Document gb0EGxDYD5k9152355GknjwBe

n jSjjr fl Hi". li ! 'ih5, i i if l| n 1- | Ona of two vartleol-ihoft 5-itoge pumps, rated 35,525 to 38,165 gpm at 161 I- to 1561-ft head, needs 21,450 hp Pumped Storage Capacity Improves Bi Two pump* rated 35,000 9pm against 1611-ft head, installed as part of 120,000-hp high-head hydro plant, economically provide a wide range of power-system operating flexibility HydrotLtcretc projects that have water-storage reservoirs offer several ad vantages when operated in parallel with other types of plants on largo power ays* terns. Pumping csn often supply in creased water storage economically when it is needed. A number of condi tions, or combinations of them, may jus tify using off-peak or dump power to pump water into storage (or dally or seasonal power generation. In Europe, the Eixel power development represent* one of these projects using high heads and a combination of natural runoff and pumped storage for large power output. thrtl power prefect, in central Switz erland, near Altendorf, usea the differ ence In elevation between Lake of Zurich and artificial Lake SiM, on a river of the aarae name. Lake Slhl, formed by three dams, has storage ca pacity of 3.4-billlon cu ft (78,000 acreft). A tunnel nearly two miles long, designed for 1130 cfs maximum flow, runs through a mountsin from Lake Sihl to a surge tank end valve chamber above Lake of Zurich. Two penstocks extend down to the powerhouse near the lake Into which a discharge tunnel empties, Fig. 6 and 5. This 1400-ft discharge is a tunnel 15 ft high by 16.5 ft wide for 1220 ft. Then it widens to 30 ft in an open channel. When the storage reservoir is filled to MttwUl tar 1*l artlel* >|| (applied by Sulsrr Bralbm, Ltd, WUftrlbar, Switrlia4. maximum elevation of 2929 fv( 4 head to Lake of Zurich Is 1506 ftl^ the Joke at mean elevation lJ43Tfl Power Units. Six vertical-shaft.? hie Pehon waterwheels are ink with a nozzle on opposite sides of^ wheel. On the operating floor IbiMs, powerhouse along its aide wells rui' of the two penstocks, to which s-fl" from each waterwheel connects, FI t These wheels are each rated ^fljOCOj 22,000 bp under an effective tween 138! and 1568 ft. This gl*^' present plant a'capacity of 12Q#D, which will be increased to 100,000 when two more units are Installed-?;? Three of the wheela eennect to 1$>| kva single-phase 10-kv 1$ 2/3-eydll erators, which supply power to th^ Si Federal Railways. The other _ wheels connect to 3-phase generstsj; the tame capacity and voltage. designed for 50 cycles. These ^ units supply power to Nordolc!,!"' ische Kraftwerke A.C. ENGINEERING AND MANAGEMENT SECTION Few pumps of this size have been built for heads over 1608 It. For this reason construction of their volutes and head covers required new designs for which previous experience was not available. The pumps ere a diffuser type, have cir cumferential split casings with the last stage discharging into a volute. Volutes, made without external ribs to intuit sound coalings, ore welded to the lourlh-stage section of tile diffuser casing to ovoid concentration of mate, rial end stresses. These joints are mode with o .double circumferential weld, at A end B, Fig. 2. After .making the welds the space between them ot C wae used to hydraulic-pressure test the joints. Thrust Bearings, Couplings. Because of design, total axial thrust and weight of the. rotor, about 100 tons, had to be taken on a thrust bearing. This bearing is supported on the cover plate of the volute. Each pump could have been connected to Its turbine by any one of several methods, but to meet spaoe re strictions and have the coupling as sim ple as possible a specially designed fric tion clutch was selected. Installed In each pump'a discharge pipe is a hydraulically operated spheri cal service and a manually operated Isolating valve. The service valve closet automatically when pump speed drops JUltai through powerhouse at on. of the pumped to 300 rpm or when there Is a serious 'jhf'turbln. con be moved out Into the assembly space betwe pressure drop in discharge connection. Power for Pumping. Surplus power in the system may not be enough for one pump motor, 20,500 hp. Any one of Her System's Operation Jjff, several methods might have been usedto control the output, but It was decided to operate the pumpe el full eapaclty when in service. Any deficiency In elec tric power for e pump generator-motor gjjSyUalr*. When the power ^designed in 1932-33, pro- ^...s made for two 38,000-gpm ijjBulthe Swiss Federal Railway# ^he-pawer company were not sure etostfpower that would be made **' 'tyUhe pumps could be used, ffiere.pot installed, but space Bflgvjdsd for them below two tur^fhcii pumps were not ordered ^f^wheD a severe power abort- L 'iM.lheir installation. |pdwp connects to the turbine of .fcphiie generator and one to that j^Jpfcsso machine, on either side of * -S?v ttansverae center line. ;h*djto be aelected not to exceed Tlj^spacity of the generators in- x operated as motors, and ^ d-lor 38.1&5 gpm each at j- *nd 500 rpm. ->'feowi # crou section through he^two pumps. Their designers w.the problem that the pumps* "Pj had been built ten years earlier for 4-stege pumps. Design im provements and the need for.highest efficiency favored 5-atage pumps. To Install them in the space available re quired connecting the pumps to the waterwheels by specially designed fric tion-clutch couplings. As the project worked out, Sulzer Brothers built the pumps including their shafts and Escher Wytt supplied the dutches for connecting the pumps to the waterwheels, the step, bearings, the spherical seating valves and connecting piping. Outside diameter of the 5-stage pumps la smaller than that of the 4-stage, and required minor changes in the founda tions. For easy assembly and dis mantling, the pumps are permanently mounted on rollers, ao they can be pushed In or pulled out from under their power units onto the pump-room floor between the two machines, Fig. 4. The powerhouse crane can then handle their parts without any difficulty. is supplied by operating Its turbine. For example, if only 15.000 hp of surplus power la available for one pump, (ho remaining 5500 hp Is supplied by using part of the-pomp's discharge to drive lta turbine. In this way the pump is operated at full capacity', bat the pump discharges only part of Its rated capacity to the reservoir, as if h were throttled. This system of regulating the pump's load has been satisfactory at an efficiency as high as would be obtained by throttling or by using wicket gates. When power foils, stopping a large pump Is a complex problem that re quires careful study. Aecoant must be taken of pump speed changes and pres sure ehonges In the piping system. Un less controlled, speed drops quickly, pump's direction of rotation reverses within a few aeconds, end the Impeller running as a turbine reaches runaway peed of 1.25 times normal. Reverse operation hod to be avoided, engineering and management section