Essay: Thesis: Performance evaluation of welding process in EPC project using grey relational analysis

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  • Thesis: Performance evaluation of welding process in EPC project using grey relational analysis
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EXECUTIVE SUMMARY
In recent years, the construction industry has been a visible shift from owner managed construction projects to EPC project with independent but different disciplines of construction. The EPC contractor takes the responsibility of completing the project in a given cost and time frame and acts as a single point interface between the promoter and all other agencies connected with the project. The Global construction industry market has been captured by EPC firms who have limited the otherwise predominant role of engineering consultants.
Delivering of the project with respect to its predetermine cost and time is the major challenge faced by any company. So to improve the project performance, we have to consider all the variables which affect the project cost or time. The formality and details of project variables will vary with the size and complexities. By going through a study of different variables, categorization is done into exogenous and endogenous variables. Project risk, project uncertainties, project scope, etc. are the variables which we considered and effect of each such variable with respect to project performance is analyzed.
A project, ‘Construction of an oil storage tank’ is undertaken and studies of all variables which affect the project performance have been done. Considering the welding defect as a major factor, the Grey Relational Analysis tool was successfully implemented and significant factors were interpreted.Data on welding from different industries were collected and a list of affecting factors ranked according to their importance or impact on welding was determined.Analysis results of sample data showed that the main factor which affect the welding are Speed Variation and Weld Rod Quality; while the least important factors need to be considered is Labour Productivity. Thus, by properly adjusting the significant affecting factors, the welding performance can be improved efficiently. Furthermore, GRA can provide a ranking scheme that rank the order of the grid relationship between dependent and independent factors and this allow us to decide which input factors need to be considered to forecast more precisely.
Table of Contents
1. INTRODUCTION 2
1.1 Construction Project 2
1.2 Fabrication projects 3
1.3 Objective of the study 3
2. LITERATURE REVIEW 5
2.1 Introduction 5
2.2 Project Performance and their variables 6
2.2.1 Project Risk 8
2.2.1.1 Variables of Risk 9
2.2.2 Procurement 10
2.2.2.1 Effect of procurement on project performance 12
2.2.3 Project Scope Management 12
2.2.3.1 Project Scope objectives 13
2.2.3.2 What is project scope? 13
2.2.3.3 Steps for defining the scope of a project 13
2.3 Fabrication 14
2.3.1 Welding Process 14
2.3.1.1 Types of Welding and Their Applications 15
2.3.1.2 Types of Electrodes 17
2.3.1.3 Electrode Defects and Their Effects 20
2.3.2 How Fabrication Quality Continues to Affect Performance 21
2.3.3 Qualities to Look for When Choosing a Company for Fabrication 22
3. CONCEPT 25
4. METHODOLOGY 26
4.1 Grey Relational Analysis: 26
5. CONCLUSION 34
5.1 Conclusion for Oil Storage Tank 34
5.2 Conclusion 35
REFERENCES 36
List of Tables
Table 1. No. of Defects Made in Tank 28
Table 2. Pre-processed Data 30
Table 3. Showing Grey Relational Coefficient 32
Table 4. Grey Relational Grade 33
Table 5. Response table of Grey Relational Grade 34
List of Figures
Figure 1- Types of Procurement 11
Figure 2-Requirement for Welding Process 15
Figure 3- Molten metal transfer with a bare electrode 17
Figure 4- Arc Action Obtained With a Light Coated Electrode 18
Figure 5- Arc Action Obtained With A Shielded Arc Electrode 18
Figure 6- Variables Considered for Fabrication Project 25
Figure 7- Flow Diagram of Grey Relational Analysis 27
CHAPTER – 1
INTRODUCTION
There are a number of challenges facing today’s project manager. Some are new to the construction industry, and some are old. But most of these challenges are because of project operations, while others are a result of indirect activities. All challenges are not from project issues, but must be addressed and taken into consideration by the project manager (PM) in order to ensure project success. Some of the project issues which today’s construction industry facing are workforce considerations, cost, scope, safety, delivery time, and the changing nature of the work etc. These are mainly endogenous variables. PMs also face non-project challenge which is a part of the business landscape includes legal issues, government regulations, environmental concerns, and socio-political pressures. These are mainly exogenous variables. It is critical that the PM understands the demanding realities that he or she faces in the planning and control of project operations.
The projects represent a unique set of activities to produce a unique product with the given time frame. The success of a project can be measured by meeting the criteria of budgeted cost, delivery time, safety, effective utilization of resources and quality which is predetermined. The purpose of Project Management is to achieve goals and objectives through the planned expenditure of resources that meet the project’s quality, cost, time, scope, and safety requirements. Tools and techniques play an important role in project management. The PM must control, deflect, or mitigate the effects of any occurrence or situation that could affect project success.
1.1 Construction Project
The construction delay is a universal evident reality, not only in India, however all the countries faced this global fact. Delay in project counts as a common problem in construction projects. On large level, there is no suspicion that the development of the country depends upon the infrastructure development. There is a French dictum ‘when the construction industry prospers everything prospers’. Escalation of construction industry is of imperative for all regions of national and international economy, as well as every stakeholder involved in the industry like contractors, workers, financiers, architects, engineers etc. The project’s success depends on meeting objectives within time and budget limits.
The major factor of construction problems is project’s delay. Delay means loss of income according to and for the owner or client. In case of contractor, delay refers to the higher costs due to longer work time, labour cost increase and higher fabrication costs. On time completion of project is an indicator of efficiency. But there are many unpredictable factors and variables resulting from various sources affecting construction projects. Some main sources are the involvement and performance of parties, contractual relations, environmental and site conditions, resources availability etc. It is very rare to see that a construction project is completed on time.
