Pipe Deterioration Research Articles

Neural networks deterioration models for serviceability condition of buried stormwater pipes

Buried stormwater pipe networks play a key role in surface drainage systems for urban areas of Australia. The pipe networks are designed to convey water from rainfall and surface runoff only and do not transport sewage. The deterioration of stormwater pipes is commonly graded into structural and serviceability condition using CCTV inspection data in order to recognize two different deterioration processes and consequences. This study investigated the application of neural networks modelling (NNM) in predicting serviceability deterioration that is associated with reductions of pipe diameter until a complete blockage. The outcomes of the NNM are predictive serviceability condition for individual pipes, which is essential for planning proactive maintenance programs, and ranking of pipe factors that potentially contribute to the serviceability deterioration. In this study the Bayesian weight estimation using Markov Chain Monte Carlo simulation was used for calibrating the NNM on a case study in order to account for the uncertainty often encountered in NNM's calibration using conventional back-propagation weight estimation. The performance and the ranked factors obtained from the NNM were also compared against a classical model using multiple discrimination analysis (MDA). The results showed that the predictive performance of the NNM using Bayesian weight estimation is better than that of the NNM using conventional backpropagation and MDA model. Furthermore, among nine input factors, ‘pipe age’ and ‘location’ appeared insignificant whilst ‘pipe size’, ‘slope’, ‘the number of trees’ and ‘climatic condition’ were found consistently important over both models for serviceability deterioration process. The remaining three factors namely, ‘structure’, ‘soil’ and ‘buried depth’ might be redundant factors. A better and more consistent data collection regime may help to improve the predictive performance of the NNM and identify the significant factors.

Numerical modeling of tight fitting flexible liner in damaged sewer under earth loads

Finite element analysis and closed form solutions are used to investigate and interpret tests conducted on a damaged rigid pipe fitted with an HDPE pipe liner. Details of the analysis are described, including the modeling of local interactions between the liner and the host pipe, different segments of the damaged host pipe across longitudinal fractures, and the host pipe and the surrounding ground. Laboratory tests on a lined sewer pipe under earth loads are studied to establish whether finite element and closed form solutions for the repaired pipe system are able to effectively represent the observed behaviour. The deteriorated rigid pipe is fractured into four fragments, and these interact to impose pairs of closely spaced vertical line loads at the crown and invert of the liner. The finite element analysis demonstrates that significant local bending develops in the liner under these contact forces. Very little thrust develops in the liner, which is almost in pure bending provided the host pipe can still carry hoop thrust across fractures. The angular expansion of the fractures at crown and invert had a negligible effect on the local bending in the liner, allowing the use of theory for rings under parallel plate loading to provide simple calculations of liner response. Nonlinear finite element analyses indicate that the interface between the liner and the host pipe is close to the full-slip (or smooth) condition. Analysis results for that condition are within 10% of the measured values. The finite element procedure also indicates that the host pipe and the liner within it deform under the effect of the full overburden pressure if the host pipe fractures after the liner is installed. Safe liner design could be achieved by ensuring that local bending associated with host pipe fracture and deformation under the full overburden pressures does not exceed tensile capacity of the polymer (in addition to liner design to resist buckling under external fluid pressure, in accordance with previous liner stability studies). Alternatively, measures might be used to avoid local bending in the liner by preventing deterioration of the host pipe and the surrounding soil during the design life of the repair.

Study on In-Pipe Corrosion Diagnosis System -Corrosion Estimation on Screw Parts Using a Surface SH Probe-

In diagnosing air-conditioning pipe deterioration, it is especially important to inspect screwed parts because their original thickness is thinner than that of straight parts and it is comparatively easy for leakage to occur if there is local internal corrosion. We examined a method of applying an ultrasonic test for the inspection, and proposed a method for detecting internal local corrosions of screwed parts and estimating the size and the position of corrosion with angle probe of surface SH waves. In this paper, we describe the results of experimental analysis on the echo from screwed parts of pipes, and we show the method to detect the internal local corrosion and estimate the size and position by using the edge echo. Finally, we describe the results of tests on artificial corrosion pipes and the limitations of this method.

