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Sarge Lundy - One of the best experts on this subject based on the ideXlab platform.
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EFFECT OF REFLECTION WAVES ON WATER HAMMER LOADS
2015Co-Authors: Eniamino Rovagnati, Sarge Lundy, Joh H. GrayAbstract:In power plants, engineering analysis is used to design piping systems for steam and water hammer events. A simple and effective approach based on hand calculation was proposed by E.C. Goodling1 which has been widely used in the industry to estimate fluid loads for Pipe Stress analysis and design of piping restraints. His approach provides a conceptual understanding of many factors that control fluid loads, which can be used both to perform approximate checks of more detailed computer solutions, and to identify parameters that can be changed to optimize system designs. In Goodling’s work, the possibility of reflection waves affecting fluid loading is mentioned. However, this effect was not explored and is often neglected when simple hand estimates of fluid loads are made. This paper looks at the effects reflection waves from pressure vessels or large headers may have on steam / water hammer loads. A few sample problems are solved with the aid of a Method of Characteristic (MOC) computer program and compared to solutions found using the Goodling approach. It is shown that neglecting reflection waves may lead to non-conservative loads (by up to a factor of two). The effects of other critical parameters (e.g., pressure pulse rise rate) are also discussed. NOMENCLATURE A = Pipe flow area, ft2 c = fluid sound speed, fps F = force, lbf g = 32.2 ft/sec2 L = Pipe length, ft Lc = critical length, ft P = pressure, psi t = time, s td = disturbance duration time, s tdwell = force dwell time, s ΔW = change in flow rate, lbm/s Φ = force correction factor τ = transmission facto
Joh H. Gray - One of the best experts on this subject based on the ideXlab platform.
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EFFECT OF REFLECTION WAVES ON WATER HAMMER LOADS
2015Co-Authors: Eniamino Rovagnati, Sarge Lundy, Joh H. GrayAbstract:In power plants, engineering analysis is used to design piping systems for steam and water hammer events. A simple and effective approach based on hand calculation was proposed by E.C. Goodling1 which has been widely used in the industry to estimate fluid loads for Pipe Stress analysis and design of piping restraints. His approach provides a conceptual understanding of many factors that control fluid loads, which can be used both to perform approximate checks of more detailed computer solutions, and to identify parameters that can be changed to optimize system designs. In Goodling’s work, the possibility of reflection waves affecting fluid loading is mentioned. However, this effect was not explored and is often neglected when simple hand estimates of fluid loads are made. This paper looks at the effects reflection waves from pressure vessels or large headers may have on steam / water hammer loads. A few sample problems are solved with the aid of a Method of Characteristic (MOC) computer program and compared to solutions found using the Goodling approach. It is shown that neglecting reflection waves may lead to non-conservative loads (by up to a factor of two). The effects of other critical parameters (e.g., pressure pulse rise rate) are also discussed. NOMENCLATURE A = Pipe flow area, ft2 c = fluid sound speed, fps F = force, lbf g = 32.2 ft/sec2 L = Pipe length, ft Lc = critical length, ft P = pressure, psi t = time, s td = disturbance duration time, s tdwell = force dwell time, s ΔW = change in flow rate, lbm/s Φ = force correction factor τ = transmission facto
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Effect of Reflection Waves on Water Hammer Loads
Volume 3: Design and Analysis, 2014Co-Authors: Beniamino Rovagnati, Joh H. GrayAbstract:In power plants, engineering analysis is used to design piping systems for steam and water hammer events. A simple and effective approach based on hand calculation was proposed by E.C. Goodling1 which has been widely used in the industry to estimate fluid loads for Pipe Stress analysis and design of piping restraints. His approach provides a conceptual understanding of many factors that control fluid loads, which can be used both to perform approximate checks of more detailed computer solutions, and to identify parameters that can be changed to optimize system designs. In Goodling’s work, the possibility of reflection waves affecting fluid loading is mentioned. However, this effect was not explored and is often neglected when simple hand estimates of fluid loads are made. This paper looks at the effects reflection waves from pressure vessels or large headers may have on steam/ water hammer loads. A few sample problems are solved with the aid of a Method of Characteristic (MOC) computer program and compared to solutions found using the Goodling approach. It is shown that neglecting reflection waves may lead to non-conservative loads (by up to a factor of two). The effects of other critical parameters (e.g., pressure pulse rise rate) are also discussed.Copyright © 2014 by ASME
David Mair - One of the best experts on this subject based on the ideXlab platform.
