Report On Life Cycle Cost Analysis Techniques For Preventing Corrosion
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Charles Darwin University
Added on 2020-02-19
Report On Life Cycle Cost Analysis Techniques For Preventing Corrosion
Charles Darwin University
Added on 2020-02-19
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AbstractSeveral techniques have been used in-order to protect ductile iron pipe fromcorrosion. Some of the techniques include joint bonding, three-layer polyethylene orpolypropylene coatings, cathodic protection, epoxy coating, neoprene coating and manymore. Steel pipelines usually have a life time of 25 years and the application of these coatingsprotect the pipelines against corrosion and thus increases the operating life of the steelpipelines. One of the most important parameter is the economics of using these kind ofprotection as once laid under water these pipelines would not be replaced for years as itwould not only be a cumbersome process but also stop the drilling work for a long time.Therefore, it is important to know the appropriate life cycle of the coatings along with theassessment of economic viability of using a particular type of coating. The best method forevaluating the economic viability of a particular type of product is to carry out a life cycleassessment of some of the coatings available in the market and use the assessment in thedecision making process. This report deals primarily with the life cycle cost analysis of threedifferent types of coatings namely fusion based epoxy coating, polyethylene coating andneoprene coatings used to protect offshore steel pipelines used in oil and gas fields. IntroductionCorrosion is defined as an electrochemical reaction that takes place between amaterial, and its environment in-order to deteriorate the material (ASTM NACE, 2012). Twodistinct phases make up the service life of a structure (Tuutti, 1982) namely initiation phaseduring which the concrete cover is penetrated by aggressive thereby, initiating corrosion inthe reinforcement and the propagation phase which causes increase in the rate of deteriorationdue to corrosion-induced damages.After the initiation of corrosion, the rate of structural deterioration increases greatly.Solid corrosion is expansive in nature and spreads easily throughout the entire structure if it isnot stopped quickly and this can cause cracks and delamination in the structural cover(Andrade et al., 1993). The structure may fail due to reduction in serviceability and strengthof the cross section. In-order to prevent failures due to corrosion extensive research havebeen carried out for developing techniques and models which describe the degradation
mechanism (Bazant, 1979). Research has been done to develop models for studying thedegradation due to corrosion even in the propagation phase (Isgor and Razaqpur, 2006).When a critical limit is reached like in the case of chloride-induced corrosion when acritical chloride threshold is achieved in the initiation phase the service life of the material isended (Alonso et al., 1998). Propagation phase has also been considered in some cases toevaluate the non-commercial service life models, but only for a fixed duration of time or onthe basis of expert opinions (Crete, 2000).When different materials are in contact with steel galvanic corrosion arises due toelectrical contact between dissimilar metals which is bridged using an electrolyte (Liu andWeyers, 1998). When the potential difference between metals induces a current to flow,galvanic corrosion occurs, due to which one metal becomes the anode whose corrosion ratewill be high and the other becomes the cathode whose corrosion rate is low (Chernin et al.,2009).Some of the factors affecting the intensity of galvanic corrosion are distance,environment and area ratio between anode and cathode. The contribution of these factors aredetailed as follows:(a) The area between anodic metal and cathodic metal influences corrosion when the metalsare wet (Jones, 1972). Accelerated corrosion occurs at the anode if it is small in proportion tothe cathode. For an example consider the rapid corrosion of anodic fasteners attached tostructural metal. Fasteners should be cathodic to the structure or should be of the same metalas the structure (Smoljko, et al., 2007). Another example occurs a noble metal such as copperor stainless steel is joined with painted steel, where, corrosion concentrates at coating flaws,causing pitting. (b) The effects of corrosion are minimum in dry environments; but as the environmentbecomes aggressive the issue becomes more and more serious (Bonds, et al.,2004). Thusenvironment influences galvanic effects.(c) When the distance between dissimilar metal junctions increases the galvanic attackdecreases. When there is a requirement of dissimilar metals in the design, then the surfaceswhich are in contact should be electrically isolated, by coating the surface of both metals(Cabrera, 1996). If coating could be applied to only one metal junction then, it should beapplied to the cathode.
