Friday, July 31, 2009

Characteristics of Piezoelectric Transducers

The transducer is a very important part of the ultrasonic instrumentation system. As discussed on the previous page, the transducer incorporates a piezoelectric element, which converts electrical signals into mechanical vibrations (transmit mode) and mechanical vibrations into electrical signals (receive mode). Many factors, including material, mechanical and electrical construction, and the external mechanical and electrical load conditions, influence the behavior of a transducer. Mechanical construction includes parameters such as the radiation surface area, mechanical damping, housing, connector type and other variables of physical construction. As of this writing, transducer manufacturers are hard pressed when constructing two transducers that have identical performance characteristics.
A cut away of a typical contact transducer is shown above. It was previously learned that the piezoelectric element is cut to 1/2 the desired wavelength. To get as much energy out of the transducer as possible, an impedance matching is placed between the active element and the face of the transducer. Optimal impedance matching is achieved by sizing the matching layer so that its thickness is 1/4 of the desired wavelength. This keeps waves that were reflected within the matching layer in phase when they exit the layer (as illustrated in the image to the right). For contact transducers, the matching layer is made from a material that has an acoustical impedance between the active element and steel.Immersion transducers have a matching layer with an acoustical impedance between the active element and water. Contact transducers also incorporate a wear plate to protect the matching layer and active element from scratching.

The backing material supporting the crystal has a great influence on the damping characteristics of a transducer. Using a backing material with an impedance similar to that of the active element will produce the most effective damping. Such a transducer will have a wider bandwidth resulting in higher sensitivity. As the mismatch in impedance between the active element and the backing material increases, material penetration increases but transducer sensitivity is reduced.

Transducer Efficiency, Bandwidth and Frequency

Some transducers are specially fabricated to be more efficient transmitters and others to be more efficient receivers. A transducer that performs well in one application will not always produce the desired results in a different application. For example, sensitivity to small defects is proportional to the product of the efficiency of the transducer as a transmitter and a receiver. Resolution, the ability to locate defects near the surface or in close proximity in the material, requires a highly damped transducer.
It is also important to understand the concept of bandwidth, or range of frequencies, associated with a transducer. The frequency noted on a transducer is the central or center frequency and depends primarily on the backing material. Highly damped transducers will respond to frequencies above and below the central frequency. The broad frequency range provides a transducer with high resolving power. Less damped transducers will exhibit a narrower frequency range and poorer resolving power, but greater penetration. The central frequency will also define the capabilities of a transducer. Lower frequencies (0.5MHz-2.25MHz) provide greater energy and penetration in a material, while high frequency crystals (15.0MHz-25.0MHz) provide reduced penetration but greater sensitivity to small discontinuities. High frequency transducers, when used with the proper instrumentation, can improve flaw resolution and thickness measurement capabilities dramatically. Broadband transducers with frequencies up to 150 MHz are commercially available.

Transducers are constructed to withstand some abuse, but they should be handled carefully. Misuse, such as dropping, can cause cracking of the wear plate, element, or the backing material. Damage to a transducer is often noted on the A-scan presentation as an enlargement of the initial pulse.

UT on weldments (Welded Joints)

The most commonly occurring defects in welded joints are porosity, slag inclusions, lack of side-wall fusion, lack of inter-run fusion, lack of root penetration, undercutting, and longitudinal or transverse cracks.
With the exception of single gas pores all the defects listed are usually well detectable by ultrasonics. Most applications are on low-alloy construction quality steels, however, welds in aluminum can also be tested. Ultrasonic flaw detection has long been the preferred method for nondestructive testing in welding applications. This safe, accurate, and simple technique has pushed ultrasonics to the forefront of inspection technology.
Ultrasonic weld inspections are typically performed using a straight beam transducer in conjunction with an angle beam transducer and wedge. A straight beam transducer, producing a longitudinal wave at normal incidence into the test piece, is first used to locate any laminations in or near the heat-affected zone. This is important because an angle beam transducer may not be able to provide a return signal from a laminar flaw.
The second step in the inspection involves using an angle beam transducer to inspect the actual weld. Angle beam transducers use the principles of refraction and mode conversion to produce refracted shear or longitudinal waves in the test material. [Note: Many AWS inspections are performed using refracted shear waves. However, material having a large grain structure, such as stainless steel may require refracted longitudinal waves for successful inspections.] This inspection may include the root, sidewall, crown, and heat-affected zones of a weld. The process involves scanning the surface of the material around the weldment with the transducer. This refracted sound wave will bounce off a reflector (discontinuity) in the path of the sound beam. With proper angle beam techniques, echoes returned from the weld zone may allow the operator to determine the location and type of discontinuity.

To determine the proper scanning area for the weld, the inspector must first calculate the location of the sound beam in the test material. Using the refracted angle, beam index point and material thickness, the V-path and skip distance of the sound beam is found. Once they have been calculated, the inspector can identify the transducer locations on the surface of the material corresponding to the crown, sidewall, and root of the weld.

Motivasi Kerja

Aku ibarat lilin (the defensive system to ensure continues integrity of a pipeline system).
A sacrificial anode, or sacrificial rod, is a metallic anode used in cathodic protection where it is intended to be dissolved to protect other metallic components.
The more active metal corrodes first (hence the term "sacrificial") and generally must oxidize nearly completely before the less active metal will corrode, thus acting as a barrier against corrosion for the protected metal.
More scientifically, a sacrificial anode can be defined as a metal that is more easily oxidized than the protected metal. Electrons are stripped from the anode and conducted to the protected metal, which becomes the cathode. The cathode is protected from corroding, i.e., oxidizing, because reduction rather than oxidation takes place on its surface.
Tuntutan Berbuat Baik & Bersabar Di Atas Perilaku Manusia

(Riwayat Muslim)

Seorang lelaki bertanya:

“Wahai Rasulullah sesungguhnya aku mempunyai beberapa orang kerabat, yang hubungan aku erat dengan mereka tetapi mereka memutuskannya. Aku berbuat baik kepada mereka tetapi mereka berperangai buruk kepadaku. Aku bersabar menghadapi sikap mereka itu tetapi mereka menganggap sikapku itu adalah bodoh.”

