Ductile Cast Iron Pipe Research Articles

Reproduction of fissure corrosion and mechanism for fissure formation on ductile cast iron

On some cast iron pipes corroded under tensile stress, corrosion with a characteristic surface appearance, known as “fissure corrosion,” was occasionally observed. Because fissure corrosion on ductile cast iron pipes has been rarely studied, the detailed conditions and mechanism for fissure formation are still elusive. In this study, the levels of tensile stress and anodic current density causing fissure corrosion on ductile cast iron were investigated through laboratory experiments to reproduce fissure corrosion and elucidate its mechanism. Fissure corrosion was reproduced at bending tensile stresses ≥200 MPa. The depth difference between the peak and valley of fissures increased with increasing anodic current density, and the fissure corrosion was attributed to the difference between the anodic current densities of the peak and valley due to plastic deformation by stress concentration. Fissure corrosion was likely to be suppressed by reducing the anodic current flowing out of ductile cast iron surface.

Online micro defects detection for ductile cast iron pipes based on twin light photometric stereo

Ductile cast iron pipes (DCIPs) are widely utilized in water and gas supply due to their exceptional mechanical and material properties. Quality control during production is paramount for optimal performance, with surface defect detection being of utmost importance. Currently, production sites primarily rely on manual visual inspection, which presents several challenges, including high labor intensity, low efficiency, and subjectivity in defect judgment. 2D detection algorithms based on single images struggle to effectively detect small defects such as pores, pinholes, and scratches, resulting in high missed detection rates and vulnerability to interference from oil and water stains. To address these issues, this paper proposes a symmetrical twin-light photometric stereo (TLPS) detection algorithm based on photometric stereo theory, and image correction algorithm for mitigating the effects of ambient light. A visual inspection prototype system was designed and successfully implemented at a production site. The system comprises eight visual inspection units, each equipped with a high-speed line scan camera and two bar light sources for image acquisition of moving DCIP. Under the Lambertian model and parallel light source assumption, the gradient expression in the texture direction of the DCIP surface is derived based on light source symmetry. Production experiment results demonstrate that the gradient map obtained through the proposed TLPS effectively enhances defect contrast and accurately detects and locates micro defects such as pores, pinholes, and scratches on cast pipe surfaces. This verifies the effectiveness of the TLPS algorithm, addresses the shortcomings of traditional 2D detection algorithms, and lays the foundation for subsequent online detection of DCIP surface defects.

A Self-Supervised Model Based on CutPaste-Mix for Ductile Cast Iron Pipe Surface Defect Classification.

Online surface inspection systems have gradually found applications in industrial settings. However, the manual effort required to sift through a vast amount of data to identify defect images remains costly. This study delves into a self-supervised binary classification algorithm for addressing the task of defect image classification within ductile cast iron pipe (DCIP) images. Leveraging the CutPaste-Mix data augmentation strategy, we combine defect-free data with enhanced data to input into a deep convolutional neural network. Through Gaussian Density Estimation, we compute anomaly scores to achieve the classification of abnormal regions. Our approach has been implemented in real-world scenarios, involving equipment installation, data collection, and experimentation. The results demonstrate the robust performance of our method, in both the DCIP image dataset and practical field application, achieving an impressive 99.5 AUC (Area Under Curve). This presents a cost-effective means of providing data support for subsequent DCIP surface inspection model training.

Full-scale determination of pipe wall and bulk chlorine degradation coefficients for different pipe categories

Abstract Having good information about parameters that impact water quality can improve the management of water distribution systems in the short-term (optimising disinfection) and the long-term (planning rehabilitation). Full-scale data on the degradation of the residual disinfectant for various pipe characteristics are difficult to obtain but necessary. As the most common disinfectant is chlorine, this paper aims to determine the most important pipe and/or hydraulic system characteristics in the chlorine degradation coefficients. Such characteristics were identified based on statistical analyses that relate them with range values of bulk and pipe wall degradation coefficients estimated in full-scale conditions in a real distribution system. The results showed that among pipe characteristics, the period of installation impacts significantly kw and kt. Results of kw for three different materials confirmed that residual chlorine degradation at the pipe walls for grey-cast iron, which is older and metallic, is much higher than that for ductile cast iron and PVC pipes. In older pipes, up to 97% of residual chlorine can be degraded at the pipe walls, while the role of bulk reactions can reach about 35% in newer pipes. The obtained information can be integrated to identify pipes for rehabilitation/renewal and locations for booster rechlorination.

