Shown: a coil storage rack aisleCoil Stacker Cranes, Modernized One at a Time, Then Automated
A steel bar mill upgraded the drives and motors on its three coil stacker cranes one crane at a time, then had Han-Tek add laser positioning and automatic store and retrieve, all run from one touchscreen.
A steel bar mill stores coils of finished bar in tall rack aisles, served by three coil stacker cranes. The cranes ran on their original motors and controls, and positioning relied on limit switches.
Han-Tek replaced the hoist and bridge motors and drives with severe-duty variable frequency drives and inverter-duty motors, one crane at a time. Then Han-Tek automated all three: a ControlLogix PLC on each crane, two laser distance sensors per crane and wireless Ethernet back to one touchscreen in the control room. Operators pick a crane, a rack position and a task, press GO, and the crane runs the move.
Aging cranes the mill could not take offline
Coils of finished bar hang on pins in long rack aisles. Each stacker crane travels its aisle, raises its carriage to the right level and stores or retrieves a coil.
Worn-out drives
The original hoist and bridge motors and controls were aging, and the mill wanted reliable, severe-duty replacements.
Limit switch positioning
Positions were found with limit switches, and the mill wanted more accurate, automatic positioning.
No long shutdown
The cranes keep coil storage moving, so the mill upgraded them one crane at a time.
The goal: modern drives on every crane, then accurate, automatic positioning for the whole fleet.
New drives first, then lasers and one screen
The work came in phases over several years, each one building on the last. Here is how it came together.
- 1
Drives and motors
On each crane, Han-Tek installed a 60 hp flux vector hoist drive with encoder feedback, a 20 hp bridge drive and new inverter-duty motors, and extended the platform to reach the new enclosure.
- 2
Laser positioning
Two laser distance sensors per crane replaced the limit switches, reading reflective targets to find every bridge and hoist position.
- 3
One screen for the fleet
A PLC on each crane talks over wireless Ethernet to a PLC and touchscreen in the control room, where operators send store and retrieve moves.
- Store, retrieve or position: the operator picks a crane, left or right pin, bridge and hoist position and the task, then presses GO.
- Brake proving: if the hoist drive senses the brake cannot hold the load, it sounds an alarm and floats the load instead of letting it drop.
- Skewed load protection: photo-eyes around the carriage stop the crane if a coil is hanging outside its envelope.
- Bad pin lockout: damaged rack pins can be flagged on screen so the crane never sends a coil to them in automatic.
- Live status and alarms: the touchscreen shows each crane's mode, faults, speed and laser position, plus current and past alarms.
A modern fleet, built up crane by crane
| Area | Before | After |
|---|---|---|
| Hoist drive | Original controls | 60 hp flux vector VFD with encoder feedback |
| Bridge drive | Original controls | 20 hp severe-duty VFD |
| Motors | Original motors | Inverter-duty motors, CMAA Class E |
| Positioning | Limit switches | Two laser distance sensors per crane |
| Crane panels | Old crane-mounted panels | New enclosures with a ControlLogix PLC on each crane |
- Done in phases: the first crane was converted in 2001, the second in 2004 and the third in 2006, the same year all three were automated.
- A proven design, repeated: each crane got the same drives, motors and platform extension, so parts and know-how carry across the fleet.
- Turnkey: Han-Tek handled engineering, panel building, removal of the old crane panels, installation and commissioning with its own people.
- Ongoing support: Han-Tek later audited the automation on all three cranes and recommended fixes and improvements, including a barcode scanner for coil tickets.
- Still coming back: in 2021 the mill hired Han-Tek for an engineering study on another crane and its strapper car.
Questions about stacker crane modernization
Can stacker cranes be modernized one at a time?
Yes. Here each crane got the same drive, motor and platform upgrade on its own schedule, and the fleet automation was added in 2006 along with the third crane.
How does laser positioning work on a crane?
A laser distance sensor on the crane reads a reflective target at the end of the runway or mast. The PLC compares the reading to stored positions and stops the motion on target.
What is brake proving?
The hoist drive checks that the brake can hold the load. If it cannot, the drive alarms and holds the load in a controlled float instead of letting it drop.
Can old cranes run automatically?
Often, yes. With modern drives, a PLC and position sensors, existing cranes can take store and retrieve commands from a central screen.
More steel and severe-duty crane projects
Modernize in phases.
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