No abstract

The first All-Union Scientific-Engineering Conference on Corrosion and Cavitation Protection of Hydropower-PLant Structures and Equipment was held in Leningrad in October. 1974. Nearly 250 delegates from 88 organizations participated, including representatives from many hydroelectric power star/ons and research organizations. Over 70 papers and communications were presented at the plenary sessions a~d at the meetings of three sections. After an introductory address by M. F. Sldadnev. Director of the B. E. Vedeneev All-Union Scientific-P.esearch Institute of Hydraulic Engineering (VNIIG) at the plenary session, the following papers were presented: The outlook in hydraulic engineering construction and problems in corrosion and cavitation protection, by L. I. Kudoyarov, Main Directorate of the Scientific-Research and Design Institute (Glavniiproekt), and Yu. U. ~del' (VNIIG)~ scientificproblems in corrosion and cavitation protection, by Ya. IVL Kolotyrkin and Go NL Florianovich, L. Ya. Karpov Physicochemical Institute, N. P. Rozanov, Magnitogorsk Mining and Ivletallurgical Institute (MGMI). and YUo Uo ~del'; and anti-corrosion measures under operational conditions and during flac design of components, by A. F. Dmirrukl-Rn. State Trust for Organization and Rationalization of Regional Electric Power PLants and Networks (ORGRI~S), E. P. Shtern, Leningrad Directorate of the Power Economy (Lsndnergo), and M. N. Fedorov, Special Design Bureau of the Moscow State Institute of Steel Construction for Hydraulic Structures (SKB Mosgidtrostal,). At the concluding plenary session, G. O. I~vit (VNllG) presented a paper on methods for determining an engineering-economic basis for protective measures. The proceedings of the section on corrosion and electrochemical protection were chaired by V. V. Krasnoyarskii Institute of Physical Chemistry (I FKh) of the Academy of Sciences of the USSR. Questions on the prediction of corrosion of iron in fresh waters were discussed by V. M. Kadek, Z.. F. Oshis and D. V. VitoLa, the G. Plekhanov Institute of Inorganic Chemistry (INKh) of the Academy of Sciences of the Latvian SSR, Yu. N. Noginov (VNllG), V. V. Kuznetsov, and L. V. Verzhbitskaya, Penn University. A paper was presented by T. I. Malyshev (VNIIG)which summarized the work during 1967-74 on the preliminary classification of the fresh waters in the USSR and their aggressive attack on carbon steels. An important, and in many cases also a determining, role in the development of corrosion in fresh waters is played by micro-organisms. The paper by M. A. Luchina (VNIIG), Yu. N. Norokh, and G. N. Emers, Dnepropetrovsk University. demonstrated the rising scientific level of investigations into microbiological corrosion, and the broad range of full-scale items investigated.The surfaces of metalwork used in the equipment at hydropower plants are subjected, as a rule. to pitting corrosion, and a paper devoted to a study of its mechanism in fresh waters was presented by V. V. Kuznetsov, L.V.Verzhbitskaya, G. V. Hakleev, and V. F. Knyazeva, Perm Uni...

No abstract

Structures and equipment operating in water, soil, or in a highly humid atmosphere are used in power engineering more than in any other branch of the national economy. When metal contacts even se-called fresh water, electrochemical processes occur which lead to corrosive damage to the metal With elevated temperatures these processes occur more intensely. In flows moving at sufficiently high velocities corrosion damage is supplemented by the considerably more intense destructive action of cavitation. As a result of cavitation not only the surface of parts of metal structures and hydraulic machines but alse the concrete surfaces of high-velocity spillways and conduits are damaged.

The "Recommendations" are a systematic and brief generalization of the abundant research data on cavitation accumulated in recent years and are a valuable guide for design organizations. The "Recommendations" cover practically all aspects of the problem: prediction of the start of cavitation, possibilities of preventing it, and measures to prevent the dangerous erosive action of developed stages of cavitation. The "Recommendations" are concerned with practically all elements of spillway structures now in use: pipe inlets, heads of spillways, hydraulic energy dissipators (deflectors and splitters), curvilinear elements of spillways, grooves, half-grooves, gate chambers, heads of dividing piers, gate slots. Problems of =he cavitation resistance of concrete and its protective coatings are examined as a supplement to the previously published standards P II-73/VNIIG and P 58-72. Examples of a calculation for predicting the start of cavitation and a method of dynamic calculations of linings are presented.On the whole the work deserves a high evaluation. Its creation required the examination and coordination of the results of investigations made by various organizations on different experimental devices and by different methods. The "Recommendations" fix the attained level of knowledge in the field and formulate problems which still require additional investigations and refinements. As any standard document, the "Recommendations'~ will be improved in the future as new data are accumulated and as new practical problems arise. It is desirable that the following considerations which come to mind while reading the document be taken into account. i. The cavitation number is determined by the classical formula Po--P~ K= p(vt/2) ,where Po and vo are the pressure and velocity at the same point 0 in the undisturbed flow in front of the investigated object exposed to the flow; Pd is the vapor pressure.The definition of the cavitation number given on p. 8 of the "Recommendations" does not quite correspond to the classical one. It is not specified that pressure Po and velocity vo (Pchar and vchar according =o the "Recommendations") are determined at the same point in the flow. It is stated that these parameters are determined "without consideration of disturbances caused ...by the body or element," i.e., in an undisturbed flow, but later this requirement is actually violated in many specific cases. As a result the cavitation number loses its sense of a parameter of the boundary conditions and becomes some random variable which depends on the object and method of investigation. This is explained by the complexity of flows in conduits, where =here are no sections with an undisturbed flow in general, or if they are present, it is technically inconvenient to use them. Apparently in the next edition of the "Recommendations" it is necessary for greater clarity and continuity to first give the classical definition of cavitation number and then to show in each specific case of its application why it cannot be used directly but must be modi...