One of the major cause of marine structural failures in the marine industry iscorrosion, which induces loss of structural strength both locally and globally, leading tofailure due to cracking and fatigue because of the stress caused by corrosion (SafinahNewsletter, 2009). There are a number of marine incidents with tankers that are a result ofaccelerated corrosion.Life cycle cost (LCC) is the total of all the expenses of a project calculated through-out the life of the entire project. The initial capital investment is only a part of the costsrequired to maintain the operation of the asset correct investment could be made only if thecost needed to be invested on the total life time of the asset is available then it is helpful inseveral decision making processes (Kroon, 2006). Such an analysis could be carried out atany stage of the life cycle of the product and helps to balance the performance of the productused. LCC acts like a perfect tool for decision making. The decisions taken about the productdepends on a lot of parameters like the procurement cost of the product, application andmaintenance cost, renewal cost and the disposal cost of the product (Helsel, et al., 2014).LCC should highlight the factors like intendent use of the product and the environment inwhich it is going to be used. It should be simple so that it could be used properly during thedecision making process, as well as during modifying and upgrading the system (Helsel, etal., 2006). LCC should be evaluated in such a way that other elements are independent.Literature ReviewReal makers of defensive coatings, steel fabricators, painting temporary workers,galvanizers, and end clients, were reviewed to recognize surface planning and coveringapplication costs, covering material costs, commonplace modern situations and accessiblenon-specific coatings for use inside those conditions, and expected covering administrationlives. The way to deal with this cost information is intended to be down to earth. Rather thanloading the covering engineer with entangled cost recipes in view of time-basedcompensations, supervision, gear rates, overhead, benefit, and other cost components, thisguide supplies add up to costs, which incorporate these components (AS/NZS 2312.1, 2014).The expenses are planned to reflect present, aggressive/business costs charged in the present
market. Surface arrangement and application costs are principally in light of significant steelfabricators and painting contractual workers. Particular occupation expenses will differ contingent upon the employment estimate,geographic area, coordination, aggressive atmosphere, and different variables includingaccessible working hours, reasonable time to finish, activity confinements and level ofassessment required. The motivation behind any guide is to give a simple tousle, down toearth intends to distinguish, think about, select, and legitimize appropriate, savvy defensivecovering frameworks for particular conditions, and to answer key inquiries, for example,What frameworks may work? What are the relative introduced costs? Nearly, to what extentwill the frameworks last? What are the relative expenses every year per square foot? The parametric model, in light of chronicled cost information, can anticipate life cyclecost for a picked future upkeep plan. The essential cost drivers are resolved, chronicled takena toll breakdowns and patterns analysed and an affectability examination directed. Theessential cost driver is work costs in outside administration contracts. Life cycle cost changeswith the yearly surface range secured by the support battles There are a few industry guidelines accessible that give direction concerning how todecide the life cycle cost of an advantage/action, for example, AS/NZS 4536 (AS/NZS 4536,1999), AS IEC 60300.3.3 (IEC 60300.3.3, 2005) and ISO 15663:1-3 (ISO 15663, 2000). Asevery standard spreads life cycle cost themes to changing degrees a decent life cycle costexamination ought to consider direction from each of the three benchmarks, to guarantee thatthe outcomes have represented every single conceivable factor. Writing audit has notdiscovered whatever other articles that have endeavoured to apply life cycle cost on a benefitwide level to three diverse resource sorts utilizing recorded information. Past articles areeither not identified with erosion support (Lee et al., 2006), utilize hypothetical contextualanalyses or their contextual investigation is constrained to a solitary upkeep movement /application.Curiously, chlorinated rubbers in view of red lead, epoxy primers and vinyl paintswere sold as of now and guaranteed to give amazing execution. This is probably going to befar-fetched as red lead works particularly by response with linseed oil, for instance, and isessentially idle in other polymer frameworks. With oxidizing polymers, for example, alkyd,
