Asbestos Cement Pipe Research Articles

Towards more realistic stochastic modelling of leakage in water distribution systems

ABSTRACT A new stochastic model is developed to predict leak types and sizes in water distribution systems. By linking records of actual failures in water networks with new tools for stochastic modelling, the study provides more accurate estimates of network leakage behaviour. District metered areas (DMAs) have been adopted internationally as best practice for monitoring and controlling leakage, with the infrastructure leakage index (ILI) as the main performance indicator. The leakage exponent (N1), which quantifies the relationship between leakage rate and pressure, is a key parameter in describing DMA leakage behaviour. After analysing thousands of stochastic networks for different combinations of pipe material and ILI, the study found that different pipe materials have distinct leakage exponent distributions. Iron and asbestos cement (AC) pipes display N1 values close to 0.5, polyvinyl chloride (PVC) pipes have the highest N1 values, and polyethylene (PE) lies between PVC and iron/AC. The study further showed that current guidelines linking ILI to N1 for different pipe materials depart substantially from the observed results, indicating that these guidelines may need to be updated. The study provides a tool for more realistic modelling of leakage that offers valuable insights into the behaviour of leakage in different pipe materials.

Long-term influences of pipe materials on bacterial communities of matured biofilms (> 40 years’ old) in drinking water distribution systems

Pipe materials appear to play an important role in the development of biofilms in drinking water distribution systems. However, there is controversy as to whether pipe materials shape the composition and diversity of bacterial communities in biofilms. To investigate the long-term effects of pipe materials on biofilms, triplicate samples of mature biofilms on unplasticized polyvinyl chloride (PVC-U), grey cast iron and asbestos cement (pipe age > 40 years) were obtained from three areas of an unchlorinated drinking water distribution system in the Netherlands. Illumina sequencing was performed and 773 OTUs (730 OTUs-814 OTUs) were detected within the biofilms on the three pipe materials, all of which were dominated by Proteobacteria (36.2%-46.1%). Both the alpha and beta diversity results showed that the bacterial communities of the biofilms formed on different pipe materials were highly similar. The neutral community model revealed that the assembly of the biofilm communities was governed by environmental selection rather than neutral processes. Among the 142 shared OTUs between the water and biofilm samples, there were 25 enriched OTUs (e.g., OTU7, assigned as Nitrospira spp.), which accounted for 62.6% of the total sequences, while 16 OTUs were disadvantaged (e.g., OTU14 and OTU40, assigned as Hyphomicrobiaceae), accounting for 2.2% of the sequences. Based on the findings, we propose and discuss a harmonisation process by which biofilms with significant differences due to the pipe material harmonize over time resulting in biofilms with similar bacterial communities. Our findings provide valuable insights into long-term biofilm development, bridging an essential gap in our current understanding of the influence of pipe materials on biofilm communities. These findings also highlight the importance of long-term studies and point to a potentially masked harmonizing process during biofilm development over years/decades.

Analysis of factors driving water main breaks across 13 Canadian utilities

Deterioration of water infrastructure is a global challenge that jeopardizes water system ability to deliver water safely. While various factors affect watermain failure, previous studies have focused on common pipe attributes or general protection strategies. The main objective of this study is to examine the relationship between pipe break characteristics and system properties. Comprehensive data from thirteen Canadian water systems (over 60,000 failures) are examined with correlation and chi-squared analyses. Joint and fitting failures are most likely for pipes aged 20 years or less, and universal joints are most associated with joint failure. Pipes in clay and sand soils are more likely to break due to improper bedding and differential settlement, respectively. Furthermore, in the summer, accidental breaks of asbestos cement pipes are more likely, as are failures of pipes with collar joints and coal tar lined pipes. By exploring these relationships, the paper provides insights into opportunities for reducing water main failure, through improved design, maintenance and rehabilitation.

Fiber-Reinforced Cement Pipes as Simulants for Deteriorated Asbestos Cement Pipes in Rehabilitation Studies

Fiber-Reinforced Cement Pipes as Simulants for Deteriorated Asbestos Cement Pipes in Rehabilitation Studies

A risk-based soft sensor for failure rate monitoring in water distribution network via adaptive neuro-fuzzy interference systems

Water Distribution Networks (WDNs) are considered one of the most important water infrastructures, and their study is of great importance. In the meantime, it seems necessary to investigate the factors involved in the failure of the urban water distribution network to optimally manage water resources and the environment. This study investigated the impact of influential factors on the failure rate of the water distribution network in Birjand, Iran. The outcomes can be considered a case study, with the possibility of extending to any similar city worldwide. The soft sensor based on the Adaptive Neuro-Fuzzy Inference System (ANFIS) was implemented to predict the failure rate based on effective features. Finally, the WDN was assessed using the Failure Modes and Effects Analysis (FMEA) technique. The results showed that pipe diameter, pipe material, and water pressure are the most influential factors. Besides, polyethylene pipes have failure rates four times higher than asbestos-cement pipes. Moreover, the failure rate is directly proportional to water pressure but inversely related to the pipe diameter. Finally, the FMEA analysis based on the knowledge management technique demonstrated that pressure management in WDNs is the main policy for risk reduction of leakage and failure.

