Posted by: novembri yusuf | April 21, 2008

AUSTENITIC SS KOQ SUSAH DI UT ….? ONO OPO…

Austenitic stainless steel

Austenitic stainless steels typically have a composition within the range 16-26% chromium (Cr) and 8-22% nickel (Ni). A commonly used alloy for welded fabrications is Type 304 which contains approximately 18%Cr and 10%Ni. These alloys can be readily welded using any of the arc welding processes (TIG, MIG, MMA and SA). As they are non-hardenable on cooling, they exhibit good toughness and there is no need for pre- or post-weld heat treatment.

Pada kenyataannya memang  baja SS austenitik susah untuk dilakukan UT. Hal ini disebakan oleh Ultrasonic Beam mengalami banya perturbation atau gangguan seperti ; deviasi beam, partitian, distorsi, dan kadang kadang echo yang menipu. Hal ini diakibatkan oleh phase dari austenitic itu sendiri. Anisotropi dan heterogen phase secara metallurgi sturktural yang terjadi dalam deposit las.

Jalan keluarnya : Mungkin bia dicoba menggunanakan tranducer dengan frekwensi lebih tinggi atau diameter lebih kecil. kalau ini nggak bisa juga ya … Bisa digunakan alternatif NDT lain seperti RT.

 

Posted by: novembri yusuf | April 20, 2008

REPAIR WELDING

REMOVE DEFECT  WELDING  BY  GRINDING

Dalam dunia welding masalah repair merepair suatu weldingan merupakan hal yang lumrah terjadi. Hampir semua project berskala besar selalu ada masalah repair.  Yang harus ditekankan adalah ratio repair harus sekecil mungkin. Itu tugasnya Pak manager project untuk merumuskan ratio repair agar project tetap untung, man haour sedikit, dan schedulle tercapai.

Kenapa sih koq ada repair…

Repair terjadi mungkin karena hasil NDT report seperti UT, RT, MT, PT menunjukkan adanya discontinity diluar acceptance criteria yang sudah disepakati. Bisa jadi karena masalah workmanship yang jelek, salah maerial, salah kawat las, salah dimensi dan lain lain…sehingga harus di repair.

OK … kita sekarang konsentrasi dulu dalam repair karena laporan NDT fail misal UT fail. Ada laporan UT dalam joint pipe 16 ” sch 120 dalam kedalaman 15 mm panjang 10 mm ada slag… Bagaimana mengseksekusi repair ini ….?

Ah langsung hajar ajalah dengan las Biasa…kata si welder ….upps stop dulu .. katanya si QC.

 Untuk mengeksekusi repair harus diperhatikan aturan mainnya. Aturan mainnya ada dimana pak QC tanya si welder….?

OK take look in AWS d1.1 Bab Repair hal 201 Bab 5.26.  Disana disebutkan bagaimana :

1. Cara membuang weld deposit yang bermasalah tadi. Bisa dengan Grinding, chipping, Gouging.  Untuk material QT nggak boleh pakai gougingan…nah lho  Knapa…?

Tentu temp gouging dan laju pendinginan yang cepat dari flow nya oksigen (angin) tadi akan merusak temper struktur dari material awal. Sehingga bukan QT lagi yang dapat tapi Q aja..Martensite phase…Hardness tinggi. Sebelum dibuang gouging material perlu dipananskan terlebih dahulu ( gunakan temp preheat)

 

2. Surface material setelah dibuang weld metal harus bersih dan bebas dari cacat akaibat penbuangan ini. lakukan MP/PT untukmengkounter checknya.

3. Lakukan welding ulang untuk mengisi kembali area yang akan di las. Disini perlu preheat lebih tinggi dari yang dipakai pada original wled(40 °C its OK). Untuk suatu repair  welding dengan proses yang berbeda dari original weld maka WPS yang digunakan harus sudah teruji dengan kondisi yang akan dipakai untuk merepair ( gunakan WPS repair).

4. lakukan NDT yang sama pada saat mengetes original wled pertama. kalau pertama di UT berarti untuk repair juga harus di UT  lagi.

 Kalau sudah OK …alhamdullilah berarti jointnya sudah accept, tapi kalau repair lagi gimana nih… Ganti aja weldernya … he he  he. Berapa kali suatu joint boleh di repair repair repair lagi ….?

Ayo berapa …?

