Selection Of Pipe Material For Low-Temperature Service

The selection of material for any specific environment is directly dependent on the material’s properties, especially those properties that are affected by that special environment.

Metal properties are classified in terms of Mechanical, Physical and Chemical properties. These are further subdivided into Structure Sensitive or Structure Insensitive properties. The following table describes these properties.

Table 1: Metal properties.


In this article, we are concerned only with the structure-sensitive mechanical properties of metal. Metals are favored as a construction material because they offer a combination of mechanical properties that are unique and not found among non-metals. Metals are generally strong and many can be loaded or stressed to very high levels before breaking. One property of metals of interest is their capacity to exhibit a high degree of elastic behavior in their early load-carrying capacity. This is a very important property for effective use of the metal as a construction material. When these metals are loaded beyond their elastic range they exhibit another set of important properties called ductility and toughness. These properties and how they are affected by change in temperature are the point of this article.

Pipeline Steels
We will focus on carbon and low-alloy steels. It may be noted that the bulk of the material that is used in conventional pipeline engineering comes from this generic group. Aptly, it is the ductility and toughness of these metals and how they are affected by the variation of temperature that is our subject. The emphasis is made on the variation under low temperature. For this purpose it is essential to know what is meant by these metal properties and by low temperature. The following definitions are understood by fracture mechanics.

Ductility is defined as the amount of plastic deformation that metal undergoes in resisting the fracture under stress. This is a structure-sensitive property and is affected by the chemical composition.

Toughness is the ability of the metal to deform plastically and absorb energy in the process before fracturing. This mechanical and structure sensitive property is the indicator of how the given metal would fail at the application of stress beyond the capacity of the metal, and whether that failure will be ductile or brittle. Only one assessment of toughness can be made with some reasonable accuracy from ordinary tensile testing, and that is the metal displays either ductile or brittle behavior. From that it can be assumed that the metal displaying little ductility is unlikely to display a ductile failure if stressed beyond its limits. The failure in this case would be brittle.

The temperature of metal is found to have profound influence on the brittle/ductile behavior. The influence of higher temperature on metal behavior is considerable. The rise in temperature is often associated with increased ductility and corresponding lowering of the yield strength. The rupture at elevated temperatures is often intergranular, and little or no deformation of the fractured surface may have occurred. When lowered below room temperature, the propensity for brittle fracture increases.

ASTM E 616 defines some of the terminology associated with Fracture Mechanics and Testing, such as:

The term fracture is strictly defined as irregular surface that forms when metal is broken into separate parts. If the fracture has propagated only part way in the metal and metal is still in one piece, it is called a crack.
A crack is defined as two coincident-free surfaces in a metal that join along a common front called the crack tip, which is usually very sharp.
The term fracture is used when the separation in metal occurs at relatively low temperature and metal ductility and toughness performance is the chief topic.
The term rupture is more associated with the discussion of metal separation at elevated temperatures.
As noted previously, two basic types of fracture occur in metals: ductile and brittle. These two modes are easily recognized when they occur in exclusion, but fractures in metal often have mixed morphology and that is aptly called mixed mode. The mechanisms that initiate the fracture are shear fracture, cleavage fracture, and intergranular fracture. Only the shear mechanism produces ductile fracture. It may be noted that like the modes discussed here, the failure mechanisms also have no exclusivity.

A crack is defined above as two coincident-free surfaces in a metal that join along a common front called the crack tip, which is usually very sharp. Irrespective of the fracture being ductile or brittle, the fracture process is viewed as having two principal steps:

1. Crack initiation, and
2. Crack propagation.

Knowledge of these two steps is essential as there is a noticeable difference in the amount of energy required to execute them. The relative level of energy required for initiation and for propagation determines the course of events which will occur when the metal is subjected to stress.

There are several aspects to the fracture mechanics that tie in with the subject of metal ductility and toughness but this article is not planned for detailed information on fracture mechanics. Hence, these are not discussed in detail but some specific-related topics are listed in Table 2.

Table 2: Topics related to fracture mechanics.