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Stress Intensification Factors for Fabricated Lateral Piping Connections
Journal of Pressure Vessel Technology, 2014Co-Authors: David MairAbstract:Stress intensification factors (SIFs) are published in the piping codes for tees; branch connections where the branch intersects the header Pipe at 90 deg. These factors when multiplied by the nominal Stress provide a measure of the increased local Stresses at the junction of the two Pipes. However, in cases where the branch Pipe meets the header at an angle of other than 90 deg, the main piping codes do not provide a method of calculating the SIFs. This presents a difficulty for the Pipe Stress engineer who must determine appropriate SIFs, usually in a conservative way and then manually enter these into the Pipe Stress program. This paper summarizes some of the published methods of calculating SIFs for a limited range of lateral branch connections and makes recommendations based on comparisons with finite element analysis (FEA) studies. It also includes recommendations on how such FEA studies should be applied in order to provide suitable SIF values.
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Stress Intensification Factors for Fabricated Lateral Piping Connections
Volume 3: Design and Analysis, 2013Co-Authors: David MairAbstract:Stress intensification factors (SIFs) are published in the piping codes for tees; branch connections where the branch intersects the header Pipe at 90 degrees. These factors when multiplied by the nominal Stress provide a measure of the increased local Stresses at the junction of the two Pipes. However, in cases where the branch Pipe meets the header at an angle of other than 90 degrees, the main piping codes do not provide a method of calculating the SIFs. This presents a difficulty for the Pipe Stress engineer who must determine appropriate SIFs, usually in a conservative way and then manually enter these into the Pipe Stressing program.This paper summarizes some of the published methods of calculating SIFs for a limited range of lateral branch connections and makes recommendations based on comparisons with FEA studies. It also includes recommendations on how such FEA studies should be applied in order to provide suitable SIF values.Copyright © 2013 by ASME
Dilan Robert - One of the best experts on this subject based on the ideXlab platform.
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Stress Prediction of Buried Pipes Subjected to Operational Loadings in Unsaturated Soils
Journal of Pressure Vessel Technology, 2019Co-Authors: Chamal Randeniya, Dilan RobertAbstract:Pipelines are used to provide variety of services in modern community and have grown rapidly in past few decades due to growing socio-economic requirements. Most of the water mains are buried in shallow depths where the soil is partially saturated with significant spatial and temporal variations. Even though the behavior of buried Pipes in such unsaturated soil condition is substantially different when compared to dry or fully saturated soil, the effect of soil saturations is overlooked in the current Pipe Stress prediction methods, leading to unrealistic predictions of the Pipe Stresses. In this study, three-dimensional (3D) finite element (FE) method was employed with advanced constitutive soil models to analyze the behavior of Pipes buried in unsaturated soil condition. Having validated the FE model using reported field test data, an analytical model was proposed to predict the maximum Stress in buried Pipes considering soil saturation effect using a series of 3D FE analyses. Results from the FE analyses reveal that the maximum Pipe Stress can be significantly different when soil is in unsaturated condition when compared to dry condition. The proposed formula shows a good agreement with the field data and FE results, so that the expression can be used in the prediction of maximum Pipe Stress when they are buried under realistic (i.e., nondry) soil conditions.
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Performance assessment and failure prediction of corroded cast iron Pipes
Geotechnical engineering, 2019Co-Authors: Pathmanathan Rajeev, Dilan RobertAbstract:The increasing failure rate in deteriorating Pipe and unplanned failures will increase economical loss and social impact. One of the important tasks in the asset management framework is to estimate the Pipe Stress of a certain Pipe section subjected to operational loads and corrosion. These factors may, however, be considered uncertain not only at a given point of time, but also have substantial time variance. The probability of structural failure of Pipes can be estimated using Monte Carlo type simulation conjunction with Pipe Stress analysis models. This paper assess the Pipe performance using different Pipe Stress prediction models and 3-D finite element analysis. Further, the effect of corrosion was modelled and incorporated with Stress prediction models to assess the Pipe performance over the lifetime. Finally, the probability of failure was computed and discussed in application with a case study of buried cast iron Pipe subjected to external corrosion and loadings.
