Polyurethanes have found extended applications in the pipe coating industry because they exhibit first-class corrosion opposition, scratch opposition, stamina, and chemical opposition, every bit good as a broad scope of utile mechanical belongingss. Though the first AWWA criterion for polyurethane liner and coating of steel pipe was published in 1999, fast-setting, high-solids polyurethane has been used to line and coat steel pipe since the 1980 ‘s. The Provo Reservoir Canal Enclosure Project ( PRCEP ) is a 21-mile, 126-inch diameter steel grapevine that was placed into service in early May 2012. This $ 150 million project is salvaging about 8000 acre-ft of H2O yearly from vaporization and ooze, and has the capacity to transport 400 MGD of natural H2O. Several pipe stuffs were considered for the building of this line, with polyurethane lined and coated steel pipe being selected as the most economical solution for the undertaking. The PRCEP line is one of the longest and largest-diameter polyurethane lined and coated steel H2O transmittal grapevines in the universe, and surely the longest in North America. This paper consistently outlines the contents of the AWWA C222 criterion for polyurethane surfacing systems and relates it to the undertaking, in tandem with treatments on the demands of the undertaking specifications. In-plant coating application and quality control are discussed. Installation and constructability issues are discussed from the Contractor ‘s position.
Introduction
Construction of the 21-mile, 126-inch diameter grapevine, known as the Provo Reservoir Canal Enclosure Project ( PRCEP ) , was originally a 3-year project that has resulted in the bar of about 8000 acre-ft, or 2.6 billion gallons of H2O loss yearly from vaporization and ooze. The pipe-laying was completed one twelvemonth in front of agenda in early April 2012, and the line was tested and placed into operation in May 2012. This landmark $ 150 million undertaking addresses public safety concerns associated with an unfastened canal located in an urbanised country ; improves H2O quality by extinguishing external beginnings of taint ; provides redundancy for imbibing H2O supplies to the Salt Lake Valley ; provides in-stream flows to assist with the recovery of an endangered fish species ; and, eventually, allows for the development of an equestrian-pedestrian recreational trail and park along the full length of the enclosed canal. Murdock et Al. ( 2011 ) provide inside informations of the undertaking and discourse the choice procedure of polyurethane lined-and-coated steel pipe as the most economical solution amongst the three conduit stuffs considered: cast-in-place concrete box culvert, reinforced concrete force per unit area pipe ( RCPP ) , and spirally welded steel pipe ( WSP ) . Canal fluid mechanicss, design considerations, pipe stuffs, jointing options, corrosion protection, fabrication considerations, transit and haling issues, and constructability are discussed.
Literature Reappraisal: Steel pipes have been lined and coated with polyurethanes since the 1980 ‘s, but the first American Water Works Association ( AWWA ) criterion for polyurethanes, AWWA C222 ( 2008 ) was n’t published until 1999 and was last updated in 2008. In recent old ages, the usage of polyurethane liner and surfacing systems on municipal steel grapevines has grown well. Literature is full with instance histories of successful undertakings in a assortment of applications. Bambei at Al. ( 2011 ) reported on adhesion proving performed sporadically on polyurethane liner in a 108-inch H2O transmittal line placed into service at Denver Water in 1997. The liner was reported to be in good status after 14 old ages of service, and still meets the coating system ‘s original public presentation demands. Rivera et Al. ( 2010 ) reported on a instance survey of a raw-sewage application in Pima County, AZ, where polyurethane was used to line and surface a 42-inch diameter WSP healthful sewer line, buried 30-ft deep. The coating system was evaluated for acceptableness under the Pima County/City of Tucson 2003 SSPI, Maricopa Association of Government ( MAG ) Standards, the City of Los Angeles Green Book Standard Specification, and the State of Washington Dept. of Ecology Criteria for Sewer Works Design ; the Arizona Dept. of Environmental Quality ( ADEQ ) provided concluding blessing of the merchandise. The line was designed for a minimal 100-year service life. Bass et Al. ( 2011 ) study on the to the full structural rehabilitation by Sliplining of a 48-inch diameter PCCP H2O transmittal chief at Halifax Water, using polyurethane lined-and-coated, gasket-joint, WSP. Compared to all other rehab options, the applied scientist determined that the polyurethane coating system would outdo withstand the high chloride concentrations within the environing backfill of the host PCCP line. The rehab solution was designed to supply a 100-year service life.
