Computer Simulation of Optimal Thickness of Polyurea Coating Using for Trenchless Renovation of Potable Water Pipes Procedia Engineering 165 ( 2016 ) 1168 – 1175 1877 7058 © 2016 The Authors Published[.]
Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 165 (2016) 1168 – 1175 15th International scientific conference “Underground Urbanisation as a Prerequisite for Sustainable Development” Computer simulation of optimal thickness of polyurea coating using for trenchless renovation of potable water pipes Vladimir Orlov a,* a Moscow State University of Civil Engineering, Yaroslavskoye sh 26, Moscow, 12933, Russia Abstract The computer simulation of strength properties of two-layer pipe construction "old pipeline + protective coating" has been conducted for quick curing polyurea formulation – Scotchkote 169HB and Scotchkote 2400 The research objective was to determine the effective range of coatings thickness for trenchless renovation of water supply pressure pipelines during its long operation (up to 50 years) Simulation was utilized the developed computer strength model of two-layer construction with through defect in a form of a hole This model was based on real physical and mechanical characteristics of the protective coatings, which were determined with taking into account the gradual aging of the polymer material during the 50 years operation of protective coatings © 2016 2016The TheAuthors Authors Published by Elsevier © Published by Elsevier Ltd Ltd This is an open access article under the CC BY-NC-ND license Peer-review under responsibility of the scientific committee of the 15th International scientific conference “Underground (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under scientific committee of the 15th International scientific conference “Underground Urbanisation as a Urbanisation as aresponsibility Prerequisite of forthe Sustainable Development Prerequisite for Sustainable Development Keywords: computer simulation; pipe renewal liner; polyurea coating; Scotchkote; strength test; trenchless technologies; water supply Introduction Today, problems of searching for reliable, cost-efficient and energy-effective coatings for trenchless renovation of worn-out water-supply pressure pipelines, as well as the determination of the effective application field of such coatings – are one of the key challenges for large city water utilities, in the problem solution of trenchless pipe rehabilitation of distribution water-supply networks [1-5] * Corresponding author Tel.: +7-499-183-36-29; fax: +7-499-183-36-29 E-mail address: orlov950@yandex.ru 1877-7058 © 2016 The Authors Published by Elsevier Ltd This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the 15th International scientific conference “Underground Urbanisation as a Prerequisite for Sustainable Development doi:10.1016/j.proeng.2016.11.835 Vladimir Orlov / Procedia Engineering 165 (2016) 1168 – 1175 1169 One of the most modern methods of worn-out water-supply pipeline trenchless renovation is spraying on their inner surface protective polymer by centrifugal splashing method on the basis of polyurea materials [6-8] For the first time, such polymeric coatings appear in 1999, when the British company «E Wood» produced protective coating Copon Hycote 169 This coating was unable to keep the structural integrity of a two-layer pipe construction, but it could help in improving of the pipeline hydraulic characteristics, as well as to keep quality parameters of the transported water Further its development, this type of coatings finds in splashing structural coatings Scotchkote 169HB and Scotchkote 2400, which started to apply in 2004 and 2011 respectively and are currently produced by «3M» [9-12] These coatings are becoming very popular as they can provide "old pipeline + protective coating" construction structural integrity, overlap through defects on the pipe and solve the improving issues of both hydraulic and strength pipeline characteristics This feature is the principal and advantageous difference between Scotchkote 169HB and Scotchkote 2400 and other liners applied by centrifugal splashing, for example cement-mortar linings [7, 13] At the same time the Scotchkote 169HB and Scotchkote 2400 coating process is quite simple and includes several key steps: cleaning of pipelines in different ways; video inspection of cleaned pipe; coating by special rotating heads (spraying could be done on the wet surface, however, there should be no water accumulations on the surface); post-coating video inspection; hydraulic tests; disinfection; flushing [14, 15] However, there is too little data in literature on the strength characteristics of the polymer coatings used for pipeline rehabilitation, especially research works concerned to coating strength properties and wall thickness selection for open holes repairing [16] Present work assumes determination of the efficient range of the thickness values of Scotchkote 169HB