Estimating time to failure of cast-iron water mains

Abstract

/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://dx.doi.org/10. 1680/wama.2007.160.2.83 Water Management, 160, 2, pp. 83-88, 2007-06-01 Estimating time to failure of cast-iron water mains Rajani, B. B.; Tesfamariam, S.http://irc.nrc-cnrc.gc.ca Estimating time to failure of cast-iron water mains NRCC-49676Rajani, B.; Tesfamariam, S.A version of this document is published in / Une version de ce document se trouve dans: Water Management, v. 160, no. 2, June 2007, pp. 83-88 doi: 10.1680/wama.2007 The material in this document is covered by the provisions of the Copyright Act, by Canadian laws, policies, regulations and international agreements. Such provisions serve to identify the information source and, in specific instances, to prohibit reproduction of materials without written permission. For more information visit http://laws.justice.gc.ca/en/showtdm/cs/C-42Les renseignements dans ce document sont protégés par la Loi sur le droit d'auteur, par les lois, les politiques et les règlements du Canada et des accords internationaux. Ces dispositions permettent d'identifier la source de l'information et, dans certains cas, d'interdire la copie de documents sans permission écrite. Pour obtenir de plus amples renseignements : http://lois.justice.gc.ca/fr/showtdm/cs/C-42 In this paper, corrosion models and a previously developed analytical model based onWinkler-type pipe-soil interaction are used to estimate time to failure. Since available data are insufficient to establish credible probability distributions, uncertainties in the input data/parameters are handled using possibility theory and fuzzy arithmetic. Sensitivity analyses are carried out to identify the critical data/parameters that merit further investigation.

Investigating in-service failures of water pipes from a multiaxial notch fatigue point of view: A conceptual study

“…The corrosion behaviour of cast iron water pipes has been investigated by considering the variety of chemical/physical processes that are involved (see Refs [5,18,19] and references reported therein). Grey cast iron can be damaged by the following different corrosive phenomena [20,21]: uniform corrosion, pitting, stress pitting has the greatest detrimental effect on the overall mechanical strength of cast iron water pipes [13].…”

“…Such approaches have been based on different mathematical formalisations involving either linear, power, or exponential functions [5]. Arguably, one of most reliable models is the exponential solution proposed by Rajani and c0-workers [24] which can be formalized as follows:  Very-high Corrosion Rate: a=0.0336 mm/year, k=15.6 mm, c=0.058 year -1  Low Corrosion Rate: a=0.0210 mm/year, k=9.75 mm, c=0.058 year -1…”

“…[16] to explain the anomalous increase in blowouts to which the city of Los Angeles was exposed during Summer 2009. Since this value was much larger than the usual ones observed during the inservice operations of conventional water pipes [5], a number of predictions were also made under p i,max =1 MPa. While 1MPa is still a large value, it is believably realistically of short duration pressures experienced within water distribution systems under transient hydraulic conditions, such as due to pump failures.…”

“…However, for detailed proactive management pipe level estimation is needed. Attempts to extend stochastic tools to pipe level have had limited success due to the complexities and uncertainties of the interacting factors effecting an individual pipe's useful lifetime [2][3][4][5]. Load models offer the potential to provide lifetime estimation for individual pipes and could potentially provide valuable new insight into the loading conditions most detrimental to a pipe.…”

A Multiaxial Notch Fatigue Methodology to Estimate In-Service Lifetime of Corroded Cast Iron Water Pipes

“…1). According to Rajani and co-workers, the pit growth rate in a corroded cast iron pipe can be modelled according to the following exponential law [1] Owing to their geometry ( Fig. 1), corrosion pits can be schematised either as hemispherical, K t =2.23 [2], or as hyperbolic notches, K t =3.2÷3.6 [2], so that their detrimental effect on the overall fatigue behaviour of pipes can be explicitly modelled in terms of fatigue strength reduction factor, K f .…”