1.2 Fabrication projects
Oil tanks were not viewed as an issue or a hazard until we better understood the environmental impact and became more sensitive to the increasing fragile nature of the environment. Maintenance of the tank is required on the time to time basis because tanks are not designed to last a lifetime and will need to be replaced. Therefore it is necessary to ensure that their equipment is in compliance with regulations to minimize these risks.
Leaks remain undetected and increases gradually for many years, or catastrophic, resulting from the sudden rupture of the fuel oil tank often being attributed to one or several of these factors:
‘ Manufacturing defects
‘ Physical damage
‘ Corrosion
‘ Fuel delivery issues
1.3 Objective of the study
The study is carried out to find out which variable creates more effect on performance of project and so that significant measures can be taken to improve the project performance. Variables which affect the project performance are studies and interpretations of each variable are done, whether the effect is positive or negative on project performance. Analysis and evaluation is done on these variables by using the tool named GREY RELATIONAL ANALYSIS and ranking or prioritization is done accordingly to their significant effect on project performance.
CHAPTER – 2
LITERATURE REVIEW
2.1 Introduction
Today, Project Industry in the need of every industry and is getting diversified in every possible sector; as this industry serves as the foundation for every other industry for their operations, for ex: infrastructure for government and industrial infrastructure for in house manufacturing or refineries and other.
.
The major differentiator between Project industry and other industries in that, in project industry every project is unique, and follows different procedures and processes. For every project the Scope for development, the procurement procedure, the resources, the Location of project, the Laws and Governance, etc. changes from project to project.
Since the Size of the projects are increasing in terms of the development size and investments, the projects are getting highly resource intensive and complex in nature. This has created a need for measuring the project performance and analysis of the project Variables. The analysis of project variables is important as, this will help project manager to understand that, what are the variables which are critically important for the successfully completion of the project.
This uniqueness of the project industry creates problems for the analysis of project variables. The Data availability for every variable of the project is not possible. But quantifying this project variable is very important to measure the performance of the project.
This study is focused on the effects of the project performance variables. This study will be analyzing all the project variables which will have effect on the project performance, as well as interpret the intensity of effect on the project performance.
There are various tools available to analyze the performance of this project variables, for ex: ANOVA Method, Various Statistical Methods, Various Software tools like SPSS, etc. This all tools are highly dependent on the data availability of the variables, more the data available more is the Answer accurate. But since every project is unique in nature, the data available from them varies and this creates problem in analyzing them. Due to lack of data availability we cannot use all this tools.
For this problem there is a tool available Called ‘Grey Relational Analysis (GRA)’. Gray Relational Analysis overcomes the problem of lack of availability of data. Grey Relational Analysis delivers more accurate results in less data, it also helps to identify the intensity of variables.
To study more on Gary Relational Analysis and its use in Analysis of Project Performance Variables. We first need to understand what is Project Performance and their variables. And further we will be focusing on Grey Relational Analysis (GRA).
2.2 Project Performance and their variables
The project performance is the overall quality of a project in terms of its impact, the value for the beneficiaries, the effectiveness of implementation efficiency and sustainability. Project performance depends on several variables, such as:
Project Risk
Procurement
Scope
Finance
Human resource Management
Integration Management
Risks and uncertainties are inherent substantially in project performance. Problem, many projects could not have achieved the objectives of the project satisfactorily. One of the most frequent failure is project delay and cost overrun. Main reason is the occurrence of external and internal project risks and uncertainties in all project phases’ ice from planning, bidding, procurement, contracts for construction. As a result, many projects completed with poor project performance. It is still questionable as to why this project failure phenomenon is occurring. Thus, the following sub-sequential issues come and wait for answers. What are the risks and uncertainties inherent in projects? How they are conventionally managed? There are limitations associated with these conventional approaches? How should it be improved? This study attempts to answer these questions.
Before moving on, the definition of “risk” and “uncertainty” is discussed in this study. In this, the risk management is discussed in project management context. Risk and uncertainty are categorized into three components namely,
1) risk / uncertainty event
2) probability of occurrence, and
3) outcome: potential loss / gain.
Note that the definition of risk and uncertainty are basically different, based on “position” of parties in a project. Here the term “risk’ and “uncertainty” are defined as follows:
“Risk” means the event / condition such that
a) Their occurrence is identifiable
b) It brings negative effect to design goal
c) the probability distribution of the outcome of the event is quantifiable
d) is controllable by a party
“Uncertainty” means the event / condition such that
a) their occurrence is not identifiable
b) may have a positive or negative effect to design goal
c) the probability distribution of the outcome of the event is unquantifiable
d) is uncontrollable by either party.
Project performance is also effected by project procurement .Project procurement has been described as an organized methods or process and procedure for clients to obtain or acquire construction products. In addition to the traditional approach, there are now innovative or fast-tracking procurement systems used by the construction industry worldwide . The different procurement systems differ from each other in terms of allocation of responsibilities, sequencing activities, process and procedure and organizational approach to project delivery. These differences have invariably affected project performance. The project performance has been defined as ‘the degree of achievement of certain effort or undertaking’ which relates to the prescribed goals or objectives that form the project parameters. There are many other elements that determine the success of the project, but the focus on the three critical parameters and project performance i.e., time, cost and quality.