Kemudian Baginda menjawab:

”Sekiranya benar sepertimana yang engkau katakan itu, maka seolah-olah engkau menyuap mereka dengan abu yang panas, sedangkan engkau sentiasa mendapat pertolongan daripada Allah Taala selama mana engkau berada di dalam kebenaran atas perkara yang demikian itu”.


1. Islam mengajar umatnya supaya banyak bersabar di dalam semua keadaan sama ada ketika senang atau pun susah, kerana ia merupakan pengukur darjat keimanan seseorang. Allah sentiasa memberi pertolongan kepada orang yang sentiasa sabar dan benar dalam bertindak.

2. Islam mengajar umatnya supaya jangan membalas keburukan orang sebaliknya menambahkan lagi kebaikan terhadap mereka. Mudah-mudahan dengan itu, hati mereka menjadi lembut dan baik.
3.Setiap umat Islam wajib menghubungkan silaturrahim dan haram memutuskannya.

Ada orang datang ke pejabat dengan perasaan penuh gembira dan ceria, ada datang dengan perasaan 'biasa' dan ada datang dengan perasaan serba tak kena. Ingatlah! sesiapa yang datang hanya dengan perasaan 'biasa' saja, hasilnya adalah 'biasa' saja. Sesiapa datang dengan ceria, hasilnya akan lebih daripada biasa ataupun luar biasa. Bekerjalah dengan ceria agar menghasilkan produktiviti yang luar biasa yang akan menggembirakan orang di sekeliling kita. Semoga hasil itu akan mendapat keberkatan, InsyaAllah.

Jadi renugilah…
1. Ada antara kita datang ke pejabat hanya memenuhi tanggungjawab DATANG KERJA tapi hampeh, hasilnya macam kita tak datang kerja.
2. Ada kala kita rasa kita BUSY gila, rupanya kita 'kelam kabut'.
3. Adakala kita rasa PRIHATIN, tapi rupanya kita 'busy body'.
4. Adakalanya kita rasa kita OPEN MINDED dan OUTSPOKEN tapi rupanya kita 'kurang pengajaran'.
5. Adakala kita rasa kita berpemikiran KRITIS rupanya kita hanya lebih kepada 'kritik ' yang mencipta 'krisis'.
6. Adakala kita rasa kita ingin menjadi LEBIH MESRA tapi rupanya kita di lihat lebih 'mengada'.
7. Adakala kita suka bertanya "KENAPA DIA NIE MACAM TAK ADA KERJA?", adalah lebi baik kita tanya "Apa lagi kerja yang boleh aku buat?"
8. Adakala kita rasa kita ni pekerja yang SEMPURNA,BAIK DAN BERDEDIKASI tapi cuba tengok dalam-dalam,selagi hati kita berdengki, jatuhkan reputasi sesama rakan sekerja (report kat bos kawan kita tak bagus dari kita) dan tak amanah (mencuri dan tak siapkan kerja),kita sebenarnya patut terima hakikat betapa kita lebih teruk dari anggapan kita itu sendiri.

Pejam mata dan renunglah diri, kalau kita perlu melakukkan anjakan paradigma maka lakukanlah SEGERA. Tetapi manusia tetap manusia, sukar untuk berubah kerana kita selalu beranggapan kita lebih baik. Adakah dengan merasakan itu kita sememangnya terbaik?

Maka untuk itu, mari kita mula senyum, ceria, mesra sesama kita dan tingkat kerjasama dalam kerja, tak rugi kita semai rasa 'kekeluargaan' dalam tugasan kita. Kalau kita kurang kerja, cari la kerja dengan membantu teman-teman lain.

Tak dapat gaji lebih pun tak apa sebab pahala dapat. Kita dapat di akhirat nanti. Kerja adalah satu ibadah. Tapi kalau kita asyik dengki mendengki bukan pahala yang kita dapat, tapi dosa. Jadi, kejarlah pahala free ini.

“Mengkritik tidak bererti menentang. Menyetujui tidak semestinya menyokong. Menegur tidak bermakna membenci dan berbeza pendapat adalah kawan berfikir yang baik.”

Renungilah, berapa orang kawan kita dan berapa orang lawan kita?.

Thursday, July 30, 2009

Kawan Makan Kawan

Sudah lama kumengenalinya .Dan aku menganggap dialah saudara kerja.
Walaupun apa saja yang aku mampu .Aku membantunya apa yang perlu .Sehingga aku tersisih. Berbalah dengan boss. Kau kata teman sejati.
Lebih sukar dicari. Memang benar orng berkata, Harus awas dan waspada. Pada yang manis dibibir .Aku tersingkir.
Kawan yang ku benar harap-harapkan. Bukan jujur seperti yang kusangkakan. Kawan kini makan kawan .Ku dalam keadaan teraniaya. Kawan makan kawan.
Kini hilang segala yang ku ada. Ku hilang kerja, maruah dan muka.Kau racunkan fikiranku dan nya. Kau ambil kesempatan merapatinya boss
Aku dah terkena dengan hasutannya. Dan rupa-rupanya ada agendanya. Kerja ku pergi kerna batu api, Kawan ku sendiri membakar ku ini.Setelah ku berikan kepercayaan .Tak terlintas di fikiran kau buat bukan-bukan. Semua tipu helah tak akan terjadi lagi .Tanyalah diri apa yang sudah jadi. Kini kau tahu bagaimana kurasa ,Menahan peritnya bisa.
Semua ini tidak kuduga. Kawan makan kawan.

"Kawan"! - Sebuah Puisi... " - Oleh burung ciok umoh!

Untuk apa ertinya berkawan... kalau kawan tak boleh nak tolong kawan! Kita kawan-kawan tak mau lawan! Terus kerja sampai ajal!

Kalau ada kawan yg suka makan kawan... Tak perlulah adanya kawan! Kawan-kawan bukan haiwan! So jangan ikut perasaan ok!

Ada kawan suka melihat kegembiraan kawan yg lain... Ada kawan yg suka melihat tangisan kawan yg lain! Kalau begitu maknanya kawan... Memang sukar menilai ertinya kawan!