Bulk and pipe wall chlorine degradation kinetics in three water distribution systems

ABSTRACT This paper presents a methodology to estimate free residual chlorine concentrations (FRCC) in full-scale water distribution system (WDS) using different degradation kinetics according to pipe material, age and diameter. Intensive field sampling campaigns and laboratory-scale tests were carried out to estimate total and bulk volume FRCC in three WDS. Bulk kinetic constants were estimated for water temperatures typical of different seasons in the Quebec City area (Canada). With field-measured FRCC at all sampling sites and an estimation of travel times through the use of a hydraulic model, total, bulk and pipe wall kinetic constants were obtained with ranges of 10.2 to 130.4, 4.1 to 43.8 and 8.5 to 114.9 10−3/h, respectively. Pipe wall kinetics tend to dominate the total degradation process for older grey and ductile cast-iron pipes, followed by newer ductile iron pipes and then PVC and pre-stressed concrete pipes (mostly installed from 1990). The developed methodology and results will be useful to improve the prediction of FRCC through hydraulic and water quality modelling.

Relation between the Degree of Corrosion Progress and the Service Limit Years of Ductile Cast Iron Pipes

Relation between the Degree of Corrosion Progress and the Service Limit Years of Ductile Cast Iron Pipes

The Effect of Tungstate and Ethanolamines Added in Tap Water on Corrosion Inhibition of Ductile Cast Iron Pipe for Nuclear Power Plants

Cast iron is primarily used in buried piping to transport water in the fire protection system of nuclear power plants; ductile cast iron is generally used for domestic nuclear power plants. In general, the fluid used as fire-extinguishing water in such fire protection systems is tap water, and corrosion inhibitors are not currently added. In this study, the synergistic effect of an adsorption barrier (monoethanolamine) and oxidized film in an environment with a corrosion inhibitor (tungstate) is examined, and the corresponding passivation properties are presented. An immersion corrosion test and electrochemical test in tap water to which only tungstate was added showed suppression of corrosion compared to molybdate at the same concentration. The polarization resistance value of a passivation film in tap water mixed with monoethanolamine and tungstate showed better results than that of the molybdate control. A surface analysis in mixed addition tap water also demonstrated that oxygen ions were sufficiently distributed, including at some spheroidized graphite sites, when tungstate was added compared to molybdate. In addition, the amount of tungsten ions adsorbed on the surface was larger than that of molybdenum ions, and it was confirmed that tungsten ions were evenly distributed over the entire surface.

Occurrence and quantification of culturable and viable but non-culturable (VBNC) pathogens in biofilm on different pipes from a metropolitan drinking water distribution system

Waterborne pathogens have been found in biofilms grown in drinking water distribution system (DWDS). However, there is a lack of quantitative study on the culturability of pathogens in biofilms from metropolitan DWDS. In this study, we quantified culturable and viable but non-culturable (VBNC) Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa and Vibrio cholerae in biofilms collected from five kinds of pipes (galvanized steel pipe, steel pipe, stainless steel clad pipe, ductile cast iron pipe and polyethylene pipe) and associated drinking water at an actual chlorinated DWDS in use from China. The results of these comprehensive analyses revealed that pipe material is a significant factor influencing the culturability of pathogen and microbial communities. Network analysis of the culturable pathogens and 16S rRNA gene inferred potential interactions between microbiome and culturability of pathogens. Although the water quality met the Chinese national standard of drinking water, however, VBNC pathogens were detected in both biofilms and water from the DWDS. This investigation suggests that stainless steel clad pipe (SSCP) was a better choice for pathogen control compared with other metal pipes. To our knowledge, this is the first study on culturable and VBNC pathogens in biofilms of different pipe materials in metropolitan DWDS.