WSP CORROSION PROTECTION STATE-OF-THE-ART
As a standard pattern, WSP is protected internally and externally with flexible and/or rigid, liner and surfacing systems. The footings stiff and flexible specify their ability to be deformed without harm ; flexible lining/coating stuffs can be deformed more so than stiff stuffs, without prolonging harm. They are farther categorized as cementitious or dielectric. Cementitious systems, stiff in nature, chiefly made of cement howitzer, per AWWA C205, map by increasing alkalinity in the immediate locality of the pipe walls, thereby passivating the steel. The augmented alkalinity provided by the Portland cement in the cement howitzer mix causes the steel to go “ inactive ” in relation to the eating effects of the fluid on the interior of the pipe, and the dirt on the exterior ; a shell against long-run corrosion is thereby created.
Dielectric barriers, flexible in nature, on the other manus provide a physical “ bed of obstructor ” that to the full separates the pipe wall from its internal and/or external environments. Examples of dielectric systems include tape coating, AWWA C214, pigments such as polyurethane lining/coating, AWWA C222, and epoxy lining/coating, AWWA C210, or extruded polyolefin coatings, AWWA C215.
PROJECT CORROSION PROTECTION NEEDS
The design squad of the PRCEP was required to accomplish a 75-year service life of the selected conduit stuff. Consequently, beginnings that could take to corrosion of the selected stuff had to be identified. These included:
Corrosivity of native dirts
Winter salting and de-icing agents that could perforate the dirt
Electrical intervention with bing pipes that paralleled the grapevine
There were 34 separate route crossings that the grapevine would track ; salts and de-icing chemicals could leach through dirts to the grapevine at these crossings in the winter months. Impressed current systems protecting the Jordan and Alpine Aqueducts that parallel about 75 per centum of the alliance of the PRCEP grapevine could do electrical intervention and lead to corrosion. Murdock et Al. ( 2011 ) provide inside informations of steps incorporated into design to forestall corrosion of each of the different pipe stuffs chosen for the concluding command. As mentioned earlier, polyurethane lined and coated steel pipe was selected as the most economical solution for the undertaking. The undertaking specifications provided the undermentioned liner and coating options for WSP, every bit good as cathodic protection to countervail the consequence of isolated currents from other grapevines protected by impressed current systems:
Lining: a. Cement-mortar ( per C205, with alterations ) , b. polyurethane ( per C222, with alterations )
Coating: a. Tape surfacing with cement howitzer over-coat for extra harm protection ( per C214 with alterations, and C205, severally ) , b. polyurethane ( per C222 with alterations ) , and c. extruded polyolefin ( per C215 with alterations )
Cathodic Protection: To countervail the effects of isolated currents from nearby impressed-current protected grapevines, a deep well anodal system with low electromotive force was specified along the length of the grapevine. Test Stationss were placed at A?-mile intervals for long-run corrosion monitoring.
From a design-standpoint, choice of the polyurethane liner and coating for the WSP minimized any possibility of harm during transit. Use of a handling ratio, D/t, of 288, once more did non present any concerns about the possibility of harm to the polyurethane. The usage of polyurethane besides made each 40-ft subdivision of pipe significantly lighter than would hold been the instance with a cementitious liner. Approximately 70 gallons of polyurethane pigment was used to line and coat each piece of 126-inch diameter pipe.