Effects of axiality of stress,
Crack arrest theory,
Stress intensity representation,
Stress gradient,
Rate of Strain,
Effect of Cyclic Stress,
Fatigue Crack,
Crack Propagation, (KIc= ? ??a)
Griffith’s theory of fracture mechanics,
Irwin’s K = ?E x G,
Crack Surface Displacement Mode,
Crack Tip Opening Displacement (CTOD), (BS 5762-1979 and BS 7448 part-I)
R-Curve Test methods
J- Integral Test method,
Linear-Elastic Fracture Mechanics (LEFM) (ASTM E 399),
Elastic-Plastic Fracture Mechanics (EPFM),
Nil Ductility Temperature (NDT).
Though the topics in Table 2 are not commonly taken into consideration when selecting suitable material for an onshore pipeline, these are essential parts of subsea pipeline and riser technology. In fact, some of the specification (e.g. API 1104, DNV-OS F101 etc.) suggest the use of fracture mechanics to determine the failure behavior of metal in these services.

Returning to our earlier discussion, lowering the temperature of metal profoundly affects fracture behavior. Strength, ductility, toughness and other properties are changed in all metals when they are exposed to temperature near absolute zero. The properties of metals at very low temperatures are of more than casual interest because pipelines, welded pressure equipment and vessels are expected to operate satisfactorily at levels below room temperatures. For example, moderate sub-zero temperatures are imposed on equipment for dewaxing petroleum and for storage of nitrogen, liquefied fuel gases and pipelines.

Much lower temperatures are involved in cryogenic services where metal temperature falls to –100 C (-150 F) and below. The cryogenic service may involve storage of liquefied industrial gases like oxygen and nitrogen. Toward the very bottom of the temperature scale, there is a real challenge for metals that are used in the construction of equipment for producing and containing liquid hydrogen and liquid helium,because these elements in liquefied form are increasingly important in new technologies. Helium in liquefied form is only slightly above absolute zero, which is 1 Kelvin (-273.16 C or – 459.69 F).

Absolute zero (1 K) is the theoretical temperature at which matter has no kinetic energy and atoms no longer exhibit motion. Man has yet to cool any material to absolute zero, so it is unknown how metals would behave when cooled to this boundary condition.

However, metal components have been brought to the temperatures very close to absolute zero, hence it presents a special challenge to metals and welded components as they would be required to serve in this extremely low temperature.

When cooled below room temperature every metal will reach a temperature where the kinetic energy will be reduced to nil. The atoms of the element will move closer and the lattice parameters will become smaller. All these changes would affect the mechanical properties of the metal.

Metal Strength At Low Temperature
As we have seen, as temperature is lowered from room temperature, 75oF (24oC or 297oK), to absolute zero, 1oK, the atoms of an element move closer together by dimensions easily compounded from the coefficient of thermal expansion. Several changes occur as a result of this smaller lattice parameter. For example, the elastic module increases. In general, the tensile strength and yield strength of all materials increase as the temperature is lowered to the nil ductility temperature (NDT) , where the yield and tensile strength are equal (?o = ?u). The change in these properties is variable in degree for different metals but change does occur.

When the temperature of low-carbon or low-alloy steel is lowered, the corresponding increase in strength of metals occurs. This is attributed to an increase in resistance to plastic flow. Because plastic flow is strongly dependent upon the nature of the crystalline structure, it would be logical to assume that metals with the same kind of structure would react similarly.

A cautionary note: The material in ASTM A 333 Grades 1,3,4,6,9 and 10 is required to have minimum of 10 ft-lbs absorbed energy (impact values).This is the same as ASTM A 350 LF1, but material ASTM A 350 LF2 and LF3 are required to have minimum of 12 ft-lbs absorbed energy (impact values). This is at any given temperature, respective of that material.

Selecting Material From Specification And Codebooks
There are several ASME/ASTM specifications specifically tailored for low-temperature services, but it is important to check if the specified test temperatures for the metal in use is in tally with the design temperature of the system. ASTM-A/ASME -SA105 is not a low-temperature material; however, it may be used for low temperature if all the other factors are conforming to the requirements and an additional impact test on the material is carried out at a temperature that is in tally with the design temperature.

Similarly, ASTM A 106 pipes (grade A, B or C) must be checked for the test temperatures because ASTM A 106 is specified as “high-temperature” material and rightfully the impact test is not even included in the non-mandatory requirement. The same is the case with ASTM A 105 forged material discussed above. Concerning ASTM A 333 grades 1, 3, 4, 6, 9 and 10 pipes for the acceptable impact values and their test temperatures, the specification must be referenced before arbitrarily using them for any service temperature range. ASTM A 350 LF1 (-20 F), LF2 (-50 F), LF 3 (-150 F) are suitable for low-temperature service to the limits set by the specification, but one should check the specified energy absorption value Cv to ensure it is in tally with the system design parameters.