 

 

 

Posted by: novembri yusuf | April 20, 2008

Rame rame jadi : WELDING INSPECTOR

Opini Pagi

Semenjak krisis energy yang melanda dunia dengan ditandainya kenaikan harga minyak yang melonjak dari US$60 perbarel 2 th lalu sampai menjadi lebih US$ 100 perbarel saat ini membuat perekonomian tambah sulit. Harga harga barang pokok lainnya pun ikut terkena imbasnya. Iya nggak … mulai dari harga BBM, Minyak Goreng dan gorengan, Beras, dll

Harga terus naik telah memicu operator minyak untuk meningkatkan pencarian dan peningkatan kapasitas produksi mumpung harga lagi tinggi dan keuntungan juga akan semakin tinggi.

Kondisi ini membuka peluang baru untuk para pekekrja tambang minyak, kilang minyak, fabrikasi alat penyedot minyak apakah itu platform, fpso, refenerry dll.  Dibutuhkan banyak tukang insinyur untuk menjalankan roda mesin ini. Salah satu nya adalah si tukang inspeksi las atau istilah kerennya WELDING INSPECTOR.

Saat ini banyak sekali ditemukan institusi institusi sekolah WI, training WI, training NDT. Banyak tukang insyinyur dari elektronika, sipil, mesin, dll ikut ikutan mau jadi WI. Apakah ini bagus….?

yang jelas tidak ada yang melarang dan itu sah sah saja. Sampai saat ini pun kita belum mempunyai sekolah sarjana khusus welding. Qualifikasi kompetensi seorang WI cukup dari international certificate atau nasional certificate yang dimilikinya.  Tinggal nanti dari si Usernya mau mengkualifikasi yang seperti apa sehingga bisa mendapatkan WI yang kompeten.

Tantangan buat para WI baru dihadapan mata. Banyaknya lulusan lulusan WI dari berbagai instansi dan lembaga akan meningkatkan persaingan. Untuk itu perlu penguasaan ilmu welding. Sepeprtinya tidak cukup mengandalkan dari Migas certificate saja, pengalaman di lapaangan , pemahaman dari req welding sesuai dengan code standard yang berlaku akan meningkatkan nilai jual WI.  Semoga para WI WI baru dapat mencapai cita citanya dalam menemukan pekekrjaan yang diidam idamkan.

Kriteria WI yang baik…

Apa ya kriterianya….? Mungkin bisa di jadikan acuan adalah konsep yang dipakai CSWIP/TWI dalam merumuskan tugas tugas seorang WI tingkat dunia. Kalau mau dijabarkan mungkinterlalu banyak. Tapi kalau mau konsisten seorang WI harus mempunyai ilmu yang lumayan banyak. kalau seorang WI sudah paham dan mengerti serta tahu apa yang di sebutkan dalam TWI tadi menurut saya berarti dia sudah layak dikatakan WI yang baik. Disamping itu tentunya dalam segi personality, komunikasi juga sangat penting. Penguasaan bahasa inggris mau tidak mau harus dikuasai. Bisa dibayangkan bagaimana dia  akan berkomunikasi dengan clientnya mungkin dari Texas sana atau dari cambridge sana kalau nggak bisa ngomong itu tadi ….

Ahhh saya mau jalan pagi dulu sambil nyeker keliling kampung Taman Sari Batam….nanti kita sambung lagi ….

See you …

 

 

 

Posted by: novembri yusuf | April 17, 2008

Stainless steel classification

Classifications of Stainless Steel  

 

Tentu para pembaca sudah sering mendengar yang namanya material stainless steel.  Untuk industry oil and gas peran material ini tidak tergantikan dengan material jenis lainnya. Baik dari ketahanan terhadap korosi juga ketahanan terhadap temperature dingin.

Untuk lebih jelasnya kita akan bahas pembagian dari stainless steel material secara umum.  Untuk lebih mendetail bisa dibaca pada jenis masing masing material tersebut dalam ASM handbook. 

 

 

    

 

    Stainless steels are commonly divided into five groups, depending on the specific amounts of alloying elements, which control the microstructure of the alloy. 

