Stacker cranes are popular in metals warehouses and fabrication shops that need bulk storage of raw materials in a long bar form. The use of a stacker crane instead of a traditional overhead crane or forklift provides more storage in less real estate. However, stacker cranes are not without their challenges.
Typically, a more experienced operator is required to operate a stacker crane because of their high-speed operation in tight quarters with as little as 6” of clearance. This type of picker crane is prone to collisions with racking if not centered properly in a row or aisle.
Shown above is a modern stacker crane built specially to handle long bar stock for a metals service center. With variable frequency drives (VFD) and more sophisticated controls, the newer stacker cranes can move at an even faster pace. Most stacker cranes, both new and existing, rely on a skilled operator to maneuver safely in each aisle.
Anti-Collision Systems To Prevent Overhead Stacker Cranes from Colliding
Laser-View Technologies’ Crane Sentry® systems have been retrofitted to existing stacker cranes to provide a combination of restricted zone management. Zone management keeps the crane from operating in protected areas. Row/aisle alignment prevents the crane and its fork from interfering with racking as the crane moves along the corridor.
Consideration must be made for the orientation of the forks since most stacker cranes do not rotate on their geometric center. The result is safer and more productive operations with your current crane operators
Interference between the stacker crane and storage racks can lead to several avoidable conditions:
- Injury to personnel via an uncontrolled load of snagging of a rack
- Damage to material
- Damage to the crane as a result of unexpected usage conditions
Some facilities have incorporated mechanical switches and visual alignment indicators to help operators with proper alignment. However, this solution still relies heavily on a senior skilled operator.
Non-Contact Measurement and Positioning with Crane Sentry®
Laser-View Technologies’ Crane Sentry® systems use long range laser distance sensors in 2-axes capable of measuring up to 500m. This technology provides an absolute position that does not require mechanical positioning of limit switches or re-zeroing of encoders.
Crane Sentry® Zone Manager is based on real measurements, not just proximity. For shorter crane runways, we can even measure on a natural surface without installing a special reflector. We incorporate sensors for mast rotation into each system so that the orientation of the mast is known.
With the Crane Sentry® system, aisle positions are taught and zones are made around the overall rack area using (2) laser sensor axis. Crane Sentry® arrives to you in a complete package, is simple to install, and intuitive to configure.
- Two axes measurement – bridge and trolley
- Simple and intuitive color touch screen controls show set point and live readings
- Program set points with simple TEACH button or key in values
- Automatic slow and stop zones with independent parameters for each zone
- Override functionality
- Remote I/O available
- Visible red eye safe laser spot
- Measures up to 100m with a natural target and 500m with a reflective target plate
When the stacker crane mast is inside of the rack area and in one of the aisles, high speed bridge motion can only be permitted when the forks are clear of the racking. It is important that the operator be able to move the mast trolley and control the forks to manipulated loads. However, an extended mount of mast rotation cannot be permitted.
The mast must be moved back into the center of the aisle before bridge rotation can be enabled again. Laser-View Technologies offers remote wireless I/O modules as modular options to the main Crane Sentry® system. This makes an I/O handshake for closed loop control.
The Crane Sentry® product line is manufactured and marketed by Laser-View Technologies for crane collision detection, zone control, and positioning applications. Crane Sentry® is designed and manufactured in the USA.