An informed selection has to be made. There are several boiler-quality plate materials specified by the ASTM specifications and ASME codes but not all are suitable for low-temperature services. Some are so designed metallurgically that they are not suitable for low-temperature service. Plate material conforming to the ASTM A 515 specification is an example. Most of the metals that are fit for low temperature are generally tested to 32oF (0 C) unless specified otherwise. So, the general assumption that all ASME material is good up to -20oF will not be correct, unless it is tested and material test report so declares.

API mandates that PSL2 pipes be tested at 32oF (0 C) or any lower temperature as agreed between the buyer and manufacturer and is expected to have 20 ft-lbf (27 J) absorbed energy. The same is not true for PSL1 pipes. In either case, it is important to determine what was the actual test temperature and what responsibility engineers have to ensure that the test temperature is in tally with the design temperature of the system.

Among pipeliners, a question is often raised if, in designing a buried pipeline, one needs to consider the low temperature. The answer is not metallurgical since it is unrelated to the material property as much as it is geographical and environmental, that is, the design conditions. The data provided by the user (clients) and the specification must be consulted.

Generally, a buried pipeline will not be subject to very low temperatures unless buried in permafrost, so no specific caution beyond the general design considerations would be required. However, the general guidance in such case should be to look at the product properties, risk analysis, product leakage, and will a reduction in pressure at a certain point reduce the temperature to what is considered a low-temperature range.

If there is a cause to expect lower temperature, then determine to what extent lower temperature will occur during the life of service. If the temperature is ever in the critical low range, it will be prudent to identify those conditions and take them into account while selecting the material.

Similar consideration applies to the aboveground pipe and components. Aboveground valves flanges and pipes are more exposed to the weather and are also carrying the similar product. Therefore, they have greater propensity to face low temperature in their service lives. The following questions must be asked and answered: Are they insulated? Are they heated? Is there any possibility of depressurization that would lead to extensive temperature reduction, etc? There is a multiplicity of factors that affect the understanding of the material behavior in extreme stress conditions. All possible factors must be identified and addressed.

Conclusion
The questions we have tried to explore are more complex than this discussion which is an attempt to simplify the basic understanding of the subject. This discussion is intended to bring out the importance of the subject and direct readers to available resources for material selection issues.

Important Additional Information
The sub-ambient temperature dependence of yield strength ?o (Rp0.2) and ultimate tensile strength ?u in a bcc metal is shown in Figure 1. Consider the graph, the material is ductile until a very low temperature, point A, where Y.S. equals the UTS of the material (?o = ?u). Point A represents the NDT temperature for a flaw-free material. The curve BCD represents the fracture strength of a specimen containing a small flaw (a < 0.1mm). The temperature corresponding to point C is the highest temperature at which the fracture strength ?f ? ?o. Thus point C represents the NDT for a specimen with a small flaw.  The presence of a small flaw raises the NDT of steel by about 200°F (110°C). Increasing the flaw size decreases the fracture stress curve, as in curve EF, until with increasing flaw size a limiting curve of fracture stress HJKL is reached. Below the NDT the limiting safe stress is 5,000-8,000 psi (~35 to 55 MPa). Above the NDT the stress required for the unstable propagation of a long flaw (JKL) rises sharply with increasing temperature. This is the crack-arrest temperature curve (CAT). The CAT curve defines the highest temperature at which unstable crack propagation can occur at any stress level. Fracture will not occur for any point to the right of the CAT curve. The temperature above which elastic stresses cannot propagate a crack is the fracture transition elastic (FTE). The temperature defines the FTE, at the point K, when the CAT curve crosses the Yield Strength, ?o curve. The fracture transition plastic (FTP) is the temperature where the CAT curve crosses the Ultimate Tensile Strength ?u curve (point L). Above this temperature, the material behaves as if it is flaw-free, for any crack, no matter how large, cannot propagate as an unstable fracture. Author
Ramesh Singh is a senior principal engineer for Gulf Interstate Engineering, 16010 Barkers Point Lane, Houston, TX 77079. He specializes in materials, welding and corrosion. He graduated from California Coast University with a master of science degree (2003) in engineering management and gained his basic metallurgical education (1984) from Air Force Technical Institute in India. He is registered with the Engineering Council in the UK and is a member of The Welding Institute, Cambridge UK. He is a NACE member and has served as secretary and vice chair of the NACE Houston chapter.