Austenitic  

     Austenitic stainless steels are the most weldable of the stainlesses and can be divided rather loosely into three groups: common chromium-nickel (300 series), manganese-chromium-nickel-nitrogen (200 series) and specialty alloys. Austenitic is the most popular stainless steel group and is used for numerous industrial and consumer applications, such as in chemical plants, power plants, food processing and dairy equipment. Austenitic stainless steels have a face-centered cubic structure. Though generally very weldable, some grades can be prone to sensitization of the weld heat-affected zone and weld metal hot cracking. 

Ferritic 

     Ferritic stainless steel consists of iron-chromium alloys with body-centered cubic crystal structures. They can have good ductility and formability, but high-temperature strengths are relatively poor when compared to austenitic grades. Some ferritic stainlesses (such as types 409 and 405) used, for example, in mufflers, exhaust systems, kitchen counters and sinks, cost less than other stainless steels. Other more highly alloyed steels low in C and N (such as types 444 and 261) are more costly, but are highly resistant to chlorides. 

Martensitic 

     Martensitic stainless steels, such as types 403, 410, 410NiMo and 420, are similar in composition to the ferrite group, but contain a balance of C and Ni vs. Cr and Mo; hence, austenite at high temperatures transforms to martensite at low temperatures. Like ferrite, they also have a body-centered cubic crystal structure in the hardened condition. The carbon content of these hardenable steels affects forming and welding. To obtain useful properties and prevent cracking, the weldable martensitics usually require preheating and postweld heat treatment. 

Duplex 

     Primarily used in chemical plants and piping applications, the duplex stainless steels are developing rapidly today and have a microstructure of approximately equal amounts of ferrite and austenite. Duplex stainless steels typically contain approximately 22-25% chromium and 5% nickel with molybdenum and nitrogen. Although duplex and some austenitics do have similar alloying elements, duplexes have higher yield strength and greater stress corrosion cracking resistance to chloride than austenitic stainless steels. 

Precipitation Hardening 

     Precipitation-hardening stainless steels are chromium-nickel stainlesses, which contain alloying additions such as aluminum, copper or titanium that allow them to be hardened by a solution and aging heat treatment. They can be either austenitic or martensitic in the aged condition. Precipitation- hardening stainless steels are grouped into three types: martensitic, semiaustenitic and austenitic. The martensitic (such as Type 630) and semiaustenitic (such as Type 631) can provide higher strength than the austenitic (such as Type 660, also known as A286). 

Selecting Stainless Steel 

     The selection of a particular type of stainless steel will depend on what requirements a particular application poses. Environment, expected part life and extent of acceptable corrosion all help determine what type of stainless to use. In most cases, the primary factor is corrosion resistance, followed by tarnish and oxidation resistance. Other factors include the ability to withstand pitting, crevice corrosion and intergranular attack. The austenitic/higher chromium stainless steels, usually required in very high or very low temperatures, are generally more corrosion resistant than the lower chromium ferritic or martensitic stainlesses. 
     Most stainless steels are considered to have good weldability. It is important to make sure joint surfaces and any filler metal be kept free from oxide, organic material or other contamination. 
     A principal concern in selecting welding filler metals for stainless steels is to match the important properties of the base metal. In addition, for nominally austenitic and duplex stainless steels, one should have some control over the weld metal’s ferrite content. Specification of ferrite in nominally austenitic and duplex stainless steel welds are based upon Ferrite Numbers (FN) defined in the AWS A4.2M/A4.2:1997 standard, Standard Procedures for Calibrating Magnetic Instruments to Measure the Delta Ferrite Content of Austenitic and Duplex Ferritic-Austenitic Stainless Steel Weld Metal. Recommended by the American Society of Mechanical Engineers Code, the magnetically determined FN is much simpler to obtain and is more reproducible than metallographically determined percent ferrite. 
     When selecting stainless steels, a welder must also consider something called “sensitization.” Ferritic stainless steels and some austenitic stainless steels, which contain appreciable free carbon (greater than about 0.04%C) can be rendered sensitive to intergranular corrosion in the heat-affected zone (HAZ) of a weld. This sensitization occurs where a peak temperature of about 900 to 1600 F (482 to 871C) is reached in the HAZ. Chromium carbides precipitate on grain boundaries, and in the process of doing so, chromium as an alloy element is depleted in the metal adjacent to the grain boundaries. Then, in corrosive service, this Cr-depleted metal is selectively attacked. Low welding heat input can limit, but not eliminate, sensitization. The best methods of preventing sensitization are selection of very low carbon base metal (less than 0.03%C) or selection of a grade stabilized with titanium or niobium (also known as columbium), such as types 321 or 347. Note also that sensitization is almost never a weld metal problem – it is largely a heat-affected zone problem.

