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UDC 628.24:620.197:620.193.8
Primin Oleg, Ten A. E., Gromov Grigorii
Protection of sewers from corrosion
Summary
Accidents on sewers accompanied by the destruction of building structures have been a most serious problem not only for the water industry but also for the entire city. In the world the damage from the deterioration of reinforced concrete sewer tunnels and in-line structures due to corrosion is estimated at billions of euros per year. A way out of the current situation with corrosion in sewers can be timely and prompt repair and rehabilitation using protective coatings applied by trenchless methods. One of the methods of sewer rehabilitation is lining the internal walls of the sewers with plate composite materials (blocks) or continuous protective coatings where polymer concrete can be used. Polymer concrete comprises a thermosetting organic binder (usually epoxy resin) and a large amount of dispersed filler (talc, aerosil, crushed quartz, basalt, granite chips, etc.). The special composition of filler materials and advanced production technologies ensures the high qualities of polymer concrete. An assessment of the technical and economic indicators of the reconstruction of existing sewers and canals using polymer concrete blocks is given. Through a realistic example it is shown that the most effective option of the reconstruction of a sewer canal while ensuring environmental safety is lining with polymer concrete blocks (segments).
Key words
reconstruction , sewerage , collector , corrosion , repair and rehabilitation operations , lining , polymer concrete
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UDC 628.21/.25
Vasilyev V. M., Malkov A. V., Verbitskii V. G.
Method of calculating gas volume and its travel direction in a sewer
Summary
In the process of operating deep sewers some problems arise such as corrosion of reinforced concrete structures of the sewerage network, saturation of the gas phase of the underground space with corrosive toxic substances, accidental emissions of these gases from the network into the atmosphere. Solving these problems is possible by arranging air exchange between the sewerage network and atmosphere. The available methods of calculating the amount of gas travelling in the sewerage network do not take into account the gas density, dynamic viscosity and other parameters that depend on the chemical composition of the gas phase. The lack of the recommendations does not allow estimating the network ventilation in relation to providing the required gas exchange rate. Consequently determining, estimating and substantiating the required capacity of the ventilation equipment are not possible. Possible flow redistribution is not considered either; and, hence, adjusting the gas exchange systems to the definite network parameters is not possible. A method of calculating gas amount and flow direction induced by fluid entraining capacity and natural draft with account of the physical and hydraulic parameters of wastewater and gas, network design features, daylight surface temperature is presented. The method provides for making calculations at the design stage with account of retrofitting ventilation units, filters and vent pipes. The following parameters are determined: the amount and direction of gas flow in the network, gas exchange rate, anticipated background concentration of corrosive gases at the preset gas exchange rate, network corrosion rate, overhaul period.
Key words
collector , sewerage network , calculation method , ventilation , gas exchange , corrosive toxic substances
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UDC 628.21.62-192
GALPERIN E. M., Strelkov A. K.
The reliability of municipal sewers
Summary
The aspects of the reliability of municipal sewers are considered. The reliable transportation of raw wastewater to the treatment facilities is extremely important for the normal town-living. At present there is no authorized quantitative index of sewer reliability. Municipal sewer is a comprehensive technical system and the reliability indices shall be designated as appropriate. The use of the mathematical model of such facilities provides for determining the complex of the sewer reliability indices. The factors that affect the sewer reliability are analyzed; specific measures of its improvement are suggested.
Key words
Failure , collector , mathematical model , clogging , reliability indices , sewer
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UDC 628.22:532.542
Chupin V. R., Melekhov E. S., Chupin R. V.
Pressure Movement of Flows in Gravity Manifolds
Summary
A new approach to the design of water disposal systems based on their simulation with hydraulic chains with unrecorded withdrawals and inflows of runoffs is offered. It makes it possible, on one hand, to determine the presence of counterflows in the network, possible effusions of flows on the ground surface, volumes of runoffs running out, carrying capacity of a water disposal system and, on the other hand, to simulate various conditions of flow transportation with due regard for possible cloggings, encrustation of pipes and other violations which can occur during the operation.
Key words
wastewater , head , water disposal system , collector , hydraulic design , well , simulation
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UDC 628.23
Vasilyev V. M., Malkov A. V., PANKOVA G. A., Klementyev M. N.
Detecting the places of corrosive gas emissions from sewers to the surface and conditions of their formation
Summary
Corrosive gas emissions from sewers to the surface happen because of the excess pressure increase in the underroof and shaft space of the sewer. The causes of the pressure increase in the shaft space are considered. The gas amount changing during entering the shaft and removed from it depends on the wastewater flow rate, sewer filling (the height of the gas flow), hydraulic gradient of the sewer, formation of stagnation zones (sludge sedimentation), and temperature. Variation of these parameters and thus the location of corrosive gas emissions to the surface depend on a number of factors that can be divided into several groups: construction, hydraulic, geodesic, operation, random, climatic. Reducing the gas emissions from sewers is possible by: introduction of construction solutions for gaseous medium redistribution; elimination of air blocks, installation of purification filters; avoiding deviations from the design solutions arising during the construction of deep sewers; proper management of wastewater flow at elevation differences; improvement of the sewer operation rules, severization of the requirements to the operating personnel qualification.
Key words
collector , sewerage network , joint movement of liquid and gas , gas emission , excess pressure , ventilation
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UDC 628.247
Vasilyev V. M., Klementyev M. N.
Specific features of sewer tunnel construction and rehabilitation in Saint-Petersburg
Summary
The basic facts about the construction of deep sewer tunnels in Saint-Petersburg are presented. The causes of gas corrosion in sewers and their structural components are considered. The methods of protecting sewer tunnels in the process of construction or rehabilitation from gas corrosion are suggested. At the stage of designing the construction of a new sewer or its rehabilitation the concentration of gases in the underroof space must be measured. On the basis of the calculation data the decision on the sewer design, elevation differences, gradient and other parameters that ensure trouble-free operation is made.
Key words
collector , sewer tunnel , gas corrosion , composite material , protection from corrosion
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UDC 628.21/.23:696.133.2
Vasilyev V. M., Malkov A. V., Klementyev M. N.
Example of air exchange arrangement and its calculation
for a sewerage network section under design
Summary
The method of calculating the volume and direction of gas travel in the sewerage network induced by the fluid carrying capacity and natural draft with account of different physical, hydraulic parameters of wastewater and gas, network design values, daylight surface temperature is presented. The method provides for making calculations at the design stage and determining the following parameters: the volume and direction of gas travel in the network, gas exchange rate, network corrosion rate, expected background concentration of corrosive gases at the assigned gas exchange rate, network corrosion rate, overhaul period. Herewith commissioning ventilation installations, filters and vent pipes is taken into account. To obtain the regularities for calculating and designing air exchange facilities in the operating urban tunnel sewers numerous experimental studies were carried out. Herewith the basic calculation formulas of the joint travel of fluid and air were obtained and the calculation method of determining the basic parameters of air exchange systems was developed. This method was used in the process of designing the Ufa wastewater disposal system expansion. The conducted economic comparison takes into account the basic technical and economic parameters of the ventilation system operating parameters; provides for assessing approximately different ventilation options and carrying out their comparison and calculating the economic effect.
Key words
collector , sewerage network , ventilation , gas exchange , air exchange calculation method
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