Vízügyi Közlemények, 1935 (17. évfolyam)

Kivonatok, mellékletek - Kivonat a 2. számhoz

22 Defects in the system must be repaired without delay. The joints may suffer loosening, and the pipes slide apart. Among the common causes of breakage in cast iron pipes are faults in design, construction, operation and maintenance, or injuries happening to other works ; but breakage may be caused by corrosion, erosion, jars from traffic, differences in volume of the soil induced by frost, or changes in the ground-water table and in the temperature of the conducted water. Breakage of pipes usually has two causes: a principal cause and an initiative cause. For instance : poor exclusion of air — water hammer ; stiff support —- jars caused by traffic ; etc. The pipe system may be severely injured by corrosion brought about by the ground-water or by stray return currents of electricity from various sources. Corrosion can be resisted by keeping the pipe-pit dry, by backfilling with a material free from salts and acids, and by coating with bitumen of good insulating quality ; stray currents should also be prevented from arising. The presence of electric current in the pipes is undesirable, because it endangers the integrity of the pipes and the safety of the operators, and may cause complaints as to odour and taste. Frozen pipes can be warmed up with steam or electric current. After breakage in pipe, the conduit has to be disinfected by chlorine. When the pipes are being reconditioned, and the conduit has been cleaned, it is advisable to recoat the inside of the pipes. In the accessories (gate valves, hydrants, public wells, air valves, etc.), in most cases, the joints become defective, scrsws get rusty, males break, etc. In preserving a pipe system, valuable experience can be acquired, which may profitably be employed for the design and construction of new works. Therefore it is of importance to note down such experience and prepare statistics of operation. X. SUPPLY WITH SURFACE WATER, AND PURIFICATION ARRANGEMENTS. By D. MOLNÁR. (Pages 298—312.) When designing water supply, great care has to be taken to find a solution of the problem of providing water unobjectionable from the technical and the hygienic points of view. Ground-water undergoes a natural filtration process, and the chance of its bacteriologic pollution is slight. A further advantage is its low and uniform temperature. The necessity for treatment may arise when the water contains iron, manganese or aggressive carbonic acid. Surface waters are softer than ground-waters ; they are not aggressive, and are mostly free from iron and manganese. Their disadvantage is the great variation of their temperature, and the ease of pollution ; besides, they usually contain suspended particles. In making use of surface water we always have to provide for its chemical and bacteriologic purification. Water purification usually begins with aeration, carried out by different methods. The next step is the removal of the suspended particles.