Development of a two-tier prioritisationalgorithm for the replacement of water reticulation pipes
Date
2018-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Water pipe replacement in ageing water networks needs to be prioritised within constraints of limited
municipal budgets. Relatively higher water pipe failure frequency in a distribution zone could point to
a higher replacement priority. Priorities are typically determined based on historically recorded pipe
failures, but actual pipe failure data is often not available – especially in developing countries. Pipe
failure records may be available for certain zones in a particular system, while no data may be available
in other zones of the same system. Replacement priority cannot be limited exclusively to zones with
failure data, so a method was devised to spatially extrapolate pipe failures from zones with failure
data to other zones where no knowledge of historical failures is available. An algorithm was developed
for this purpose to prioritise pipe replacement based on a two-tier structure, comprising physical and
hydraulic characteristics. The following model parameters were incorporated: pipe material,
diameter, remaining useful life, static pressure, residual pressure and reserve pressure ratio. Actual
pipe failure frequency data for a South African study site with 2021 km of pipes and 12802 reported
failure events over a period of 180 consecutive months was obtained and used to devise the model.
Actual pipe failures were linked to the different model parameters, with all parameter values known
per pipe in the case study area. Pipe failure likelihood index values were then calculated for each pipe element in the water network model (as failure/year/meter). Each pipe was then prioritised for
replacement in terms of a failure likelihood index, and grouped per water distribution zone. The water
distribution zones were ranked for replacement prioritisation. The model was verified by evaluating
failure likelihood index values and comparing replacement priority per zone based on actual data to
the model results (for those zones with known data). The model was subsequently used to extrapolate
the replacement priority to other zones without failure records in the case study area, with
acknowledgement of in accuracy due to the lack of model validation. The model results are illustrative
and apply to the specific study site – results should not be generalised. The results were represented
spatially in GIS format, allowing the user to visually identify the most critical areas for pipe
replacement. Future research could involve model validation and possible application beyond the
study sample.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar
Description
Thesis (MEng)--Stellenbosch University, 2018.
Keywords
Water-pipes -- Materials, Water-pipes, Municipal budgets, UCTD, Water-pipes -- Failure analysis (Engineering), Water-pipes -- Monitoring