Test on a buried pipe network subjected to an artificial earthquake produced by multi-millisecond blasting

Buried pipe networks are important components of lifeline systems. An experiment is conducted to test a buried pipe network subjected to an artificial earthquake produced by multi-millisecond blasting. The motivation of the research is to verify the feasibility of using multi-millisecond blasting to simulate earthquakes and to validate the deformation relationship between pipe and soil obtained in a single-point explosion test. Multiple explosives are used with a time-delay technique to create an extended period of loading on pipes. The dimension of the buried pipe network is 24 m × 24 m. The artificial earthquake is produced by trinitrotoluene (TNT) charges. The pipe network consists of ductile cast iron (DCI) pipes, which represent a water distribution network, and welded steel (WS) pipes, which represent a gas supply network. Eighty-five kilograms of TNT charges, which are divided into three parts, are detonated by millisecond blasting. The ground motion of the test field, including the accelerations and velocities at different points, and the pipe dynamic responses, including the joint deformations of DCI pipes and the axial strains of WS pipes, are described in detail. Finally, the deformation law of buried pipe networks and the deformation relationship between pipe and soil are discussed.

Formation of biofilms from new pipelines at both ends of the drinking water distribution system and comparison of disinfection by-products formation potential

The gradual updating of the water supply network is one of the crucial ways to ensure the safety of drinking water all over the world. The phenomenon and regularity of the biological risk and chemical risk of biofilms of the new pipes in drinking water distribution system (DWDS) is inadequate researched by now. In order to explore the biochemical risks of biofilms after new pipes are used, this paper studied the growth of biofilms, the content of disinfection by-products (DBPs) and the potential for disinfection by-products (DBPsFP) after 2-year use by establishing a pilot test platform at both ends of the DWDS in City S. The results showed that the total bacterial count in new pipelines was between 1.38 × 108–9.97 × 108/cm2; the DBPsFP at the front end and at the back end was subtly different. The overall DBPsFP of biofilms was the highest, followed by the ductile cast iron pipe and the galvanized pipe whereas the stainless steel pipe was the lowest. The HPC content of the 2-year-old pipe (1.68 × 105–7.09 × 106 CFU/cm2) was remarkably higher than that of the 1-year-old pipe (1.04 × 105–8.76 × 105 CFU/cm2), and the generation DBPsFP was about 50% higher. When a new pipeline was put into use in the urban drinking water distribution system, biofilms with certain biological hazards and risks of DBPs disinfection by-products would form in a short period of time.

Evaluation of “C” Values to Head Loss and Water Pressure Due to Pipe Aging: Case Study of Uni-Central Sarawak

Samarahan has transformed from a small village into education hub for the past 2 decades. Rapid development and population growth had led to speedy growth in water demand. The situation is getting worse as the pipes are deteriorating due to pipe aging. Therefore, there is a need to study the adequacy of water supply and relationships among roughness coefficient (C) values in Hazen Williams’ Equation with head loss and water pressure due to pipe aging at Uni-Central, a residential area located at Samarahan Sarawak. Investigations were carried out with Ductile Iron, Abestos Cement and Cast Iron pipes at age categories of 0 - 10 years, 10 - 30 years, 30 - 50 years, 50 - 70 years and >70 years. Six critical nodes named as A, B, C, D, E and F were identified to study the water pressure and head loss. Model was developed with InfoWorks Water Supply (WS) Pro software. The impact of pipe aging and materials to water pressure and head loss was not significant at Nodes A, B, C and F. However, max water pressure at Nodes D and F were only reaching 6.30 m and 7.30 m, respectively for all investigations. Therefore, some improvement works are required. Results also show that Asbestos Cement pipe has the least impact on the head loss and water pressure, followed by Ductile Iron pipe and lastly Cast Iron pipe. Simulation results also revealed that older pipes have higher roughness coefficients, indicated with lower “C” values, thus increase the head loss and reduce the water pressure. In contrast, as “C” values increased, head loss will be reduced and water pressure will be increased.

