As a result of this, during operation of the unit the bushings of the oil header are extremely heated and bind the rods and frettings occur on the rods and through cracks on the bushings.In the majority of cases misalignment of the shaft and oil header occurs as a consequence of a considerable increase of the gap between the shaft and bearing of the generator, which, as a rule, leads to binding of the upper end of the rods.In the case of considerable heating of the oil header and oil, stopping of the unit should be preceded by conversion of the blades to manual control. In the case of emergency stopping, owing to the automatically occurring turning of the blades to a starting angle (downward movement of the piston rod of the servomotor of the runner) the flange connection of the rods with the piston rod can be broken off as a consequence of their binding in the bronze bushings of the oil header.Careful attention to the oil header in the stage of its development, manufacture, assembly, and operation invariably ensures reliability and trouble-free operation. For this purpose, the design thickness of the rod walls, correct centering of the unit, and thorough cleaning of the oil of the control system are necessary. The main cause of sliting of mountain reservoirs is the sediment load of the rivers. Silting can also be causedby landslides and falls, mudflows, products of reworking of the reservoir banks by waves, and wind-borne sediments. If the reservoir is large, the process of silting is divided into two periods. In the first period all sediments remain in the reservoir and the volume of silting is equal to Ws= (Wt~m+V)T, ~us =Ha/Pdep, (i) The end of the first period is determined by the relation [i]W--O,2Vm, r (2) Tult = W1.su s + V"In the second period, when the sediments begin tobe partially discharged into the lower pool, the volume of silting is determined by the following formula [2]:W,. sus~ wult J where Vm. r is the mean annual runoff of water to the reservoir; T, silting time, years; Wul t, ultimate volume of silting, equal to the volume of the reservoir minus the volume of the channel which remains in the reservoir after its complete silting; Wl,su s, volume of the suspended load which remains in the reservoir in the first year of its silting or, if there is a first period of silting, in the first year of the second period where ~a is the mean annual mass of the suspended load (dry), determined from the State Water Inventory (when a reservoir already silted is present on the river a correction is desirable, since the runoff of the suspended load is underestimated); ~r and ~ri, crosssectional area of the dam stretch of the reservoir and river under natural conditions during passage of the dominant discharge; n an exponent which varies for mountain rivers fromTranslated from Gidrotekhnicheskoe Stroitel'stvo, No. 9, pp.
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