Analisa Kegagalan Poros Pompa Centrifugal Multistage (GA101A) Sub-Unit Sintesa – Urea PT. Petrokimia Gresik

Setiawan, Angga (2016) Analisa Kegagalan Poros Pompa Centrifugal Multistage (GA101A) Sub-Unit Sintesa – Urea PT. Petrokimia Gresik. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Amonia Feed Pump GA101A merupakan pompa jenis centrifugal multistage dan merupakan salah satu critical equipment pada pabrik urea PT. Petrokimia Gresik. Kegagalan yang terjadi pada pompa GA101A adalah patahnya poros (shaft fracture). Pemicu patahnya poros adalah modifikasi geometri ring dan poros yang menyebabkan perubahan clearance serta penggantian material ring dari stainless steel 410 menjadi 304. Disisi lain, thermal expansion material yang terjadi antara ring dan poros melampuai batas clearance yang ada, ditambah dengan adanya vibrasi berlebih yang membuat poros dan ring bergesekan dan menyebabkan temperature sekitar meningkat, sehingga menyebabkan ring mengunci (locking) poros pada saat beroperasi. Patah poros pompa dianalisa dengan melalui beberapa tahapan, yaitu pengamatan pola patahan secara makroskopis, melakukan pemodelan menggunakan program CAD, kemudian melakukan analisa thermal expansion menggunakan metode Finite Element Analysis (FEA). Analisa thermal expansion yang dilakukan yakni dengan membandingkan material ring sebelum dan sesudah modifikasi serta mengetahui thermal expansion yang terjadi pada poros. Setelah itu, dihitung sisa clearance yang ada dengan adanya pemuaian material poros dan ring. Dari analisa didapatkan mekanisme yang menyebabkan poros pompa GA101A patah, yaitu vibrasi tinggi pada pompa yang menaikkan temperatur ring dan melebihi tempeartur kerja pompa. Saat suhu mencapai sekitar 200oC, gesekan akan semakin besariv bahkan menurut spektrum warna pada poros, suhu mencapai sekitar 1227oC sebelum poros putus. Temperatur akibat gesekan menyebabkan ekspansi material kedua komponen, sehingga ring mengunci poros hingga akhirnya patah. Langkah preventif dari hasil analisa adalah memperbesar clearance poros-ring sebesar 0.40mm tanpa mengganti jenis material, yakni stainless steel 304, sedangkan jika dengan material 410 clearance minimal yang dibutuhkan adalah sebesar 0.35mm ======================================================================================================== Ammonia Feed Pump GA101A is a centrifugal multistage pump and one of the critical equipment in urea plant PT. Petrokimia Gresik. Failure that occurs on GA101A pump is shaft fracture. Geometry modification on ring and shaft influenced shaft fracture and affected clearance changing, also material on ring was changed from stainless steel 410 to 304. On the other hand, material thermal expansion between ring and shaft overreached the existing clearance, coupled with excessive vibration which made shaft and ring on friction and caused temperature around rising. As a result, locking ring on shaft occurred. Pump shaft fracture is analyzed through several stages, namely macroscopic analysis on fracture pattern, modelling on CAD software, thermal expansion analysis using Finite element analysis (FEA). Thermal expansion analysis is done by comparing the ring material before and after modification as well as determine the thermal expansion that occurs on the shaft. After that, the rest of existing clearance is calculated by thermal expansion of the shaft and the ring material. The analysis found that the mechanism that cause shaft fracture on GA101A pump shaft is high vibration on pump that rise the temperature on ring and shaft area which is beyond the working pump temperature. When the temperature reached around 200oC, friction would be greater and according to the spectrum thatvi identified on shaft, the temperature reached 1227 oC before shaft fracture. Friction temperature cause material thermal expansion on both component, then locking ring on shaft occurred before shaft fracture. Preventive action that needs to take according to the analysis is enlarging the amount of clearance between ring and shaft to 0.40mm without changing the type of material, namely stainless steel 304 or using material 410 with minimum clearance 0.35mm

Item Type: Thesis (Undergraduate)
Additional Information: RSM 620.112 Set a
Uncontrolled Keywords: Centrifugal Multistage Pump, Finite Element Analysis, Thermal Expansion
Subjects: T Technology > TJ Mechanical engineering and machinery
Divisions: Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User: Mr. Tondo Indra Nyata
Date Deposited: 23 Apr 2020 01:31
Last Modified: 23 Apr 2020 01:31
URI: https://repository.its.ac.id/id/eprint/75883

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