매설 구상흑연주철관의 물리화학적 특성 평가

매설 구상흑연주철관의 물리화학적 특성 평가

The stiffness of axial pipe–soil springs and axial joint springs tested by artificial earthquakes

This study proposes an experimental method to obtain the stiffness of axial pipe–soil and axial joint springs in time and frequency domains. The proposed method can determine axial pipe–soil spring stiffness by using the pipe strains and slippages between pipes and soil. It can also determine axial joint spring stiffness by utilizing pipe strains and joint deformations. The pipe–soil spring stiffness values of ductile cast iron (DCI) and welded steel (WS) pipes are obtained and analyzed through artificial earthquake tests on a 24m × 24m buried pipe network. Artificial earthquakes are produced with trinitrotoluene explosives. Three theoretical models are discussed, and their results are compared with the test results. The comparisons indicate that the proposed experimental method is valid to obtain the stiffness of axial pipe–soil and axial joint springs. The stiffness values can be a benchmark to study the pipe–soil interaction and flexible joints. The effects of axial pipe–soil spring stiffness on the joint deformations of DCI pipes and pipe strains of WS pipes are also discussed.

Avaliação do potencial corrosivo do solo em dutos utilizados para o transporte de água no Sertão de Pernambuco

Em meio à emergência hídrica do país, principalmente no sertão nordestino, as adutoras se consagram como um meio de transporte de água eficaz. O solo é largamente explorado nas construções e representa um dos meios corrosivos mais influentes neste segmento. A corrosão pode causar fissuras e rupturas das estruturas construídas ocasionando prejuízos econômicos e ambientais. Visando prevenir tais incidentes, foi avaliada a corrosividade do solo e, monitorada a perda de massa nos tubos de ferro fundido dúctil sob a ação do solo. Nas análises químicas do solo foram determinados: pH, Ca, Mg, P, K, Na, Al, H, Fe, Cu, Zn, Mn, matéria orgânica (MO), carbono orgânico (CO) e calculadas a soma de bases (SB), capacidade de troca de cátion (CTC), percentagem de saturação por alumínio (m%) e percentagem de saturação por bases (V%). Para corrosividade do solo utilizou-se o índice de Steinrath, sendo analisados pH, teor de umidade, resistividade, íons cloreto e sulfato. Os ensaios de perda de massa do tubo de ferro fundido dúctil foram realizados em amostras de solo como meio corrosivo, monitorando temperatura, resistividade, e perda de massa por corrosão. Os resultados obtidos mostraram que os solos são pouco corrosivos e o duto apresenta boa resistência à corrosão, apesar de apresentarem perda de massa ao longo do período do uso. É possível concluir que o solo em contato com os dutos de transporte de água apresenta baixa agressividade.