DEVELOPMENT OF INNOVATIVE PILE FOUNDATION DESIGNS ON SUBSIDENCE SOILS

New technical solutions for the elimination of negative friction forces in the construction of pile foundations on subsidence soils are considered. The friction forces arising between the subsidence soil and the side surface of the pile, according to the Amonton-Coulomb law and the theoretical justifications of B.V. Deryagin, are presented as the sum of a term depending on adhesion and the product of the coefficient of friction by normal pressure. There is some function approximating the total friction force along the side surface of the pile. Differentiating this function, we obtain a formula that determines the change in soil pressure on the side surface of the pile, which varies with the depth of the pile location in the subsidence soil. To sharply reduce the forces of negative friction, the author has developed the design of a pile foundation made of asbestos cement pipes. Studies have shown that in these piles, the forces of negative friction are reduced by 20-30 %, compared with concrete piles manufactured in factory conditions. The author has developed two variants of the method of building a pile foundation on subsident soils, in which the role of antifriction lubricant is performed by a layer of humbrine. Humbrin is a waste of the technology of purification of technical oils. This waste accumulates in large quantities in the landfills of oil refineries. The author has proposed a new design of a pile foundation, in which recycled tires are used as an outer shell to remove the forces of negative friction. Experimental studies have shown that even with vertical deformations of the tire screen of more than 0.04 m, the amount of pile precipitation turned out to be negligible, only 0.02 mm. The author also developed a pile foundation erected on subsident soils. This pile foundation has an external cylindrical shell. In the gap between the cylindrical shell and the side surface of the pile there is a spiral-wound elastic rubber rolling harness. When the surrounding soil subsides, the outer cylindrical shell moves vertically down the rolling spiral bundle, removing negative friction from the side surface of the pile. In addition, the rolling spiral elastic harness also performs the function of a seismic isolator.

Modelling of Water Distribution Network for Hayin Banki, Kaduna State

Water distribution systems are designed to adequately satisfy the water requirement for domestic, commercial industrial and firefighting purpose. A spatial database of the water distribution systems (WDS) for Hayin-Banki was created in a Geographic Information System (GIS) environment (ArcGIS), drawing inputs data from water supply and demand. Environmental Protection Agency Network (EPANET, 2.0) was used to analyze the WDS to explore its reliability in current and future scenarios. Mapping of the existing 12.270 km long distribution network revealed that the total length of ductile iron pipe (DIP) is 11.12 km and asbestos cement (AC) pipes is 1.15 km. Running the analysis identified supply gaps, which includes deficiencies in the distribution system (small diameters pipes, system losses) resulting to negative and very small pressures. Running simulations with EPANET and geospatial techniques was used to solve the identified deficiencies.

A comparison between multivariate adaptive regression splines and regressive convolution neural network with support vector regression for pipe burst rate prediction on limited dataset

ABSTRACT By accurate predicting of pipe bursts, it is possible to schedule pipe maintenance, rehabilitation and improve level of services in Water Distribution Networks (WDNs). In recent years, artificial intelligence techniques have been used vastly in pipe burst prediction. These techniques need big input dataset for deep learning but big dataset might not be available in old WDNs. This paper aimed to compare the performance of multivariate adaptive regression splines (MARS) and regressive convolution neural network with least square support vector regression (RCNN-LSSVR) for predicting of Pipe Burst Rate (PBR) with limited dataset. Pipes age, diameter, depth of installation, length, average and maximum hydraulic pressure are considered as effective parameters of PBR. Data collected from real-case study in Iran include 158 cases for polyethylene and 124 cases for asbestos cement pipes during 2012–2019. The results indicate that RCNN-LSSVR model has a great performance of PBR prediction on limited dataset.

