Shown: the new 15-ton stacker crane in serviceA Single-Girder Stacker Crane That Doubled Capacity in the Same Building
A refractory manufacturer needed a 15-ton fork stacker crane to feed molten refractory into molds at two furnaces. Han-Tek delivered a single-girder design that fit where a standard double-girder crane could not.
A manufacturer of fused-cast refractories casts the bricks that line glass furnaces. Its 7.5-ton stacker crane was wearing out and could not handle the larger refractories its customers wanted.
The usual answer, a double-girder stacker crane with a center mast, would not fit the building without a costly redesign. Han-Tek engineered and installed a 15-ton single-girder fork stacker crane with a side-mounted mast that reaches the furnace taps, working with a crane manufacturing partner that built the crane. The existing runway was reinforced for the higher wheel loads, and the crane was installed in three weeks.
Twice the load, in a building built for half
The crane is the heart of the plant. It carries silica molds to two furnaces that tilt to pour molten refractory through a tap at the bottom, then swaps each full mold for an empty one, around the clock.
Outgrown and worn out
The 7.5-ton crane needed excessive maintenance and could not lift the larger refractories the glass industry wanted.
No room for the usual design
A double-girder stacker crane with a center mast would not fit the building or reach the furnaces without a costly building redesign.
Severe, nonstop duty
The crane had to handle offset loads next to molten refractory, run nearly 24/7 and keep maintenance downtime to a minimum.
The goal: double the capacity, keep the building, and reach both furnaces exactly where the old crane did.
A side-mounted mast on a single girder
Instead of hanging the mast between two girders, the design mounts it on the side of a single box girder, so the forks reach past the end of the crane to the furnace taps. Here is how a pour cycle runs.
- 1
Pick the mold
The operator uses the forks on the mast to reach into the staging area and pick up an empty silica mold, an offset load up to 10 feet high.
- 2
Set it at the furnace
The crane travels the 100-foot runway to one of two furnaces, which tilts to pour molten refractory into the mold through its tap.
- 3
Swap and repeat
The crane backs out, sets down the full mold, picks up the next empty one and returns, several pours every half hour.
- Same reach as before: with the new bumpers fully compressed against the end stops, the forks sit exactly where the old crane's did, so molds land in the same spot at the furnace.
- Built for molten metal service: designed to CMAA Class E, with a three-stage telescoping mast and safety dogs that grip the guide rails if a rope goes slack or fails.
- Brake check before every lift: the hoist drive applies full torque against the brake before each release and will not release if it detects slippage.
- Load float and slack cable protection: the hoist can hold a load in place without setting the brake, and a slack cable system stops the hoist if the carriage is lowered onto something.
- Controls where the operator works: a festooned pendant plus two pedestal control stations at the furnaces, with the drives in a separate air-conditioned enclosure.
Bigger refractories, no building redesign
| Area | Before | After |
|---|---|---|
| Capacity | 7.5 tons | 15 tons |
| Crane design | Worn single-girder stacker | New single-girder stacker, CMAA Class E |
| Drives | Contactor controls | Variable frequency drives on all motions |
| Building | Too tight for a double-girder crane | No building redesign needed |
| Runway | Built for the 7.5-ton crane | Reinforced for higher wheel loads |
- A bigger product line: the plant can now make the larger furnace linings glassmakers want and compete for that business.
- Less wear: soft starts, torque proving and load float reduce wear on the brakes and mechanical parts.
- Simple maintenance: routine work is mainly lubricating moving parts and checking the wire rope and bearings.
- Adjustable: speeds, acceleration and braking distance can all be tuned at the drives to suit the process.
- Two shifts trained: Han-Tek trained two full shifts of operators to run the crane safely and efficiently.
- A cover story: the crane was featured as the cover story of the December 2003/January 2004 issue of Hoist magazine.
Questions about stacker cranes
What is a stacker crane?
An overhead crane with a rigid mast and forks instead of a hook, so it can pick up, carry and place loads precisely without swinging. This one carries molds to and from furnaces.
Why choose a single-girder stacker crane?
Mounting the mast on the side of one girder lets the forks reach past the end of the crane, closer to walls and equipment. Here it fit a building where a double-girder crane with a center mast would not.
Can a heavier crane run on an existing runway?
Often, if the runway is checked and reinforced. On this project the existing runway girders and columns were reinforced for the higher wheel loads before the crane arrived.
What is CMAA Class E?
A Crane Manufacturers Association of America service class for severe duty, used for cranes that handle loads near capacity many times an hour.
More severe-duty crane projects
Keep the building.
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