Surge: causes, analysis and prevention methods

Summary

Engineers busy with designing pumping units are well familiar with the terms «hydraulic hammer», «pressure jump» or «surge» (shock wave) related to water. The problem is how at the designing stage to take into account the risks of surge occurrence and take necessary measures in time to prevent or minimize devastating consequences which is a challenging issue. As applied to the long water mains of large diameter, the damage caused by a pressure wave can be quite considerable, whereas eliminating the consequences involves considerable costs. The owners or operators of the pipelines subjected to the surge reluctantly provide the information on the damages caused by this phenomenon. That is why during designing the standard calculations are made and standard measures of surge prevention are suggested that do not take into account the negative experience of similar projects and the measures that were taken to prevent any further pressure jumps. In the given article the general theoretic notions related to the surge phenomenon and the methods of calculation are considered, the analysis of the surge is presented carried out by the experts of KSB company by the example pressure pipelines of a certain project the name and identification data of which are hold confidential. The given example describes in detail the encountered problem onsite and measures taken to solve it. The calculations, diagrams and charts are presented that show the differences between the system protected from the surge and the system not protected from this phenomenon.

Key words

pipeline system , surge , Zhukovski equation , surge analysis , surge protection , designing water supply systems and sewers

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UDC 628.144:532.542

Yepifanov S. P., Zorkaltsev V. I.

The task of flow distribution with nonfixed junction points of consumption

Summary

A model of flow distribution in the water supply and distribution system with nonfixed junction points of consumption is considered. The model provides for more detailed characteristics of flow distribution both in normal conditions and emergency mode. The suggested junction point flow rate – water head ratios provide for the actual consumption amounts at the consumers’. The flow distribution algorithm in the form of nonlinear algebraic equation system is presented supported with the demonstration of differences in the results of calculating flow distribution with both fixed and nonfixed junction points of consumption.

Key words

water supply , water leaks , pipeline system , flow distribution , nonfixed junction point of consumption , hydraulic head

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UDC 628.14:004.415.53

Primin Oleg, Gromov Grigorii, Stepanov D. L., Kozlova O. V.

Calibration of an electronic model of a water supply system
(through the example of the water distribution network of Salavat city)

Summary

In accordance with the RF legislation within the frames of the water supply schemes development for the Russian cities designing an electronic model of a water supply system is envisaged. In order to obtain trustworthy results of modeling the model verification is required that is carried out by the calibration on the basis of operation and statistic data of the water supply system. The action of the electronic model calibration through the example of the Salavat water distribution network is described (Republic of Bashkortostan). The calibration was aiming at maintaining hydraulic head at the nodal points of the design model according to the assumed calculation as well as maintaining water source flows according to the assumed estimation hour. The calibration of the electronic model of the water supply system was carried out by varying the maximum values of steel and cast iron pipeline roughness that corresponded to their maximum working lifespan. The calibration process involved a considerable amount of hydraulic calculations (256). The mean total difference of hydraulic head between the estimated values and actual measurements was 4.03%; the mean total difference of water source flows – 0.31%. With the purpose of the calibration process automation an algorithm based on VBA language with the use of Excel tables and ActiveX library of «ZuLuNetTools» was developed. The developed algorithm of automated calibration of the electronic model is applicable to «ZuLu» Russian software.

Key words

water supply system , hydraulic design , pipeline system , electronic model , calibration , pipe roughness

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UDC 628.144:532.542

Baranchikova N. I., Yepifanov S. P., Zorkaltsev V. I., Kurtin A. V., Obuzdin S. Iu.

Flow distribution in water supply and distribution systems with automatic pressure regulators

Summary

The task of flow distribution in general pipeline systems including the systems of water supply and distribution with automatic pressure regulators is considered. To improve the reliability of the system operation pressure regulators are often installed «downstream» (reducing valves) and «upstream» (tank release valves). Pressure regulators manufactured by Bermad have been installed in the water distribution networks of Irkutsk; that provided for reducing and stabilizing the pressure in some zones. However zones exist that are supplied from several water pipelines with different pressure at the connection points, therefore sometimes complete closing of some regulators occurs (more often with small diameters) or flow reversal is possible, and the water flows through the regulator in the opposite direction. In this case the regulator fails to fulfill its function. Mathematical modeling of such situations is very important because it is them which significantly complicate the operation of the water supply and distribution systems. Mathematical models of automatic «upstream» and «downstream» pressure and pressure drop regulators are suggested with account of their version: normally open or normally closed. The mathematical formulation of the problem of flow distribution in the systems of water supply and distribution with pressure regulators is presented. The critical for the practice task of flow distribution in the pipelines with automatic regulators has been solved for the setting that describes different scenarios of the automatic regulators operation. A simple and efficient method of solving the set task of flow distribution that does not require derivation and has rapid enough convergence is suggested. On the basis of the numerical experiments it is fair to assume that the number of iterations moderately depends on the dimension of the problem (number of nodes and semicircular arcs), considerably depends on spread of hydraulic resistance values and to a lesser extent – node selection.

Key words

pressure , mathematical model , pipeline system , flow distribution , hydraulic head , systems of water supply and distribution

FaLang translation system by Faboba