Laboratory and field experiment validations on the use of hydraulic transients for estimating buried water pipeline deterioration

This paper investigates the validity of using fluid transients as a rapid screening tool to augment existing methods for assessing the condition of buried water systems. In particular, the paper provides one of the first detailed investigations on the impact of pipe wall deterioration on the characteristic of transient waves in both laboratory and field experiments. Laboratory pipeline sections were deteriorated by an accelerated corrosion process using controlled electrolytic cell reactions, and three cases were considered: where corrosion is limited to the internal wall, limited to the external wall, and where both internal and external walls are corroded. Hydraulic transient tests were carried out to measure the transient wave speed in these corroded pipe sections, and the measurements are found to be consistent with the theoretical predictions using the observed wall thickness loss, confirming that wave speed can be used as an indicator of pipe wall deterioration. Field experiments were carried out in the water supply network in the Waimakariri District, New Zealand, to validate the performance of this pipe condition diagnostic methodology. Transient tests were conducted on selected 60-year-old sections of asbestos cement (AC) pipelines and sensors were connected to standard fire hydrants to measure the wave speeds and wave reflections. Compared with the theoretical calculated wave speed of intact pipelines, a 140–300 m/s wave speed decrease was observed in most of the tested sections which is in line with the expectation for pipelines of this age. The wave speeds were used to predict the in-situ thickness of the pipe wall and these predictions were found to match with computed tomography X-ray scan results of the excavated pipe with good accuracy. The same methodology was also used to correctly detect an unrecorded plastic pipe section in the AC pipe network.

The analysis of asbestos-cement shell pile performance under off-center loading and forced torsion

The paper discusses the new design of a round pile with a relatively smoother surface, developed in an attempt to eliminate excessive negative friction forces. A theoretical study has been conducted into the performance of asbestos-cement shell pile exposed to off-center loading, which occurs in response to uneven deformations in the surrounding soil and seismic loads. The cross section of the upper eccentrically compressed part of a flexible asbestos-cement-pipe-concrete pile element is considered. When considering the stress-strain state of flexible eccentrically compressed asbestos-cement-pipe-concrete piles, the premise of compliance with the hypothesis of flat sections is accepted. With the predicted intensive development of loading friction forces, a method is proposed for preliminary turning these round piles around the axis to remove the main part of the adhesion between the side surface of the pile with the base soil. Theoretically, the stress-strain state of the indicated pile, which is formed during its torsion around the axis, was estimated. The pile is considered as a composite element consisting of a concrete cylinder and an asbestos-cement pipe. As a first approximation, we assume that there are no body forces, and the concrete core and the asbestos-cement shell are rigidly linked. According to the Saint-Venant principle, it can be considered that for a twisted rod at a sufficiently large distance from its ends, the stresses depend on the torque and do not depend on the method of distribution of the forces that give this moment over the end sections. Based on the basic equations of the theory of elasticity, it follows that in a pile of circular cross section, bounded by a concentrically round shell, the cross sections remain flat during torsion.

CT Scans of Asbestos Cement Pipes as a Reference for Condition Assessment of Water Mains

The water distribution network of The Netherlands contains around 30,000 km of asbestos cement (AC) pipes, which constitutes around 25% of the total network. As a pipe material, AC has a relatively poor performance, and therefore is a high priority for renewal. To help decide an effective order of replacement, the water utilities need condition assessment techniques that help them determine which pipes have the highest risk of failure. In the presented work, X-ray computed tomography (CT) was used to measure the degradation of AC pipes taken out of the field. These scans provide a description of the pipe degradation with unmatched detail. The results are compared with strength tests performed on the same pipes, revealing that detailed knowledge of the complete pipe degradation is more important than previously assumed. Moreover, comparison of the CT results to those of a commercial, non-destructive inspection technique was used as a new avenue for validation of this technique, demonstrating its future usefulness for attaining the detailed measurement of pipe degradation required by water utilities.

Degradation of asbestos – Reinforced water supply cement pipes after a long-term operation

Potable water supply system in major countries still uses a large proportion of asbestos-cement (AC) pipes for fresh drinking water delivery. Generally, after installation and initial purging, the AC tubes are believed to self-passivate by calcite scale and bio-film, especially when conveying hard water. However, the overall performance of AC tubes after decades of operation is significantly reduced and is still mainly unknown. In the current research, we investigated the AC water supply tube after 56 years of operation with high-hardness conveyed water. Our results show that asbestos fibres are emitted from degraded AC pipes as a result of wall softening due to calcium leaching from hydrated cementitious materials, resulting in the loss of mechanical stability. Although the water pumped into the system is not considered aggressive, the seasonal variations of water temperature and chemistry results in an interplay of calcite scaling and Ca leaching, the latter being the dominating process. By comparing the experimental observations with the long-term chemistry reports of the water supplied through the pipes, a positive relationship was established between the temperature and quality of the conveyed water with the corrosion and the calcite scale formation, which are dictating the emission of the fibres into the drinking water. In addition to the health risks posed by asbestos, these processes have many adverse effects on drinking water supply, such as pipe malfunction and destruction resulting in water loss, reduction of hydraulic capacity, microbial proliferation, and water quality deterioration, a topic of interest for global water industries process.