and Scotchkote 2400 polyurea liners for trenchless renovation of water supply pressure pipelines For this purpose the studies of strength properties of “old pipeline + protective coating” construction were conducted with simulation of its long exploitation (up to 50 years) Experiments were based on the research of computer strength model of the indicated construction with a defect in the hole form on it At the same time this model was based on real physical and mechanical characteristics of the protective coatings, which should be determined with taking into account the gradual aging of the polymer material during the 50 years of its exploitation [17-19] Experimental Experimental study of physical and mechanical properties of coatings Scotchkote 169HB and Scotchkote 2400 was carried out on single column electromechanical universal tensile-testing machine “Instron 3345" For tests on tensile-testing machine polymer coatings Scotchkote 169HB and Scotchkote 2400 were sampled in the form of rectangular-sectioned strips with the following parameters (are taken from [20] and close to ASTM Standard [21]): Scotchkote 169HB: length – 250 mm, width – 25 mm and thickness – mm; Scotchkote 2400: length – 260 mm, width – 25 mm and thickness – mm Basing on the results of experimental studies on tensile-testing machine the values of main physical and mechanical properties of Scotchkote 169HB and Scotchkote 2400 liners were obtained The test results are shown in the Table Table Physical and mechanical characteristics of coatings Characteristic Scotchkote 169HB Scotchkote 2400 Maximum load applied to the sample F, Н 1433.24 1481.33 Maximum tensile strength at break σ, MPa 14.93 29.63 Maximum elongation of the sample x, mm 25.57 2.961 Maximum longitudinal strain ε, mm/mm 0.1311 (~ 13 %) 0.0148 (~ 1.5 %) During the test of Scotchkote 169HB coating sample, at a certain moment (at the load equal to 1337 N) the stress growth in the sample are almost completely stopped with the continued significant increasing of longitudinal strain Stress-strain curve obtained during the tests of Scotchkote 169HB coating sample (Fig 1) shows the moment of transition from elastic deformation to the plastic one Thus the elastic limit of material was reached 1170 Vladimir Orlov / Procedia Engineering 165 (2016) 1168 – 1175 At this stage of the experiment the values of key physical-mechanical properties of Scotchkote 169HB coating were fixed There are: loading: F = 1337 N; stress in the sample: σ = 13.92 MPa; elongation of the sample: x = 9.165 mm; longitudinal strain: ε = 0.047 mm/mm (~ 4.7 %) During the test of Scotchkote 2400 coating sample an obvious zone of transition from elastic to plastic deformation was not observed The elongation increment of the sample is proportional to the increment of the load applied to the sample and to the stresses arising in the sample during the whole experiment This fact indicates that the Scotchkote 2400 coating is much closer to conditionally brittle materials, rather than Scotchkote 169HB coating Stress-strain curve obtained during the test of Scotchkote 2400 coating is presented in Fig Sharp break at the end of curve indicates the break of the sample A number of physical and mechanical properties of Scotchkote 169HB and Scotchkote 2400 liners were obtained by computational and analytical way [22] Young's modulus E, MPa: E V , H (1) where: σ – the stress in the sample, MPa; ε – the strain in the sample, mm/mm In addition, taking into account that Young's Modulus describes the sample behavior in the elastic range of a stress, for Scotchkote 169HB it is necessary to take a stress value σ of 13.92 MPa and a strain value ε of 0.047 mm/mm The material density was taken from the information provided by liner manufacture – «3M» company Poisson's ratio of the coating material was taken on the basis of the rigid polyurethane materials Poisson's ratio research results, because they are structurally similar to polyurea Table Physical and mechanical characteristics of coatings Characteristic Scotchkote 169HB Scotchkote 2400 Maximum tensile strength at break σ, MPa 14.93 29.63 Young's Modulus, MPa 296.2 2002.03 Density, kg/m 1500 1576 Poisson's ratio 0.3 The summary Table shows the physical and mechanical properties of Scotchkote 169HB and Scotchkote 2400 coatings, which were obtained from tests and on the basis of the following computational and analytical research [23-25] It should be noted that for Scotchkote 169HB with years lifetime the manufacture establishes the calculated Young's modulus E169 HB equal to 600 MPa [26] This value is significantly different from the value obtained during our experimental and analytical studies In order to determine the actual value of Young's modulus the following equation is used to determine the decrease of Young's modulus in time for plastic pipes [27]: m EW Đbà E0 ă , âWạ where: E0 – the initial Young’s modulus, MPa; (2) 1171 Vladimir Orlov / Procedia