In our highly mechanized world, cranes are the workhorses that have increased productivity and economic growth in construction, mining, logging, maritime operations, and maintenance of production and service facilities. It is not unusual in large metropolitan areas to see several crane booms outlined against the skyline within a few blocks of each other and in rural areas to see cranes performing a great variety of jobs.
Statistics show, however, that there are inherent hazards that occur during normal working circumstances. A crane can be a very dangerous piece of equipment. Most crippling injuries and deaths from crane accidents can be attributed to several basic hazards.
Risks Presented by Overloading
It is estimated that one crane upset occurs during every 10,000 hours of crane use. Approximately 3 percent of upsets result in death, 8 percent in lost time, and 20 percent in damage to property other than the crane. Nearly 80 percent of these upsets can be attributed to predictable human error when the operator inadvertently exceeds the crane's lifting capacity.Thus the operator must always know the weight of the load. This is why employers must ensure their operators' competence.
Instruments and Components
Cranes and derricks with variable angle booms must have a boom angle indicator that is visible to the operator. Cranes with telescoping booms must be equipped with a device to clearly indicate the boom's extended length, or an accurate determination of the load radius to be used during the lift must be made prior to hoisting personnel. Cranes and derricks also must be equipped with an anti-two-blocking device that prevents contact between the load block and overhaul ball and the boom tip or a two-block damage-prevention feature that deactivates the hoisting action before damage occurs.
During the last tens of years much progress has been made in the availability of systems to prevent crane upset due to over-loading. Crane operation is no longer a “seat-of-the-pants” skill but requires both planning and training in the use of the latest technologies such as load measuring systems or load moment indicator LMI.
With the advent of micro-processing electronics, load measuring systems evolved. Such systems can sense the actual load as related to boom angle and length, warn the operator as rated capacity is approached, and stop further movement. Load moment indicator systems automatically prevent exceeding the rated capacity at any boom angle, length or radius. Today most crane are equiped with crane computer system as standard equipment on new cranes. Meanwhile, there are after-market suppliers of these devices for old or refurnished cranes , WTAU is one of them, which has been focusing on crane safety equipment especially load moment indicator/safe load indicator for continuously 17 years.
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