Intensification of loosening of asbestos fibers by means of hydromechanical processing

Acceptance of high-quality aqueous suspensions based on chrysotile asbestos is an urgent technical task in a number of industries. Asbestos-cement mortar is used as an asbestos-cement crust for insulation of walls and other building surfaces, due to this composition of the treated surfaces perfectly retain heat, resistant to moisture, and most importantly - asbestos fibers contribute to the smoothness of the surface and crack is not formed. No less popular is the use of asbestos-cement mortar with a high content of asbestos in the insulation of ventilation ducts and pipelines. This composition of asbestos-cement mortar is used to strengthen the joints of asbestos-cement pipes, as well as as a filler in the laying of cast iron pipes to give the joints additional elasticity.
 Asbestos-cement mortar has plasticity, resistance to stretching and reinforcement of asbestos, as well as strength and versatility in the use of cement. Due to these properties, asbestos and cement perfectly adhere to each other to obtain a durable, strong, frost-resistant, virtually waterproof and fire-resistant building material.
 The result of the microscopic examination is reason to believe that from the technological process of production of slate can be removed electromechanical mixer for the preparation of a solution of asbestos + water + portland cement. In this case, given the fact of continued loosening of asbestos in the preparation of the mold mixture of asbestos + water + portland cement, it will be sufficient to ensure the degree of loosening of asbestos in the ripper at the minimum required level (for example, not more than 85%). It is assumed to obtain a mold mixture with a high degree of homogeneity of the components with reduced costs of Portland cement due to its physico-chemical activation by hydraulic fluxes.

Pipe breaks and estimating the impact of pressure control in water supply networks

The deterioration and fracture of water supply pipes present a major threat for the continuous provision of drinking water. The hydraulic pressure in pipes is an influential factor for the occurrence of pipe breaks. However, little evidence has been provided so far for the quantitative assessment of the impact of pressure control on reducing the number of pipe breaks. In this paper, we applied logistic regression with polynomial terms, and a sensitivity analysis to assess the potential impact of pressure control on reducing pipe breaks. A large dataset of historic pipe breaks was used to develop and validate the presented method. Cast iron and asbestos cement pipes were examined in detail. Results showed that pipe breaks could be decreased by 18% to 30% by reducing the mean pressure for the investigated cohorts of asbestos cement and cast iron pipes. Pressure range reduction could provide larger impacts on both pipe materials. These results indicate that proactively controlling the hydraulic pressure may have a potentially significant impact on the reliability and sustainability of water supply networks.

Evaluation of potential gastrointestinal carcinogenicity associated with the ingestion of asbestos.

The inhalation of asbestos, depending on the fiber type and dose, may be associated with the development of mesothelioma and other asbestos-related diseases. However, little is known about the potential adverse effects associated with the ingestion of asbestos. Evidence of asbestos fibers released from asbestos-cement pipes used in water distribution systems has led to concerns of potentially contaminated drinking water. The purpose of this study is to determine whether ingestion of asbestos fibers may lead to cancerous effects on the gastrointestinal (GI) tract. Data from animal and human studies were analyzed using a weight-of-evidence approach to evaluate the potential risk of GI cancers associated with asbestos ingestion. Seventeen human and 23 animal studies were identified and evaluated in this study. Animal studies were conducted in multiple species with inconsistent dosing protocols. Overall, animal studies reported that the asbestos fibers, irrespective of fiber type and dose, failed to produce any definitive GI carcinogenic effect. The 17 identified human epidemiological studies reported the ingestion of asbestos-contaminated water with concentrations from 1 to 71,350 million fibers per liter (MFL). A majority of the epidemiology studies reported statistically significant increases in multiple GI-specific cancers. However, these findings are confounded due to several critical study limitations including flawed study design, small sample size, selection bias, lack of individual exposure history, lack of adequate latency, and the inability to account for confounders including occupational history, diet, and smoking history. Based on our weight-of-evidence assessment, there is insufficient evidence of causality between the ingestion of asbestos and an increased incidence of GI cancers.