Engineering 165 (2016) 1168 – 1175 τ – the coating operation time, hours; b, m – coefficients: b = 10–5 h; m = 0,04 [27] Fig Stress-strain curve of coating Scotchkote 169HB Fig Stress-strain curve of coating Scotchkote 2400 It should be noted that the Scotchkote 169HB liner samples, which were tested on tensile-testing machine, by the time of the experiment were at the age of years as far as it are came to the laboratory of Water Supply Department as early as 2010 Then τ = 3·365·24 = 26,280 hours Inserting numerical values into the equation (2) Young's modulus was obtained: E169 HB Đ 10 5 à 600ăă áá â 26280 0.04 252 MPa Thus, one can see that the calculated value obtained on the basis of theoretical curve is comparable to the experimentally obtained data The equation (2) can be used to determine the value of Young's modulus for Scotchkote 169HB and Scotchkote 2400 coatings with 50-year-old lifetime It is also necessary to determine other key physical and mechanical properties of Scotchkote 169HB and Scotchkote 2400 coatings with 50-year-old lifetime – the shear modulus and bulk modulus: Shear Modulus (G, MPa): G E 2( Q ) (3) 1172 Vladimir Orlov / Procedia Engineering 165 (2016) 1168 – 1175 Bulk modulus (K, MPa): K E 3( 2Q ) (4) The value of the maximum tensile strength decrease of Scotchkote 169HB and Scotchkote 2400 coatings was determined using the analysis of strength characteristics behavior in time for HDPE and PVC pipes since its original physical and mechanical properties are closest to Scotchkote 169HB and Scotchkote 2400 properties respectively Table shows the basic physical and mechanical properties of Scotchkote 169HB and Scotchkote 2400 liners during its operation for 50 years Table Physical and mechanical characteristics of coatings during its operation for 50 years Characteristic Scotchkote 169HB Scotchkote 2400 Maximum tensile strength at break σ, MPa 10.66 26.69 Young's Modulus, MPa 225.2 751.3 Shear Modulus, MPa 86,6 289 Bulk Modulus, MPa 187.7 626 Density, kg/m3 1500 1576 Poisson's ratio 0.3 Computer modeling The study of strength properties of construction “old pipeline + protective coating” was made by computer modeling The object was the renovated steel pipeline with internal diameters from 100 to 610 mm and with through defect in the hole form The maximum diameter of the hole on the pipe was taken equal to 50 mm that is caused by the limiting possibility of coatings Scotchkote 169HB and Scotchkote 2400 to ensure structural integrity of the "old pipeline + protective coating" construction with the maximum possible thickness of the coatings The creation of a computer model was made on the basis of the physical and mechanical properties of Scotchkote 169HB and Scotchkote 2400 coatings, which were obtained during the experimental work Calculation of model was made based on the conditions of the 50 years lifetime of coatings The result of the computer model calculation was the determination of the efficient range of Scotchkote 169HB and Scotchkote 2400 coatings thickness while working in the "old pipeline + protective coating" system with various internal and external loads Table Initial modeling parameters for construction "old pipeline + protective coating" Parameter Value Pipeline material steel Inner pipeline diameter, mm 100…610 The length of the pipeline section, mm 200 Diameter of the hole on the pipeline, mm 50 Internal pressure in the pipeline, MPa 0.6; 1.2 The height of the soil layer above the pipeline, m ≤ 3.4 Load of the groundwater layer, MPa 0.034 Water temperature, C ≤ 20 Physical and mechanical properties of coatings See Table Coatings lifetime, years 50 o 1173 Vladimir Orlov / Procedia Engineering 165 (2016) 1168 – 1175 The internal water pressure with values of 0.6 and 1.2 MPa was taken as a main structural load The selection of such values is justified by boundary operation conditions of urban water supply network (the pressure no more than 0.6 MPa) and by possibility to conduct a hydraulic-pressure test of a rehabilitated pipeline with a maximum test pressure no more than 1.2 MPa The impact of the overlying soil layer and the groundwater layer to the pipeline were considered as additional loads The height of the soil layer above the pipeline is 3.4 m and was selected on the basis of the coating producer recommendations with taking into account values of burial depths of the majority of water supply pipelines in the central zone of the Russian Federation Initial conditions of strength properties modeling for construction "old pipeline + protective coating" are presented in Table The required values of Scotchkote 169HB and Scotchkote 2400 protective coating thicknesses were searching based on the analysis of arising stresses in the construction when it exposed to loads for various pipeline diameters To estimate the efficiency of specific coating thickness the program complex is used to determine the following key parameters of the