Application of probabilistic neural networks in modelling structural deterioration of stormwater pipes

In Australia, when stormwater systems were first introduced over 100 years ago, they were constructed independently of the sewer systems, and they are normally the responsibility of the third level of government, i.e., local government or city councils. Because of the increasing age of these stormwater systems and their worsening performance, there are serious concerns in a significant number of city councils regarding their deterioration. A study has been conducted on the structural deterioration of concrete pipes that make up the bulk of the stormwater pipe systems in these councils. In an attempt to look for a reliable deterioration model, a probabilistic neural network (PNN) model was developed using the data set supplied from participating councils. The PNN model was validated with snapshot-based sample data, which makes up the data set. The predictive performance of the PNN model was compared with a traditional parametric model using discriminant analysis on the same data set. Structural deterioration was hypothesised to be influenced by a set of explanatory factors, including pipe design and construction factors—such as pipe size, buried depth—and site factors—such as soil type, moisture index, tree root intrusion, etc. The results show that the PNN model has a better predictive power and uses significantly more input variables (i.e., explanatory factors) than the discriminant model. More importantly, the key factors for prediction in the PNN model are difficult to interpret, suggesting that besides prediction accuracy, model interpretation is an important issue for further investigation.

하수구조물용 항균콘크리트의 개발 및 현장적용

Sewage facilities are positively necessary for environment improvement such as rainwater removal, sewage disposal, preservation of the qualify of water and health of the citizens in present-day. Meanwhile, a deterioration of the concrete sewer pipe is increasing rapidly due to the chemical and physical attack and especially biochemical attack that is to say biodeterioration. In this study, researches for the development of antibiotics and antimicrobial concrete were conducted to reduce biochemical corrosion of sewage concrete. First of all, desired performance, such as watertightness, antibiosis, homogeneity, workability and harmlessness, was proposed and performance of antibiotics and antimicrobial concrete were evaluated by them. And developed antimicrobial concrete was applied to actual construction field. As results of this study, dispersibility and antibiosis of liquid antibiotics superior to powdery antibiotics. Antibiosis of antimicrobial concrete was verified, and amount of elution of harmful and effective ingredients was little. In workability, setting time of antimicrobial concrete was delayed. Compressive strength and resistance to carbonation of antimicrobial concrete were more increased than ordinary concrete. Finally, as there were no problems in quality and construction progress of antimicrobial concrete produced in plant, applicability of antimicrobial concrete to actual construction field was verified.

Deterioration of tin-rich organ pipes

Tin-rich organ pipes are often affected by localised deterioration in the form of grey pustules, pinholes, cracks and exfoliations at the surface. Two main types of decay of tin-base materials that might have a similar appearance, i.e. the surface of the object covered with dark grey pustules, are known. The first is the allotropic transformation of white metallic tin into grey tin, the so-called “tin-pest”. The second form of decay is due to corrosion in the form of localised oxidation of tin. The identification of the causes of deterioration is of main concern because, whereas oxidised material can be treated, an object that suffers “tin pest” cannot be reconstituted. In the present paper the results of investigations on ancient tin-rich organ pipes affected by localised degradation are presented. The study of the composition and the microstructure of the pipes has been coupled with the results of analyses on the corrosion products. It was shown that oxidation clearly has a significant role in the deterioration of tin pipes, but it was not possible to establish if the allotropic transformation took place or not, because of the low probability of detecting the residual grey tin.