 

 

 

Posted by: novembri yusuf | April 15, 2008

WELDABILITY

Weldability of materials

(rewrite from TWI.COM)

Stainless steel

Stainless steels are chosen because of their enhanced corrosion resistance, high temperature oxidation resistance or their strength. The various types of stainless steel are identified and guidance given on welding processes and techniques which can be employed in fabricating stainless steel components without impairing the corrosion, oxidation and mechanical properties of the material or introducing defects into the weld.

Material types

The unique properties of the stainless steels are derived from the addition of alloying elements, principally chromium and nickel, to steel. Typically, more than 10% chromium is required to produce a stainless iron. The four grades of stainless steel have been classified according to their material properties and welding requirements:

  • Austenitic
  • Ferritic
  • Martensitic
  • Austenitic-ferritic (duplex)

The alloy groups are designated largely according to their microstructure. The first three consist of a single phase but the fourth group contains both ferrite and austenite in the microstructure.

As nickel (plus carbon, manganese and nitrogen) promotes austenite and chromium (plus silicon, molybdenum and niobium) encourages ferrite formation, the structure of welds in commercially available stainless steels can be largely predicted on the basis of their chemical composition. The predicted weld metal structure is shown in the Schaeffler diagram in which austenite and ferrite promoting elements are plotted in terms of the nickel and chromium equivalents.

Because of the different microstructures, the alloy groups have both different welding characteristics and susceptibility to defects.

Austenitic stainless steel

Austenitic stainless steels typically have a composition within the range 16-26% chromium (Cr) and 8-22% nickel (Ni). A commonly used alloy for welded fabrications is Type 304 which contains approximately 18%Cr and 10%Ni. These alloys can be readily welded using any of the arc welding processes (TIG, MIG, MMA and SA). As they are non-hardenable on cooling, they exhibit good toughness and there is no need for pre- or post-weld heat treatment.

Avoiding weld imperfections

Although austenitic stainless steel is readily welded, weld metal and HAZ cracking can occur. Weld metal solidification cracking is more likely in fully austenitic structures which are more crack sensitive than those containing a small amount of ferrite. The beneficial effect of ferrite has been attributed largely to its capacity to dissolve harmful impurities which would otherwise form low melting point segregates and interdendritic cracks.

As the presence of 5-10% ferrite in the microstructure is extremely beneficial, the choice of filler material composition is crucial in suppressing the risk of cracking. An indication of the ferrite-austenite balance for different compositions is provided by the Schaeffler diagram. For example, when welding Type 304 stainless steel, a Type 308 filler material which has a slightly different alloy content, is used.

Ferritic stainless steel

Ferritic stainless steels have a Cr content typically within the range 11-28%. Commonly used alloys include the 430 grade, having 16-18% Cr and 407 grade having 10-12% Cr. As these alloys can be considered to be predominantly single phase and non-hardenable, they can be readily fusion welded. However, a coarse grained HAZ will have poor toughness.

Avoiding weld imperfections

The main problem when welding this type of stainless steel is poor HAZ toughness. Excessive grain coarsening can lead to cracking in highly restrained joints and thick section material. When welding thin section material, (less than 6mm) no special precautions are necessary.

In thicker material, it is necessary to employ a low heat input to minimise the width of the grain coarsened zone and an austenitic filler to produce a tougher weld metal. Although preheating will not reduce the grain size, it will reduce the HAZ cooling rate, maintain the weld metal above the ductile-brittle transition temperature and may reduce residual stresses. Preheat temperature should be within the range 50-250 deg.C depending on material composition.

Martensitic stainless steel

The most common martensitic alloys e.g. type 410, have a moderate chromium content, 12-18% Cr, with low Ni but more importantly have a relatively high carbon content. The principal difference compared with welding the austenitic and ferritic grades of stainless steel is the potentially hard HAZ martensitic structure and the matching composition weld metal. The material can be successfully welded providing precautions are taken to avoid cracking in the HAZ, especially in thick section components and highly restrained joints.