MATERIAL HISTORY
A German polymer scientist, Prof. Dr. Otto Bayer[ 1 ]of I. G. Farbenindustry ( today ‘s Farbenfabriken Bayer ) , is given recognition for his pioneering work on the chemical science of polyisocyanates ( Xiao et al. 2012 ) and polyurethanes get downing in 1937 ; his findings were published ten old ages subsequently in the Angewandte Chemie diary ( Bayer 1947 ) . Wallace Hume Carothers ‘ ground-breaking work on the production of the universe ‘s first man-made fibres was the starting point of Bayer ‘s work. In his efforts to besiege Carothers ‘ patents on polymeric amides and polyesters, Bayer chose the urethane reaction, which led to the find of polyurethanes. Since its innovation, polyurethanes have been utilized in a broad array of applications, including coatings. During WWII, a little sum of polyurethane was produced for “ super-coating ” of German military planes, but large-scale production did non get down until Bayer and Monsanto formed the Mobay Corporation ( Seymour et al. 1992 ) . The diverseness of polyurethane applications today include icebox insularity, unreal variety meats, automotive constituents including bumpers, panels and even seating, ski-boots and places, big orbiter aerials, etc. Coatings presently represent 5 % to 10 % of the domestic polyurethane market, and are steadily turning. In 2002, 5.5 billion lbs of polyurethane was used for surfacing applications in the United States ( Xiao et al. 2012 ) .
Chemistry
ASTM classifies polyurethanes into six general types ( ASTM 2003 ) . The type permitted in the AWWA C222 ( 2008 ) steel pipe coatings by and large consists of an “ ASTM D16 Type V thermoset, aromatic polyurethane plastic polymer that is the reaction merchandise of diphenylmethane diisocyanate ( MDI ) rosin and polyol rosin or polyamine rosin or a mixture of polyol and polyamine rosins ” ( AWWA 2008 ) . Associating of the diisocyanate and polyol/polyamine occurs by step-growth polymerisation, or polyaddition. Figure 1 illustrates the typical synthesis of polyurethane, where the urethane groups, – NH- ( C=O ) -O- , link the molecular units.
Figure 1: Associating Molecular Unit of measurements by Urethane Groups ( Rahman, 2011 )
Referred to as a plural constituent ( or “ two bundle ” ) system, the reaction between the polyol/polyamine and diisocyanate reactants occurs in situ, and is the typical commercial method used to bring forth polyurethane coatings ( Seymour et al. 1992 ) . When suitably formulated, polyurethanes provide the chemical opposition and corrosion protection belongingss of other dielectric pigment systems such as epoxies, but with added lastingness, flexibleness, elongation, rapid remedy times, and scratch and impact opposition. Most polyurethane steel surfacing systems are solvent free ( 100 % solids ) and are fast-setting, bring arounding in under 30 proceedingss. The rapid remedy clip of polyurethane is an advantage over pigments such as epoxy when used for surfacing pipes.
PRCEP POLYURETHANE REQUIREMENTS
With the AWWA C222 ( 2008 ) criterion as the footing, the undertaking corrosion applied scientist incorporated assorted alterations into the concluding undertaking specification for the polyurethane liner and coating. The basic polyurethane demands were listed as follows:
Lining: For liner, the stuff was required to be self-priming, plural constituent, 100 per centum solids ( zero VOC ) , non-extended[ 2 ], and suited for submergence. Despite being a natural H2O line, NSF 60 and 61 enfranchisements were needed for the stuff. One coat, of 35-mil minimal dry movie thickness ( DFT ) was specified.
Coating: For coating, the polyurethane was required to be self-priming, plural constituent, 100 per centum solids, and non-extended, and suited for burial or submergence. One coat, of 35-mil minimal DFT, was specified.
AWWA C222 STANDARD
Physical and Performance Requirements: The C222 criterion for polyurethane coating and run alonging systems sets physical and public presentation demands of both shop-applied and field-applied polyurethane for steel H2O pipe, particular subdivisions, welded articulations, connexions, and adjustments. These demands are for the polyurethane stuffs, proving, substrate surface readying, handling, and packaging. There are presently eight pre-qualification belongingss of the stuff that must be tested, all conducted under laboratory conditions:
Cathodic Disbondment: Intended to measure a coating ‘s ability to keep a corrosion barrier, with a vacation, exposed to an electrolyte ( wet dirt ) on a cathodically protected grapevine, and is performed per ASTM G95. Minimum value is 12mm in 28 yearss.
