Water supply mains in industrialized countries have grown over many decades and present complex systems today. In addition to continuous expansion they have been affected by the use of different pipe materials, variable installation techniques and exogenous environmental factors. The requirements for systematic maintenance of the pipe networks have increased due to the aging of the pipes, rising repair costs and failure rates. At the same time, legal requirements demand regulative measures in order to guarantee the security of supply for future generations (see DVGW W 401 and OVGW W 100).
The asset value of the pipe networks presents the most cost-intensive investment in the municipal infrastructure. Since underground pipe networks can only be assessed conditionally through direct inspection, indirect means, such as analyses of significant failure statistics, provide valuable information concerning the current state and future development of pipe networks.
Based on the decision support system PiReM, both the long-term and mid-term rehabilitation requirements are calculated and the financial resources required can be planned proactively.
The software PiReM is a decision support system for the rehabilitation management of pipe networks on the basis of efficient processing of existing geoinformation. PiReM primarily answers two questions regarding rehabilitation management:
Examining the annual failure rates is one of several key figures used in professional rehabilitation management and enables an important efficiency control by means of long-time interpretation and comparative evaluation with executed maintenance measures. The risk of failure acts as an indicator for the calculation of the economical ideal time for the rehabilitation of a pipe leg. The efficient rehabilitation management with PiReM allows for the exploitation of economic and socio-economics benefits. Considering ideal time for rehabilitation from an economic standpoint promotes on the one hand the reduction of repair and maintenance costs for old pipes and on the other hand the reduction of social costs, such as traffic jam resulting from repairing a pipe burst, which could permanently damage the public image of businesses.
Individual GIS data is integrated into the PiReM database system through a simple interface. After the evaluation of the existing data, the water supply system is subdivided into main groups which exhibit similar attributes. For these homogenous main groups, suitable aging functions are modeled and initial analyses are made, such as material distribution in the pipe network and annual failure rates. Missing GIS data can be compensated for through the integration of existing standard groups and findings from scientific research projects. Supplementing the main groups with information on costs facilitates an economic examination using PiReM.
The annual failure rates for the different main groups are calculated using statistical methods. This allows an improved estimation of annual rehabilitation need in the entire pipe network. The flexible choice of function parameters using PiReM and the adaptation to the specific data of the particular business enable, moreover, transparency in the scenario calculation and show the effect of individual parameters on the development of the pipe network.
The long-term rehabilitation management with PiReM helps to estimate future failures and thereby to estimate costs. Based on failure prognoses which are for individual networks as well as standardized, scenarios for individual pipe groups and the entire pipe network can be compared. Repercussions as to failure trends, middle pipe network age, or net book value can be shown. Should sufficient data regarding age-related failures not be available, values from standard groups can be drawn on for the calculation.
For each pipe network operating company, internal data regarding renewal, rehabilitation and repair is integrated into the mid-term rehabilitation management with PiReM. Precise pipe legs within the network which are in need of renewal are filtered out by means of criterion catalogue in the form of a priority list for necessary action.The priority list establishes a ranking of annual rehabilitation need. Thus, PiReM enables an objective risk constraint and supports the pipe network operating company's security of supply.
PiReM does not require complex data recording in order to be able to create significant pipe network analyses and comprehensive findings for the rehabilitation management. The function table provides the necessary asset servise data about the pipe network on the basis of possible pipe network analyses using PiReM.
Continuative analyses with PiReM are possible depending on how detailed the records of asset service are. This way, local boundary conditions such as failure rates, diameters, material, public transport, stagnation zones, incrustation, corrosion, age, risk of breakage, non-revenue water and stray current are incorporated into the calculations. The defined rehabilitation priorities, visualizable in GIS, can be tested for possible synergies in the execution of construction work.
Decision support using PiReM