Source: http://pgjonline.com/2010/02/08/selection-of-pipe-material-for-low-temperature-service/

GIS - Enabled: Modeling Simplifies Pipeline Route Selection

The implementation of a Geographic Information System (GIS) can have a profound effect on management of large water and wastewater infrastructure assets. A GIS-enabled Suitability Model can be used to aid engineers and analysts in the selection of routes in large linear projects, greatly enhancing quality control while minimizing environmental impact.
This innovative technology was employed by URS on a recent project undertaken on behalf of the City of Austin, TX. The city was called upon to expand its water and wastewater infrastructure in a limited time frame, driven by rapid growth in the southeast area of the city, particularly along and east of IH 35. The city evaluated the existing Austin Water Utility (AWU) Long-Range Master Plan and determined that the best approach was to establish the South IH 35 Water/Wastewater Infrastructure Improvements Program, which would be committed to fast-track design and construction of key water and wastewater infrastructure projects.

South IH-35 Program
The South IH-35 Program includes 13 miles of water transmission main and three miles of wastewater interceptor.
The City of Austin brought in URS as Program Management Consultant (PMC) to ensure the South IH-35 Program was successful. URS began with preliminary engineering design of 13 miles of water transmission main, three miles of wastewater interceptor, a 20 mgd pump station, and an elevated storage tank.

Pipeline Route

Determining the route of a pipeline is one of the most critical elements in the development of a linear infrastructure project. The cost and impact of the project are directly related to the quality and success of the routing process. The primary objective is to select a location that is cost-effective, environmentally appropriate, and meets the needs of the project.
Traditionally, potential routes are sketched on paper and a set of criteria is developed for the evaluation of those routes. Criteria generally include environmental hazards, physical barriers, challenging road crossings, a count of affected properties, and the length of the project area.
The handful of probable, or likely, routes are tweaked to avoid critical flaws and evaluated with a scoring matrix. Viable options are selected from a brief desktop study of real estate, rights-of-way, significant environmental features, highway crossings, and length. The potential routes are then evaluated in more detail. The elements of any scoring matrix vary by project and the needs of the owner but some general criteria are cost, environmental impacts, public disruption, number of required easements, and technical challenges. Each route is evaluated objectively and scored. The scores determine the route that best meets the overall needs of the project.
This method of routing evaluation has been employed for as long as water pipelines have been used to transport drinking water to the public. However, advances in technology have improved the evaluation process, and GIS has provided some of the most dramatic changes.

New Approach

GIS specialists and modelers at URS developed a GIS-enabled Suitability Model that was employed in the South IH-35 project. Once constituted, the model does the route analysis based on information provided by the modeler. The process begins with a map of all constraints that comprise the evaluation criteria for route analysis. These evaluation criteria are the same as those used in a traditional route analysis: cost, environmental impacts, public disruption, number of required easements, technical challenges, etc. Each criterion is assigned a suitability value based on a scale of 1 to 9, with 1 being the most suitable and 9 being the least suitable. Each criterion is then weighted based on project requirements, specific concerns, and values of the owner. Some features such as critical habitat or historic resources can be designated as avoidance criteria or "no-go" areas. All suitability criteria are summed to form a suitability surface.
From the suitability surface, an optimal path for the water pipeline is determined by applying an optimal path algorithm. By applying the algorithm, the model takes a stepwise approach between a starting and ending point and it proceeds to calculate the most suitable route between the points by evaluating the criteria from the suitability surface. The optimal path algorithm focuses on minimizing constraints (i.e., crossing streams) and maximizing opportunities (i.e., paralleling property boundaries or existing infrastructure) that were previously defined in the suitability model.

The Austin project included construction of an elevated storage tank and associated pipe lines flowing to and from the tank.
In Austin, the GIS-enabled Suitability Model was used for route evaluation of the South IH-35 Program's 13 miles of water transmission main (WTM). In keeping with a compressed schedule, the PMC employed several techniques to accelerate the work, including subdivision of the WTM into 21 segments for analysis, with those segments eventually regrouped into 17 design projects. To keep the program on schedule, a fully analyzed pipeline route was given to each design firm upon notice to proceed with design. The GIS-enabled Suitability Model was used to define a route for the transmission main in order to provide a consistent methodology for all projects in an efficient and timely manner.
Early on in the process, the PMC began gathering the necessary data to develop the study area base map. At the same time, it conducted aerial surveys as well as windshield tours of the program area to allow engineers and analysts to gain a deeper understanding of the program area that would be modeled. The analysts met regularly with the AWU and the City of Austin staff as well as area developers to determine the needs of each group. Evaluation criteria were established and a cumulative suitability surface was defined upon which the analysts and engineers applied the optimal path algorithm to define the WTM route for the South IH-35 Program.