Flexibility: Performed per ASTM D522, this trial determines a coating ‘s opposition to checking when elongated ; a sample is dead set 180 grades over a 3 ” spindle. No snap or delamination is the passing standards.
Impact Resistance: This trial determines the energy required to tear coatings applied to shriek from a falling weight. Performed per ASTM G14, the stuff is required to defy a minimal 75 in-lb of energy.
Abrasion Resistance: This trial determines the opposition of coatings to scratch produced by a Taber Abraser, per ASTM D4060. 100-mg loss of stuff per 1000 revolutions is the maximal loss permitted.
Chemical Resistance: This is an rating of a coating ‘s opposition to chemical reagents specified, and is performed per ASTM D543. Chemicals include 10 % H2SO4, 30 % NaCl, 30 % NaOH, and # 2 Diesel fuel.
Dielectric Strength: Determination of the dielectric strength ( ability of stuff to physically insulate lined/coated pipe surface from environment ) of solid insulating stuffs at commercial power frequences. ASTM D149 is utilized for this trial. Minimum value in C222 is 250 V/mil.
Water Absorption: Determines the comparative rate of soaking up of H2O by plastics when immersed, per ASTM D570. 2 % maximal soaking up is permitted by C222.
Hardness: Determination of indentation hardness of gum elastic, per D2240. Minimum acceptable value is 65 Shore D.
The adhesion trial, performed per ASTM D4541, is listed as a demand in C222 merely for post-coating-application quality control review. The trial is designed to measure the tensile ( perpendicular/normal force ) adhesion of surfacing to the substrate after application. Minimum adhesion value in C222 is 1,500 pounds per square inch. The PRCEP specification, nevertheless, required that the adhesion trial be performed foremost, as portion of pre-qualification testing, under research lab conditions, at a lower limit acceptable value of 3,000 pounds per square inchs, followed by its usage as a post-coating application quality control review, with a lower limit acceptable value of 1,750 pounds per square inchs.
Extra Pre-Qualification Trials in PRCEP Specification: The undertaking specification required three trials to be run on the stuff that are non presently listed in the C222 criterion, discussed below. The specification did non necessitate the chemical opposition, dielectric strength, and hardness trials ( discussed in points 5, 6, and 8 above ) .
Permeance: This is a step of H2O vapour transportation through the stuff, tested per ASTM E96, Water Method ( App. Eleven ) . Undertaking permitted 0.050 inch-pound.
Wet Adhesion: Performed per ASTM D870, this trial evaluates the surfacing stuff ‘s opposition to H2O utilizing H2O submergence, and was utilized on the PRCEP to analyse loss of adhesion in open countries versus non-exposed countries. Undertaking specification allowed no greater than 10 percent loss of adhesion.
Tensile Strength: This trial is designed to verify the ability of the stuff to defy tensile forces for equal public presentation based on the application. Performed per ASTM D412, with 4000 pounds per square inch lower limit specified for the undertaking.
Whenever alterations to the C222 criterion ‘s physical/mechanical parametric quantities are made in a undertaking specification, there should be sound technology concluding behind those alterations as it can sometimes ensue in well higher costs to the Owner. On this undertaking, the Owner felt that a higher cost was justifiable based on the coveted life anticipation of the grapevine.
IN-PLANT APPLICATION PROCEDURES
Surface Preparation: The length of service and effectivity of any coating system is straight related to the surface readying that the substrate undergoes prior to application of the coating. To this terminal, the C222 criterion requires that the pipe foremost be cleansed of oils, lubricating oil and soluble contaminations ; this is followed by an scratchy blast cleansing with mineral or scoria abradants or steel grit with an angular profile. The near-white metal blast, performed per SSPC-SP 10/NACE No. 2 ( 2006 ) , is required to hold a blast ground tackle form or profile deepness of 2.5 mil minimal ( measured in conformity with ASTM D4417 ) . The PRCEP specification required a white metal blast cleansing per SSPC-SP5/NACE No. 1 ( 2006 ) , with a minimal 3 mil angular profile.