2.2.1 Project Risk
Risk management in construction projects is considered as an important part of the management process. Risks in construction projects associated with three main principles, which are time, cost and quality. Risks and uncertainties which are caused by the performance of workers, material and component quality, delays in the supply of important materials to the site, the project budget and cost control, or the complexity of the project procurement processes, which can threaten the project performance. The Risk is caused by the complexity of the construction procurement process. Risk identification methods should start with the creation of a risk profile, risk prevention, basic risk assessment, useful measures of risk mitigation for project management participants, especially the architects and project managers to understand the risks associated in the process of construction, including how to mitigate these risks.
Risks and uncertainties occur in each type of project, and as such, each project must be considered individually and should not be underestimated. In focusing on construction industry itself, it was found that maximum possible risk to the contractor occurs in the Lump Sum contract in which the extent of the work is moderately well identified and the cost of the work is tendered as a non-possible change project. In the case of rising prices the project due to economic factors and / or extension of the duration of construction, due to industrial action, inclement or material shortage time, these are a great disadvantage to the contractor.
Risks in construction procurement process were considered in relation to the separation of the construction project, lack of integration, lack of communication, uncertainty, change of environment and economic changes, such as inflation and deflation, the regional economic crisis, etc. including increased competition in the construction field. These factors led to the construction industry to seek alternative procurement strategies, such as management contracting; design and construction meet in an improved process designed to reduce the risks as indicated above. There are many risks and uncertainties inherent in all construction and in every project size. The size of the project can be a risk factor due to its complexity, and it can also become unstable in political or commercial planning. On the other hand, there are some risks that cannot be quantified and are therefore sensibly Priced.
Risk is generally covered in construction contracts as follows:
Fundamental Risk is risk such as war chaos or similar events. These risks are all covered by government and construction contracts, which usually refer to, and place the effects of them if they occur. Anyway, the typical construction contract does not cover this risk and no insurance is normally required within the contract for risk, or in fact could normally be obtained.
Pure and Particular Risk: The examples of this kind of risk are personal injury and damage to neighboring building during construction, or similar events. Construction contracts usually require the contractor to compensate employers against some of the effects of occurrences. Contractors are also generally required to takeout relevant policies as protection against such events.
Speculative Risk is risk that can be varied in its incidence between each project participant.
2.2.1.1 Variables of Risk
Risks in each construction project have been identified by the project management level using brainstorming techniques or expert panel discussions. However, risks are defined as events that could arise and affect the critical factors of the project. Some of the major risks usually found in construction projects include:
delay in letting contract
obtaining appropriate approvals
poor tenders
technological improvements
construction material delays
construction equipment delays
material quality and specifications
industrial action
inclement weather
Occupational, health, welfare and safety.
In regard to the construction procurement process, the sources of risks in this procurement or contractual process can be summarized as:
client/government/regulatory agencies
funding/fiscal
definition of projects
project organization
design
local rules or conditions
permanent supplier/plant
construction contractors or subcontractors
construction materials
labour
logistics
estimating data
some national economic indicators such as inflation, currency exchange rate or consumer price index
force majeure or unforeseen events
construction plant
lack of procurement experience
2.2.2 Procurement
It is the act of obtaining or buying the goods and service. This process includes preparation and process of demand as well as end receipt and approval of payment. It often involves:
Purchase planning
Standard determination
Specification development
Supplier research and development
Value analysis
Financing
Price negotiation
Making the purchase
Supply contract administration
Inventory control and stores
Disposal and other related functions
Generally procurement is meant to be acquisition of goods, service or works from an external source. It is favorable that the goods, service or works are appropriate and that they are procured at the best possible cost to meet the need of the purchaser in terms of quality and quantity.
When comes to procurement decision, almost all purchasing decision include factors such as delivery and handling, marginal benefit and price fluctuations. Procurement generally involves making or buying decision under conditions of scarcity.
The different category and sub-classification of construction project procurement systems can be shown in Figure below
Figure 1- Types of Procurement
2.2.2.1 Effect of procurement on project performance
Cost, time and quality are the three main parameters of operation of the project. It was emphasized that in the highly competitive and uncertain business environment today, customers are demanding a better return on your investment. They want your project is completed on time, within the estimated cost and with the right quality. The use of different procurement systems projects shows that the construction industry is now trying to meet the needs of customers. This is because the different procurement method will have different effects on the cost, time and quality of the project. Each project procurement system has its own peculiarities in terms of pre- and post-tender conditions and processes, risk-sharing arrangements between client and contractor, and the effectiveness of the monitoring and control of project activities.
It is very important to carefully consider from the outset of the project, all factors in selecting the most appropriate method of procurement for a construction project. That’s because each system has its own function and nature, the impact on the cost, time and quality of the project that will have the energy project.
2.2.3 Project Scope Management
As a project manager, there is a need of project scope, no matter what method he choose to define the scope. If the project scope is not defined correctly, the entire execution will go wrong.
To define scope the first step we need is creating a project timeline, establishing project objectives and allocation of resources to the project. These measures will help project managers to define which work to be done. Once done, the next step is to assign task and provide direction to the team, in order to deliver the project on time and within budget.
In the life cycle of the entire project, project scope may vary i.e. client may change the scope in planning or in execution period. The scope may be the omission of some part of the development or adding development can be mainly or change specifications or design.
2.2.3.1 Project Scope objectives
In order to define the scope of a project, you must first create the project objectives. The aim of a project may be to produce a new product, create a new service within the organization, to provide or develop a new piece of software. There are a number of objectives that could be of vital importance for a specific project – and it is the role of the project manager to see that your team or contractor may deliver an outcome that meets the specified functions and features.
2.2.3.2 What is project scope?
The work and resources that go into creating the product or service is substantially the things that make the project scope. The scopes of the project are the project goals and objectives to be met in order to achieve a satisfactory result. Each project manager should understand how to determine the scope of the project and there are steps that can be followed here.
