Haruhiko Watanabe

Bio: Haruhiko Watanabe is an academic researcher. The author has contributed to research in topics: Water supply & Water conservation. The author has an hindex of 2, co-authored 8 publications receiving 19 citations.

Study on failure rate analysis for water distribution pipelines

Abstract: Many of the waterworks facilities in Japan were constructed during the rapid economic growth period. Today, the deterioration and renovation of these aged facilities have become a pressing issue. There are approximately 600,000km worth of water pipelines laid out across Japan, accounting for about 70% of the nation's water-related assets (totalling ¥40 trillion). To provide water that is safe to use, it is necessary to improve and innovate water purification technologies; not only that, it is also vital to properly maintain and manage the pipelines. The current research aims to apply reliability engineering in the waterworks field as one possible approach and to show its viability; it will also obtain vital messages revealed within pipeline incident data. In other words, we collected the information concerning water distribution pipeline incidents through questionnaire surveys and then analysed the cumulative failure distribution (unreliability) by pipeline material, the failure probability density and failure rate, among others.

Estimation of failure rate of water distribution pipeline based on questionnaire survey data of actual pipeline leakage accident

Abstract: 本論文では, 全国の水道事業体を対象に実施した送配水管路に係る漏水事故の実態調査アンケートデータを基礎に, 管種別の故障率曲線に関する推定方法を検討した.具体的には, 事故データのみを用いて作成される不信頼度関数 (累積故障分布関数) に関して, その事故データの元になる母集団, すなわち埋設管路 (事故を起こしていない無事故管路) を考慮するための改善を試みた.既存の統計資料から埋設管路延長に関する情報を収集・整理し, 無事故データを加味した場合の補整済み不信頼度関数から故障率曲線を作成する手順を示した.実際に提案した方法から故障率曲線を作成した結果, 故障率が年月の経過に伴って増加して行く様子を記述することができた.

A planning model using fuzzy linear programming for replacement of water distribution system considering uncertainty of future water demand

Abstract: 本論文では，将来水需要量の不確実性を考慮し，経済性と堅実性の2つの目的を有する管路更新計画モデルを提案する．経済性については，総費用期待値の最小化を取り扱う．堅実性については，将来水需要量の不確実性が費用の変動幅として現れるものとし，その最小化を取り扱う．経済性並びに堅実性を単一の目的とする線形計画モデルをそれぞれ定義し，その上で，ファジィ線形計画法を適用して2つのモデルの特徴を兼ね備えたモデルの定式化を行う．ケーススタディにおいて，提案したファジィLPモデルが，2つの目的をバランス良く達成する点で各単一目的のLPモデルよりも優れていることが明らかとなり，その有用性が確認された．さらに，計画案の比較を通して，管路更新における経済性と堅実性の意義を考察した．

A Study on Evaluation Method for Stability of Water Supply System based on Network Structure

Abstract: 水道供給の維持・改善のためには, 管路を適切に改良・更新していくことが必要である. 膨大な管路から構成される管網の中から改良・更新の対象を選定する場合や, 効果的な布設ルートを検討する場合, 考え得る全てのケースについて検討を行うことが求められる. しかし管網解析をはじめとする水理解析では実管網への対応が難しく, 簡便な代替指標によるアプローチが有効と考えられる. そこで本研究では, 管網系の供給能力は管路のつながりに強く規定されることに着目し, ネットワーク構造に基づいた管網系の安定性を表す指標を提案し, 同指標を用いた水供給システムの安定性の網羅的な評価手法を提案した.

Approaches to Failure Risk Analysis of the Water Distribution Network with Regard to the Safety of Consumers

Abstract: Contemporary risk assessment makes reference to current world trends, whereby there is increased emphasis on safety. This paper has thus sought mainly to present new approaches to failure risk assessment where the functioning of a water distribution network (WDN) is concerned. The framework for the research involved here has comprised of: (a) an analysis of WDN failure in regard to an urban agglomeration in south-east Poland; (b) failure rate analysis, taking account of the type of a water pipe (mains, distribution, service connections (SC)) and months of the year, with an assessment of results in terms of criterion values for failure rate; (c) a determination—by reference to analyses performed previously—of the compatibility of experts’ assessments in terms of standards of failure and obtained results, through rank analysis; and (d) the proposing of a modified Multi-Criteria Decision Analysis with implementation of an Analytical Hierarchy Process, to allow failure risk assessment for the WDN to be performed, on the basis of the calculated additive value of obtained risk. The analysis in question was based on real operating data, as collected from the water distribution company. It deals with failures in the WDN over a period of 13 years in operation, from 2005 to 2017.

Forecasting failure rate of water pipes

Abstract: This paper presents the results of failure rate prediction by means of support vector machines (SVM) – a non-parametric regression method. A hyperplane is used to divide the whole area in such a way that objects of different affiliation are separated from one another. The number of support vector determines the complexity of the relations between dependent and independent variables. The calculations were performed using Statistical 12.0. Operational data (provided by the Water Utility) for one selected zone of the water supply system for the period 2008–2014 were used for forecasting. The whole data set (in which data on distribution pipes were distinguished from those on house connections) for the years 2008–2014 was randomly divided into two subsets: a training subset – 75% (5 years) and a testing subset – 25% (2 years). Dependent variables ( λ r for the distribution pipes and λ p for the house connections) were forecasted using independent variables (the total length – L r and L p and number of failures – N r and N p of the distribution pipes and the house connections, respectively). Four kinds of kernel functions: linear, polynomial, sigmoidal and radial basis functions were applied. The SVM model based on the linear kernel function was found to be optimal for predicting the failure rate of each kind of water conduit. This model9s maximum relative error of predicting failure rates λ r and λ p during the testing stage amounted to about 4% and 14%, respectively. The average experimental failure rates in the whole analysed period amounted to 0.18, 0.44, 0.17 and 0.24 fail./(km·year) for the distribution pipes, the house connections and the distribution pipes made of respectively PVC and cast iron.

Failure mechanisms and condition assessment of PVC push-fit joints in drinking water networks

Abstract: This paper presents and discusses the significant role played by joints in the failures registered in drinking water distribution networks. The three most important failure mechanisms related are presented and a procedure to detect them through the visual measurement of the gap between pipes inside a joint is proposed. The procedure is proved to be a valuable source of information on joint condition after the assessment of a 600-m DN500 PVC pipe.