CHAPTER XII THE EQUIPMENT consists of the hydraulic, electric generating, auxiliary plant, and electric transmission. The first two are always housed in the power station, the third may or may not be, while a portion of the fourth is also there located. All equipment is generally subdivided into units, those of hydraulic and generating electric corresponding in capacity, while the auxiliary installation may conform to the hydroelectric unit characteristics or differ, which is also true of the transmission plant as far as it relates to the transformers. The maintenance and operation of the equipment is wholly of a mechanical character, and involves details which could be adequately treated only in a large volume, which will not herein be attempted; only those essentials which relate chiefly to the hydro-electric end of it will receive attention, with some general outline of the economical constitution of auxiliary power installation. ARTICLE 112.-The hydraulic equipment consists of the turbines and governors. Reaction turbines are drowned, in open chambers or bays, or encased in draft chests, so called, into which the water is fed by pipes; shafts may be horizontal or vertical. In either event the most frequent troubles are caused by floatage, principally small blocks of wood which find their way into the turbine runner, blocking it or chipping its buckets. This is a common occurrence when lumber-mills are located on the stream above, and can be guarded against only by frequent raking of trashracks, which should contain an especially close-spaced section from low to high flow surface. Reaction turbine gates are of cylinder, register, or wicket type, the last of which is more likely to develop leakages with time than the first two. Turbine gate shafts will develop defects before any other part by wear in the bearings, which have to be relined when this occurs. The causes of ice interference have already been mentioned; when anchor ice blocks the turbine gate opening, the safest method to secure relief is to close the penstock gate and disperse the ice accumulations by mechanical means or steam. If this is attempted by operating the turbine gates, it is quite likely that some of the gate riggings will be injured and the turbine put out of commission for repairs. On multiple horizontal turbine lines the shafts may bind because of the uneven wear of some of the lignum-vitæ blocks; these are adjustable. If the stream carries much silt the runner blades will be ground off, thus enlarging the normal clearing between runner and case ring and increasing leakage; all means of intercepting sand before the water reaches the turbine should therefore be exhausted, as there is no remedy afterwards excepting runner renewal. Erosion and pitting of the runner blades is likely to develop when their design is faulty. When turbines are cased a pressure-gauge should be installed on the top of the draft-chest and its hourly reading recorded in the Log, so should the gate openings and speed be subjects of hourly measurements and entry and water-gauges should be maintained in open penstocks. Impulse wheels receive the water from nozzles and are free from injuries caused by floatage or from interruptions by ice. The buckets, or cups, have a short life compared with that of reaction runners, but are readily renewed. Turbines should be frequently examined, and, by keeping a careful record of gate openings, active head, and output, any considerable efficiency loss is readily detected, when the cause should be determined and corrected. The draft-chest, supply penstock, and draft-tubes should be kept well coated with a suitable paint. The turbine speed is controlled by hydraulic or mechanical governors, which regulate the supply of water passing through the gates to the runner or, in some later types, the head by admitting air into the draft-tube. Governors should be adapted to the speed-regulation requirements of the plant, which are influenced by the character of the current service and load fluctuations. Governors require the same intelligent care as does any precisely operating machine. ARTICLE 113.-The electric-generating equipment consists of exciters, generators, and the regulating devices. Exciters are direct-current motors required to excite or magnetize the field magnets. These may be driven by individual turbines or by belting them to the generator or turbine shaft; their speed is generally three or four times that of the generator. Exciters are readily maintained in efficient operating condition; their only parts requiring frequent attention are the commutator brushes which are adjustable. The generators, which in hydro-electric plants are most generally of the alternator type, are not likely to develop defects, provided they are not overlooked beyond the safe heating limit. The armature is the part which may become injured by overheating, and it is proper practice to keep in reserve an extra one at the station. The regulating devices are assembled on what is called the switchboard, generally a stone panel, on which are mounted the instruments which measure and indicate the exciter and generator output characteristics; when properly installed these will require little maintenance attention. The important feature in the operating of the electric-generating equipment, whence the current is transmitted to a distant point, is to secure the best constant harmony of output characteristics of the different units. This is accomplished at the starting of a unit by aid of the governor, whose speed-balls can be standarized for the desired regulation scope, but, as the load and the power-generating factors fluctuate, it requires more or less constant attention. All electrical equipments need "blowing out" at frequent intervals, for which purpose a suitable air-compressor should be installed, which is motor driven. ARTICLE 114. Auxiliary power equipment may or may not form a part of the hydro-electric station's outfit, but no station should be without some electric-storage capacity for station operating purposes, such as assisting in the regulation of the voltage on exciter outlets, operating of high-tension switches, and lighting the station. A storage battery will always prove a resourceful investment by taking care, in whole or part, of peak loads, and supplementing the exciter units in case of need. Storage batteries require constant operating care in charging and proper maintenance of their elements; they should be housed separately from the other equipment, where the temperature may be regulated by the aid of motor-driven fans. When neglected the depreciation of storage batteries may become high. The location of a steam auxiliary should be decided largely by the conditions as to economical fuel supply, and in most cases these will point to the service rather than the hydro-generating end. The capacity of the auxiliary plant should be such as to guarantee the continuous power output which may be realized from the maximum hydro-motive equipment by supplementing deficiences caused by flow and fall reductions. The auxiliary plant units should always harmonize with those of the hydro-electric installation. The make-up of the steam-plant may differ greatly. The capacity being fixed upon, the steam consumption of the prime movers and auxiliaries must be determined in order to decide upon boilers: 0.73 boiler horse-power are required per kilowatt output, and 10 square feet of water-tube boilers heating surface per boiler horsepower. Two boilers should be provided for each prime-mover and one extra prime-mover unit beyond the required capacity. The plant should be located convenient to ample water supply, and fuel tracks and fuel and ash handling should be planned for all obtainable economies. Steam turbines are the best prime-movers, those of horizontal type with coupled generator mounted on one bed-frame. Cost of steam auxiliary plants and of their output is an important topic when the provision of an auxiliary is to be determined from such a searching analysis as has been outlined in Article 51, "Development Scope," and when efforts are made to convince steam-power users that it is much more costly than they believe and that the hydro-electric power current will bring a great saving to their business. The steam-engine or water-turbine effective unit output is the mechanical horse-power which may be converted into electric horse-power with the loss of ten per cent. The commercial unit of electric energy is the kilowatt (1000 watts), and, as one horse-power equals 746 watts, a kilowatt represents one and one-third electric horse-power or about one and a half mechanical horse-power. The final commercial measurement of electric service is the kilowatt-hour, combining quantity and time of service, and this is therefore the proper comparative unit basis of power cost. The cost of power in manufacturing establishments is, as a rule, not definitely known to the operators; in most of them no doubt the total cost of the manufacturing product is conclusively established, but the segregating of the total into the component items, especially as relating to power, is only rarely sufficiently detailed. And it is therefore not to be wondered at that the actual cost, where generated by the plant, is greatly underestimated. The items of fuel, wages, oil, and waste are probably entered in the power account, but those of maintenance, repairs, depreciation, interest on plant's cost, taxes, insurance, etc., are rarely found properly apportioned. The following are the results of several years of investigations of first cost and fixed and operating charges of steam-plants of various mill capacities, which are believed to represent reliable cost estimates for present conditions and material and labor prices. |