System Selection

 

ATB also (A2B):  Anti-Two-Block.  A system that warns the crane operator of an approaching two-block condition.  A two-block is when the headache ball or hook block impacts with the tip of the boom.  This can happen when hoisting up, telescoping out or booming down.  It is a dangerous situation that can result in the load falling and damaging the boom.  The most severe risk is to personal in the area.  With a hydraulic crane the boom damage can be very expensive far exceeding the cost of a anti-two-block warning system.  There are different regulations for each state but most require an ATB warning system and for lifting personal in man baskets require an ATB warning system with lock-outs.  We have ATB Systems in hardwired and wireless versions for both hydraulic and lattice cranes.  The wireless model 145 is less expensive for hydraulic boom cranes since it eliminates the need for the cable reel.   

Boom Angle Indicator:  Boom angle indicators are cab mounted displays the show the operator the exact angle of the boom.  For lattice cranes this can help the operator to know the boom radius which is what the load chart capacities are based on.  There are different regulations for each state but most require a boom angle indicator for cranes over a certain capacity.  We carry the Wylie 830 boom angle system which works well for both hydraulic and lattice cranes and has user settable limits.

HDR:  Hoist Drum Rotation Indicator.  A system that warns the operator when the hoist line is moving either direction.  The HDR has a sensor on the winch for the hoist line which carries a signal to a sensor mounted on the hoist control lever.  Our HDR system is the Wylie 135.  This is an inexpensive warning device that aides the operator to prevent accidents. 

Load Indicator:  A load indicator which is often confused with an LMI (load moment indicator) or RCI (rated capacity indicator) is a device that gives the operator the weight of the load on the hook.  Most often this is measured from the tension on the hoist line. 

This can be done with a tension / load link which is mounted at the dead-end of the hoist line.  The load link measures the force being pulled on the hoist line and combined with the number of parts of line translates into the weight of the load.  The accuracy of this type system is effected by the number of parts of line and the friction in the sheaves.  The more parts of line the more friction and the less accurate the measurement.  This can be somewhat compensated for during calibration.  Load links work well on many lattice crane applications.

The other common method for measuring the load from the tension in the hoist line is by using a dynamometer or dyno for short.  The dyno is a line ridding device that has sheaves that ride above and below the hoist line and the center sheave has a load pin through it.  The force from the hoist line is measured by this load pin and combined with the number of parts of line translates into the weight of the load.  Dynos are usually mounted on a swing arm that allows them to move with the hoist line.  They can be mounted side by side as in the picture here or staggered and at the base of the boom or near the tip.  The ideal position varies with each crane. 

Dyno based load indicators are easy to install and work well on both lattice and hydraulic cranes.  On hydraulic cranes they are installed at the base of the boom and provide an excellent cost effective solution for simple load indication.  Our Wylie 2190 is a great solution for basic load indication.

LMI:  Load Moment Indicator.  An LMI 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 must measure 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 efficent.   The Wylie 3100 is a perfect solution of a complete LMI system.  The Wylie i3000 is the top of the market system for crane LMI's.

An 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.  An 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 hoist with the same pressure sensors.  The initial calibration is more time consuming than a dyno system but in the long term it is more accurate, lower maintenance and has the fewest components out on the boom.
 
RCI:  Rated Capacity Indicator.  An RCI is a more common system than the LMI but is often wrongly refered to as an LMI.  The RCI gives the operator the same information as the LMI but measures the load differently.  The RCI uses sensors like a load indicator to measure the tension in the hoist line as opposed to the load on the boom.  The RCI uses dynamometers and / or load links to measure the hoist line tension from which the weight on the hook is calculated.  With the boom angle and length measurements used to determine radius and the capacity charts programmed into the display you arrive at rated capacity.  The end result is the same for the operator in that they see on the display load, capacity, boom angle and radius its just calculated differently.  RCI's are usually less expensive for lattice cranes but not quite as accurate as LMI's. 

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Crane Warning Systems Atlanta Inc. 
1-877-672-2951

Crane Warning Systems Atlanta