Ada kawan hanya bersama ketika senang... Ada kawan hanya melihat saja kawan yg sedang kesusahan! Ada pula kawan ygsuka melihat kejatuhan kawan-kawan! Malah ada juga kawan yg sentiasa berusaha menikam kawan dari belakang!

Untuk apa ertinya berkawan kalau bukan sebagai kawan! Untuk apa ertinya berkawan kalau tak mampu menjadi kawan! Untuk apa ertinya berkawan kalau masing-masing suka berlawan! Untuk apa ertinya berkawan kalau kawan suka makan kawan!

Kawan yg baik adalah kawan yg mahu berada bersama kawan ketika susah dan senang! Kawan yg baik adalah kawan yg sentiasa sporting! "

Berkawan dengan prinsip hasad dengki lama-kelamaan membawa mati!

Kawan tanpa kawalan memang menyeronokan! Namun awas akan kebatilan seorang kawan yg mungkin akan membahayakan!

Apa gunanya erti berkawan kalau kawan tak mahu memahami hati seorang kawan! Apa gunanya erti berkawan kalau kawan hanya mementingkan diri sendiri sehingga melupakan kawan!

Apa gunanya erti berkawan kalau ada kawan yg tak sanggup menangis kerana kawan! Kawan adalah kawan!

Tanpa kawan akan kosonglah ertinya berkawan!

Untuk berkawan memanglah mudah! Namun utk menjaga hubungan antara kawan adaah sesuatu yg maha sukar! Berkawan memerlukan pengorbanan! Berkawan memerlukan kesefahaman! Berkawan memerlukan kesesuaian!

Tanpa kawan dalam kehidupan... akan suramlah perjalanan! Untuk apa ertinya berkawan kalau bukan sebagai sebuah sandaran!

Untuk apa ertinya berkawan kalau bukan sebagai sebuah platform utk meluahkan perasaan! Untuk itu...

sama-samalah menjaga kawan! Jangan sampai kawan makan hati kerana bengang dengan sikap kawan! Jangan sampai kawan jadi serba-salah apabila terpaksa berhadapan dengan karenah seorang kawan!

Hormati kawan umpama menghormati diri sendiri! Nescaya akan terbitlah makna sebenar "Untuk Apa Ertinya Berkawan"

KIta kawan-kawan tak mahu lawan! aku caya sama lu! nie puisi khas untuk kau... bernama kawan!!

Mangsa tikam belakang dan kaki ampu..... burung ciok umoh

Wednesday, July 29, 2009


Bintulu Crude Oil Terminal

Sarawak Shell Bintulu Plant (SSBP) formerly known as Bintulu Crude Oil Terminal (BCOT) was the first major industrial project to go off the ground Tg. Kidurong in 1979.

The Project comprises three crude oil storage tanks, each with a capacity of 410,000 barrels. Located on the western boundary of the MLNG site, the plant coprises 3 areas of operations namely:

1.Crude Oil Operations (BCOT)

2.Condensate Stabilisation (BSTAB)

3.Gas Sales Facilities (BAGSF)

Daily Crude Production nett is 60,000 barrels per day. Daily Condemate Production is about 80,000 barrerls per day. Daily Gas Sales to downstream customers such as SMDS, ABF, SESCO and Petronas Gas Berhad is about 190 MMSCF per day. The Crude Oil and Condenate from the plant is either exported locally or to outside customers.


SMDS Plant

Shell MDS (Malaysia) Sdn. Bhd. a joint-venture company between Shell Gas, Petronas, Mitsubishi Corporation and the Sarawak State Government was formed in 1986. The company owns and operates the Shell Middle Distillate Synthesis (SMDS) plant, the world's first commercial gas to liquid plant, in Bintulu Sarawak.

The plant converts natural gas into high quality synthetic oil products and specialty chemicals which are paraffnic and colourless. Some 100 million standard cubic feet per day of natural gas are converted into 470,000 tonnes per annum of middle distillates (gasoil, kerosene, naphtha) and specialty products (detergent feedstocks, solvent feedstocks, various grades of waxes). The plant started operations in May 1993 and its products are sold globally. For more information, please contact 086-252211 / 292405. Email:

Monday, July 27, 2009

SapuraCrest awarded RM3B Shell Gumusut-Kakap Offshore Field Contract

Kuala Lumpur, March 17, 2009 - Charting another milestone in its involvement in deepwater technology, leading regional oil and gas services provider SapuraCrest Petroleum Berhad will be undertaking a contract worth RM3 billion for offshore installation works at the Gumusut-Kakap Field, operated by Sabah Shell Petroleum Company Limited (Shell). This follows the recent award of a lump sum contract to SapuraCrest’s wholly owned subsidiary, TL Offshore Sdn Bhd. The contract is expected to be executed over a three year period beginning this year.
SapuraCrest will deliver the contract through its joint venture company Sapura Acergy Sdn Bhd (SASB) where a major part of the work will be executed using the Sapura 3000, its state-of-the-art dynamically positioned heavy lift and deepwater pipelay vessel. Engineering and procurement work will commence with immediate effect and offshore installation will begin in 2010. The Gumusut-Kakap field is located about 200 km offshore Sabah with a water depth of 1,200 meters.

The field is the first deepwater development for Shell in Malaysia. However, it presents SapuraCrest its second and most advanced deepwater construction work to date, having earlier completed the Kikeh gas pipeline in Sarawak at a water depth of 1,400 meters. This project will involve more Malaysian engineers and managers, giving them opportunities to further develop in this highly-specialised field.

"The award reflects Shell’s and Petronas’ confidence in our capability and reaffirms the position of SapuraCrest as a leading provider of technologically superior and high quality services in the region. We have invested heavily in strategic assets and resources to the tune of RM1 billion over the last 5 years, and this has helped us position SapuraCrest to undertake projects of this magnitude and complexity. It is an honour to be selected by Shell, one of the biggest players in the global oil and gas industry today," said Datuk Shahril Shamsuddin, Executive Vice-Chairman of SapuraCrest Petroleum.

