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Master Theses from JBPTITBPP / 2017-09-27 14:53:51
Oleh : TO DARA (NIM : 23109014); Pembimbing : Prof. Dr. Ir. Indra Nurhadi ; Dr. Ir. Sandro Mihradi, S2 - Mechanical Engineering
Dibuat : 2011, dengan 7 file

Keyword : Bolted flanged joint, Raised Face Weld Neck Flange, Plate Flange Joint, Flange rotation, bolt preload, flange separation, flange pivot rotation, FEA, water hammer.

Flanged joints with gaskets are widely used in pressurized system like pressure vessel and piping systems, and they are designed mainly to resist internal pressure. These joints are also used in special applications such as in nuclear reactors and space vehicles. According to the failure accidentally occurred during the operation phase (caused by the amplitude loading like vibration of engine,

earthquake, etc), flanged joint is becoming an interesting topic for researchers. In this thesis, pipe and its joints are discussed and analyzed by using theoretical and

numerical analysis. The main purpose of this thesis is to investigate the sealing capability of the joints. Three kinds of bolted flange joints are discussed: Plate flange joint (PFJ), raised face weld neck flange (RFWNF) and compact flange joint (CFJ). PFJ and RFWNF are modeled by 3-dimentional solid element and it is analyzed under the static operating load, by using finite element package software (ANSYS v 12.1), while CFJ is discussed and evaluated based on the results of the existing research.

There are two types of loadings applied in the joints, namely bolt preload and internal pressure. Bolt preload is modeled by applying thermal condition (decreasing the temperature) on the bolt solid elements, while internal pressure is represented by the combination of the axial load (hydrostatic end force) applied on the pipe cross section and radial pressure distributed uniformly on the internal surface of the pipe flanges. Important parameters under the investigation are the contact pressure or gasket pressure, and flange deflections which are affected by

gasket material properties, bolt preload and operating load (internal pressure).

It has been demonstrated through the design criteria that the sealing capabilities of the joints depend on the contact pressure on gasket component,resulting from bolt preload and internal pressure. The contact pressure is required to be higher than hydrostatic pressure and it should be uniformly distributed. The variation of contact pressure due to the rotation of the flange and the material

properties of the gasket play important roles in achieving a leak proof joint.

According to the results of finite element analysis (FEA) software (ANSYS v 12.1), it was found that the contact pressure is distributed non-uniformly; the high pressure concentration can be minimized by optimizing the stiffness of gasket material. There are two possible solutions for minimizing the non-uniform pressure: optimize stiffness based on the non-linearity behavior or stiffness based

on Young’s Modulus of gasket material.

Referring to the FEA results, the feasible non-linear material which can be selected for gasket design is a composite such as spiral wound gasket (AF and GF). This selection is based on the nonlinearity properties of material. However, due to the non-linearity, this kind of gasket is not recommended to be use with the equipments undergoing high dynamic vibration (like pump, turbine, and other rotating components). For example, if the gasket is suddenly compressed and decompressed, the gasket material may not recover to the original shape in a due, so there could be a leakage during the operation. To overcome this shortcoming, composite material with high flexibility property will be more preferable for adapting the high frequency and magnitude of loading.

Based on most optimum value of Young’s Modulus and the working compressive stress of the gasket, it has been found that the materials like polymers (PTFE = lytetrafluoroethylene) and Elastomers (Polyurethane) are both in the design requirement. It has been demonstrated in [7] and [21] (Int. J. Pers. Ves. & Piping) that PTFE is considered as the best material due to its excellent properties such as non-pollution material, good flame resistance, very low rate of smoke generation, extremely long service life and very high corrosion resistant, etc.

Deskripsi Alternatif :

Sambungan pipa memakai flange, baut dan gasket sangat banyak digunakan dalam sistem bertekanan seperti bejana tekan dan sistem perpipaan. Sambungan seperti ini juga digunakan dalam aplikasi khusus seperti reaktor nuklir

dan wahana ruang angkasa sehingga kemampuannya dalam menahan tekanan tanpa terjadi kebocoran merupakan isu yang penting. Berdasar investigasi terhadap kerusakan selama pengoperasian (akibbat lonjakan beban, getaran, gempa), sambungan seperti ini menjadi topik riset yang menarik.

Dalam tesis ini dikaji sambungan pipa memakai flange, baut dan gasket secara teoritis dan memakai Metode Elemen Hingga dalam menahan tekanan dan beban kerja lainnya tanpa mengalami kebocoran. Tiga macam sambungan yang dikaji antara lain plate flange joint (PFJ), raised weld neck flange (RFWNF) dan compact flange joint (CFJ).

Sambungan jenis PFJ dan RFWNF dianalisis memakai model elemen hingga 3 dimensi (ANSYS v 12.1) sedangkan sambungan jenis CFJ dikaji berdasar teori dari riset yang telah ada.

Beban yang dikenakan pada sambungan adalah beban awal baut (bolt preload) dan tekanan dalam. Beban awal baut disimulasikan dengan memberikan kondisi “penurunan suhu” pada elemen baut sedang tekanan dalam disimulasikan memakai gaya hidrostatik di ujung pipa dan tekanan radial merata pada dinding pipa. Parameter penting dalam kajian ini adalah tekanan kontak gasket dan defleksi flange yang dipengaruhi oleh material gasket, beban awal baut dan

tekanan dalam.

Kemampuan menahan tekanan dari sambungan ini ditentukan oleh tekanan gasket yang terjadi akibat beban awal baut dan tekanan kerja. Salah satu kriteria desain yang harus dipenuhi adalah tekanan kerja harus terbagi merata pada bidang gasket. Dari hasil analisis elemen hingga diperoleh bahwa tekanan gasket tidak terdistribusi dengan merata. Hal ini dapat dikurangi dengan mengoptimalkan sifat material gasket yang secara mendetil dibahas dalam tesis.

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  • Pembimbing : Prof. Dr. Ir. Indra Nurhadi ; Dr. Ir. Sandro Mihradi, Editor: PKL-SMK

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