The hydraulic capacity of deteriorating sewer systems

Sewer and wastewater systems suffer from insufficient capacity, construction flaws and pipe deterioration. Consequences are structural failures, local floods, surface erosion and pollution of receiving waters bodies. European cities spend in the order of five billion Euro per year for wastewater network rehabilitation. This amount is estimated to increase due to network ageing. The project CARE-S (Computer Aided RE-habilitation of Sewer Networks) deals with sewer and storm water networks. The final project goal is to develop integrated software, which provides the most cost-efficient system of maintenance, repair and rehabilitation of sewer networks. Decisions on investments in rehabilitation often have to be made with uncertain information about the structural condition and the hydraulic performance of a sewer system. Because of this, decision-making involves considerable risks. This paper presents the results of research focused on the study of hydraulic effects caused by failures due to temporal decline of sewer systems. Hydraulic simulations are usually carried out by running commercial models that apply, as input, default values of parameters that strongly influence results. Using CCTV inspections information as dataset to catalogue principal types of failures affecting pipes, a 3D model was used to evaluate their hydraulic consequences. The translation of failures effects in parameters values producing the same hydraulic conditions caused by failures was carried out through the comparison of laboratory experiences and 3D simulations results. Those parameters could be the input of 1D commercial models instead of the default values commonly inserted.

무기질 항균제 도포에 의한 콘크리트의 경화성상 및 내구성상 향상에 관한 실험적 연구

Sewage facilities are positively necessary for environment improvement such as rainwater removal, sewage disposal, preservation of the quality of water and health of the citizens in present-day. Meanwhile, a deterioration of the concrete sewer pipe is increasing rapidly due to the chemical and physical attack and especially biochemical attack that is to say biodeterioration. So, in advanced countries, prediction techniques and corrosion inhibition system for sewer concrete are developed and are being applied. Also, antibiotics were developed already but application of that is low because it is not economical and has no practical use. But, in domestic, countermeasures for the corrosion of sewage concrete are not sufficient and biochemical attack is not reflected in those essentially. In this study, to prevent biochemical corrosion of the sewer concrete, surface of the concrete was spread with liquefied inorganic antibiotics and then its engineering properties were experimentally investigated. As a result, compressive strength of the specimen spread with antibiotics were similar to those of non spread, Both bond strength and abrasion amount of the specimen spread with antibiotics were inferior to non spread. Properties of absorption and air permeability of the specimen spread with antibiotics were superior to non spread. Finally, carbonation depth, chloride ion penetration depth and weight change ration of the specimen spread with antibiotics were smaller than non spread.

Estimate of pipe deterioration and optimal scheduling of rehabilitation

This study proposes an optimal scheduling model for rehabilitation based on the deterioration prediction of existing pipes by using the deterioration survey method for a water distribution system. The deterioration prediction model divides the deterioration degree of each pipe into 5 degrees by using the Probabilistic Neural Networks (PNN). Furthermore, the maximum residual service time is estimated by the calculated deterioration degree for each pipe and pipe diameter. The optimal rehabilitation model by integer programming (IP), based on the shortest path, can calculate the time and cost of maintenance, rehabilitation, and replacement. Consequently, the model proposed by the study can be utilized as a quantitative method for the management of a water distribution system.

Automated detection of cracks in buried concrete pipe images

The detection of cracks in concrete infrastructure is a problem of great interest. In particular, the detection of cracks in buried pipes is a crucial step in assessing the degree of pipe deterioration for municipal and utility operators. The key challenge is that whereas joints and laterals have a predictable appearance, the randomness and irregularity of cracks make them difficult to model. Our previous work has led to a segmented pipe image (with holes, joints, and laterals eliminated) obtained by a morphological approach. This paper presents the development of a statistical filter for the detection of cracks in the pipes. We propose a two-step approach. The first step is local and is used to extract crack features from the buried pipe images; we present two such detectors as well as a method for fusing them. The second step is global and defines the cracks among the segment candidates by processes of cleaning and linking. The influences of the parameters on crack detection are studied and results are presented for various pipe images.