"This contract award is a tribute to the extensive experience and expertise of our engineers as it involves advanced and complex engineering design in the execution of deepwater works and highlights the capabilities of our latest advanced vessel, the Sapura 3000. The project will give us the opportunity to develop Malaysian engineers and managers in this new frontier and will allow Malaysians to undertake future deepwater engineering, construction and installation in Malaysia and across the region. This will move Malaysia higher up in the value chain in the ability to execute jobs with increasing complexities," Datuk Shahril added.

The contract entails project management, procurement, engineering, transportation and installation services, and works for an oil export pipeline and catenary riser, including the shore approach. It will also involve the installation of flowlines, jumpers, Steel Catenary Risers (SCRs), Pipeline End Terminations (PLET) and flowline inline structures. SASB will also be required to supply and install mooring wires, chains and piles for a semi-submersible Floating Production System (FPS) including towing and installation of the FPS at offshore location. More than 50 percent of the project will be carried out by local manpower and resources.

“We are delighted to be part of Malaysia’s long term growth plans and are pleased to be building solid relationships, creating additional localised support for all our clients in the region. This project will also help promote growth in the oil and gas industry by fostering technology transfer and local talent development, creating new employment opportunities and maximizing local procurement in Malaysia. We also hope that this project will in some small way assist local industries during these trying economic times," said Datuk Shahril.
The Gumusut-Kakap contract will propel SapuraCrest to the next stage of its expansion plans into higher technology services for the oil and gas industry. The contract is also expected to significantly boost current and future revenues.

* Exchange rate of USD1 = RM3.6 used
About SapuraCrest Petroleum Berhad

SapuraCrest Petroleum Berhad, a public-listed subsidiary of the Sapura Group of Companies, is one of the largest local oil and gas integrated service providers in Malaysia.

Through its subsidiaries, SapuraCrest Petroleum is involved in marine installation and construction, offshore drilling and marine services in Malaysia, Asia Pacific and South Asian regions. In particular, SapuraCrest Petroleum services cover the provision of accommodation and support vessels and tender assisted drilling rigs, installation of offshore pipelines and structures, provision of offshore hook-up, commissioning and topside maintenance services, provision of underwater services and provision of offshore geotechnical and geophysical services.

For more information, please visit
For Media Enquiries, please contact:
Norliza Kamaruddin, Sapura Group Corporate Communications
Tel: +603 8949 7727

FPSO Kikeh

Malaysia has completed the FPSO Kikeh, its first deepwater floating production storage and offloading (FPSO) facility, a significant event in the nation's endeavour to develop world class deepwater engineering and construction capability.

FPSO Kikeh, completed in 26 months, is also notable in that it is the largest such facility to be constructed in Malaysia. Built by Malaysia Marine & Heavy Engineering (MMHE), a subsidiary of MISC, at its yard in Pasir Gudang, Johor, peninsular Malaysia, the floating production unit was converted from the 337m long 279,000dwt VLCC SS Atlas. FPSO Kikeh, owned and operated by Malaysia Deepwater Terminal, a joint venture between MISC and SBM Offshore, is now on location in block K offshore Sabah, East Malaysia. Leased to Murphy Sabah Oil, the production sharing partner of Petronas Carigali, the FPSO is contracted for an initial period of eight years with options for five three-year follow-on extensions.

Moored in a water depth of 1320m about 120km northwest of Labuan Island, the FPSO will unload its cargo of oil to shuttle tankers every ten days, produced from Malaysia's first deepwater discovery using subsea wells connected to the FPSO by pipelines on the seabed and flexible risers.

Murphy Oil estimates the Kikeh field had proved reserves of 47.5mmbo and 74.6bcf of gas as at year-end 2006. Initial oil production, scheduled for startup in the second half of this year, is expected to be 40,000b/d of oil with a one-year ramp up to a plateau of 120,000b/d.

The turret

FPSO Kikeh's external turret, at around 2300t, is the heaviest ever designed by SBM. It affords permanent mooring, achieved with 10 anchor legs in a 4-3-3 configuration consisting of 127mm studless chain and 98mm wire rope, and acts as a support for the production, injection and utilities lines.

Product, water, power and communication data will be transferred between FPSO Kikeh and the anchored Kikeh DTU (dry tree unit) truss spar by way of fluid transfer lines (FTL) that utilise SBM's Gravity Actuated Pipe (GAP) system.

The turret provides fluid transfer and control functions to and from the vessel to the seabed and the DTU. Flexible subsea risers suspended from the turret feed commingled production fluids from the wells into the turret manifold. Jumpers connected to the GAP take care of fluid transfer to and from the DTU.

Produced fluids, a mixture of oil, gas, water and solid particles, flow to the topsides process modules via the turret swivels.

Treated water will pass through the turret into injection wells and produced gas not used for power generation on board will be initially injected, then exported by pipeline to Labuan Island, about a year after field production starts up.

Wellheads and DTU are controlled from the FPSO through the turret swivels and umbilicals to the seabed and DTU.

Malaysia rising

Through the transfer of technology resulting from the joint effort between MISC and SBM, the FPSO Kikeh project team from MISC and MMHE were able to develop expertise in deepwater construction. This collaboration also supported the growth and development of local vendors by providing business opportunities to more than 80 Malaysian subcontractors and service suppliers.

Marking this achievement the FPSO Kikeh naming ceremony was held at the MMHE yard on 29 March in the presence of Mohd Hassan Marican, MISC chairman and Petronas president and CEO, Claiborne Deming, Murphy Oil president and CEO, Didier Keller, SBM president, and Shamsul Azhar Abbas, MISC president and CEO.

Saturday, July 25, 2009

Basic Principles of Ultrasonic Testing

Basic Principles of Ultrasonic Testing

Ultrasonic Testing (UT) uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, material characterization, and more. To illustrate the general inspection principle, a typical pulse/echo inspection configuration as illustrated below will be used.

A typical UT inspection system consists of several functional units, such as the pulser/receiver, transducer, and display devices. A pulser/receiver is an electronic device that can produce high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy. The sound energy is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the transducer and is displayed on a screen. In the applet below, the reflected signal strength is displayed versus the time from signal generation to when a echo was received. Signal travel time can be directly related to the distance that the signal traveled. From the signal, information about the reflector location, size, orientation and other features can sometimes be gained.