or ideally linseed oil, the fundamental red lead responds with the carboxylic corrosivebreakdown items to frame lead cleansers, for example, lead azelates. These are the genuineinhibitors and capacity by thickening and repairing the normally shaped oxide layer on steel.This has been exhibited by planning chlorinated elastic red lead groundworksplasticized with traditional chloroparaffins and linseed oil. The linseed oil based materialgave fundamentally better execution. Tragically, the utilization of linseed oil in coatingsgives other unfavourable properties, for example, diminish in water resistance andimperviousness to saponification, which made its utilization inadmissible to the seawardcondition (RP0169, 2002). A change to the framework was to use zinc silicate as apreliminary, hence enhancing both under film erosion crawl and long haul consumptionresistance. This sort of multi-coat thermoplastic tar based framework, particularly with inorganiczinc silicate as preliminary, was utilized for 30-40 years with extensive achievement andnumerous stages are still as of now covered. It is important that an option framework utilizingpolyvinyl butyral/zinc tetroxy chromate wash preliminary direct to steel and after that bestcovered with the multi-coat vinyl framework additionally gave brilliant execution in the Gulfof Mexico. Early vinyl coatings were not confined by Health and Safety and Environmentalnecessities to what kind of plasticizer was utilized, again adding to long haul solidness toweathering, consumption and warm anxiety. As time advanced and costs for multi-coat frameworks turned out to be morerestrictive, the propensity moved toward becoming to use low sub-atomic weight vinyl tars soas to acquire high solids, higher form and less coats, and furthermore to utilize mixes ofacrylic pitch with the vinyl. These moves all added to diminishing the general adequacy ofthe coatings. What were the shortcomings or deformities of these materials? (i) Low solids 20% at first, expanding to around 40% with vinyl/acrylics howeverunmistakably issues with VOC emanations. (ii) Thermal security - warm debasement (dehydro chlorination) winds up plainly conceivableat temperatures more noteworthy than 80°C (176°F). (iii) Thermoplasticity - warm zones. (iv) Chlorine containing polymers now have an issue with squander transfer where deficientignition can cause development of to a great degree harmful dioxins (Hassana et al., 2010).
Coatings of this sort were effectively utilized by many organizations in the Gulf ofMexico, for example Exxon, Philips, Inlet and so forth., and by Statoil, Philips and others inthe North Sea. Early epoxy frameworks depended on medium atomic weight epoxy tars,crosslinked at first with low sub-atomic weight aliphatic amines. Thixotrope innovation wasnot appropriate for high form coatings so again multi-coat frameworks were utilized. Theutilization of medium atomic weight epoxy in truth gave two noteworthy favourablecircumstances, the sub-atomic weight of around 1000 gave adequate holes between crosslinksto give some characteristic adaptability, and hydroxyl bunches introduce on the anchor addedto grip. Low solids additionally diminished dissolvable maintenance and ensuing anxietiesactuated by means of film shrinkage and once more, as with vinyl coatings, multi-coats addedto general execution. Run of the mill coatings were around 40-45% volume solids and wereconnected at 50-75 microns (2-3 mils) dry film thickness per coat, with add up to thickness of200-250 microns (8-10 mils).Once more, zinc silicates were additionally utilized as preliminaries for theseframeworks, enhancing under film crawl what's more, general erosion resistance. Insubmerged and sprinkle zone zones, the most well-known framework was multi-layers ofcoal tar epoxy, normally 300-500 microns (12-20 mils) dry film thickness. In earlycircumstances, with unadulterated vinyls, it was likewise conceivable to utilize these aroundthere. Seaward support programs are ending up progressively costly and complex,unmistakably painting tends to fall behind numerous different exercises as far as needs,however a considerable lot of the old methods of insight are not any more conceivable. Innumerous zones of the world dry impacting seaward is never again permitted, substitution byUHP water impacting is currently dubious after impressive seaward involvement in the NorthSea in light of Health and Safety contemplations, i.e. perils of the high weight stream and thecalculated challenges of working this substantial gear consistently. Coordinations of moving painting ranges around can be viewed as high hazard andpossibly unsatisfactory in chance evaluation forms. This all puts encourage accentuation ongreat new development frameworks being utilized, which can offer upkeep free lifetimes ofnumerous years (>20 years) (SSPC, 2000). Prequalification testing, is the most utilizedcourse to attempt to accomplish this.
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