Effect of Residual Chlorine Concentration on Water Pipe Corrosion

1. Introduction Water pipe corrosion corrodes the iron by the oxidation reduction reaction, and the corrosion rate is accelerated by the oxidizing agent used as disinfectant in the tap water. The major oxidizing agent in tap water are ozone and chlorine. pH, alkalinity and residual chlorine concentration are factors of internal corrosion. We are replacing the ductile cast iron pipe with inner coating and stainless steel pipe. However, it is still used in many cases, such as gray cast iron pipes and galvanized steel pipes without internal coatings in Korea. Chlorine is a very strong oxidant for all metals and organics, and the reaction between chlorine and iron is as follows. HOCl + 2Fe2+ + 5H2O → 2Fe(OH)3↓ + Cl- + 5H+ Recently, as the problem with sinkholes has arisen on the a buried road as water pipes, sewage pipes, etc, interest in corrosion has been growing. The purpose of this study is to evaluate the effect of residual chlorine on the corrosion factor by analyzing the water quality and to evaluate the necessity of the proper residual chlorine on in the water purification plant. 2. Experimental Method In order to evaluate the corrosion of residual chlorine concentration of tap water, we were carried out Tafel experiment and water quality analysis. The corrosion rate was measured by a Tafel experiment using an electrochemical corrosion measurement system (PAR VMP-3). For tap water in Seoul, corrosion evaluation was performed according to alkalinity and hardness, residual chlorine concentraion. 3. Summary of results The tap water quality of Seoul was as follows that residual chlorine is 0.4 mg/L, and alkalinity is 50 mg/L as CaCO3, with a pH of 7.3. The results of experiments on the rate of corrosion of Carbon Steel specimens to residual chlorine in seoul tap water, can be seen in Fig. 1. As a result of the Tafel experiment according to the initial residual chlorine concentration under the same conditions (same LI index), The corrosion rate was 0.01 mmpy at 0 mg/L of residual chlorine and 0.074mmpy at 0.8mg/L of residual chlorine, corrosion rate for residual chlorine in carbon steel specimens was more than 7 times. It was confirmed that the higher the concentration of residual chlorine, the faster the corrosion rate was increased. The corrosivity of tap water in Korea is evaluated by the LI index, but residual chlorine has a large effect on corrosion, so it is required to add residual chlorine for the tap water corrosion evaluation. It is reducing the concentration of residual chlorine for reduce the chlorine odor of tap water in the distribution water system in Korea. But, residual chlorine guideline for corrosion reduction is necessary in Korea. Figure 1

Change regularity of water quality parameters in leakage flow conditions and their relationship with iron release

The long-term stagnation in metal water supply pipes, usually caused by intermittent consumption patterns, will cause significant iron release and water quality deterioration, especially at the terminus of pipelines. Another common phenomenon at the terminus of pipelines is leakage, which is considered helpful by allowing seepage of low-quality drinking water resulting from long-term stagnation. In this study, the effect of laminar flow on alleviating water quality deterioration under different leakage conditions was investigated, and the potential thresholds of the flow rate, which can affect the iron release process, were discussed. Based on a galvanized pipe and ductile cast iron pipe pilot platform, which was established at the terminus of pipelines, this research was carried out by setting a series of leakage rate gradients to analyze the influence of different leakage flow rates on iron release, as well as the relationship with chemical and biological parameters. The results showed that the water quality parameters were obviously influenced by the change in flow velocity. Water quality was gradually improved with an increase in flow velocity, but its change regularity reflected a diversity under different flow rates (p < 0.05). The iron release was remarkably correlated to the redox potential, dissolved oxygen, pH, iron-oxidized bacteria and sulfate-reducing bacteria. The cumulative total iron release (r = 0.587, p < 0.05) and total iron release rate (r = 0.71, p < 0.022) were significantly influenced by the changes in flow velocity. In short, they tended first to increase and then to decrease with an increasing flow velocity with the threshold as approximately 40% of the critical laminar flow velocity (1.16 × 10−3 m/s). For the pipes at the terminus of the drinking water distribution system, when the bulk water was at the critical laminar flow velocity, the concentration of total iron, the quantity and rate of total iron release remain relatively in an ideal and safe situation.

Experimental validation of a model for seismic simulation and interaction analysis of buried pipe networks

A finite-element model is established to evaluate the seismic responses of buried pipe networks. In the model, pipes are simulated as beams on elastic foundation, the joints of the segmented pipes are modeled by axial and rotational springs, and the pipe–soil interactions are simulated by springs. The seismic wave acts on one end of the soil springs to induce the seismic responses of the pipe networks. The test results of a buried pipe network subjected to an artificial earthquake is adopted as benchmark to validate the model. The tested pipe network has a size of 24m×24m and consists of ductile cast iron and welded steel pipes. The artificial earthquake is produced by 30kg of TNT explosives. Two important responses are compared, i.e., the joint deformations of the ductile cast iron pipes and the strains of the welded steel pipes. Results indicate that the model can evaluate the seismic responses of the buried pipe networks well. The pipe interactions are analyzed using the model by comparing the seismic responses of the single pipe and its counterpart in the pipe network.