Ultrasonic Inspection is a very useful and versatile NDT method. Some of the advantages of ultrasonic inspection that are often cited include:

* It is sensitive to both surface and subsurface discontinuities.
* The depth of penetration for flaw detection or measurement is superior to other NDT methods.
* Only single-sided access is needed when the pulse-echo technique is used.
* It is highly accurate in determining reflector position and estimating size and shape.
* Minimal part preparation is required.
* Electronic equipment provides instantaneous results.
* Detailed images can be produced with automated systems.
* It has other uses, such as thickness measurement, in addition to flaw detection.

As with all NDT methods, ultrasonic inspection also has its limitations, which include:

* Surface must be accessible to transmit ultrasound.
* Skill and training is more extensive than with some other methods.
* It normally requires a coupling medium to promote the transfer of sound energy into the test specimen.
* Materials that are rough, irregular in shape, very small, exceptionally thin or not homogeneous are difficult to inspect.
* Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise.
* Linear defects oriented parallel to the sound beam may go undetected.
* Reference standards are required for both equipment calibration and the characterization of flaws.

The above introduction provides a simplified introduction to the NDT method of ultrasonic testing. However, to effectively perform an inspection using ultrasonics, much more about the method needs to be known. The following pages present information on the science involved in ultrasonic inspection, the equipment that is commonly used, some of the measurement techniques used, as well as other information

Physics of Ultrasound

Refraction and Snell's Law

When an ultrasounic wave passes through an interface between two materials at an oblique angle, and the materials have different indices of refraction, both reflected and refracted waves are produced. This also occurs with light, which is why objects seen across an interface appear to be shifted relative to where they really are. For example, if you look straight down at an object at the bottom of a glass of water, it looks closer than it really is. A good way to visualize how light and sound refract is to shine a flashlight into a bowl of slightly cloudy water noting the refraction angle with respect to the incident angle.

Refraction takes place at an interface due to the different velocities of the acoustic waves within the two materials. The velocity of sound in each material is determined by the material properties (elastic modulus and density) for that material. In the animation below, a series of plane waves are shown traveling in one material and entering a second material that has a higher acoustic velocity. Therefore, when the wave encounters the interface between these two materials, the portion of the wave in the second material is moving faster than the portion of the wave in the first material. It can be seen that this causes the wave to bend.

Snell's Law describes the relationship between the angles and the velocities of the waves. Snell's law equates the ratio of material velocities V1 and V2 to the ratio of the sine's of incident (Q1) and refracted (Q2) angles, as shown in the following equation.

VL1 is the longitudinal wave velocity in material 1.
VL2 is the longitudinal wave velocity in material 2.

Note that in the diagram, there is a reflected longitudinal wave (VL1' ) shown. This wave is reflected at the same angle as the incident wave because the two waves are traveling in the same material, and hence have the same velocities. This reflected wave is unimportant in our explanation of Snell's Law, but it should be remembered that some of the wave energy is reflected at the interface. In the applet below, only the incident and refracted longitudinal waves are shown. The angle of either wave can be adjusted by clicking and dragging the mouse in the region of the arrows. Values for the angles or acoustic velocities can also be entered in the dialog boxes so the that applet can be used as a Snell's Law calculator.
When a longitudinal wave moves from a slower to a faster material, there is an incident angle that makes the angle of refraction for the wave 90o. This is know as the first critical angle. The first critical angle can be found from Snell's law by putting in an angle of 90° for the angle of the refracted ray. At the critical angle of incidence, much of the acoustic energy is in the form of an inhomogeneous compression wave, which travels along the interface and decays exponentially with depth from the interface. This wave is sometimes referred to as a "creep wave." Because of their inhomogeneous nature and the fact that they decay rapidly, creep waves are not used as extensively as Rayleigh surface waves in NDT. However, creep waves are sometimes more useful than Rayleigh waves because they suffer less from surface irregularities and coarse material microstructure due to their longer wavelengths.

Wave Propagation
Ultrasonic testing is based on time-varying deformations or vibrations in materials, which is generally referred to as acoustics. All material substances are comprised of atoms, which may be forced into vibrational motion about their equilibrium positions. Many different patterns of vibrational motion exist at the atomic level, however, most are irrelevant to acoustics and ultrasonic testing. Acoustics is focused on particles that contain many atoms that move in unison to produce a mechanical wave. When a material is not stressed in tension or compression beyond its elastic limit, its individual particles perform elastic oscillations. When the particles of a medium are displaced from their equilibrium positions, internal (electrostatic) restoration forces arise. It is these elastic restoring forces between particles, combined with inertia of the particles, that leads to the oscillatory motions of the medium.
In solids, sound waves can propagate in four principle modes that are based on the way the particles oscillate. Sound can propagate as longitudinal waves, shear waves, surface waves, and in thin materials as plate waves. Longitudinal and shear waves are the two modes of propagation most widely used in ultrasonic testing. The particle movement responsible for the propagation of longitudinal and shear waves is illustrated below.

In longitudinal waves, the oscillations occur in the longitudinal direction or the direction of wave propagation. Since compressional and dilational forces are active in these waves, they are also called pressure or compressional waves. They are also sometimes called density waves because their particle density fluctuates as they move. Compression waves can be generated in liquids, as well as solids because the energy travels through the atomic structure by a series of comparison and expansion (rarefaction) movements.

In the transverse or shear wave, the particles oscillate at a right angle or transverse to the direction of propagation. Shear waves require an acoustically solid material for effective propagation, and therefore, are not effectively propagated in materials such as liquids or gasses. Shear waves are relatively weak when compared to longitudinal waves. In fact, shear waves are usually generated in materials using some of the energy from longitudinal waves.

Precision Velocity Measurements

Changes in ultrasonic wave propagation speed, along with energy losses, from interactions with a materials microstructures are often used to nondestructively gain information about a material's properties. Measurements of sound velocity and ultrasonic wave attenuation can be related to the elastic properties that can be used to characterize the texture of polycrystalline metals. These measurements enable industry to replace destructive microscopic inspections with nondestructive methods.