construction behavior [17]: maximum equivalent stress σе, MPa, occurring at any point of the structure, is determined by the equation: Ve > @ V1 V2 V2 V3 V3 V1 , (5) where: σ1, σ2, σ3 – the main stresses, MPa; safety factor – the ratio of the ultimate tensile strength of the material to arising in it maximum equivalent stress – is defined by the equation: K sf Vuts Ve (6) Calculated value of the safety factor at each thickness was checked for compliance with inequality: K sf t 2.0 (7) In case of non-compliance with the inequality (7), the thickness value of the coating was gone up, the recalculation was made and the resulting value of the safety factor was checked again for compliance with inequality (7) The calculation results of the strength model of "old pipeline + protective coating" construction are presented on Figure as graphic dependences of coating thickness on inner pipeline diameter for internal pressures of 0.6 and 1.2 MPa The analysis of graphic relationships presented in Fig shows that the required coating thickness can be expressed as a log-normal function of the pipeline inner diameter For application of Scotchkote 169HB and Scotchkote 2400 coatings these functional dependencies can be expressed by the following equations: for Scotchkote 169HB: 0.6 S169 HB 1.18 ln D 0.1986 , (8) for Scotchkote 2400: 0.6 S 2400 0.795 ln D 0.1726 (9) Similarly, the functional dependencies of the required coating thickness on the pipeline inner diameter can be expressed for internal pressure of 1.2 MPa For applications of Scotchkote 169HB and Scotchkote 2400 coatings the following equations are obtained: 1174 Vladimir Orlov / Procedia Engineering 165 (2016) 1168 – 1175 for Scotchkote 169HB: 3.676 ln D 8.3644 , 1.2 S169 HB (10) for Scotchkote 2400: 1.2 S 2400 1.171ln D 0.1015 a (11) b Fig The dependences of Scotchkote 169HB and Scotchkote 2400 coatings thickness on the inner diameter of the pipe at a pressure of 0.6 MPa (a) and 1.2 MPa (b) Equations (8) – (11) obtained by a computer simulation allow us to determine Scotchkote 169HB and Scotchkote 2400 coating thicknesses which are necessary to ensure the structural integrity of the pipeline Therefore, it is possible to find a solution for the effective thickness of splashing coating based on polyurea materials for renovation of a pipeline with a specific inner diameter The result of strength calculation became the effective value range of splashing coating Scotchkote 169HB and Scotchkote 2400, as well as functional dependencies of the required coating thickness on the inner diameter of the pipeline being restored Conclusions The computer simulation of strength properties of two-layer pipe construction "old pipeline + protective coating" has been conducted It indicates that modern splashing polyurea protective coating materials are able to provide efficient rehabilitation of the worn-out water supply pressure pipeline, restore its structural integrity and achieve a significant margin of safety Functional dependencies of required thickness value of polyurea protective coatings on the inner pipeline diameter are obtained These relationships can be used by water utilities and specialized companies dealing with trenchless renovation of water-supply networks to calculate the polyurea material splashing protective coating effective thickness for specified pipe diameter and its operating conditions References [1] A Deb, Y Hasit, H Schoser, J Snyder, G Loganathan, P Khambhammettu, Decision Support System for Distribution System Piping Renewal, AwwaRF, Denver, CO, 2002 [2] Y Jung, S Sinha, Evaluation of Trenchless Technology Methods for Municipal Infrastructure System, J Infra Syst 13(2) (2007) 144-156 Vladimir Orlov / Procedia Engineering 165 (2016) 1168 – 1175 1175 [3] G.J Kirmeyer, G.R Boyd, N.K Tarbet, R.F Serpente, Lead Pipe Rehabilitation and Replacement Techniques, AWWA Research Foundation & AWWA, U.S.A, 2000 [4] R Sterling, L Wang, R Morrison, White Paper on Rehabilitation of Wastewater Collection and Water Distribution Systems, U.S EPA, Office of Research and Development, 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2002-2005 [26] Technical datasheet Scotchkote Rapid Setting Polymeric Lining 169HB (previously Copon Hycote 169HB) 3M Russia, Moscow, 2010 [27] G.K Klein, Calculation of underground pipelines, Stroyizdat, Moscow, 1969 ... determination of the efficient range of the thickness values of Scotchkote 169HB and Scotchkote 2400 polyurea liners for trenchless renovation of water supply pressure pipelines For this purpose... possible to find a solution for the effective thickness of splashing coating based on polyurea materials for renovation of a pipeline with a specific inner diameter The result of strength calculation... dependences of coating thickness on inner pipeline diameter for internal pressures of 0.6 and 1.2 MPa The analysis of graphic relationships presented in Fig shows that the required coating thickness