Avoiding weld imperfections

High hardness in the HAZ makes this type of stainless steel very prone to hydrogen cracking. The risk of cracking generally increases with the carbon content. Precautions which must be taken to minimise the risk, include:

  • using low hydrogen process (TIG or MIG) and ensure the flux or flux coated consumable are dried (MMA and SAW) according to the manufacturer’s instructions;
  • preheating to around 200 to 300 deg.C. Actual temperature will depend on welding procedure, chemical composition (especially Cr and C content), section thickness and the amount of hydrogen entering the weld metal;
  • maintaining the recommended minimum interpass temperature.
  • carrying out post-weld heat treatment, e.g. at 650-750 deg.C. The time and temperature will be determined by chemical composition.

Thin section, low carbon material, typically less than 3mm, can often be welded without preheat, providing that a low hydrogen process is used, the joints have low restraint and attention is paid to cleaning the joint area. Thicker section and higher carbon (> 0.1%) material will probably need preheat and post-weld heat treatment. The post-weld heat treatment should be carried out immediately after welding not only to temper (toughen) the structure but also to enable the hydrogen to diffuse away from the weld metal and HAZ.

Duplex stainless steels

Duplex stainless steels have a two phase structure of almost equal proportions of austenite and ferrite. The composition of the most common duplex steels lies within the range 22-26% Cr, 4-7% Ni and 0-3% Mo normally with a small amount of nitrogen (0.1-0.3%) to stabilise the austenite. Modern duplex steels are readily weldable but the procedure, especially maintaining the heat input range, must be strictly followed to obtain the correct weld metal structure.

Avoiding weld imperfections

Although most welding processes can be used, low heat input welding procedures are usually avoided. Preheat is not normally required and the maximum interpass temperature must be controlled. Choice of filler is important as it is designed to produce a weld metal structure with a ferrite-austenite balance to match the parent metal. To compensate for nitrogen loss, the filler may be overalloyed with nitrogen or the shielding gas itself may contain a small amount of nitrogen.

Copyright ©2004 TWI Ltd

Posted by: novembri yusuf | April 10, 2008

PIPING STRESS ANALYSIS

Sadur dari DON85

Piping Stress Analysis

Introduction

I. Definisi

Didalam sebuah Plant, entah itu LNG Plant, Petrochemical Plant, Fertilizer Plant, Nuclear Plant, Geothermal Plant, Gas Plant, baik di On-Shore maupun di Offshore, semuanya mempunyai dan membutuhkan Piping.

Piping mempunyai fungsi untuk mengalirkan fluida dari satu tempat ke tempat lainnya. Fluida yang berada didalamnya bisa berupa gas, air, ataupun Vapour yang mempunyai temperature tertentu.

Karena umumnya material pipa terbuat dari metal, maka sesuai dengan karakteristiknya yaitu jika diberi temperatur atau dialirkan temperatur didalamnya, maka metal atau pipa tadi akan mengalami pemuaian, jika fluidanya panas, maupun pengkerutan, jika fluidanya dingin.

Setiap kejadian pemuaian ataupun pengkerutan dari pipa tadi, akan menimbulkan pertambahan ataupun pengurangan panjang pipa dari ukuran semula, dalam skala horizontal.

Karena kita tahu bahwa pipa tersebut tersambung dari satu alat (equipment) ke equipment lain, maka perpanjangan ataupun pengurangan tadi, secara otomatis akan membawa pengaruh terhadap titik dimana pipa tersebut tersambung.

Misalnya, jika pipa tersebut digunakan untuk penyambungan dari sebuah nozzle pompa ke nozzle Tanki, maka akibat dari pengaruh temperatur fluida didalam pipa, maka pipa akan memuai atau mengkerut yang pada gilirannya akan menarik atau menekan ke arah nozzle pompa dan nozzle tanki tersebut.

Akibat pergerakan pipa tadi, maka akan ada gaya yang menekan atau menarik nozzle pompa dan nozzle tanki tersebut, disamping juga akan menimbulkan gaya balik terhadap pipa tadi.

Pergerakan pipa tersebut atau juga sering disebut behaviour pipa, akibat adanya pengaruh temperature fluida, perlu dihitung sedemikan sehingga pergerakkan tersebut masih mampu ditahan dan diterima oleh sang pipa tanpa harus mengalami perpatahan ataupun pecah sesuai dengan kekuatan material pipa tersebut, sekaligus gaya yang diberikan akibat perpanjangan ataupun pegkerutan pipa tidak sampai merusak nozzle pompa dan nozzle tanki.