For quality control, C222 requires that the temperature be measured and recorded to guarantee it is above the dew point at the clip of scratchy blast cleansing. After the blast cleansing, the surface of the pipe is cleaned, profile deepnesss measured and recorded, and a ocular comparing of the colour of the blame surface is made with the SSPC cleansing method specified. The criterion besides requires that brassy rusting of the prepared surface be prevented. Figure 2a shows a completed exterior blast surface undergoing concluding cleansing, figure 2b shows a completed interior blast surface, and figure 2c shows surfacing profiler strips that are used to mensurate and enter blast profile deepnesss, per ASTM D4417 ( 2011 ) .
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Figure 2a, B, degree Celsius: Exterior, Interior Abrasive Blast Cleaning, Profiler Strip
Polyurethane Application: The PRCEP specification required that the Coating Applicator ( pipe maker in this instance ) and the supervisor shall hold 5 old ages of experience with the specified coating system, forces covering straight with the application have 2 old ages of experience, and that the Applicator shall be certified by the polyurethane maker within the past 1 twelvemonth. While C222 is non specific on the figure of old ages of experience, the criterion does necessitate that the Applicator undergo preparation by the coating maker. The PRCEP specification besides required a 2-year guarantee on craft and stuff from the Contractor and Applicator ; guarantee is non addressed in the C222 criterion.
The subdivision on Coating Application in C222 pays peculiar attending to temperature and environmental conditions during application, and calls for “ fast-setting, short pot-life surfacing systems ” to be applied by manual crop-dusting, automatic crop-dusting or by centrifugal applications, utilizing appropriate plural constituent equipment. Two types of surfacing conveyer equipment systems are briefly described ; in world, the existent equipment normally varies from one applier to another, so elaborate counsel on this subject is non provided in the criterion. On the PRCEP, a stationary but revolving pipe and a going spray gun were utilized for the external coating, Figure 3a and B. The internal liner was applied by maintaining the pipe stationary, but revolving, figure 3c, and utilizing a polyurethane spray spear, shown in Figure 3d that bit by bit extended longitudinally, along the full inside length of the pipe, as the stuff was sprayed.
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Figure 3a, B, degree Celsius, vitamin D: Coating Application Progression, Pipe Rotation System for Lining, Lining Spray Lance
Post-application quality control steps outlined in C222 includes: 1. ocular review of the coating ( “ no blisters, clefts, bubbles, delamination, or any other seeable defects ” ) , 2. measuring of dry movie thickness ( DFT ) ( “ if the thickness is found to be less than the sum required, all of the pipe coated since the last thickness measurement shall be checked and overcoated if necessary ” ) , 3. vacation proving per NACE RP-0188 ( NACE 1999 ) , with a minimal electromotive force scene of 100 V/mil, and, 4. adhesion proving per ASTM D4541. NACE RP-0188 has been changed to NACE SP0188-2006.
DFT Quality Control: The C222 criterion specifies 20 mil DFT for liner, and 25 mil minimal DFT for coating, but does non stipulate a maximal thickness ; this is left to the maker ‘s recommendation, every bit long as the stuff passes all the prequalification tests antecedently discussed. The PRCEP specification required a minimal DFT for both the liner and coating of 35 mil. While C222 requires the measuring of DFT in conformity with SSPC-PA 2, the PRCEP specification excluded the usage of SSPC-PA 2 and alternatively, required the usage of a graduated magnetic rest area or eddy current equipment.
Electrical Continuity/Holiday Testing: The PRCEP specification required that vacation proving be conducted utilizing the high electromotive force spark trial per NACE RP-0274 alternatively of the trial specified in C222. The Elcometer Model D236A® or tantamount high electromotive force examiners with 0 to 30 kilovolts electromotive force capableness was specified.