2.2.3.3 Steps for defining the scope of a project
To define a project scope, project manager must first identify the following things:
Project objectives
Goals
Sub-phases
Tasks
Resources
Budget
Schedule
Once they are established, project managers need to clarify the limitations of the project and identify all aspects that should not be included. In determining what is included and what is not included in the project scope should make it clear to stakeholders, managers and team members that the product or service being delivered.
As a project manager, understanding and defining project scope can give us a focus and determination in implementing the project. Understanding the scope provides the project manager the basics for change management and project risk management.
2.3 Fabrication
Metal fabrication is a value added process that involves the construction of machines and structures from various raw materials. A metal fabrication usually based on the engineering drawings. Large fab shops will employ a multitude of value added processes in one plant or facility including welding, cutting, forming and machining. Metal fabrication jobs usually start with shop drawings including precise measurements then move to the fabrication stage and finally to the installation of the final project. Fabrication shops are employed by contractors, OEMs and VARs. Typical projects include; loose parts, structural frames for buildings and heavy equipment, and hand railings and stairs for buildings.
Welding is the main focus of steel fabrication. The formed and machined parts will be assembled and tack welded into place then re-checked for accuracy. A fixture may be used to locate parts for welding if multiple weldments have been ordered.The welder then completes welding per the engineering drawings, if welding is detailed, or as per his own judgment if no welding details are provided.
Special precautions may be needed to prevent warping of the weldment due to heat. These may include re-designing the weldment to use less weld, welding in a staggered fashion, using a stout fixture, covering the weldment in sand during cooling, and straightening operations after welding which may affect the project delivery.
2.3.1 Welding Process
Welding is a process of joining similar or dissimilar metals by application of heat with or without application of pressure and addition of filler material.Welding is used for making permanent joints. The application of welding are so varied and extensive that it would be no exaggeration to say that there is no project or branch of engineering that does not make use of welding.It is used in the manufacture of automobile bodies, aircraft frames, railway wagons, machine frames, structural works, tanks, furniture, boilers, general repair work and ship building.For welding process there are 4 main requirements. They are:
Heating- Heating of enough intensity to cause melting of base metals and filler metals.
Protection- Protection of molten filler metal in transit and base metal from oxidation and to protect the heat source and metals from ingress of gases such as hydrogen and oxygen.
Cleaning- Cleaning of weld metal to remove oxides and impurities and refine the grains.
Mixing- Mixing of alloying elements to the weld to produce the desired mechanical properties.
Figure 2-Requirement for Welding Process
2.3.1.1 Types of Welding and Their Applications
Because the conditions, demands, and materials to be joined vary widely, different types of welding processes have been developed. Each process serves a different need and has its own set of pros and cons and general applications. What follows is a description of several of the most common and important welding services.
Shielded Metal Arc Welding (SMAW)
Gas Tungsten Arc Welding (GTAW)
Gas Metal Arc Welding (GMAW)
Flux-Cored Arc Welding (FCAW)
Submerged Arc Welding (SAW)
Shielded Metal Arc Welding (SMAW)
Shielded Metal Arc Welding is also known as ‘SMAW’ or as ‘stick welding.’ The stick in question refers to the electrode, which is coated in a protectant flux. An electrode holder holds the ‘stick’ in place and an electric arc is created using either direct or alternating current. This in turn causes the electrode to slowly melt away while also melting the metals to be joined. At the same time the flux coating releases a gas vapor which, together with the slag, creates a shielded environment to protect the weld area from contamination.
Gas Tungsten Arc Welding (GTAW)
Gas Tungsten Arc Welding, also known as ‘GTAW’ or ‘TIG welding’ uses a tungsten electrode to produce the weld. Unlike SMAW welding the electrode is not consumed during the welding process. Instead the weld area is protected from atmospheric contamination by an inert gas, often Argon or Helium gas. The acronym ‘TIG’ refers to ‘Tungsten Inert Gas.’
Gas Metal Arc Welding (GMAW)
Gas Metal Arc Welding, also known as ‘GMAW’ or ‘MIG welding’ uses a consumable wire electrode that is fed through a welding gun. An inert shielding gas such as Argon or a mixture of Argon and Carbon Dioxide is also sprayed over the welding puddle to protect it from contamination. MIG welding has become the most common welding method in industrial settings because of its versatility and relative ease. However, it is not ideal for use outdoors or in other areas with high air volatility.
Flux-Cored Arc Welding (FCAW)
Flux-Cored Arc Welding, or ‘FCAW,’ is very similar to MIG welding; however, it features the use of a special tubular wire that is filled with flux. The flux may be sufficient by itself to protect the welding puddle from contamination or a shielding gas may also be used, depending on the filler material and other circumstances.
Submerged Arc Welding (SAW)
Submerged Arc Welding, or ‘SAW,’ uses a consumable electrode that is fed automatically. It also uses a characteristic blanket of granular fusible flux, consisting of several compounds including silica, lime, calcium fluoride, and manganese oxide among others. This blanket of granular flux thus completely ‘submerges’ the welding area thereby protecting it.
Together these, and other welding services, do an outstanding job of servicing the industrial fabrication industry, especially when they are performed by highly qualified, experienced welders.
2.3.1.2 Types of Electrodes
Bare Electrodes
Bare welding electrodes are made of wire compositions required for specific applications. These electrodes have no coatings other than those required in wire drawing. These wire drawing coatings have some slight stabilizing effect on the arc but are otherwise of no consequence. Bare electrodes are used for welding manganese steel and other purposes where a coated electrode is not required or is undesirable. A diagram of the transfer of metal across the arc of a bare electrode is shown in figure.