Effect of flushing on the detachment of biofilms attached to the walls of metal pipes in water distribution systems

Biofilm detachment caused by flushing can result in secondary contamination in drinking water distribution systems (DWDSs). To evaluate the impact of flushing on biofilm detachment, actual water supply pipes including ductile cast iron pipes (DCIPs), gray cast iron pipes (GCIPs), and stainless steel compound pipes (SSCPs) were used in this study. Real-time quantitative polymerase chain reaction and 454 pyrosequencing were used to quantify bacteria and analyse microbial community composition, respectively. The results showed that the pipe material greatly influences the resistance of a biofilm to flushing. Biofilms attached to DCIPs were able to resist quite strong flushing, while those attached to GCIPs and SSCPs were sensitive to flushing. Both flush-resistant and flush-sensitive bacteria were present in all the biofilms, but their frequency differed among the different metal pipes. Thus, the resistance to flushing of bacteria is related not only to the nature of the bacteria, but also to the pipe material. Although flushing can remove some of the biofilm and may be a good way to clean the DWDS, the shear stress needed to remove the biofilm differs among different pipe types. The results of this study provide technical support for the management and operation of DWDS.

Bacterial community radial-spatial distribution in biofilms along pipe wall in chlorinated drinking water distribution system of East China.

Biofilms in the pipe wall may lead to water quality deterioration and biological instability in drinking water distribution systems (DWDSs). In this study, bacterial community radial-spatial distribution in biofilms along the pipe wall in a chlorinated DWDS of East China was investigated. Three pipes of large diameter (300, 600, and 600mm) were sampled in this DWDS, including a ductile cast iron pipe (DCIP) with pipe age of 11years and two gray cast iron pipes (GCIP) with pipe ages of 17 and 19years, and biofilms in the upper, middle, and lower parts of each pipe wall were collected. Real-time quantitative polymerase chain reaction (qPCR) and culture-based method were used to quantify bacteria. 454 pyrosequencing was used for bacterial community analysis. The results showed that the biofilm density and total solid (TS) and volatile solid (VS) contents increased gradually from the top to the bottom along the pipe wall. Microorganisms were concentrated in the upper and lower parts of the pipe wall, together accounting for more than 80% of the total biomass in the biofilms. The bacterial communities in biofilms were significantly different in different areas of the pipe wall and had no strong interaction. Compared with the upper and lower parts of the pipe wall, the bacterial community in the middle of the pipe wall was distributed evenly and had the highest diversity. The 16S rRNA genes of various possible pathogens, including Escherichia coli, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Salmonella enterica, were detected in the biofilms, and the abundances of these possible pathogens were highest in the middle of the pipe wall among three areas. The detachment of the biofilms is the main reason for the deterioration of the water quality in DWDSs. The results of this study suggest that the biofilms in the middle of the pipe wall have highly potential risk for drinking water safety, which provides new ideas for the study of the microbial ecology in DWDS.

LABORATORY EXPERIMENTATION COMPARISON OF CENTRIFUGAL CASTING MACHINES FOR DUCTILE CAST IRON PIPES

Centrifugal casting machines are a production machines used to produce ductile cast iron pipes in the casting method in El Nasr Casting Company . The Casting Machines were manufactured by Thyssen Rheinstahl Technik GmbH. They are usually driven by three-phase separately excited DC motor of a nominal voltage of 400V and nominal power 222 kW . Lower overall efficiency leads to higher electricity consumption [1]. Motor performance characteristics and control strategies are described for both AC and DC machines ,However, with advances in AC motor drives (vector flux variable frequency drives) their dynamic response has improved dramatically, making them an attractive alternative to DC drive systems. Due to improved dynamic response and better motor efficiency of AC drives (compared to DC drives), centrifugal casting machines using AC drives can run faster than using DC drives, resulting in improved productivity and significant electrical energy savings.