Path Evaluation

The Suitability Model provides a pipeline alignment that is rough and follows the model input criteria directly. However, the world does not exist in the GIS-created block units of the model. So, it is typical to go through an evaluation of the model route and make minor adjustments. Much of the time, the evaluation reveals minor differences requiring small adjustments in straightening out the route or improving its fit along property and easement boundaries.
For the South IH-35 Program, the typical minor adjustments were made, particularly in one area along IH-35 where the model was seeking to avoid congested areas within a retail development. The design team determined that a route aligned with the South IH-35 right-of-way would better serve the needs of the AWU than a model-generated route away from the right-of-way line.

Versatility of the Model

The GIS-enabled Suitability Model is adaptable to a wide variety of linear projects. It has proven to be effective in improving efficiency in route evaluations and is well suited to large, complex projects - particularly those providing a corridor alignment - that normally would require many weeks of evaluation and several iterations of available routes. The model also is useful for rural environments that are difficult to evaluate visually.
On the IH-35 project, the GIS-enabled Suitability Model provided a significant benefit over traditional ranking matrix evaluations in terms of cost and time efficiency. It allowed for adjustments to criteria to be evaluated quickly and easily by simply adjusting the suitability criteria and re-running optimal path routing.
About the Authors: Ron Mick is a civil engineer and project manager with URS Corporation in Austin. He has extensive experience in the design, construction, and management of water delivery systems, including transmission pipelines, pump stations, well fields, and treatment systems. He is a licensed professional engineer in Texas. Kristi Teykl serves as the Section Leader of the Geospatial Technology and Planning Services practice in the Austin office of URS. She has extensive experience developing and implementing geospatial technology and data and is responsible for conceptualization, technical design, and management of projects with a geospatial component for public and private sector clients.

Source: http://www.waterworld.com/articles/print/volume-29/issue-4/departments/automation-technology/gis-enabled-modeling-simplifies-pipeline-route-selection.html

Get sick easily?

You found yourself susceptible to ill or disease? Are you easily get influenza or have been hospitalized yearly because of some disease? I used to be in that condition when i was in junior high school. That time , I have been hospitalized yearly for two or three years because of dengue fever. My family and I felt that I was very susceptible to disease at that time. For me and my family it was a rough time because, beside I have to suffer from the illness, the cost for medical treatment to cure my disease is very expensive. But after I enter senior high school my health condition is getting better and better. That is because I realized that those bad health condition of me could worry my family and myself and i struggle to keep my health in good condition. If you had the same condition like me in the past, I have some experiences and advices to share to you.

First, to keep you healthy and away from disease, you have to manage your diet well. By eat regularly and eat hygiene and nutritious food, it is enough to get away your body  from illness. I know it is hard to have your meal regularly because of certain reason like your full activity so you don't have time to have some meal. Me myself still can't keep my meal regularly , but maybe if you provide yourself with some snacks in your bag, you can minimize this matter. This is very important to keep you healthy because food is the supply of your nutrition to and nutrition can improve your immune well. Besides from food you can add nutrition from other supply like food supplement or vitamin like i always consume everyday up to now and don't forget to consume enough water every day. Second is to have enough sleep. Sleep is important because sleep keeps you fresh every day to do your activity. If you not have enough sleep your body will easily to get tired and that is the time the disease could attack your body. The average time of sleep is about 8 hours a day. Avoid to stay up late! it was and effective way to have enough sleep and your will be away from sickness.

The third one is having a regular sports to keep your body fit. When i was in junior high school, i didn't do exercise regularly and that made my body weak. In senior high school, i join a club that like to have outdoor activity like hiking, climbing, rafting and many else. In my country it's called 'pecinta alam'. Because of the harsh environment in the outdoor, i have to strengthen my body by doing some sports like running, push up , sit up and many else. Because of joining that club i came to have sports habit. It makes my body stronger and could fight back the disease that attacks me. You don't have to join 'pecinta alam' to become more healthy but have a sports habit is very important to keep your health condition good. Three times a week, that's enough to keep your body healthy.

