Bulk-handling crane

Early French crane loading coal for a gasworks

A bulk-handling crane is one that, instead of a simple hook that can handle a range of slung loads, has an integral grab for lifting bulk cargoes such as coal, mineral ore etc.

Where the grab is a two-piece hinged bucket, it is known as a shell grab or shell bucket. Working the grab requires extra cables from the crane jib, so requires a specialised design of crane throughout, not merely an attachment. Some grabs use 2 cables for lift and control, others use 4.

In 1927, Stothert & Pitt of Bath, Somerset produced the first specialised bulk-handling crane.[1] This was to unload coal at Barking power station in London.

Orange-peel grabs

Orange-peel grab attached directly to jib

Where a cargo is coarser in size than minerals, commonly for scrap metal, then an orange-peel grab may be used instead of a shell. These have six or eight segments of "peel" independently hinged around a central core. They are better able to grab at an uneven load, rather than just scooping at small pieces. If the load is made of long thin pieces, a grab may also be able to carry far more than a single "grabful" at one time.

Although orange-peel grabs may be hung from cables on a jib, they're also commonly mounted directly onto a jib. This is more suitable for grabbing at awkward loads that might otherwise tend to tip a hanging grab over. They may also use hydraulics to control the segments rather than weight and hoist cables.

Clamshell buckets, now retired at a coal dock re-development in Cardiff

Kangaroo cranes

Another of Stothert & Pitt's innovations was the kangaroo crane. Rather than slewing (rotating) the crane to reach the delivery hopper on-shore, a kangaroo crane has its own in-built hopper beneath the jib, that slews with it as the crane rotates. Dumping the grab contents into the hopper now only requires the quicker luffing movement, without needing to slew for each load.

The term "kangaroo crane" has also been applied more recently to jumping cranes, tower cranes used in the construction of skyscrapers that are capable of raising their towers as construction grows upwards.

See also

References

  1. ↑ "Bulk Handling Cranes". Clarke Chapman. Archived from the original on May 6, 2008. External link in |publisher= (help)
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