Figure 3- Molten metal transfer with a bare electrode
Light Coated Electrodes
Light coated welding electrodes have a definite composition. A light coating has been applied on the surface by washing, dipping, brushing, spraying, tumbling, or wiping. The coatings improve the characteristics of the arc stream. The coating generally serves the functions described below:
It dissolves or reduces impurities such as oxides, sulfur, and phosphorus.
It changes the surface tension of the molten metal so that the globules of metal leaving the end of the electrode are smaller and more frequent. This helps make flow of molten metal more uniform.
It increases the arc stability by introducing materials readily ionized (i.e., changed into small particles with an electric charge) into the arc stream.
Some of the light coatings may produce a slag. The slag is quite thin and does not act in the same manner as the shielded arc electrode type slag.
Figure 4- Arc Action Obtained With a Light Coated Electrode
Shielded Arc or Heavy Coated Electrodes
Shielded arc or heavy coated welding electrodes have a definite composition on which a coating has been applied by dipping or extrusion. The electrodes are manufactured in three general types: those with cellulose coatings; those with mineral coatings; and those whose coatings are combinations of mineral and cellulose. The cellulose coatings are composed of soluble cotton or other forms of cellulose with small amounts of potassium, sodium, or titanium, and in some cases added minerals. The mineral coatings consist of sodium silicate, metallic oxides clay, and other inorganic substances or combinations thereof. Cellulose coated electrodes protect the molten metal with a gaseous zone around the arc as well as the weld zone. The mineral coated electrode forms a slag deposit. The shielded arc or heavy coated electrodes are used for welding steels, cast iron, and hard surfacing. See figure 5-31 below.
Figure 5- Arc Action Obtained With A Shielded Arc Electrode
Tungsten Electrodes
Non-consumable welding electrodes for gas tungsten-arc (TIG) welding are of three types: pure tungsten, tungsten containing 1 or 2 percent thorium, and tungsten containing 0.3 to 0.5 percent zirconium.Tungsten electrodes can be identified as to type by painted end marks as follows.
Green — pure tungsten.
Yellow — 1 percent thorium.
Red — 2 percent thorium.
Brown — 0.3 to 0.5 percent zirconium.
Pure tungsten (99. 5 percent tungsten) electrodes are generally used on less critical welding operations than the tungsten’s which are alloyed. This type of electrode has a relatively low current-carrying capacity and a low resistance to contamination.
Thoriated tungsten electrodes (1 or 2 percent thorium) are superior to pure tungsten electrodes because of their higher electron output, better arc-starting and arc stability, high current-carrying capacity, longer life, and greater resistance to contamination.
Tungsten welding electrodes containing 0.3 to 0.5 percent zirconium generally fall between pure tungsten electrodes and thoriated tungsten electrodes in terms of performance. There is, however, some indication of better performance in certain types of welding using ac power.
Direct Current Arc Welding Electrodes
The manufacturer’s recommendations should be followed when a specific type of welding electrode is being used. In general, direct current shielded arc electrodes are designed either for reverse polarity (electrode positive) or for straight polarity (electrode negative), or both. Many, but not all, of the direct current electrodes can be used with alternating current. Direct current is preferred for many types of covered, nonferrous, bare and alloy steel electrodes. Recommendations from the manufacturer also include the type of base metal for which given electrodes are suited, corrections for poor fit-ups, and other specific conditions.
In most cases, straight polarity electrodes will provide less penetration than reverse polarity electrodes, and for this reason will permit greater welding speed. Good penetration can be obtained from either type with proper welding conditions and arc manipulation.
Alternating Current Arc Welding Electrodes
Coated electrodes which can be used with either direct or alternating current are available. Alternating current is more desirable while welding in restricted areas or when using the high currents required for thick sections because it reduces arc blow. Arc blow causes blowholes, slag inclusions, and lack of fusion in the weld.
Alternating current is used in atomic hydrogen welding and in those carbon arc processes that require the use of two carbon electrodes. It permits a uniform rate of welding and electrode consumption. In carbon-arc processes where one carbon electrode is used, direct current straight polarity is recommended, because the electrode will be consumed at a lower rate.
2.3.1.3 Electrode Defects and Their Effects
If certain elements or oxides are present in electrode coatings, the arc stability will be affected. In bare electrodes, the composition and uniformity of the wire is an important factor in the control of arc stability. Thin or heavy coatings on the electrodes will riot completely remove the effects of defective wire.Aluminum or aluminum oxide (even when present in 0.01 percent), silicon, silicon dioxide, and iron sulphate unstable. Iron oxide, manganese oxide, calcium oxide, and stabilize the arc.
When phosphorus or sulfur are present in the electrode in excess of 0.04 percent, they will impair the weld metal because they are transferred from the electrode to the molten metal with very little loss. Phosphorus causes grain growth, brittleness, and “cold shortness” (i. e., brittle when below red heat) in the weld. These defects increase in magnitude as the carbon content of the steel increases. Sulfur acts as a slag, breaks up the soundness of the weld metal, and causes “hot shortness” (i. e., brittle when above red heat). Sulfur is particularly harmful to bare, low-carbon steel electrodes with a low manganese content. Manganese promotes the formation of sound welds. If the heat treatment, given the wire core of an electrode, is not uniform, the electrode will produce welds inferior to those produced with an electrode of the same composition that has been properly heat treated.
2.3.2 How Fabrication Quality Continues to Affect Performance
Quality is important in every type of business transaction. Industrial fabrication is particularly important because the quality of the fabrication will continue to affect performance for many years to come. This article highlights several of the key areas that fabrication quality impacts.