Adhesion Testing: The adhesion testing of polyurethanes utilizing ASTM D4541 has been the topic of farther research in recent old ages due to the variableness in proving consequences that may be obtained. Bambei et Al. ( 2011 ) and McFatridge ( 2012 ) provide treatments on the variableness. Croll et Al. ( 2012 ) provide consequences of research conducted to analyze causes of the variablenesss. For credence, the C222 criterion requires that 2 pipes per displacement be selected at random, one at the beginning of the displacement, the other half-way through the displacement, which are so tested for adhesion per ASTM D4541. Acceptable adhesion per C222 is 1,500 pounds per square inch. If the adhesion values are unsatisfactory, so 2 extra trials are conducted at two different locations on the same pipe. The pipe surfacing on this pipe is rejected if either extra trial fails. All pipes coated on that displacement are so consistently inspected for credence or rejection. The PRCEP specification required that acceptable adhesion value be 1,750 psi minimal. Two types of pneumatic equipment were cited as acceptable adhesion examiners: Defelsko Positest ATA® , or ElcometerA® HATE Model 108. Figure 4a shows dollies glued to surfacing surface for proving, and figure 4b shows trial public presentation utilizing Defelsko Positest ATA® equipment.
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Figures 4a, B: Dollies Glued to Coating for Adhesion Test, Test Performance
Based on the manner in which the frequence of proving was defined in the PRCEP specifications ( specific surface country of pipe coated ) , every other piece of pipe was tested for adhesion. None of the pipe on the full 21-mile undertaking failed the adhesion testing.
Coating Repair: Pipe surfacing fix guidelines are provided in C222 every bit good as the PRCEP specifications. Emphasis is placed on vacation proving in C222 to guarantee successful fix ; adhesion testing of fixs is non required. The undertaking specification differentiates between “ minor fix ” ( less than 6-inch in greatest dimension ) and “ major fixs ” ( transcend 6-inch in greatest dimension ) , and bounds major fixs to no more than two per pipe subdivision and non to transcend 50 % of the pipe.
INSTALLATION & A ; CONSTRUCTABILITY
The C222 criterion provides counsel on the in-field completion of welded and gasketed articulations following assembly. It besides provides guidelines on handling of polyurethane coated pipe in relation to impinge conditions and backfill and bedclothes stuffs. Similar counsel is besides provided in the PRCEP specifications.
Joint Completion: For both internally and externally welded articulations, C222 requires that an 18-inch broad strip of heat-resistant stuff be taped on each side of the joint holdback to forestall harm to the polyurethane from weld-splatter. Following completion of welding, C222 permits external and internal articulation completion utilizing a figure of options, every bit long as the stuff is compatible with the originally applied liner and surfacing stuff. The PRCEP specification for polyurethane lined and coated WSP permitted merely polyurethane to be used for internal joint completion, and merely heat shrink arms, per AWWA C216, to be used for external joint completion.
For internal joint completion, C222 requires joint surface readying to be the same as that used when shop-applying polyurethane on the pipe. Material application on a articulation is besides held to the same criterion as shop-coated and lined pipe. Following joint completion, DFT, adhesion and vacation proving are applied to guarantee quality control. The PRCEP specifications required that internal joint completion be performed by qualified appliers who had done at least 3 similar undertakings within the past 3 old ages, utilizing the same coating system. The PRCEP besides provided added guidelines on external articulation completion utilizing heat-shrink arms, per AWWA C216, and besides to ease weld-after-backfill. Figure 5a shows heat-shrink sleeve application readying, figure 5b shows heat being applied to a arm with a torch, and figure 5c shows pipe with accomplished articulations being backfilled in the trench.
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Figures 5 a, B, degree Celsius: Heat-shrink Sleeve Application, per AWWA C216
Field Managing: Despite the tough nature of polyurethanes, bar of harm to the coating system during pipe transit and handling is emphasized in C222. The usage of broad belt slings alternatively of ironss, overseas telegrams, or tongs is given accent, as is the importance of forestalling metal tools or heavy objects from coming into direct contact with the finished coating. The dragging or skidding of coated pipe is besides out. Figure 6a shows pipe being hoisted utilizing broad belt slings and placed into the trench on the PRCEP grapevine ; figure 6b shows the pipe being adjusted to line and class.