Of interest in velocity measurements are longitudinal wave, which propagate in gases, liquids, and solids. In solids, also of interest are transverse (shear) waves. The longitudinal velocity is independent of sample geometry when the dimensions at right angles to the beam are large compared to the beam area and wavelength. The transverse velocity is affected little by the physical dimensions of the sample.

Pulse-Echo and Pulse-Echo-Overlap Methods

Rough ultrasonic velocity measurements are as simple as measuring the time it takes for a pulse of ultrasound to travel from one transducer to another (pitch-catch) or return to the same transducer (pulse-echo). Another method is to compare the phase of the detected sound wave with a reference signal: slight changes in the transducer separation are seen as slight phase changes, from which the sound velocity can be calculated. These methods are suitable for estimating acoustic velocity to about 1 part in 100. Standard practice for measuring velocity in materials is detailed in ASTM E494.

Precision Velocity Measurements (using EMATs)

Electromagnetic-acoustic transducers (EMAT) generate ultrasound in the material being investigated. When a wire or coil is placed near to the surface of an electrically conducting object and is driven by a current at the desired ultrasonic frequency, eddy currents will be induced in a near surface region. If a static magnetic field is also present, these currents will experience Lorentz forces of the form

F = J x B

where F is a body force per unit volume, J is the induced dynamic current density, and B is the static magnetic induction.

The most important application of EMATs has been in nondestructive evaluation (NDE) applications such as flaw detection or material property characterization. Couplant free transduction allows operation without contact at elevated temperatures and in remote locations. The coil and magnet structure can also be designed to excite complex wave patterns and polarizations that would be difficult to realize with fluid coupled piezoelectric probes. In the inference of material properties from precise velocity or attenuation measurements, use of EMATs can eliminate errors associated with couplant variation, particularly in contact measurements.
Differential velocity is measured using a T1-T2---R fixed array of EMAT transducers at 0, 45°, 90° or 0°, 90° relative rotational directions depending on device configuration:

EMAT Driver Frequency: 450-600 KHz (nominal)

Sampling Period: 100 ns

Time Measurement Accuracy:

Resolution 0.1 ns

Accuracy required for less than 2 KSI Stress Measurements: Variance 2.47 ns

Accuracy required for texture: Variance 10.0 Ns




Time Measurement Technique

Fourier Transform-Phase-Slope determination of delta time between received RF bursts (T2-R) - (T1-R), where T2 and T1 EMATs are driven in series to eliminate differential phase shift due to probe liftoff.

Slope of the phase is determined by linear regression of weighted data points within the signal bandwidth and a weighted y-intercept. The accuracy obtained with this method can exceed one part in one hundred thousand (1:100,000).

Ultrasonic welding

NDT - Non Destructive Testing

NDT – Non Destructive Testing is noninvasive techniques to determine the integrity of a material, component or structure or quantitatively measure some characteristic of an object. In contrast to destructive testing, NDT is an assessment without doing harm, stress or destroying the test object. The destruction of the test object usually makes destructive testing more costly and it also inappropriate in many circumstances.

NDT plays a crucial role in ensuring cost effective operation, safety and reliability of plant, with resultant benefit to the community. NDT is used in a wide range of industrial areas and is used at almost any stage in the production or life cycle of many components. The mainstream applications are in aerospace, power generation, automotive, railway, petrochemical and pipeline markets. NDT of welds is one of the most used applications. Is very difficult to weld or mould a solid object that has no risk of breaking in service, so testing at manufacture and during use is often essential.

NDT is vital for constructing and maintaining all types of components and structures. To detect different discontinuities or defects such as cracking and corrosion, there are different methods of testing or inspection available. The common
NDT products and methods are like Ultrasonic Testing, (UT), Radiographic Testing (RT) using X-Ray or Gamma-Ray, Magnetic Particle Inspection (MPI), Eddy Current Testing (ET), Dye Penetrant (DP), Remote Visual Inspection (RVI) etc.

Sample of applications:

MSNT member

Message From MSNT President
Non-Destructive Testing (NDT) has played vital role in the progress of Malaysian industries. Application of both conventional and advance NDT methods and various plants and system have allowed our industrial plants to operate safely and productively. I must congratulate all members of NDT community, particularly members of Malaysian Society for NDT (MSNT) for your finest contribution in making NDT technology beneficial for the betterment of our society.
Today MSNT make another significant progress when we joined hundreds of other NDT societies throughout the world to launch our own website. Although we are a little bit late, but I really believe that the launching of this website will provide a very wide platform for us to link members of our Society with members of world community.
I must congratulate members of MSNT Publication Committee and other individual that involved for their effort in making our dream to have our own website becomes true. It is just a beginning and I am sure from time to time the webmaster will include more and more materials to make this website more informative and more attractive.
Thank you.

Dr. Abd Nassir Ibrahim
President of MSNT 2008 - 2010

Ustaz Azhar Idrus
Solatku,Ibadatku,Hidupku,Matiku Kerna Allah Taala
AHAD -Surau Al-Ikhwan - Flat Gelong Bilal
SELASA - Surau Hj Awang - Ladang
RABU - Surau Flat Bu-kit Kecil II
KHAMIS - Masjid Batu Buruk
JUMAAT - Surau Hj Awang - Ladang
SABTU - Surau Al-Hidayah - Belakang Stadium Negeri
KULIYAH (Minggu Pertama)
ISNIN - Masjid Pinang Merah - Paka
SELASA - Masjid @ Surau daerah Kemaman
RABU - Surau Bukit Bading - Ajil
KHAMIS - Surau Wan Esah - Seberang Baroh
JUMAAT - Surau Pak Tuyu - Gong Badak
SABTU - Surau Pulau Musang
KULIYAH (Minggu Ke 2)
ISNIN - Masjid Simpang 4 Chendering
JUMAAT - Surau Limbong - Kemaman (Kuliyah Muslimat jam 9.00 pagi)
KULIYAH (Minggu Ke 3)
SABTU - Masjid Titian Baru - Kedai Buloh
ISNIN - Masjid @ Surau daerah Kuantan
SELASA - Masjid Pengadang Baru
RABU - Masjid @ Surau daerah Dungun
KHAMIS - Masjid Taqwa Batu 6
KULIYAH (Minggu Ke 4)
ISNIN - Masjid Pulau Ketam