Maintenance
Output Quality
Efficiency and Operating Costs
Reliability
Lifespan
Upgrades and Retrofits
Safety
Maintenance
From routine service and maintenance to more full scale shutdowns and turnarounds, maintenance costs have a huge impact on a company’s bottom line. In many cases a high quality fabricated product will incur much lower maintenance costs over the course of its service life span than a poorly fabricated product. In addition to maintenance costs, the ease and efficiency of maintenance is also an important factor.
Output Quality
The output quality of many types of industrial equipment is also affected by the quality of fabrication. In some cases the quality of output may be reduced right from the start, whereas in other cases the quality of output may gradually, or even sharply, decline over time.
Efficiency and Operating Costs
Efficiency and operating costs are another crucially important element affected by fabrication quality. A poorly fabricated item may have a much less efficient output, burn more fuel, or generally be much more expensive to run and keep running.
Reliability
A major obstacle of any industrial facility or plant is an unplanned outage. Such outages bring production and profits to a halt and often require costly repairs and replacement parts to fix. Unplanned outages can also destroy a production schedule or cause a company to miss deadlines and benchmarks. Poorly fabricated equipment and infrastructure can cause production to decrease or even worse’stop.
Lifespan
Good fabrication quality can also increase the overall lifespan of the structure or equipment, thereby saving the company time and money on a replacement. Obviously all things being equal it is much more budget friendly to replace something once every ten years versus once every five years.
Upgrades and Retrofits
Even the best equipment needs to be upgraded or retrofitted occasionally. Not only can proper fabrication delay the need for retrofitting but it can also ease the transition when an upgrade is absolutely necessary.
Safety
Poorly fabricated parts and equipment can also pose a safety risk in some cases. Since safety is a major concern at all workplaces, especially industrial workplaces, this reason alone is often enough to make a company think twice about using a less than high quality fabricator.
2.3.3 Qualities to Look for When Choosing a Company for Fabrication
In many ways industrial fabrication is the very backbone of industry itself. It is industrial fabrication that creates the equipment, parts, and structures that ultimately form the framework of industrial facilities and that allows them to reach their full production potential. Thus, it is vital that the company performing industrial fabrication for having facilities be the best that it can be. Yet, competition is fierce and finding the best industrial fabrication company isn’t always easy. The following list of important qualities to look for when choosing an industrial fabrication company:
Capacity & Fabrication Space
ASME Certification
Welding Capabilities
Transport Access
Manpower & Craftsmen Expertise
Equipment Fleet
Breadth of Experience
Dedication to Quality
Commitment to Safety
Capacity & Fabrication Space
One of the most basic, but important qualities to consider is the company’s capacity and fabrication space. Assuming that the company also has the manpower, equipment, and other requisite resources, more fabrication space obviously means higher capacity. Sufficient capacity is important to prevent bottlenecking and backlogs which, if left unchecked will rapidly derail production schedules.
ASME Certification
ASME, the American Society of Mechanical Engineers, is an organization that provides standards certification for industrial shops and companies. ASME certification is important because in order to receive ASME’s certification stamps the facility must meet a series of crucial quality and safety standards. Thus, it is a very good sign if industrial fabrication company has received ASME certification.
Welding Capabilities
Welding is at the core of most industrial fabrication processes. The industrial fabrication company we choose should have a wide range of welding capabilities since this will in turn dictate the type of fabrication they can do and will also ensure that the best welding technique possible is being used for a given application. Some important industrial welding services include the following: GMAW, GTAW, SMAW, SAW, and FCAW.
Transport Access
Transport access is an important quality to consider when choosing an industrial fabrication company because it will dictate how quickly and efficiently the fabrication company can send out and receive finished fabricated products or the raw materials used to create them.
Manpower & Craftsmen Expertise
It is important to consider the experience and expertise level of those workers. Industrial fabrication often requires sophisticated techniques that only an advanced craftsman can perform. Make sure to enquire with potential fabrication companies about the training and experience of their craftsmen as well as the size of the company’s overall labor force.
Dedication to Quality
Dedication to quality is an important characteristic for just about any type of company or business to possess. However, it is extremely important for an industrial fabrication company because a defective or sub-par part could result in a full-scale outage at a plant or factory or even endanger the lives of employees at the facility or those in the surrounding community. Breakdowns and outages are also typically extremely costly, both in terms of actual repairs as well as lost productivity and downtime.
Commitment to Safety
A strong commitment to safety is also non-negotiable. We must be able to trust that the fabricated parts and equipment are completely safe to use, have been fabricated in a safe, secure way, and that the materials used are also safe and high quality. No industrial company can afford the human toll, financial burden, or bad publicity that will arise if there is a major accident or safety failure.
CHAPTER ‘ 3
CONCEPT
Figure 6- Variables Considered for Fabrication Project
The above model depicts the concept behind our thesis approach. As we have considered medium project i.e. Fabrication of Oil Storage tank , for that the above six factors have been identified, namely, Project Uncertainties, Labour Productivity, Weld Rod Quality, Preparation of Material, Speed Variation and Voltage Fluctuation.
In our study we will be discussing how these factors affects the performance of the project by prioritising these factors in accordance with their ranking by using Grey Relational Analysis and comes out with the conclusion.
CHAPTER ‘4
METHODOLOGY
4.1 Grey Relational Analysis:
The Grey relational theory was established by Dr. Deng (1982). It gives an efficient solution to the unknown, multi-input and discrete data problem. It uses information from grey system in order to compare each factor quantitatively. This approach is used to establish relation between various factors which have similarity and variability among all the factors. This analysis suggests from the report that how to make decision for selecting any vendor, what are the factors affect the project performance by giving ranking to the factors. This analysis clarifies the relation among all the factors. The main advantage of doing Grey Relational analysis is that it requires small data for doing analysis as compare to any other statistics method.
