Efektivitas Desain Surge Tank untuk Mengendalikan Efek Water Hammer pada Pembangkit Listrik Tenaga Air

Setiawan, Anindita Hanalestari (2019) Efektivitas Desain Surge Tank untuk Mengendalikan Efek Water Hammer pada Pembangkit Listrik Tenaga Air. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Water hammer adalah fenomena yang terjadi pada saluran perpipaan tertutup ketika kecepatan dan aliran air berubah akibat penutupan saluran secara tiba-tiba. Fenomena ini dapat mengakibatkan kerusakan pipa (bursting of pipe lines) karena tekanan fluida yang sangat tinggi. Kasus kerusakan pipa banyak terjadi pada pipa berdimensi panjang seperti pipa penstock yang menyalurkan air dari bendungan ke rumah pembangkit (power house) pada sistem PLTA bendungan. Untuk mengurangi efek dari water hammer pada pipa penstock, digunakan bangunan surge tank sebagai peredam energi dari tekanan air di dalam pipa. Alat surge tank akan digunakan sebagai model fisik untuk simulasi kondisi hidrolika. Alat ini dilengkapi dengan dua tempat tampungan, pipa penstock, pipa surge tank, dan katup (valve) pada bagian ujung pipa. Tampungan pertama pada alat surge tank mewakili volume dari inflow sungai, sedangkan tampungan kedua mewakili fungsi reservoir. Pengamatan akan dilakukan terhadap tinggi muka air dan waktu osilasi air pada pipa surge tank setelah katup ditutup secara cepat. Penelitian surge tank dilakukan dengan menggunakan beberapa variasi alternatif sebagai model, yaitu perubahan panjang pipa penstock dan diameter pipa surge tank. Pada penelitian ini, dimodelkan dua variasi diameter pipa surge tank dan tiga panjang pipa penstock dengan dua jenis aliran. Variasi dilakukan dengan mengubah pemasangan diameter alat surge tank dan panjang pipa penstock. Parameter yang diamati pada penelitian ini adalah elevasi muka air pada pipa surge tank dan waktu aliran mencapai steady state flow saat terjadi fenomena water hammer. Berdasarkan hasil analisis, diameter pipa surge tank memengaruhi tinggi muka air pada surge tank. Semakin luas permukaan pipa surge, maka amplitudo osilasi air akan semakin rendah. Variasi d1 menghasilkan perbedaan tinggi muka air hingga 21,5 cm lebih rendah dari variasi d2. Panjang pipa penstock juga berpengaruh elevasi muka air pada pipa surge dan dalam menentukan waktu osilasi massa. Semakin panjang pipa penstock, maka waktu yang diperlukan aliran air untuk bertransmisi akibat water hammer akan semakin lama. Aliran air pada pipa tertutup juga dipengaruhi oleh gaya gesek air dengan pipa yang menyebabkan kehilangan energi. Hal ini akan memengaruhi kecepatan aliran dan waktu transmisi air di dalam pipa. Hubungan antara elevasi muka air pada surge tank dan waktu steady state menghasilkan persamaan eksponen regresi asimtot. Dari penelitian ini, diperoleh desain surge tank dengan variasi yang dapat menurunkan amplitudo osilasi air pada pipa surge tank dengan waktu steady state yang paling cepat. Model dengan diameter pipa surge 7,64 cm dan panjang penstock 1,56 m adalah model surge tank yang paling efektif dalam mereduksi efek water hammer. ================================================================================================ Water hammer is a phenomenon that happens in closed conduits when the water velocity and flow changes because of the sudden closed. This phenomenon can cause the bursting of pipe by the very high fluidal pressure. The cases of bursting pipe often happen on the long dimensional pipes such as penstock that distributes water from reservoir to the power house in hydroelectric power plants system. To reduce the water hammer effect in the penstock, surge tank is used as an energy reducer. Surge tank would be used as a physical model to simulate hydraulic condition. This model is equipped with two container boxes, penstock, surge tank pipe, and a valve at the end of the pipe. The first container represents volume from inflow, meanwhile the second container acts as the reservoir. The observation comprises of water level and mass oscillation in surge tank after the valve is closed rapidly. Fluctuation of mass oscillation in surge tank is temporary until the water level reaches its steady state level and represents the water level of upstream condition. The research of surge tank would use some alternative variants as parameters, such as the length of penstocks and surge tank pipe’s diameter. In this research, two variations of surge tank diameter and three different length of penstock pipes with two kind of flows are being observed. These variations will be installed in the surge tank model. The parameters of this research are water level in the surge tank and the wave travel time to reach steady state flow when water hammer phenomenon occurs. Diameter of surge tank affects water level because of its surface area. The amplitude of water oscillation will be decreased as the surface area of surge tank increases. When d1 is used, it resulted in decreasing the water level to 21,5 cm lower than the result of d2. The length of penstock governs the elevation of water level and water oscillation time. Penstock with longer size will make the longer time for wave transmission to propagate along the pipe. Furthermore, the friction factor takes role in the head loss and wave time travel in penstock. Subsequently, the relation of water level and steady state reaching time would be determined as an asymptot regression of exponential equation. The objective of this research is to design of surge tank which can decrease the water oscillation amplitude with the fastest steady state periode. Hence, the most suitable design of surge tank to reduce the effect of water hammer is by using the diameter of surge tank in 7,64 cm and length of penstock in 1,56 m.

Item Type: Thesis (Masters)
Additional Information: RTS 620.106 4 Set e-1 2019
Uncontrolled Keywords: water hammer, surge tank, hydro-electric power plant, osilasi massa
Subjects: T Technology > TC Hydraulic engineering. Ocean engineering > TC167 Dams, reservoirs
T Technology > TC Hydraulic engineering. Ocean engineering > TC424 Water levels
T Technology > TC Hydraulic engineering. Ocean engineering > TC555 Spillways. Energy dissipation. Hydraulic jump.
T Technology > TJ Mechanical engineering and machinery > TJ935 Pipe--Fluid dynamics. Tubes--Fluid dynamics
T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK3226 Transients (Electricity). Electric power systems. Harmonics (Electric waves).
Divisions: Faculty of Civil Engineering and Planning > Civil Engineering > 22101-(S2) Master Thesis
Depositing User: Anindita Hanalestari Setiawan
Date Deposited: 19 Jul 2021 02:57
Last Modified: 19 Jul 2021 02:57
URI: https://repository.its.ac.id/id/eprint/60985

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