Thursday, July 23, 2009

Sour Oil and Gas

High Performance Age-
Hardenable Nickel Alloys Solve Problems in Sour Oil and Gas Service
S. A. McCoy.
Special Metals Wiggin Ltd
Holmer Road
Hereford, UK

B. C. Puckett & E. L. Hibner
Special Metals Corporation
Huntington, WV


The new frontier of oil and gas exploration will be with deep wells, particularly in deepwater. Most
of the “easy-to-pick” fruit have been taken with shallow field development. Compared to shallow
wells, deep wells generally require more high-performance, nickel-base alloys. Wells are
categorized as being either “sweet” or “sour.” Sweet wells are only mildly corrosive, while sour
wells are very corrosive. Sour wells can contain hydrogen sulfide, carbon dioxide, chlorides, and
free sulfur. There are different levels of corrosive conditions that are compounded by temperatures
up to 500F (260C) and pressures up to 25,000 psi (172 MPa). Deep wells generally have higher
temperatures and pressures. Material selection is especially critical for sour gas wells. The materials
of choice must be corrosion-resistant, cost-effective, reliable, and have the required strength for the
well conditions. As these conditions become more severe, material selection changes from carbon
steels for “sweet” wells, to duplex (austenitic-ferritic) stainless steel, to INCOLOY alloys 825 or
925™, to INCONEL alloys 725HS and 725™ for sour well service.

Materials have to meet criteria for corrosion resistance and mechanical properties in service
environments needing increased reliability for the lifetime of the exploited asset. Age-hardened
nickel-base alloys and cold-worked solid solution nickel-base alloys offer many advantages such as
high-strength, toughness, low magnetic permeability and excellent corrosion resistance. The choice
of material for a particular set of well conditions is based on a number of selection criteria
*Mechanical properties
*General corrosion resistance
*Pitting & crevice corrosion resistance
*Chloride stress corrosion cracking resistance
*Sulfide stress corrosion cracking resistance
Mechanical Properties
The strength levels of age-hardened materials are increasing in importance, particularly for offshore
applications exploiting high-pressure deep well reserves, where weight considerations can affect the
economic viability of a project. Material selection for down-hole and wellhead equipment such as
hangers, sub-surface safety valves, pumps and packers require age-hardenable alloys to obtain the
necessary strength in heavier cross-sections which cannot be strengthened by cold work. Nickel
alloys commonly used for these applications include INCOLOY alloy 925, MONEL alloy K-500,
and INCONEL alloys 718, X-750, 725, and 725HS. Typical mechanical properties of highperformance
nickel alloys used in oil country applications.

The age-hardened alloys are used at different strength levels depending on the application.
Generally INCOLOY alloy 925 is used at a 758 MPa (110 ksi) minimum yield strength level. The
minimum yield strength level for INCONEL alloys 718 and 725 is 827 MPa (120 ksi). INCONEL
alloy 725HS is used at a 965 MPa (140 ksi) minimum yield strength level. The enhanced strength
properties of INCONEL alloy 725HS have been achieved through optimized thermal and
mechanical processing.

Galvanic Compatibility

Galvanic corrosion can be a concern when dissimilar materials are in contact in a conductive fluid.
The INCOLOY and INCONEL alloys are generally noble and consideration is given towards the
system design when in contact with less noble materials. In galvanic compatibility tests performed
in ambient temperature seawater for 92 days at LaQue Center for Corrosion Technology, INCONEL
alloys 725 and 625 were determined to be galvanically compatible. Coupling a large surface of
INCONEL alloy 725 to MONEL alloy K-500 promoted corrosion of the alloy K-500 component.

General Pitting and Crevice Corrosion Resistance
Traditionally, corrosion-resistant alloys are screened first by their pitting resistance equivalent
number (PREN), and then by the equivalent cracking data generated in sour brine environments1.
Equation 1 shows a typical formula used to compare the pitting resistance of stainless steels and
nickel-base alloys.

PREN = %Cr + 1.5( %Mo + %W + %Nb) + (30 x %N) Equation 1

The critical pitting temperature (CPT) for an alloy is determined by exposing samples in acidified
6% ferric chloride solutions, according to ASTM Standard Test Method G48, Method C 2, and
raising the temperature by incremental amounts until the onset of pitting. New unexposed test
specimens and fresh ferric chloride solution are used at each test temperature. The tests are only
valid up to 85C because at higher temperatures the test solution becomes unstable. The minimum
accepted CPT for an alloy is 40C for many offshore applications (e.g., the North Sea).
Determining the critical crevice temperature (CCT) of an alloy involves exposing samples to the
same aggressive test solution but with a multiple crevice device (TFE-fluorocarbon washer)
attached to the surface of the test specimen. The temperatures shown in Table 3 indicate the onset of
crevice corrosion.

Resistance of Age Hardened Nickel-Base Alloys to Corrosion by Seawater.

Nickel alloys with a PREN greater than 40 are very resistant to crevice corrosion in natural seawater
service. Table 4 compares the crevice corrosion resistance of corrosion-resistant alloys in seawater.
Under both stagnant and flowing conditions, the weight losses are extremely low.

Resistance to General Corrosion in Sour Environments

In mineral acids3, INCONEL alloy 725 in the age-hardened condition has comparable corrosion resistance to INCONEL alloy 625. Good general corrosion resistance can be important in resisting the various chemicals injected as inhibitors and dispersants.
Environmental Cracking
Wellhead and downhole components must resist stress corrosion cracking (SCC). The potential for
SCC becomes greater with higher temperature and higher concentration of H2S and the presence of
chloride ions and elemental sulfur. Lower temperature hydrogen embrittlement and sulfide stress
cracking (SSC) are also potential failure mechanisms which may be promoted by galvanic
corrosion, acidic conditions, and dissolved H2S.
Resistance to Sulfide Stress Cracking and Hydrogen Embrittlement

In general, resistance to SCC, SSC, and hydrogen embrittlement increases with increasing content
of nickel, chromium, molybdenum, tungsten and niobium in an alloy.
Stress Corrosion Cracking
Alloy strength is a factor in environmental cracking susceptibility. Materials become more prone to
environmental cracking as their strength increases. In order to obtain the optimum level of strength,
ductility and toughness, and cracking resistance, maximum hardness levels are specified for each
alloy in NACE International’s Materials Requirement MR0175'5.