There are three main steps in Grey relational analysis. The first step is to process the raw data by data pre-processing method. In this method original data sequence is transferred to comparable sequence. This process is called generation of grey relation. There are two ways to do generation of grey relation:
If expectancy is higher-the-better then it is expressed by
X^* (k)=(X_i^o (k)-min”X_i^o (k)’)/max”X_i^o (k)-minX_i^o (k)’
If expectancy is lower-the-better then it is expressed by
X^* (k)=max”X_i^o (k)-X_i^o (k)’/max”X_i^o (k)-minX_i^o (k)’
Where,
X_i^o (k)is the original sequence
X^* (k)is the sequence after data pre-processing
k=1,’n where n is the number of parameters
The second step is to find the Grey relational coefficient in order to represent the desired and actual data by using equation
??_i (k)=(‘min”+’??max’)/(‘_(0,i) (k)+’??max)
Where,
?? is known as identification coefficient
After the Grey relational coefficient is done then Grey relational grade (GRG) is calculated and it is between 0 to 1. Grey relational grade is calculated by
??_i=1/n ‘_(k=1)^n”??_i (k)’
Where,
?? is Grey Relational Grade
Depending upon GRG we rank the factors which affect more or less. Following is the flow diagram of Grey Relational Analysis:
Figure 7- Flow Diagram of Grey Relational Analysis
In our study we have considered a fabrication project i.e. Oil Storage Tank Project. For a tank project we have identified five factors which affects the tank project by visiting tank manufacturing industries. During our visit we have collected data from industries. Table-1 shows data for a Oil storage tank project and its affecting factors.
Voltage Fluctuation Over Load 4 3 5 3 5
Under Load 4 4 5 4 5
Speed Variation Over Speed 4 4 3 4 5
Under Speed 0 0 1 0 0
Preparation of Material Material Not Heated 3 5 4 4 1
Material Pre-heated 2 1 1 2 1
Rod Not Heated 3 5 4 4 3
Rod Pre-heated 2 1 1 2 1
Weld Rod Quality Mangalam 4 4 5 4 6
Sitron 3 3 4 4 3
Mailam 2 2 3 2 3
Labour Productivity Skilled 1 0 2 2 2
Semi-Skilled 3 3 2 4 3
Oil Storge
Tank Tank 1 Tank 2 Tank 3 Tank 4 Tank 5
Table 1- No. of Defects
For carrying out Grey relational analysis we have to first normalize the original data by using data pre-processing in order to form grey relational generation. This is carried out to form relationship between desired data and actual data. In our study we have considered lower the better expectancy which means the lower value is ranked first which affects the tank project more and similarly the other one.
By using formula:
X^* (k)=max”X_i^o (k)-X_i^o (k)’/max”X_i^o (k)-minX_i^o (k)’
We have normalized the data and it lies between 0 to 1.
Voltage Fluctuation Over Load 0.5 0 1 0 1
Under Load 0 0 1 0 1
Speed Variation Over Speed 0.5 0.5 0 0.5 1
Under Speed 0 0 1 0 0
Preparation of Material Material Not Heated 0.5 1 0.75 0.75 0
Material Pre-heated 1 0 0 1 0
Rod Not Heated 0 1 0.5 0.5 0
Rod Pre-heated 1 0 0 1 0
Weld Rod Quality Mangalam 0 0 0.5 0 1
Sitron 0 0 1 1 0
Mailam 0 0 1 0 1
Labour Productivity Skilled 0.5 0 1 1 1
Semi-Skilled 0.5 0.5 0 1 0.5
Oil Storge
Tank Tank 1 Tank 2 Tank 3 Tank 4 Tank 5
Table 2- Pre-processed Data
After normalizing data we have calculated Grey relational coefficient from the normalized data in order to form relation between desired and actual data. Grey relational coefficient is calculated by formula
??_i (k)=(‘min”+’??max’)/(‘_(0,i) (k)+’??max)
Here we have considered ?? =1 because it gives moderate distinguishing effect and stability. And the value of identification coefficient changes the magnitude of grey relational coefficient but won’t change the grey relational grade.
Voltage Fluctuation Over Load 0.667 0.5 1 0.5 1
Under Load 0.5 0.5 1 0.5 1
Speed Variation Over Speed 0.667 0.667 0.5 0.667 1
Under Speed 0.5 0.5 1 0.5 0.5
Preparation of Material Material Not Heated 0.667 1 0.8 0.8 0.5
Material Pre-heated 1 0.5 0.5 1 0.5
Rod Not Heated 0.5 1 0.667 0.667 0.5
Rod Pre-heated 1 0.5 0.5 1 0.5
Weld Rod Quality Mangalam 0.5 0.5 0.667 0.5 1
Sitron 0.5 0.5 1 1 0.5
Mailam 0.5 0.5 1 0.5 1
Labour Productivity Skilled 0.667 0.5 1 1 1
Semi-Skilled 0.667 0.667 0.5 1 0.667
Oil Storge
Tank Tank 1 Tank 2 Tank 3 Tank 4 Tank 5
Table 3- Grey Relational Coefficient

After deriving Grey relational coefficient we have calculated Grey relational grade by averaging the value of Grey relational coefficient. Grey relational grade is calculated by the formula
??_i=1/n ‘_(k=1)^n”??_i (k)’
Depending upon the Grey relational grade value we have given the rating as we have considered lower the better expectancy which means lower value of the factor affects the tank project more.