Semua perhitungan tersebutlah yang menjadi tugas utama dari seorang piping stress engineer, yaitu melakukan pekerjaan apa yang dikenal dengan Piping Stress Analysis.

Dengan kata lain, Seorang Piping Stress Engineer mempunyai tugas untuk menghitung dan menganalisa suatu system pemipaan dalam sebuah Plant sedemikian rupa sehingga system piping dan plant secara keseluruhan mampu tetap beroperasi secara aman didalam berbagai kondisi.

II. Organisasi didalam Piping

Piping Department adalah bagian dari Divisi Engineering, yang selain Piping, juga terdiri dari Process, Mechanical, Civil/Structural, Electrical & Instrument.

Piping Department sendiri mempunyai 3 sub bagian dan dipimpin oleh seorang Piping Manager, yaitu:

  • Piping Design/Lay Out
  • Piping Material Engineering dan Material Control
  • Piping Stress Engineering dan Pipe SUpportSecara singkat tugas masing-masing bagian tersebut adalah:Piping Design

    Ini adalah group yang paling anyak anggotanya. Group ini mempunyai tugas untuk men-design atau membuat layout dari piping system. Mereka bertanggung jawa untuk menghasilkan layout piping yang cukup flexible dan cukup mempunyai supporting system. Mereka juga harus memastikan bahwa semua in-line instrument tergambar dengan tepat pada lokasi tertentu, dengan equipment equipment dan pipa yang sesuai dengan project criteria.

    Group ini juga harus sudah mempertimbangkan faktor operasi, maintenance, safety dan constructability.

    Piping Material Engineering dan Material COntrol

    Piping Material Engineer mempunyai tanggungjawab untuk membuat Master Specification untuk semua piping system. Specification untuk Piping Material biasanya terdiri dari pipa, valves, fittings, flanges, bolt and nut, gaskets, branch connections, fabrication criteria dan installation criteria. Juga termasuk insulation, paint dan special coatings lainya, dan tak kalah pentingnya adlah specialy items.

    Sedangkan material control berfungsi untuk melakukan perhitungan total material piping yang diperlukan pada sebuah project. Termasuk didalamnya melakukan perhitungan Material take Off (MTO), production of Bill of Material (BOM), RFQ (Request For Quotation), Bid Tabulation.

    Piping Stress Engineer dan Pipe Support

    Tugasnya adalah melakukan perhitungan dan analisa terhadap seluruh piping system (critical system) dan men-design pipe support. Group ini juga memproduksi Specification untuk Stress Analysis, Spring Support, Standard Pipe Support, Special Pipe Support, expansion joints, dan special engineered item.

    Untuk selanjutnya, kita akan lebih memfokuskan kepada Piping Stress Analysis, khususnya membicarakan tentang step-by-step didalam melakukan pekerjaan stress analysis.

    Teori Dasar

    Kenapa Harus di lakukan Stress Analysis?

    Seperti diketahui bersama bahwa tujuan dilakukannya perhitungan Stress Analysis dari piping system, secara singkat adalah untuk menjamin (to ensure) bahwa piping system tersebut dapat beroperasi dengan aman tanpa mengalami kecelakaan.

    Dalam “kehidupannya”, piping yang didalamnya mengalir fluida, baik panas, dingin atau angat-angat kuku, akan mengalami pemuaian (expansion) atau pengkerutan (contraction) yang berakibat timbulnya gaya yang bereaksi pada ujung koneksi (connection), akibat dari temperature, berat pipa dan fluida itu sendiri serta tentu saja tekanan didalam pipa.

    Dengan demikian, sebuah piping system haruslah didisain se-flexible mungkin demi menghindari pergerakan pipa (movement) akibat thermal expansion atau thermal contraction yang bisa menyebabkan:

    1. Kegagalan pada piping material karena terjadinya tegangan yang berlebihan atau overstress maupun fatigue.
    2. Terjadinya tegangan yang erlebihan pada pipe support atau titik tumpuan.
    3. Terjadinya kebocoran pada sambungan flanges maupun di Valves.
    4. Terjadi kerusakan material di Nozzle Equipment (Pump, Tank, Pressure Vessel, Heat Exchanger etc) akibat gaya dan moment
    yang berlebihan akibat expansion atau contraction pipa tadi.
    5. Resonansi akibat terjadi Vibration.

    Read More…

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