Using generalized additive models to investigate the environmental effects on pipe failure in clean water networks

Predicting pipe failures using statistical modelling benefits from detailed knowledge of the conditions and circumstances which influence such failures. Incorporating this knowledge into model building improves failure predictions. In this study, we model weather, soil and hydrogeological variables in a generalized additive model for five common pipe materials separately, using partial dependence plots to understand the partial effects of each variable on pipe failure. We show how severe temperatures are associated with high pipe failure. Cold temperatures and air frost and their interaction with soils represent the key factors for pipe failures during the winter for metal pipes. Warm temperatures, high soil moisture deficit and soil movement results in higher pipe failures in asbestos cement pipes during the summer. Warm temperatures, ground movement and soil wash out, and water demand are key factors for polyvinyl chloride pipe failure during the summer. Frost is a key factor influencing polyethylene pipes during winter. An understanding of the physical principals concerning pipe failures can enable the development of more accurate models, guiding network management plans to help reduce asset leakage through appropriate interventions.

The Application of Coconut Fiber as Insulation Ceiling Board in Building Construction

This study considers the applications of natural fiber composites in affordable housing projects located in Malaysia with the goal of addressing issues of the thermal comfort. Roof thermal insulation is one of the effective methods that can save cooling energy in places with an equatorial climate especially in Malaysia. The use of recycled products or industrial waste materials is now a potential trend in the industry. Therefore, natural fiber was chosen as a material for the ceiling board in this study. During the day, heat can enter the room from the roof so that insulation material is needed to reduce heat flux by maintaining the temperature of the building. The problems faced by consumers are cost increases due to the use of large amounts of electricity. Besides, asbestos use becoming less frequent because the government has banned its use as a ceiling, side panels, roofing material, asbestos cement-pipes, many types of fireproof and insulation material. The objectives of this study was to determine the mechanical and physical properties of coconut fiber with fire retardant paint as a thermal comfort for ceiling board. The next objective is to study the percentage difference in sodium hydroxide and sodium chloride during the treatment of coconut fiber. The data result is that the fiber is ideal as an insulating material for the house ceiling board because it has a low temperature quality of 0.225W. The water absorption value was as high as 11.20% which is slightly lower than previous studies. Finally, the density test has a value of 74.23 kg / m3 where the fibers are lighter than the other fibers even after immersion with different sodium hydroxide and sodium chloride. In addition, this study achieved a house ceiling that could help reduce the heat entering the house by 0.225W which used only a thickness of 10mm. The use of these fibers does not need the thickness between 20 mm or 40 mm. Therefore, it successfully lowered home electricity consumption in hot weather. It was found that the difference in temperature drop between 0 % and 3 % was 0.4W.

Using pipes from various materials for sewage network: theoretical analysis

The paper presents the analysis of data on Russian settlements sewage networks as of 2014-2018, published in the public domain. All the settlements are divided into six groups depending on the population size. For each group, the distribution of sewage networks depending on the material of the pipes is established. In this country, the most widespread pipes are ceramic and cast-iron pipes, which have been widely used in the last 100 years. Asbestos-cement, reinforced concrete and steel pipes were used much less frequently. Active construction of sewage networks from plastic pipes began only in the last 20 years, so their share in the total volume does not exceed 6%. The authors believe that there will be a significant increase in the number of plastic pipes in the total length of sewage networks in the next few years.

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.

Repairing earth dam drainage systems

Introduction: when reconstructing or overhauling dams, great attention should be paid to drainage systems as the most critical components of the installations. The article describes the typical malfunctions of earth dam pipe drainages. The research considers geological and hydrogeological features that were not taken into account when developing projects.
 Materials and methods: control and measuring instrumentation (piezometer network), full-scale experiments on disabling pipe drainage and mathematical modelling were used as the filtration regime research methods.
 Results: analysis of the hydrogeological features of the base of the right-bank floodplain dam of the Nizhegorodskaya hydroelectric power plant and field filtration observations revealed a strong drainage effect of the base on the filtration flow at several areas of the dam body. At the other areas, a high groundwater level position at the dam downstream and its outlet into the pipe drainage at the downstream were recorded. Substantiated by filtration calculations, the proposed repair of the drainage system consisted in designing open drainage along the dam axis and backfilling the territory at the downstream by 2.0 m that excludes impoundment of the territory without the pipe drainage.
 Conclusions: the following engineering solutions can be recommended for repairing earth dam drainage systems: construction of backfill drainage trenches in the dam downstream, new pipe drainage at higher elevations or an open drainage channel in solid reinforced concrete arranged along the axis of the dam. The proposed version of the pipe drainage repair provides for constructing an open drainage channel in solid reinforced concrete on a reverse filter with an arrangement of gravel-filled asbestos-cement pipes in the dam slopes and bottom. Such a design solution allows repairing the drainage system without dewatering and, if necessary, completely refusing the existing pipe drainage.