Crane Collision Avoidance and Distance Detection Systems
Reducing the potential for collisions between overhead cranes, monorail systems and fixed objects/obstructions has been a challenge for the overhead material handling industry for many years. Until recently it was only possible to minimize the resulting impact from collisions using mechanical means such as bumpers or limit switches. With today's advances in electrical technology, it is now possible to prevent these collisions using more sophisticated means in a variety of operating environments.
A metals processor was handling coils with four cab operated overhead cranes in a common bay. The coils were unloaded, stored, processed and shipped to a variety of users. The average coil was handled four times between receipt and shipment. The layout of this facility, with a common centrally located shipping and receiving, presented a high potential for crane to crane collision.
By automating two of the cranes at the far ends of the bay and limiting their use to secondary processing or long term storage, their potential for use at the central receiving and shipping areas was prevented. The automated cranes included features for positioning control using laser based distance detection devices on the bridge and trolley. Feedback for the hoist position was taken from the hoist motor encoder and the IMPULSE® Flux Vector Adjustable Frequency Crane Control. The remaining two cranes were left to manual cab operation. All four cranes were equipped with Electromotive IMPULSE crane controls on hoist, bridge and trolley motions to maximize their performance and reduce wear and tear on mechanical components. In addition, the cranes were equipped with an Electromotive Systems ReFlx™ 120 "Plus" Crane Collision Avoidance System. When two cranes would approach each other, a primary signal is sent by the collision avoidance system to the AFD to initiate a slow down of the bridge. As the two cranes continue to approach each other a second signal is created by the ReFlx™ system to bring the cranes to a complete stop prior to contact. An additional measure of safety, a third distance sensor was provided to act as an emergency stop in case the first two collision avoidance sensors failed.
Automating the two outer cranes, and retrofitting the manual cranes (with IMPULSE adjustable frequency drives and ReFlx collision avoidance sensors) created an efficient, safe material handling system. The addition of the IMPULSE drives and ReFlx™ collision avoidance systems to the cranes reduced maintenance costs and enhanced performance and safety of the entire system. By automating two of the cranes, personnel normally required to operate the cranes were able to be used in other areas of the plant.
Electronic Technologies Employed by Magnetek for Collision Avoidance Systems
If the application requires collision avoidance between cranes, monorail carriers, and other obstructions, Electromotive Systems has the solution. Below are some of the technologies Electromotive Systems applies to collision avoidance for the overhead material handling marketplace.
ReFlx™ 120 and ReFlx™ 120 "Plus"
Intended for use with overhead crane bridges and trolleys to prevent collisions or limit their approach to adjacent bridges and trolleys. The systems are designed to be immune to most electrical noise including that which can be created by variable frequency crane controls and other parasitic interference affecting the reliability of RF-based systems. The range of this system is from 10 to 120 ft. It uses a two- channel infrared sensor, which allows for a separate slowdown and stop command when used with Electromotive Systems IMPULSE crane controls.
Laser Based Distance Detection
Laser based distance detection and collision avoidance are primarily used in an automated environment where the distances between monorail carriers or cranes can be relatively great. The range of a laser based system (from 0 to over 1000 ft.) allows the ability to monitor distances between cranes, trolleys and monorail carriers, and when interfaced with a PLC, can be used to prevent collision between this equipment. Laser based systems also offer the advantage of precise positioning accuracy which is critical in an automated environment.