Pipe network analysis

Duties and principles of pipe network analysis

A water supply facility or waterworks that has typically grown, over the span of decades, and its corresponding distribution network requires a competent design, long-term investments, professional management, constant servicing and, from time to time, a hydraulic analysis of the pipelines for the purpose of maintenance and preventative extensions and renovations in order to maintain its safe and economical operation.

Hydraulic network analyses increase the efficiency and capacity of the waterworks and its distribution network. Surveys of the premises and detection of hydraulic anomalies result in better distribution and often in reduced water losses, and thereby lead to an increased security of supply and a guaranteed supply of fire extinguishing water. Less energy wastage through optimization of tank management in pump operation lowers the operating costs significantly.

Exact planning with substantiated facts as the decision basis by selection of the best possible options allows cost savings on future renovations and extensions.

Creating the simulation model

Essentially, a “hydraulic network analysis” project involves determining the current condition by gathering data (pipe network data from GIS), preparing the data (creating nodes and strings with terrain heights, assigning the consumption and defining all switches in the model database) and, imperatively, checking the plausibility by calibration of the mathematical model.

CURRENT CONDITION minimal consumption - maximum pressure conditions

The plausibility check of the current condition is done by determining the real pressure and flow behaviour by targeted active pressure and volumetric measurements in order to calibrate the hydraulic model to the respective pipe network under real operating conditions in each individual zone.

Taking pressure and volumetric measurem

This system analysis involves creating real measured data and loads in order to evaluate the current hydraulic pressure and flow conditions in the pipe network. This is done by recording and analyzing pressure, volumetric flow, fill level and pump operation at selected measuring points in accordance with DVGW 303 (worksheet 303 of the German Gas and Water Industry Association). Any weak points or operating states not yet accounted for in the model are then determined and clarified with the operator (including: false container level readings and undetected inflow resistance, incorrect diameter specifications, lacking connections, local resistances such as incorrectly closed or throttled sliders, foreign bodies in the pipe, actual pipe or pipe network roughness and clarification of any other anomalies). Used in this process, in each zone, are the appropriate number of digital pressure loggers, mobile ultrasound flowmeters, pressure sensors and hydrant testing equipment. Data from the remote operating plant are adopted and integrated. Stepless pump operation and filling of containers as well as their feeding are technically monitored by pressure sensors and analyzed.

Comparative analysis to calibrate the model

Prerequisites for the reliability of a simulation model are checked, complete and correct pipe network data, an integrated metrological pipe network analysis, and competent verification of the simulation model by comparing calculation results reconciling the measurement results in the scope of model calibration and, finally, years of practical experience. Every hydraulic model must be verified against data actually measured from the network and compared with calculated theoretical values. Deviations from measured flow and pressure indicate significant errors in the delivered data.

For this, in the light-load case, proof of correct altitude measurement and maximum occurring pressure conditions is furnished. In the heavy-load case, the pressure loss caused by simultaneously strong withdrawal is recorded and thereby actual pipe roughnesses and any local resistances are detected and their possible causes investigated and clarified with the operator. Fire outbreak simulations reveal the actual hydraulic capacity at hydrants.

Among other things, hydraulic pipeline analysis allows the findings to be extrapolated to all points and all times of the existing pipe network, to all future pipe network extensions, as well as to unusual and future operating states by creation of a simulation model.

Applying the calibrated model

Simulations are run to compare variants, for the purpose of conceptual planning of extension and maintenance measures and as a basis for planning renovations and renewals. Tasks such as identifying the most economic dimensioning of pipelines and tanks, pump design and tank management including control concepts, expedient pressure reductions, proof of hydraulic capacity at arbitrary points in the distribution network, detection of weak points/bottlenecks, simulation of faults and failure scenarios, energy efficiency, correct supply of extinguishing water and setup of optimal water-loss monitoring areas are solved in the catalogue of measures, including cost estimates and ordering by priority, with greatest accuracy and no planning risk for the operator.

Evaluating the results

The most significant and most determining factor is expert knowledge and specialist competence in hydraulics, i.e. the human operator.

A serious error in the design or a mistake can cause dramatically false investments that, once made, cause all kinds of problems during operation of the plant. (E.g.: oversizing or inadequate capacity and therefore technical and economic inefficiency over decades).

Falsely positioned and dimensioned elevated tanks, inefficient pumping stations and unnecessarily oversized pipeline sections (stagnation) are poignant examples all too familiar to waterworks operators.

The fact that networks that have grown over the span of decades, while erected in the best of knowledge, are never regarded as a whole demonstrably results in a high probability of hydraulic anomalies in certain subsections.

Only a specialized engineering office such as SETEC can provide the indispensable pressure and volumetric measurements and the necessary equipment and experience to create a calibrated hydraulic model, because their main duty has been to work on all kinds of networks and provide solutions over many decades. In contrast, a water supplier will rarely create more than a single model of his own plant.

This independent pipeline analysis thus guarantees the most efficient employment of future investments in the pipe network and its corresponding plants. As current national and international SETEC references show, we always endeavour and are able to optimize existing fixed assets and to minimize the costs for future investments.

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