Studi Numerik Pengaruh Modifikasi Reducer Dengan Variasi Opening Adjuster Pada Pipa Ejektor Terhadap Performance Lube Oil Turbin

Aopik, Agus (2022) Studi Numerik Pengaruh Modifikasi Reducer Dengan Variasi Opening Adjuster Pada Pipa Ejektor Terhadap Performance Lube Oil Turbin. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Kriteria keberhasilan suatu unit pembangkit dapat ditinjau dari seberapa besar nilai keandalan unit secara equivalen (EAF: Equivalent Availability Factor). Berdasarkan Pareto Loss Output (PLO) PLTU Adipala menunjukkan bahwa kegagalan pipa main lube oil turbin merupakan gangguan terbesar yang terjadi pada tahun 2021. Dengan adanya gangguan berulang pada pipa main lube oil turbin maka dilakukan modifikasi pada reducer existing yang berbentuk sudden contraction dimana pipa main lube oil turbin mengalami kegagagalan. Modifikasi yang dilakukan pada reducer yang sebelumnya berbentuk sudden contraction menjadi bentuk conical untuk mengurangi jumlah welding yang berpotensi terjadinya kegagalan pada reducer sehingga dapat mengurangi dampak terjadinya kegagalan berulang. Selain itu, reducer dilengkapi dengan adjuster untuk mengatur tekanan lube oil turbin. Dari hasil modifikasi tersebut belum dilakukan studi terhadap modifikasi reducer sehingga belum diketahui dampak dari perubahan bentuk reducer dan perubahan opening adjuster terhadap parameter proses maupun aliran pada pipa main lube oil turbin.
Modifikasi reducer yang telah dilakukan akan diteliti dan dianalisa dengan studi numerical tentang pengaruh modifikasi reducer existing (sudden contraction) menjadi reducer conical dengan variasi opening adjuster pada pipa ejektor terhadap performa lube oil turbin. Pengujian akan dilakukan dengan variasi opening adjuster 112.62mm, 122.75mm, 139,00mm (jarak antara dinding dengan ujung check valve) pada adjuster existing dan adjuster yang telah dimodifikasi (bentuk conical).
Hasil simulasi menunjukkan bahwa perubahan tekanan sebanding dengan perubahan kecepatan. Adjuster yang telah dimodifikasi mengalami peningkatan tekanan di titik F dengan nilai 0.2813 MPa jika dibandingkan dengan adjuster existing dengan nilai 0.2795 MPa pada bukaan adjuster yang sama 139.00mm. Nilai tersebut selaras dengan penurunan kecepatan di titik F. Hasil tersebut sesuai dengan representasi analitik kekekalan energi dari persamaan Bernoulli. Aliran pada adjuster existing mendapat hambatan yang lebih besar menyebabkan terjadinya penurunan tekanan jika dibandingkan dengan adjuster conical/modifikasi. Adjuster modifikasi memiliki pressure drop yg lebih rendah dari adjuster existing. Dari ketiga model bukaan adjuster, adjuster modifikasi dengan variassi model 2 (bukaan 122.75mm) menghasilkan pusaran yang lebih sedikit jika dibandingkan dengan adjuster modifikasi 1 & 2 (bukaan 112.62 mm & 139.00 mm). Sehingga dengan jumlah pusaran yang lebih sedikit maka modifikasi adjuster lebih baik dari pada adjuster lainnya.
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The criteria for the success of power plant can be seen from how large the unit's reliability value is equivalently (EAF: Equivalent Availability Factor. Forced Outage is undesirable in the operation of power plants because it can interfere with the performance of the power plant in an equivalent manner (EFOR: Equivalent Forced Outage Rated). In 2021, One of caused the Forced Outage at Adipala Power Plant is the failure in the main lube oil turbine pipe. Modifications are made to the existing reducer to prevent repeated failures. The previous failure occurred in the reducer using a sudden contraction shape in the main lube oil turbine pipe system. Modifications are made to the reducer using a conical shape to reduce the number of welding which has the potential to cause failure so that it can reduce the impact of repeated failures. Therefore, a study on reducer modification needs to be carried out to study the impact of changing the shape of the reducer and changing the opening check valve on process parameters and flow in the main lube oil turbine pipe.
The change to existing adjuster which shaped sudden contraction to be modification adjuster which shaped sudden conical to be attention by researcher about Flow Specific Phenomenon. The aim this research is to analyse the pressure of turbine lube oil in adjuster existing and modified using the Computational Fluid Dynamics Technique with check valve adjuster variations (distance between tip of check valve and the inner wall of reducer) which the existing is installed that is 122.75mm, then done the optimum aperture to check valve adjuster is get the distance 139mm and minimum aperture is 112.62mm. The inlet boundary condition is defined by pressure inlet 285.803.4 Pa. Outlet boundary condition is set by mass flow 65.72 kg/s. The curve surface is setting in wall boundary condition with stationary wall, no-slip and standard roughness models.
The simulation results show that the change in pressure is proportional to the change in velocity. Adjuster has modified get increased of pressure in point F if compared with existing adjuster with the higher value 0.2813 MPa in adjuster-opening 139.00mm and the same thing in opening 139.00mm with 0.2795 MPa. That value was aligned with reduction of velocity in point F. The result conforms to analytical representation of energy conservation from Bernoulli equation. The flow of the existing adjuster has gotten more resistance that caused the existing adjuster occurred pressure drop increased when compared with modification adjuster. The modification-adjuster pressure drop (low) is better than the existing adjuster. From the three adjuster-opening models, was the modification adjuster 2 (opening 122.75mm) has produced less vortex when compared with modification adjuster 1 & 2 (opening 112.62 mm & 139.00mm). So that, with a smaller value of vortex, the modification adjuster is better than other adjuster.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Pareto Loss Output, reducer, sudden contraction, conical, adjuster, Power-Plant Performance, Adjuster
Subjects:	T Technology > TJ Mechanical engineering and machinery > TJ935 Pipe--Fluid dynamics. Tubes--Fluid dynamics
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21101-(S2) Master Thesis
Depositing User:	AGUS AOPIK
Date Deposited:	14 Feb 2022 07:52
Last Modified:	14 Feb 2022 07:52
URI:	http://repository.its.ac.id/id/eprint/93807

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