Study on In-Pipe Corrosion Diagnosis System (Corrosion Estimation on Screw Parts Using a Surface SH Probe)

In diagnosing air-conditioning pipe deterioration, it is especially important to inspect screwed parts because their original thickness is thinner than that of straight parts and it is comparatively easy for leakage to occur if there is local internal corrosion. We examined a method of applying an ultrasonic test for the inspection, and proposed a method for detecting internal local corrosions of screwed parts and estimating the size and the position of corrosion with angle probe of surface SH waves. In this paper, we describe results of experimental analysis on the echo from screwed parts of pipes, and we show the method to detect the internal local corrosion and estimate the size and position by using the pipe-end echo. Finally, we describe the results of tests on artificial corrosion pipes and the limitations of this method.

Deterioration of polyethylene pipes exposed to chlorinated water

Pipes of high-density polyethylene were exposed to chlorinated water at elevated temperatures. The materials were stabilised with hindered phenols and phosphites. Oxidation induction times measured by DSC showed that the stabilising system was rapidly chemically consumed by the action of chlorinated water. Size exclusion chromatography and DSC showed extensive polymer degradation strictly confined to the immediate surface of the unprotected inner wall material and to the amorphous phase of the semicrystalline polymer. The rate of growth of the layer of highly degraded polymer was constant. It is obvious from the data that the species responsible for the loss of antioxidant are soluble in the polymer but not very reactive with the polymer itself. The species responsible for polymer degradation, on the other hand, are very reactive with the polymer and/or have a very low solubility in the polymer.

Deterioration of polyethylene pipes exposed to chlorinated water

Pipes of high-density polyethylene were exposed to chlorinated water at elevated temperatures. The materials were stabilised with hindered phenols and phosphites. Oxidation induction times measured by DSC showed that the stabilising system was rapidly chemically consumed by the action of chlorinated water. Size exclusion chromatography and DSC showed extensive polymer degradation strictly confined to the immediate surface of the unprotected inner wall material and to the amorphous phase of the semicrystalline polymer. The rate of growth of the layer of highly degraded polymer was constant. It is obvious from the data that the species responsible for the loss of antioxidant are soluble in the polymer but not very reactive with the polymer itself. The species responsible for polymer degradation, on the other hand, are very reactive with the polymer and/or have a very low solubility in the polymer.

Forecasting Variations and Trends in Water-Main Breaks

Effective planning for the renewal of water distribution systems requires accurate quantification of the structural deterioration of water mains. Direct inspection of all water mains in a distribution system is almost always prohibitively expensive. Identifying water-main breakage patterns over time is an effective and inexpensive alternative for gauging the structural deterioration of a water distribution system. While the structural deterioration of the pipe is generally considered to be a steady, monotone process, some of the environmental and operational stresses acting upon it are time dependent, steady, or transient. These stresses result in sets of “noisy” breakage rate data that often mask the underlying deterioration (aging) patterns, especially in small data sets. If the cause of these random stresses can be identified and attributed to measurable phenomena (for example, temperatures, precipitation, and so on), a more accurate pipe deterioration pattern can be obtained. Further, better predictio...

Diagnostics of high-temperature steel pipes in industrial environment by laser-induced breakdown spectroscopy technique: the LIBSGRAIN project

In this paper are presented the results of the feasibility study for the application of non-destructive spectroscopic methods to the diagnostics of steel pipes in industrial environment. The activities here described are part of the LIBSGRAIN project, funded by the European Commission; the main aim of the project is correlating the probability of failure of industrial plants components with the results of space-resolved elemental analysis carried out with laser-induced breakdown spectroscopy (LIBS) technique. Several simulations have been made in order to check the detectability of dangerous deterioration of steel pipes and to optimize some experimental parameters as the laser focal spot size and the traverse scanning step of the laser head. A design of a laser head which can operate in a real plant and can overcome the problems related to high temperature and vibration is proposed. The feasibility of remote controlled measurements at high temperature has been demonstrated in laboratory tests. The accuracy of LIBS measurements on steel target has been tested on NIST certified steel samples.