Oil Storge
Tank Labour Productivity Weld Rod Quality
Preparation of Material
Speed Variation Voltage Fluctuation
Tank 1 0.667 0.50 0.7918 0.5835 0.5835
Tank 2 0.5835 0.50 0.75 0.5835 0.5
Tank 3 0.75 1 0.6168 0.75 1
Tank 4 1 0.75 0.8668 0.5835 0.5
Tank 5 0.8335 0.75 0.50 0.75 1
??_i 0.7668 0.70 0.7051 0.6501 0.7167
Ranking 5 2 3 1 4
Table 4- Grey Relational Grade
`
CHAPTER 5
CONCLUSION
5.1 Conclusion for Oil Storage Tank
Based on Grey relational analysis, we can conclude that, in any fabrication project the fabricator should focus their attention more on welding speed as it is responsible for maintaining the weld quality. If speed varies under-cut develops and for that we need to again perform welding for that portion which incurs delay in delivery, cost increases and the quality is not up to the mark as expected.
After speed variation, quality of welding rod i.e. filler rod plays important role in any fabrication project. If filler rod quality is good then the strength of welding is good which in turn decreases the defects during welding and hence saves time and cost.
Data Analysis Result
TANK
Labour Productivity
Weld Rod Quality
Preparation of Material
Speed Variation
Voltage Fluctuation
Tank 1 0.667 0.50 0.7918 0.5835 0.5835
Tank 2 .5835 0.50 0.750 0.5835 0.5
Tank 3 0.75 1 0.6168 0.750 1
Tank 4 1 0.75 0.8668 0.5835 0.5
Tank 5 0.8335 0.75 0.50 0.75 1
??_i 0.7668 0.70 0.7051 0.6501 0.7167
Ranking 5 2 3 1 4
Table 5- Response table of Grey Relational Grade
The above table demonstrates the calculated value of grey relational grade (GRG) for each affecting factors used in this study. From table, we can see that GRG value are in the range of [0, 1] and each affecting factors and No. of defects in fabrication have positive correlation. This indicates that each affecting factors influence the fabrication project.
Based on the calculated value of the gray relational grade, ranking of each affecting factors is determined. GRG represents the correlation between No. of defects occurred in fabrication project and the affecting factors and in this we have considered lower-the-worst expectancy i.e. the lower value of GRG affects the fabrication project more as compared to other factors. Therefore, depending upon the GRG value we have ranked the factors accordingly.
0.6501 < 0.70 < 0.7051 < 0.7167 < 0.7668
Thus, based on the ranking, we conclude that while doing welding speed variation affects the fabrication project most, followed by welding rod quality, preparation of material, voltage fluctuation and labor productivity.
5.2 Conclusion
GRA is part of grey system theory, which is suitable for solving complicated interrelationships between multiple factors and variables; in this case, how influential, affecting factors such as Project risk, Procurement, Scope, Finance, HRM and Integration management gave effect to control variables in Project Performance.
This approach is based on the level of similarity and variability among all variables to establish relationship. The GRA suggest how to make prediction and decision, and generate reports that make suggestions how to choose the affecting factors. This analytical model magnifies and clarifies the grey relation among all factors. It also provides data to support quantification and comparison analysis. In other words, the GRA is a method to analyze the relational grade for discrete sequences.

REFERENCES
Roselina Sallehuddin, Siti Mariyam Hj. Shamsuddin, Siti Zaiton Mohd Hashim (2008) – Grey Relational Analysis And Its Application On Multivariate Time Series
Rosli Abdul Rashid, Ismail Mat Taib , Wan Basiron Wan Ahmad, Md. Asrul Nasid, Wan Nordiana Wan Ali & Zainab Mohd Zainordin (2006) -Effect Of Procurement Systems On The Performance Of Construction Projects
IULIAN TROFIN (2004) -Impact Of Uncertainty On Construction Project Performance Using Linear Scheduling
Jirapong PIPATTANAPIWONG, Tsunemi WATANABE -An Effective Risk And Uncertainty Management Process For Infrastructure Projects: Development Of Multi-Party Risk And Uncertainty Management Process
Liu Jun, Wang Qiuzhen, Ma Qinggue (2011) – The Effects Of Project Ucertainity And Risk Managenent On Is Development Of Project Performance A Vendor Perspective, International Journal Project Management 29 (923-933)
Chih-Hung Tsai, Ching-Liang Chang, and Lieh Chen (2003) – Applying Grey Relational Analysis to the Vendor Evaluation Model, Vol. 3 pp. 45-53
Ching-Liang Chang, *Chih-Hung Tsai, and Lieh Chen (2003) – Applying Grey Relational Analysis to the Decathlon Evaluation Model, Vol. 11, No.3, 2003, pp. 54 – 62
Websites:
http://comp.utm.my/pars/files/2013/04/Grey-Relational-Analysis-And-Its-Application-On-Multivariate-Time-Series.pdf
http://web.nchu.edu.tw/pweb/users/arborfish/lesson/10394.pdf
http://etd.fcla.edu/UF/UFE0003700/trofin_i.pdf
http://www.journal.au.edu/ijcim/2003/sep03/ijcimv11n3_art4.pdf
http://www.lanl.gov/orgs/eng/engstandards/esm/welding/vol2/WFP%202-12%20Procedure-R1.pdf
http://www.tds.tu.ac.th/jars/download/jars/v5/08_Risks%20in%20the%20Construction%20Project.pdf
http://www.academia.edu/4099261/IMPACT_OF_UNCERTAINTY_ON_CONSTRUCTION_PROJECT_PERFORMANCE_USING_LINEAR_SCHEDULING
 

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