Upcycle of GP-N type underground fire hydrant

Summary

GP-N underground hydrant (GOST R 53961-2010) is designed to abstract water with the help of standpipes (KPA type) from the water distribution network for firefighting. Hydrant of the given type has a fundamental defect that is autogeneration of periodic surges. The studies carried out in a hydraulic test stand arise at the beginning or at the end of the fire hydrant valve closing (at the partial opening). Autogeneration of periodic surges happens in case of incorrect fire hydrant handling when the side valves of the standpipe (KPA) have been underclosed or not closed at all; or in case of hydrant being opened-closed without a standpipe. Autogeneration of surges is caused by the low pressure zone arising according to Bernulli law in the point of the maximum water velocity in the continuous steady flow. Surges can lead to the extrusion of the gasket between the fire hydrant flange and its support and hence to the damage of the fire hydrant or even of the pipeline itself to which the hydrant has been fixed in the radius of several dozen meters from the point of the hydrant installation. In order to reduce the accident rate the experts of SUE «Vodokanal of St. Petersburg» have developed, tested and patented a device that prevents surges. The engineering solution is based on blocking all possible aggregate valve plays. In order to prevent accidents related to fire hydrant and vent pipes pullout from the T-coupling the experts of SUE «Vodokanal of St. Petersburg» have developed, patented, successfully tested and put into production a compensator of the fire hydrant motion.

Key words

water supply network , water hammer , underground hydrant , motion compensator

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UDC 621.643:691.175.699.841

Granovsky A. V., Dottuev A. I., Khasanov T. M.

Investigating seismic stability of REHAU cross-linked polyethylene pipelines

Summary

The results of experimental evaluation of seismic stability of REHAU pipelines of different trademarks and diameters are presented. The experiments were carried out on a vibroplatform of pendulum type with two degrees of freedom. The pipelines were filled with water at 10–95 C temperature and 7–11 bar pressure. From the experimental tests (impact tests and repeated pulse tests) the integrity of pipelines made of cross-linked polyethylene at vibration and frequency-amplitude range equal to 7–9 numbers on the MSK-64 scale was evaluated.

Key words

water hammer , seismic forces , pipes of cross-linked polyethylene

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UDC 628.214:532.595.2

Primin Oleg

Ensuring reliable and environmentally safe operation of pressure sewers

Summary

Surge in a pipeline is a significant factor that is affecting the environmental safety and reliability of the public wastewater disposal system. In case of an emerging surge noticeable pressure fluctuations occur that could cause pipeline burst and damage of the related hydraulic and mechanical equipment (pumps, valves etc.). It results in sewage spills, material and environmental losses. The main causes of an emerging surge in municipal pressure sewers can be as follows: mains failure, imperfections of the control schemes of the main pumping units at the sewage pumping stations. To ensure reliable operation of the pumping stations the use of hydromechanical devices as well as of high-speed emergency switching on automatic and protection devices including controlled electric drives and softstarters is provided. It was determined that in wastewater disposal practice hydromechanical fittings that reduce the surge effect shall be used. To prevent from surge water discharge through bypasses with installing safety valves and hydraulic tanks is used. In addition to wastewater discharge from pumping stations pressure sewers of intricate shape shall be equipped with air intake and relief devices at the intermediate points. It is found that surges in operation of sewage pumping stations can be eliminated by improving the reliability of external power supply by establishing truly independent power sources, designing combined power supply schemes, high-speed automatic switchover devices in 6–10 kV switchboards of big stations.

Key words

pipeline , sewerage , pumping station , water hammer , ecological safety

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UDC 628.156

Khrenov K. E., Bogomolov M. V., KOZLOV M. N., Shushkevich E. V., Khramenkov S. V., Menshchikova O. A.

Experience of Introduction of Innovation Technique for Prevention of a Water Hammer

Summary

The water hammer is a serious threat to pipeline systems and pumping equipment. This phenomenon constitutes a special hazard to the systems of water supply and sewerage of a big city. Emergencies and interruptions in the operation of water supply and sewerage networks may lead to grave consequences for the whole of municipal services. Examples of such situations making it possible to assess the scales of possible consequences are given. Basic reasons for generation of the water hammer are described; a brief excursus into the history of study of this phenomenon is presented. A considerable part of the article is devoted to measures aimed at prevention of the water hammer in the systems of water supply and sewerage of Moscow and to the use of energy efficient innovation technique.

Key words

pipeline , pumping station , water supply and sewerage networks , water hammer , energy efficient innovation technique

DOI 10.35776/MNP.2019.11.07
UDC 628.24:628.292:532.595.2

Zhitenev A. I., Kurganov Iu. A., IGNATCHIK V. S., Sarkisov S. V., Vinokurov Pavel

Results of experimental studies of water hammer arising in the operation of sewage pumping stations

Summary

The results of studies of water hammer arising in the operation of sewage pumping stations are presented. The studies were carried out at two stations of the same type in St. Petersburg. At present, there are no practical recommendations aimed at reducing the strength of water hammer at sewage pumping stations including the choice of location, type of check valves, a combination of their joint operation with smooth start, etc. Therefore, a set of experimental studies is conducted in St. Petersburg aimed at the solution to this problem. During the research, piezoresistor pressure transducers and a modular signal register were used. The use of check valves with hydraulic brakes is a more effective measure to combat water hammers compared to the smooth start and halt of the pumping unit. Water hammers that occur at the startup of pumping units while operating in combination with check valves without hydraulic brakes can exceed water hammers that occur when they stop.