Power and Utilities | Crane Systems | By STAHL CraneSystems | Feb 14, 2016
What first appeared to be a standard order of four standard heavy-duty double girder overhead traveling cranes for power plant builders VVE became more complex when specified foundations threatened to exceed the budget. STAHL CraneSystems’ Slovakian crane building partner Jaroslav Beneš – ŽERIAVY accepted the challenge. The crane system was modified so VVE could reduce cost-intensive measures. Intelligent crane controls were implemented to analyze the load and position data of all the cranes, trolleys, and hoists in real time and control the lifting and travel motions of the whole system.
VVE took a major step toward self-sufficient production by commissioning its own production line for hydroelectric power plants. Four cranes work in a new industrial building, with safe working loads of 180 and 90 tons in one bay and 175 and 85 tons in the other. The solution is based on load measurement, laser-based position monitoring of the crane bridges and trolleys, distance between the cranes, and continuous communication among the cranes.
Every crane is equipped with redundant PLC controls that analyze the crane data in real time, even if a crane is not in operation or even shut down. When the specified limits are approached, the controls reduce lifting or traveling speeds of individual cranes, trolleys, or hoists or they reduce the speeds of the complete crane system. If a single crane or a number of cranes combined reach the maximum permissible load of the building, the system halts all movements that might increase the load.
Since the lifting capacity of each of the two largest cranes could exceed the load capacity of the crane runways, the maximum permissible load for these two depends on the position of the trolleys. The lifting capacity of the largest crane decreases from 180 tons in the center of the crane bridge towards the outside. The movement of the crane bridges and relation to one another are also analyzed. If the 180-ton crane is working with full load, the 175-ton crane in the second bay can only travel past it if it is unloaded and its hoists are at the opposite end of the crane bridge. The cranes communicate continuously and redundantly on separate WiFi channels.
The two hoists or trolleys on the individual cranes or the two cranes in each bay can be combined to operate in tandem if required for large machinery components.
The high lifting capacities are achieved by combining STAHL CraneSystems hoists. The larger cranes are each equipped with a twin hoist, type ASF 7 ZW with 125-ton safe working load, supplemented by an auxiliary ASF 7 hoist. The “smaller” cranes are each equipped with a 50-ton ASF 7 wire rope hoist and a 40 or 35-ton ASF 7 auxiliary hoist. Frequency converters ensure smooth lifting and travel, which reduces the load on the building structure.
Expert crane builder Jaroslav Beneš – ŽERIAVY explains the mode of operation of the goliath cranes he designed.