Problem of cranes exploitation with dangerous defects

A great number of load-lifting cranes with expired standard service terms are being employed in Russia nowa-days. The paper presents a number of defects detected in the expert surveys of load-lifting cranes. Among the most dangerous defects causing failures and accidents are the following: cracks in the welded joints and the base metal of supporting structures; extreme negative sagging of the flight structure of bridge-type cranes; the weakening of bolted joints connecting sections, towers, arrows and portals; excessive wear?out and wire drop-offs of cargo ropes; unreliable securing cargo ropes ends; maximum wear-out of hoisting mechanisms couplings and brake pulleys; weakness and lack of bolts supporting-rotary devices of truck cranes, pneumatic valves, caterpillar and tower cranes; reduced braking torque of hoisting mechanisms brakes, swivel brakes, flight change brakes, movement of cranes and carriages; full or partial absence of, or an undesirable operating state of anti-theft devices; inability or the fault of the limit switching mechanisms; the failure or lack of capacity constraints; lack of or inoperable anemometers; unsatisfactory condition of the crane ways; the absence or poor condition of the dead-end stops; the unsatisfactory condition of power cables insulation; inability of voltage light-signalling on main bridge cranes trolleys; inefficiency of sound alarm, etc. The paper presents the ways to reduce the amount of load-lifting cranes with dangerous defects, i. e. cranes operated in the warning state.