H. R. Copson 6 originally reported the beneficial effect of alloy nickel content on chloride SCC
resistance of austenitic type alloys in 1959. Alloys 825, 925, 718, 625 and 725 all contain 42% or
greater nickel and, as a result, are all very resistant to stress corrosion cracking in water containing

A more severe test in ranking materials performance is the slow strain rate (SSR) test.
Common pass/fail criteria for SSR testing is a ratio of time to failure (TTF), %
reduction of area (%RA) and % elongation (%El) measured in a simulated oil patch
environment relative to the same parameter in an inert environment (gases such as
air or nitrogen). These are referred to as "critical ratios". TTF, %RA and %El ratios of
0.80 typically represent passing behavior in SSR tests. If the ratios are below 0.90,
the specimen is examined under a scanning electron microscope for evidence of ductile
or brittle fracture on the primary fracture surface. Tests exhibiting ductile behavior
are acceptable while those with brittle fracture are not. All specimens are examined
for secondary cracking in the gage length away from the primary fracture. The absence
of secondary cracking is indicative of good SCC or SSR resistance and passes. The
presence of secondary cracks is cause for rejection. One or more inert (air) SSR tests
are conducted along with two or more environmental SSR tests for each test lot of
material 7. The decision to use the critical ratio of 0.80 as the acceptance criterion in
SSR tests was based upon results obtained earlier for cold worked solid solution
nickel-base alloys 8,9. Studies 10 have shown that INCOLOY alloy 925 is consistently more
crack resistant in severe Mobile Bay type sour brine environments than alloy 718, based on SSR
stress corrosion cracking data.
Ultimately, it is the user's responsibility to establish the acceptability of an alloy for a specific
oilfield environment. The data presented here should be helpful in selecting materials for the
corrosive environments of sour oilfields. A group of alloys that represents a range of alternatives
can be selected for testing in an environment simulating the oilfield environment under study. A
final material selection for a specific application should be made based on test results and an
economic analysis of cost-effective alternatives.
INCONEL alloy 725 offers resistance to corrosion in extremely sour brine environments and in the
presence of elemental sulfur at temperatures up to 242C. The maximum permitted hardness under
NACE MR0175 requirements is 40 HRc. The stress corrosion cracking resistance of age-hardened
INCONEL alloy 725 is superior to that of INCONEL alloy 718 in sour environments.
A high-strength grade of alloy 725, INCONEL alloy 725HS, has been assigned a NACE MR0175
maximum hardness level of 43 HRc and can be used for high-strength applications in sour service
up to NACE test level VI at 175C.
The corrosion resistance of age-hardened nickel-base alloys in sour brine environments is as
INCONEL alloy 725> INCONEL alloy 725HS > INCOLOY alloy 925 > INCONEL alloy 718 >
MONEL alloy K-500 and INCONEL alloy X-750
INCOLOY, INCONEL®, MONEL®, 925™ and 725™ are trademarks of the Special Metals
Corporation group of companies.

1. E. L. Hibner and C. S. Tassen, “Corrosion Resistant Oil Country Tubular Goods and Completion
Alloys for Moderately Sour Service,” EUROCORR 2000, paper no. C014/18, London, UK,
September 2000.

2. ASTM G48 ASTM Standard Test Method G48, Annual Book of ASTM Standards, vol. 03.02 (West
Conshohocken, PA: ASTM, 1995)
3. E. L. Hibner, et. al., Effect of Alloy Content vs. PREN on the Selection of Austenitic Oil Country
Tubular Goods for Sour Gas Service,” CORROSIOIN/98, paper no. 98106, NACE International,
Houston, TX, USA, 1998.
4. Standard TM-01-77. “ Testing of Metals for Resistance to Sulfide Stress Cracking at Ambient
Temperatures”. NACE, Houston, TX 1986 revision.
5. NACE Standard Test Method MR0175-2000, “Sulfide Stress Cracking Resistance Metallic Materials
for Oilfield Equipment”.
6. H. R. Copson, T. Rhodin (ed.), Effect of Composition on Stress Corrosion Cracking of Some Alloys
Containing Nickel, “Physical Metallurgy of Stress Corrosion Fracture,” Interscience Publishers, Inc.,
New York, 1959.
7. E.L.Hibner, "Improved SSR Test for Lot Acceptance Criterion," Slow Strain Rate Testing for the
Evaluation of Environmentally Induced Cracking: Research and Engineering Applications, ASTM
STP1210, R.D.Kane, Ed., p.290, American Society for Testing Materials, West Conshohocken, PA,
USA, 1993.
8. H.E.Chaung, M.Watkins and G.A.Vaughn, "Stress-Corrosion Cracking Resistance of Stainless Alloys
in Sour Environments," Corrosion/85, Paper no. 277, NACE International, Houston, TX, USA, 1985.
9. M.Watkins, H.E.Chaung and G.A.Vaughn, "Laboratory Testing of SCC Resistance of Stainless
Alloys," Corrosion/87, Paper no. 0283, NACE International, Houston, TX, USA, 1987.
10. R. B. Bhavsar and E. L. Hibner, “Evaluation of Testing Techniques for Selection of Corrosion
Resistant Alloys for Sour Gas Service,” CORROSION/96, paper no. 59, NACE International,
Houston, TX, USA, 1996.
1. E. L. Hibner and C. S. Tassen, “Corrosion Resistant OCTG’s and Matching Bar Products for a range
of sour gas service conditions,” CORROSION/2001, paper no. 01102, NACE International,
Houston, TX, USA, 2001.