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Contribution of cement mortar lining to structural capacity of cast iron water mains
Aci Materials Journal, 2016Co-Authors: Dilan Robert, Pathmanathan Rajeev, Rui Jiang, Jayantha KodikaraAbstract:Cast iron water mains represent a significant component of the water Pipe networks in many cities across Australia. Such Pipes are usually furnished with an internal cement mortar lining, mainly to act as a physical barrier to flowing liquids to reduce internal corrosion and to reduce energy losses. Although the lining is not intended to resist internal and external loadings to the Pipe, recent observations of corroded cast iron water mains showed that the cement lining can withstand some internal water pressure on its own. This reveals that the lining may contribute to the structural capacity of deteriorated Pipes, although the level of this contribu- tion is unknown. This paper investigates the likely contribution of cement lining to the structural capacity of deteriorated Pipes. This research is undertaken through numerical modeling of Pipe-liner- soil interactions. The properties of cement linings were obtained by testing actual specimens obtained from field Pipes and casting simulated lining specimens of cement-sand mixtures. The study revealed that, depending on the level of Pipe corrosion, cement lining can reduce Pipe Stress by as much as 5 to 12% or 10 to 25% if the lining tensile strength is 1 or 4 MPa (145 or 580 psi), respectively.
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equation to predict maximum Pipe Stress incorporating internal and external loadings on buried Pipes
Canadian Geotechnical Journal, 2016Co-Authors: Dilan Robert, Pathmanathan Rajeev, Jayantha Kodikara, Balvant RajaniAbstract:Pipelines used for water and other services are very important lifelines in modern society. Commonly, these buried Pipes are subjected to significant Stresses due to external (traffic and earth) and internal (water pressure) loads. As many of these Pipelines were laid sometime in the last century or earlier, in most cases their condition has deteriorated primarily by electrochemical and (or) microbiological corrosion. Corrosion activity (internal and external) can manifest in various forms, but in many cases will lead to reduced Pipe thickness, which in turn leads to an increase in Pipe Stresses induced by the external and internal loads. Currently available analytical procedures to estimate Pipe Stresses are based on oversimplifications such as the two-dimensional (2-D) analysis based on Winkler springs, limiting their application to general Pipe burial conditions. This paper describes the application of a three-dimensional (3-D) finite element method to analyse a buried Pipe subjected to external and in...
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Stress analysis of buried Pipes
2014Co-Authors: J Merrin, Pathmanathan Rajeev, Dilan Robert, Hp Hung, Jayantha KodikaraAbstract:Pipeline plays a vital role in transporting water, gas and oil from one place to another. Over the years, several failures have been reported in Pipeline mainly due to aging (i.e., corrosion). The failure occurs when the Stresses in a Pipe segment due to applied loads exceed the capacity of the Pipe. Therefore, it is important to predict the realistic Pipe Stress at the design and assessment stages to ensure the safety across the entire lifetime. As significant portion of the Pipeline is buried in the underground in most of the occasions, the soil-structure interaction analysis is important as part of the Stress analysis. Depending on the location of the network, the Pipe will be subjected to varying levels of traffic and pressure loads that need to be accurately determined in order to perform reliable Pipe Stress estimations. Several Pipe Stress prediction methods have been developed over the years and reported in the literature. However, these methods are either analytical or empirical based models. The former uses the structural mechanics of the Pipe by discarding the complex soil-structure interaction effect while the later fully depends on the experimental results. To overcome these problems, the numerical methods can be used to incorporate the soil-structure interaction effect more efficiently in Pipe Stress analysis together with traffic and internal pressure loads. In this study, the finite element method is used to analyse the Pipe-soil system subjected to external traffic and internal pressure loads. Further, the model developed is used to understand the effect of soil properties, Pipeline characteristics, and loading on Pipe Stress through sensitivity analysis. Finally, the response surface method is used to develop a new Pipe Stress predictive equation using the results of finite element analyses.