Markov Model for Storm Water Pipe Deterioration

Effective management of storm water pipe networks requires an accurate assessment of the structural condition of the pipes. Indeed, the recent introduction of Australian accounting standard AAS27 compels local governments to prepare annual financial statements, including the depreciated value of their storm water network. A rational approach to assessing depreciation is to base it on structural deterioration. This study presents a Markov model for the structural deterioration of storm water pipes. The model is calibrated, using Bayesian techniques, to structural condition data from the storm water asset database of the Newcastle City Council (Australia). It is shown that the Markov model is consistent with the data. The pipe characteristics of diameter, construction material, soil type, and exposure classification were found to influence the deterioration process. It is also shown that the depreciation methods required by AAS27 significantly overestimate the structural deterioration.

Acoustic monitoring of prestressed concrete pipe

The Bureau of Reclamation has made extensive use of Prestressed Concrete Pipe (PCP) in several of its major water projects. Widespread corrosion and failure of the reinforcing wire on over 6 miles of PCP used for the Central Arizona Project was found in 1990. This pipe had been in service less than 15 years which is significantly shorter than its expected design life. It was apparent that if wires continued to fail, catastrophic rupture of the pipe would result. Repair methods were developed to restore the prestressing forces to a deteriorated pipe section. This would extend its service life; however, locating the deteriorated areas in a buried pipeline was difficult. Numerous technologies were tested inside and outside the pipe in attempts to locate the distressed areas. None of the techniques tested could reliably locate areas of distress, however, one method has shown great promise. The use of hydrophones (underwater microphones) to detect the sound caused by the failure and subsequent slippage of the reinforcing wire has been demonstrated to be quite effective. The development of this technology is described, from initial field testing using a single pair of hydrophones, to the system currently being used for the continuous monitoring of a 2-mile pipeline. This system uses an array of 12 hydrophones and a sophisticated computer system to detect sounds in the pipeline, classify them as either wire-related sounds or extraneous sounds, and, based on the location of the wire-related sounds, map areas of pipe deterioration.

A Gradual Rehabilitation Programme for Combined Sewerage Systems

ABSTRACTThe Kannai‐Yamashita district, which is Yokohama's administrative and economic heart, was the first part of the city to be installed with a modern sewerage system. This district is served by combined sewers, many of which have extensive pipe deterioration, shallow covering, and insufficient capacity. Whilst rehabilitation of these sewers has therefore been an urgent priority, flood alleviation has been given even greater precedence.It was consequently decided (a) to construct supplementary storm trunk sewers and a stormwater pumping station to mitigate flooding, and (b) to implement a systematic rehabilitation of the sewers on a gradual basis. Studies of branch sewer rehabilitation also used a surcharge model in the interest of achieving an economical and efficient design.

Performance of Water Distribution Networks: Integrated Approach

This paper presents the performance dimensions of water distribution networks. In the absence of physical models for pipe deterioration, the evaluation of different performance factors such as maintenance and operating costs, serviceability of water supply, water quality, structural integrity of mains, and system reliability, is analyzed. In particular, predictive models for pipe breakage rates are reviewed, and a method based on the Cox regression for failure time analysis is presented, along with the insightful results of its application to two large urban systems. The assessment of water main conditions requires the combination of a number of data sources, due to the difficulty in inspecting visually buried infrastructure. Descriptive, predictive, and physical analyses are performed on inventory, condition assessment, testing, and maintenance history data. The break causing mechanisms and patterns of failure are reviewed. Factors affecting breakage rates are listed, and their synergistic effect is analyzed. Forces acting on water mains during service are reviewed, along with their contribution to the break event.

Service Life Assessment of Concrete Pipe Culverts

The durability and service life of concrete pipe culverts are discussed. The study reported includes the analysis of important enabling and triggering events that have caused or have the potential to cause the deterioration of concrete pipes. Regression analyses were used to produce prediction equations for the expected service life of culverts. The findings reveal an expected service life of 86 years. The service life reported herein may be of value to cost engineers performing life-cycle cost studies of these types of culverts. However, the prediction equations given should not be used to predict the service life of a particular culvert.