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Figures 6 a, B: Pipe Hoisted and Placed into Trench, Grade Adjustment
Bedding & A ; Backfill: C222 specifies that in bouldery terrain trenches with difficult objects that could do harm to the coating, a 6-inch bed of dirt with a maximal atom size of A?-inch should be placed prior to shriek puting. In cases where stones or other difficult objects are in the backfill stuff, “ screened backfill with a maximal atom size of A?-inch shall be placed around the coated pipe to a minimal deepness of 6-inch above the polyurethane coating before the balance of the trench is backfilled. On the PRCEP, Controlled Low-Strength Material ( CLSM ) was specified on the bottom half of the pipe in the haunch country ( Murdock, 2011 ) . Pipe zone stuff above the CLSM to 1-ft above the top of the pipe was specified as well-graded, 1-inch subtraction, farinaceous stuff compacted to 90 per centum. Trench backfill from the pipe zone stuff to a lower limit of 4-ft above the top of the pipe was specified as a 6-inch subtraction earthfill, compacted to 90 per centum. At roadway crossings, the full pipe zone stuff was CLSM, followed by a farinaceous stuff compacted to 96 per centum. None of these scenarios presented any menace of damaging the polyurethane coated pipe.
Contractor ‘s Position: The PRCEP was the first clip that the Contractor had installed polyurethane lined and coated steel pipe of such big diameter and long length. From an equipment point of view, the light-weight of the pipe, compared to concrete pipe or even cement-mortar lined steel pipe of the same diameter, was an advantage. The pipe subdivisions were besides easier to manage. Savingss were realized through the usage of equipment that was more suitable to manage lighter weight pipes. The coating was really lasting, sing the imperfect conditions of a job-site, and performed really good. The 40-ft length of each pipe subdivision was another advantage as it reduced the figure of articulations that had to be welded together. During the design stage, the applied scientist recognized that the 40-ft long subdivisions of pipe would do it hard to negociate the legion curves along the canal ‘s alliance without the usage of mitered subdivisions and adjustments. To maximise the usage of 40-ft subdivisions, the applied scientist allowed for the center line of the pipe to be adjusted up to 4-ft on both sides ( Murdock 2011 ) . The ability to vacation prove all internal articulations following joint completion was another advantage that provided the Contractor peace-of-mind. For external joint completion, the Contractor built a particular platform that made heat-shrink arm application both easier every bit good as safer, figures 5a and B. Overall, the usage of polyurethane lined and coated steel pipe was a sound determination that contributed to the completion of the undertaking one twelvemonth in front of agenda.
Decision
The terminal of pipe-laying operations on the Provo Reservoir Canal Enclosure Project grapevine in April 2012, and the testing and subsequent operation that began in May 2012, marked the completion of a landmark undertaking one twelvemonth in front of agenda. Use of polyurethane lined and coated spirally welded steel pipe offered assorted advantages that contributed to the early completion of the undertaking, with no important incidents to impede its rapid advancement. The lighter weight and longer lengths of the pipe articulations translated into costs nest eggs for the Contractor. The design applied scientist was able to stipulate a D/t ratio of 288 despite the pipe ‘s big diameter chiefly because of the flexible nature of the polyurethane stuff and its high opposition to damage. Using the AWWA C222 criterion as the footing for the coating system will guarantee that the necessary corrosion protection for the long-run public presentation of the grapevine is met. Whenever alterations to the C222 criterion ‘s physical/mechanical parametric quantities are made in a undertaking specification, there should be sound technology concluding behind those alterations as it can sometimes ensue in well higher costs to the Owner. On this undertaking, the Owner felt that a higher cost was justifiable based on the coveted life anticipation of the grapevine.
The 150 pounds per square inch working force per unit area steel grapevine, with a 225 pounds per square inch transient force per unit area capableness, will enable the Owner to alter operating conditions, if needed in the hereafter, from the current low norm runing force per unit area of 42 pounds per square inchs.
Recognitions
The Authors would wish to thank and admit the cooperation of Ames Construction, Burnsville, MN, for the input they provided on the subject of constructability.