Jayantha Kodikara - One of the best experts on this subject based on the ideXlab platform.
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Contribution of cement mortar lining to structural capacity of cast iron water mains
Aci Materials Journal, 2016Co-Authors: Dilan Robert, Pathmanathan Rajeev, Rui Jiang, Jayantha KodikaraAbstract:Cast iron water mains represent a significant component of the water Pipe networks in many cities across Australia. Such Pipes are usually furnished with an internal cement mortar lining, mainly to act as a physical barrier to flowing liquids to reduce internal corrosion and to reduce energy losses. Although the lining is not intended to resist internal and external loadings to the Pipe, recent observations of corroded cast iron water mains showed that the cement lining can withstand some internal water pressure on its own. This reveals that the lining may contribute to the structural capacity of deteriorated Pipes, although the level of this contribu- tion is unknown. This paper investigates the likely contribution of cement lining to the structural capacity of deteriorated Pipes. This research is undertaken through numerical modeling of Pipe-liner- soil interactions. The properties of cement linings were obtained by testing actual specimens obtained from field Pipes and casting simulated lining specimens of cement-sand mixtures. The study revealed that, depending on the level of Pipe corrosion, cement lining can reduce Pipe Stress by as much as 5 to 12% or 10 to 25% if the lining tensile strength is 1 or 4 MPa (145 or 580 psi), respectively.
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equation to predict maximum Pipe Stress incorporating internal and external loadings on buried Pipes
Canadian Geotechnical Journal, 2016Co-Authors: Dilan Robert, Pathmanathan Rajeev, Jayantha Kodikara, Balvant RajaniAbstract:Pipelines used for water and other services are very important lifelines in modern society. Commonly, these buried Pipes are subjected to significant Stresses due to external (traffic and earth) and internal (water pressure) loads. As many of these Pipelines were laid sometime in the last century or earlier, in most cases their condition has deteriorated primarily by electrochemical and (or) microbiological corrosion. Corrosion activity (internal and external) can manifest in various forms, but in many cases will lead to reduced Pipe thickness, which in turn leads to an increase in Pipe Stresses induced by the external and internal loads. Currently available analytical procedures to estimate Pipe Stresses are based on oversimplifications such as the two-dimensional (2-D) analysis based on Winkler springs, limiting their application to general Pipe burial conditions. This paper describes the application of a three-dimensional (3-D) finite element method to analyse a buried Pipe subjected to external and in...
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Stress analysis of buried Pipes
2014Co-Authors: J Merrin, Pathmanathan Rajeev, Dilan Robert, Hp Hung, Jayantha KodikaraAbstract:Pipeline plays a vital role in transporting water, gas and oil from one place to another. Over the years, several failures have been reported in Pipeline mainly due to aging (i.e., corrosion). The failure occurs when the Stresses in a Pipe segment due to applied loads exceed the capacity of the Pipe. Therefore, it is important to predict the realistic Pipe Stress at the design and assessment stages to ensure the safety across the entire lifetime. As significant portion of the Pipeline is buried in the underground in most of the occasions, the soil-structure interaction analysis is important as part of the Stress analysis. Depending on the location of the network, the Pipe will be subjected to varying levels of traffic and pressure loads that need to be accurately determined in order to perform reliable Pipe Stress estimations. Several Pipe Stress prediction methods have been developed over the years and reported in the literature. However, these methods are either analytical or empirical based models. The former uses the structural mechanics of the Pipe by discarding the complex soil-structure interaction effect while the later fully depends on the experimental results. To overcome these problems, the numerical methods can be used to incorporate the soil-structure interaction effect more efficiently in Pipe Stress analysis together with traffic and internal pressure loads. In this study, the finite element method is used to analyse the Pipe-soil system subjected to external traffic and internal pressure loads. Further, the model developed is used to understand the effect of soil properties, Pipeline characteristics, and loading on Pipe Stress through sensitivity analysis. Finally, the response surface method is used to develop a new Pipe Stress predictive equation using the results of finite element analyses.