The fiat gate is the basic type employed to close the ports of water passages in domestic hydraulic structures. Owing to their technological nature, economic setting in the structure, and ease of installation, operation, and repair, flat gates of various design modifications are universally employed in deep and surface ports of considerable size over a broad range of working pressures. They have been the subject of considerable study and are quite reliable in operation. At some hydrofacilities, however, there have been instances of damaged flat gates. Analysis of the causes of these damages has yielded voluminous data, on the basis of which design standards have been rendered more precise, and rules governing the fabrication, installation, and operation of the equipment are upgraded. A few characteristic cases of damages incurred by fiat gates in the post-war period with a description of accompanying instances and an analysis of the causes are examined below.* During a temporary period of operation in March 1952 at one of the concrete spillway dams on the Svir' River, an emergency situation arose with a flat wheeled gate covering an opening of 27 m and designed for a head of 6.6 m. The gate was designed in accordance with technical specifications and norms issued in 1935, and was constructed by welding grade St. 3 steel with type E42 electrodes (TsM-7 coating). The mechanical properties and chemical composition of the steel met standard requirements. For three months prior to the emergency, the gate was set into the grooves of the repair gate and operated under a head of 6.0-6.5 m; at the time of the emergency the effective head was 5.72 m. For one weak prior to the emergency, a severe cold spell settled over the construction region, and nighttime temperature dropped to -30"C; at the time of the emergency the air temperature was-22"C.The emergency occurred on closing the spillway opening. Workers on the bulkhead heard a noise and grinding, experienced jolting, and saw that the facing of the gate had deflected severely in the downstream direction. First the left, and then the right end of the gate was torn away out of the grooves and the gate became pinned against the right-bank abutment (Fig. 1). On examination of the failed gate, the following were observed: rupture of the downstream flange of the cross beam at its splice point (at a distance of approximately 1/3 the opening from the left support), vertical and horizontal fracture and bulges in the lining, large deformations in the upper angle brackets on the gate, and fracture of the grate supports. The balance wheel was torn away. It was also established that the construction joint in the downstream flange of the cross beam at its splice point had been welded with gross disregard of techuical specifications.It was ascertained that a small opening in the ice was maintained in front of the gate during the winter. However, a layer of ice became encrusted on the cross beam, and particularly on the faces of the gate and on the lining, its thickness reaching 40 cm. ...
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