p'ant similar to most steam plants or all steam systems where the load is fixed by conditions external to the plant, and the object is to use as little water for fuel) as possible. But these conditions seldom our, especially at low head plants, which usually lack long time storage facilities, for if the load and pant capacity are such that the hydro plant can carry the entire load at minimum flow, during most of the time there is excess water and efficiency is of to importance. It is more usually the case that the aim is to secure maximum output, the hydro plant being tied in with other plants so that its output is foot absolutely fixed by external conditions. When the hydro p'ant cannot carry the entire load ard it is tied in with other plants, especially a steam pant, many complications are introduced, all of which theoretically should be taken into account in evi uating the operating ratio In low flow the Evro pant usually takes the peaks of the load, ging the steam plant the base load at high load tator. This decreases the efficiency ratio and makes it d'ependent on the shape of the system load curve. En account of an unusually variable or fluctuating d the hydro plant may have to keep considerable stare capacity on the bus. The forehay may be grown down to catch freshet water which otherwise t be spalled The steam plant may operate at E' power factor, throwing heavy reactive load on the hydro p'ant, necessitating operation of an exra un.t All these occurrences will lower the erov ratios previously listed, but it may be good stion to do so ese difficulties are met fined not to di courage r's to fo, ow up operating economy, but to she w at enerating ratios such as kwh per a given quan***y of water do not go far enough, and that they von! be compared with standards for existing maximum practicable amount of energy in any of four principal ways: First, by waste of water over spillways; second, by leakage of water; third, by reduced efficiency of water wheels through wear, and fourth, by improper distribution of lead between generating units. The first and fourth items are problems of operation, and in regard to the tourth, it may be that operation for maximum j'ant etti ciency will not necessarily produce maximum system economy. This problem requires caretu' stuly for each individual system. The second and thr litems are problems of maintenance. It should be remembered that, in general, turbines in high head plants are subject to wear at a greater rite, and, conse quently, sutter a more rapid dej reviation of efficiency than turbines in low head plants Continuous records of station efficiency enable a very definite determination of the economie point for the replace ment of parts subject to wear. In regard to the making of measurements for es ntinuous records of performance, the water for most Egh head plants is conducted through controlled channels or pipe lires, or a combination of both, and many different methods may be used to obtain continuous, or practically continu us, measurements of ion While accuracy of measurement is always desirable, it is not essential for this particular kind of work The ines rtant consideration is that the measuring device sha¦ be rugged and reliable, and shall attord reiserably correct relative meastire–ments Such relative measurements will determine most suitable operating oor bins ar i w⠀ show decreases in overall plant et vency ether by reason of leaks, or through wear of water wire's As ar li Gated elsewhere in ་་ . . ! Two companies show on their monthly records the "ratio generated to 24-hour available energy" as a per cent. The fifth company uses a "Second-foot constant," which is the kw-hr. generated by one second foot of water used through each plant each hour. This is recorded and checked for each shift of operators, and if poor economy is shown it is checked every hour and cause determined. The sixth company on three of its larger plants carefully measures the water used for each period of twenty-four hours and keeps daily record of acre feet used, thus enabling a check to be made for daily water economy. Ice Handling Methods-Design of Hydraulic Works to Relieve Ice Troubles During the early days of hydro-electric developments it was quite common to hear of serious interruptions of the electric service in cities and towns due to water-wheels and canals being clogged with ice. In those days very few engineers had a clear conception of the underlying causes of ice troubles. During the last fifteen years, however, a great deal of time and money have been spent in connection with this very important problem by hydro-electric plants located in countries having cold climates and, as a result, we have now reached a point where, with a fair amount of success, the designer of a power plant can either provide means to eliminate ice troubles entirely or lay out intakes, racks and water passages in such a way that the ice can be disposed of without seriously interfering with the successful operation of the plant. frazil ice is to lift or remove all or part of the screens and to allow the ice to pass through the runners. This method of operation has been adopted among many others by the Pennsylvania Water and Power Company at Holtwood, Pa., and the Cedars Rapids Manufacturing & Power Company at Cedars, Quebec, with almost 100 per cent efficiency. There is, of course, no universal cure for all kinds of ice trouble; each individual case must be treated separately. Attached to this