karena terjadinya penyumbatan pada Impeller oleh kotoran-kotoran, keran-keran atau binatang laut yang masuk melalui Sea Chest sehingga menyebabkan terjadinya penurunan tekanan pompa ait laut. Kebocoran pada bagian gland packing pompa berupa tetesan zat cair yang jumlahnya tidak lebih dari 0,5 cm3/s. Jika jumlah tetesan lebih dari ini, penekan Packing harus di kencangkan pelan-pelan dan merata dengan mengencangkan kedua mur secara bergantian sampai tetesan menjadi normal, apabila setelah di kencangkan tetesan masih tidak normal gland packing wajib diganti dengan yang baru.

Simulation of Dynamic Characteristics of Pneumatic Control Valve With Smart Valve Positioner

In this research, in order to predict the dynamic characteristics of a regulating valve, a mathematical model is proposed for a pneumatic control valve using a smart valve positioner (AVP300), and the dynamic characteristics of the control valve were simulated. We modeled the components of the control valve (i.e., nozzle flapper, pilot valve, Auto/Manual (A/M) screw, bleed orifice, pneumatic actuator, gland packing, and pressure reducing valve), and simulated the dynamic characteristics using SimulationX, a one-dimensional analysis software. For the nozzle flapper, we proposed a model that considers the influence of fluid force due to pressure change as well as the influence of the change in effective area by measuring the displacement, pressure, and flow rate of the nozzle flapper. The diaphragm chamber, which operates the pilot valve of the positioner, was made of transparent acrylic. The displacement of the pilot valve was measured by a laser displacement sensor, and its movement against pressure change was clarified. The sonic speed conductance and critical pressure ratio of the A/M screw and bleed orifice were determined experimentally and reflected in the model. In the pneumatic actuator, the effective cross-section of the diaphragm was obtained from the change in pressure and displacement. The change in volume was calculated from the experiment using a fixed chamber. The friction force of gland packing was modeled using static and dynamic friction forces. The experiment on the dynamic characteristics of valve displacement was performed with the input signal of the valve displacement set from 20% to 80%. A comparison of the experimental results of the valve displacement and simulation results showed good agreement. The simulation in this study is considered effective in predicting the dynamic characteristics of the control valve.

The Problems of Measuring Profile and Roughness of Turbine Blades

The article presents a study of a turbine blade profile and roughness measurement processes - the task facing any manufacturer of this part. The blade is one of the most complex regarding parts manufacture because of its complex profile. This profile should be measured in several sections on the feather on all profile elements - the suction side, pressure surface, leading and trailing edge of a blade. If the blade has a shroud platform, its profile should be also measured (and possibly the gland packing profile). It is also necessary to measure the feather end and base of blade profile. Finally, a separate independent task is the blade tang profile measurement.