Impact of Failure Mode, Crack Area, and Pressure on Leakage Outflow

Abstract

The calculation of leakage outflow is of interest for several tasks in water distribution system analysis, e.g. investigation of pipe burst consequences, efficiency estimations of pressure management or model based leakage localisation. Several studies on pressure -leakage dependencies have shown that this dependency can be much higher than defined with the orifice equation of Torricelli. The findings of these studies differ significantly, even for the same pipe material, failure modes and sizes. In this paper, we describe the influence of uncertainties in assumptions of emitter exponents and crack areas on discharge rates for different failure modes. An approach for modelling elastically deforming leaks in water distribution pipes (Cassa et al. 2013, van Zyl et al. 2014) was implemented into systematic discharge rate calculations with EPANET2 by the means of an iterative estimation of the emitter exponent. For a partial pipe network of the city of Vienna, the results of the original EPANET2 and the extended emitter approach were compared. The largest differences in leakage outflow and hence in the amount of pipes with potential high failure consequences were found for longitudinal cracks. For this failure mode material, crack size and dimensions have a significant influence on the emitter exponent. Consequently, it is recommended for systematic discharge rate calculations to gather historic data about typical failure modes and failure dimensions of the investigated system. Further, if failure modes with a high sensitivity on the emitter exponent (like longitudinal crack or spiral crack) are relevant for the investigated system, a detailed calculation of the discharge rate is suggested.

Toward Sustainable Water Infrastructure: The State‐Of‐The‐Art for Modeling the Failure Probability of Water Pipes

“…This failure mode occurs when holes are created at a localized region on the pipe due to loss of metal (Farh et al., 2022; Grigg, 2017). Circumferential cracking: This occurs when a pipe cracks at its circumference (Fuchs‐Hanusch et al., 2014). This type of failure is typically caused by bending moments on the pipe, which can be caused by external forces such as frost penetration, backfill, and inadequate bending conditions.…”

“…This failure mode occurs when holes are created at a localized region on the pipe due to loss of metal (Farh et al, 2022;Grigg, 2017). • Circumferential cracking: This occurs when a pipe cracks at its circumference (Fuchs-Hanusch et al, 2014).…”

Systematic material and crack type specific pipe burst outflow simulations by means of EPANET2

“…Friedl et al (2012) further analysed material and failure mode specific crack sizes based on failure protocols and expert knowledge. The parameter range of crack sizes (A) described therein was used in Fuchs-Hanusch et al (2014) to investigate the global sensitivity of leakage outflow on the input parameter of the general power law. The main findings of these sensitivity analyses were that for a pipe specific calculation of leakage outflow in water networks, where longitudinal cracks are likely to occur, better estimations of ee might reduce model uncertainties.…”