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Construction sites consist of a variety of activities executed with a number of equipment and tools. The complex, dynamic, and continually changing nature of construction work has been recognized as an important contributor to the high rates of injuries and fatalities in the industry. Cranes are a central component of many construction operations and are associated with a large fraction of construction accidents. There are some statistics indicating that a significant number of construction injuries and fatalities are caused due to crane related accidents. Such accidents not only result in casualties but also take a quite big toll on the financial investment.

Overloading is one of the most common causes of crane accidents. Around 80% of all cranes accidents are caused by overloading the safe working capacity of the equipment. When a crane is overloaded, it is put under excessive stress that can cause damage to the equipment. This damage can result in a collapse of the crane. Overloading can also cause the load to swing or drop suddenly, and knock the crane off balance that would result in the entire crane tipping over. Without the proper crane safety and warning system installed, operator may not realize that the load on the crane exceeds the limit.

Load Moment Indicator (LMI) is one of the safety devices used in the crane safety system to eliminate the risk of crane overloading and accidents related to it. A proper LMI system will warn the crane operator with buzzers and lights whenever overloading occurs thus ensuring that crane operation is carried out safely and securely.

Mobile & Tower cranes are the two basic cranes, each available in many different configurations, which are employed at construction sites. Mobile cranes can have extendable telescoping or lattice booms designed for working at varying boom angles. And tower cranes may have a fixed horizontal (“hammerhead”) boom with a trolley-mounted hoist, or a moveable, variably-angled-above-horizontal (“luffing”) boom with a rigged tip. The lifting capacity of the mobile crane, whether equipped with a lattice or telescopic boom, changes with the boom's length and inclination angle; and lifting capacity of the tower crane is different at different hoist position on the boom. As a result, every lift has the potential to modify the crane's maneuverability, stability, and load capacity

The boom length and angle, in case of mobile crane, and hoist position, in case of tower crane, changes the working radius of the crane. As a result crane's moment changes, which is the product of radius and load. Load Moment Indicators helps the crane operator sense (directly or indirectly) the overturning moment on the machine, i.e., load multiplied by radius.

Load-Moment Indicator (LMI), in some cases referred to as a rate capacity indicator (RCI) or a rate capacity limiter (RCL), is a system that measures the load on the boom and has the load capacity charts programmed in the display.  The system will show the operator the load, the capacity, boom angle and radius. The system measures the boom angle and length to calculate radius in order to read the capacity charts which are based on radius.  These systems save the operator the trouble of looking up the capacity from a load chart making their job much safer, easier and efficient.  

LMI calculates the load on the boom by either measuring the pressure in the lift cylinders on a hydraulic boom crane or by the tension in the pendant lines on a lattice crane.  LMI is also known as a total moment system since it measures the total "force" or moment on the boom.  The best LMI system for a hydraulic crane is the pressure transducer type.  Since this system uses pressure transducers on the lift cylinders it is very accurate and cost effective.  It measures the load for both hoists with the same pressure sensors.  The initial calibration is more time consuming than a dynamometer system but in the long term it is more accurate, lower maintenance and has the fewest components out on the boom.

Load Moment Indicator determines whether a load is stable enough to be carried by the crane. It compares the lifting condition to the crane's rated capacity, and indicates to the machinist the percentage of capacity at which it is working. It uses lights, bells, or buzzers to alert the operator in case of overload condition. It can also stop the crane from functioning if the weight is more than the specified moment. It also enables the operator to keep an eye on the functioning of different parts of a crane, including hook height, hook amplitude, slewing angle of the main jib, angle of the luffing jib, black box recorder without any limitation of downloading times, alarming process replay and wind speed. The crane operator can know with ease all important data sitting right in the cabin.

Cranes are heavy, inherently dangerous machines. Worksite safety is ultimately dependent on the crane operator. Load moment indicators are considered operator aids and are designed to remove as much guesswork from their critical tasks as possible. Load Moment Indicator gives the operator the information necessary to fully utilize the cranes capacity while keeping within the working limits of the crane.

Installing crane warning systems are a great way to ensure that your project is completed successfully. With the right Load Moment Indicator, you can rest assured that you can work with ease without worrying about crane accidents due to overloading