That was the last advice from me. I think those all was a general treatment to prevent your body from ill. I hope my writing will be help you to have a healthy body so you couldn't infected by disease easily. Last words from me, to prevent your body from disease is way lot cheaper than to cure your body from disease. That's all from me, Thank you for reading . sfbe

evaluating our character educational

Because the latest series of student brawls has causing two deaths, it is now becoming the top issue of the teenager in indonesia. Believed to have a long history of brawling, students from two senior high school in south jakarta fought each other after school hours on monday has claimed two lives tragically. Some people have argued that the incident was an assault not a student brawl, but this case might caused by the student brawl. While violent teenage behavior occurs everywhere, school brawls are more common in Indonesia. A student brawl is a form of collective social behavior of adolescent aberration and aggressive behavior resulting from group conformity. Usually a conflict flares up between two schools, and on the battlefield, students are actually wearing their school uniforms. This student brawls has harshly reminded us to reevaluate our system of chararacter education. Moreover, the more devastating is that the number of cases is increasing. Therefore, we should revisit and evaluate the current system of character education.

Character education is not simply a formal lesson that occurs at a cognitive level, but rather, it should go beyond understanding and arrive at reflecting upon what is right and doing the right thing. The only thing to fulfill that requirement is to practicing the good attitudes not anly memorizing it. Character education should not be only teachers responsbility. There should be a harmonious sinergy among families, schools, communities, and the goverment. Parents, teachers, communities and the government should be models, motivators and supporters for young generations by modeling good character, motivating youth to do a good things and supporting them to do the right thing. Character building is a long-term project that requires patience and perseverance. To make a good character building we have to aside our egos and be more sensitive to the teenagers feelings. I think that is the best idea to prevent and stop the student brawls. Lets start to make a better character education by ourself first.

the correlation between wii sales and kid's fatness(?)

are there a correlation between wii sales and kid's fatness? of course there is. kids these days are obsessed to playing games instead of playing outside or have a workout or anything else that burn calories more than just sitting on the couch and playing games. these sedentary lifestyle usually called couch potato.  these habits could lead the kids to become fat and gain obesity, because they only spend their times on the couch playing games and pile up calories in their bodies. according to the author of the article i just read, wii once believed could solve the problem couch potato problem as wii players suffer more exercise than only just their thumbs. however, based on the study that published in journal pediatrics, kids that given active games from wii burned no more calories than those who played the more passive one, that is caused by some reason. the author also write that wii sales in the second quarter have been reduce massively. but that is because the current version is getting old. nintendo hopes to get back on track with the new version of wii, wii u game pad. but no matter how it work, still can't prying kids from their couches. beside that, the author add another case from a famous book titled "when things bite back". the books present a fascinating collection of technologies that had unintended consequences, even some that undo precisely what those technologies were meant to foster.

what i said about this problems is all the kids that have a console games or any else games that don't require a big exercise could have this couch potato lifestyle but it's all according the way of the kids in deal with the games that they own. if the kids know how to arrange time so they didn't spend all day and night sitting on the couch, they could be spared from this bad habit. parents should concern to this problem and have to do something to prevent their kids to become fat kids. parents these day think that if they give their children console games they could make them happy and they don't have to interact frequently with their children so they could occupy themself to their business. these thoughts were wrong, the children could be happy in a short time but the effect of couch potato habits like obesity and laziness are pathetic. parents should give some of their spare time to their kids like urge them to play basketball in the garden or bring them to travel or go outside the home. i believed that if parents do these things, their children will be happy and the relationship between parents and child will improved. of course parents could give their children a console game to make them happy but they also have to give the children a little discipline so the children won't play games all of their time. i think that's all my response to an article titled "wii sales may recover, but kids will still be fat". Thank you for reading my writing and don't forget to give feedback on the comment box. sfbe

introduction

Hello universe , this is my first post in my first new blog. My name is Siraragi Banta or you can call me agi , i'm student of Civil and Environment Engineering Faculty ITB. The reason I created this blog because my Academic Writing Lecturer told to make a blog and make a writing in it. Actually I don't like to writing in English, but because I entered academic writing class so i have to write in English frequently to fulfill my lecturer's assignment for me. I like to play guitar so much , that's the cause i chosen agionguitar for my blog address. For the future, i will write here monthly to fulfill my assignments . I hope my writing will be good and useful for anyone that read it. I think this is the end of my first post in my blog. Thank you for reading, sorry for bad english.