report is a list of references which by no means is complete, but which contains the titles and authors of some articles and books worth reading. Especially we may recommend that hydraulic engineers carefully study the several publications on "Ice Formation," by H. T. Barnes, Professor of Physics, McGill University. These publications can be obtained from the Publication Department, Department, King's Printers, Ottawa, Ontario. Professor Barnes, who for a number of years made a careful study of ice formations in the St. Lawrence River, gives in his publication a clear idea to the reader of the characteristics of the various kinds of ice, such as sheet ice, frazil ice and anchor ice. He also describes how these various kinds of ice are formed. Mr. John Murphy, of Ottawa, has also made valuable contribution to our knowledge of ice problems, particularly with reference to the problem of combatting frazil ice. He has successfully demonstrated the possibility of reducing troubles from frazil and anchor ice in the power plants by the means of applying a small amount of heat to racks and wheel casings. In this connection it should be remembered that, by raising the temperature of structures and machine parts a few thousandths of one degree above the temperature of the frazil and anchor ice, the ice will not stick and clog up the water passages. Ice Trouble in the Power House In modern low head installations where the openings between the guide vanes are large, and particuin plants where vertical single runner units are usual method adopted today in combatting In removing the racks the water passages are usually so large that frazil and small sheet ice has no chance of clogging the openings. Considering the fact that runs of frazil ice, as a rule, only last for a few hours at the time, there will usually be a sufficient amount of heat stored in the concrete scroll cases to prevent the ice from sticking. Head covers, shafts and guide vane stems are, in case of the single runner vertical unit type, as a rule in contact with the warm air in the power house, and enough heat is transmitted to prevent the ice from seriously sticking to these parts. In plants where horizontal type units are built into an open flume, or where vertical type units with small openings are used, it has been found that by heating racks and other metal parts with a small Fig. 250. 1000-kw., 3-Phase Electric Steam Boiler. amount of steam or hot water the units can be kept in continuous operation. Water-wheels have also been built with arrangement for heating the speed ring vanes with hot water. in high head plants, xe trouble is usually limited to intakes and racks. The wheel casings are, in this case, as a rule, in contact with the warm air in the power house. Heat in the form of steam is usually supplied to the metal parts from small stationary steam boilers or dinkey engines. In some plants the border is kept ready for contingencies during the entire winter. The nature of the requirements for steam is such that under conditions of high fuel cost or in remote locations operating companies may hind it advantigeous to consider the installation of an electric ber Pecini boilers similar to the one shown in 1g 250 have been built in sizes from 100 hp up to 25 m kw. at a remark by low cost. A bo'er of this type can be brought up to fuil steam pressure in a few minutes. Electrica y heated racks have been installed in some plan's, but as the insta"ation is rather expen sive this method has not been adopted to any large extent. In plants where the racks are not located insi le of a heated building some operating companies have found it advisable to lag the racks above the water level and to install steam pipes between the l d the racks. 11-inch plough steel cables for the purpose of quick removal in case of a sudden run of frazil. The gatehouse crane has sufficient capacity to pull the top racks against the tul hydrostatic head Fig 253 shows the top racks removed after they were entirely covered with e Reterring again to Fig. 252, it should also be noted that the headgates are in two sections, the top section being operated by means of a screw and the bottom section by means of wire ropes wound over a drum. The bottom sections of the gate can only Fig. 252. General Arrangement of Gates and Racks. Cedars Rapids Manufacturing & Power Company, Cedars, Quebec. precautionary measures before the ice his clogged kes and wheels rather than to tight the alter the plant is shut down e An artice in Peter June 3, 1919, by Mr. Charles Bromley, entitled "Operation at Holtwd," and Mr. R M Won's paper read betore the gineering In true of Catala, May, 1919, entitled "Desgn of Hydro c'ectric Plants for Combatting lee." gives two very good il us trations of mesures to be taken in low head prits. Ice Trouble Outside the Power House Mt hydraulic engineers agree that ice troubles we practically eliminated proving the intake nat. I the river above the intake have a sufficient coating of ice to prevent trazil and anchor ice 1m bong formed. This is undoub'e 'v true prog the river is frozen over for a sucent dis ice to prevent any frazil and anchor ice formed in raps and open stretches of water to reach the wer cand and burd up underhung dans The at muority of parts in the North are not so ately situated It is, therefore, as a rule. ves ity to provide means for geng riot the ke when it reaches the power works One of the Fig. 24. Arrangement of Ice Booms, The Niagara Falls Power Company |