Cranes and hoists - the options are growing.
Today, so-called "secondary" cranes such as jibs and gantries are in wide use in localized areas, complementing the large bridge crane's total building coverage with missions focused on specific work areas or stations. A relatively new entry into this arena is the work station crane, which is a bridge crane that is lighter-duty than the traditional big overhead crane, and which often operates within a free-standing structure instead of on building girders. Some of these cranes are now made of aluminum.
The work-station crane-a concept that originated in Europe and was first introduced here in the '70s--represents a general overhead-handling trend in industry. Overall, crane capacities are coming down, and handing tasks are becoming more specific. Part of the reason for this trend is the reorganization of American industry.
Years ago, the management ideal was the integrated organization, which took in raw minerals at one end of its operations, and shipped out final products ready for the consumer at the other end. All manufacturing, fabricating, processing, and packaging steps in between were performed by this organization. In such a setting, the large, all-purpose crane--with capacities set high enough to meet any future operating requirements--was the logical choice. It often operating in tandem with similar cranes or related equipment in adjacent areas of the plant.
Today, "rightsizing," "re-engineering," and "outsourcing" represent current management wisdom, and this restructuring of industrial companies is making an impact on the handling requirements organizations are facing. As certain operations are farmed out to outside contractors, the remaining manufacturing steps are more focused, and require more specialized types of support equipment than before.
In the case of cranes, the large, general-purpose unit, sized to meet almost any unforseen contingency, is in less general demand than in the past. The growing demand, instead, is for the lighter-duty, easily installed and/or disassembled system that is focused on a specific mission within a more localized work area. Such systems will still work in tandem with the big, heavy-duty units, but the trend is for more of the former and fewer of the latter in a given plant.
Giving cranes new life
For some crane users, older equipment has reached the point where it is draining productivity in a facility, either because its components are wearing, or because it cannot meet new operating requirements in terms of load handling capacity and throughput. The answer may be a program of modernizing and upgrading of existing cranes.
If a crane is structurally sound, the cost of modernizing may represent only half the price of a new crane. And, often the job can be completed in half the time it takes for a new crane to be delivered. Another advantage is that modernizing may often be treated as a maintenance expense, whereas acquiring a new crane generally involves capital fund approval.
Upgrades can be in both electric and mechanical areas. Typically they can include the follwing:
* Replace old controls with pendant, remote radio, or infrared controls. (A trend with remote radio is spread spectrum, which does not require FCC licensing for the user.).
* Uprate hoist lift capacity.
* Provide adjustable-frequency motor controls.
* Install self-aligning brakes.
* Replace end trucks and wheel assemblies for higher productivity, lower maintenance.
* Install new limit switches.
* Reinforce girders.
If modernization of an existing crane is not feasible, an alternative to a new crne can be a used unit that has been modernized and upgraded by a crane manufacturer. As with an in-plant upgrade, this alternative can also provide the advantages of lower cost and shorter lead time. Such "pre-owned" equipment can be obtained fully rebuilt with a newcrane warranty; repaired and modified for a specific application with a limited warranty; or sold "as is", with or without an inspection.
Finally, hoists for overhead handling are available in engineered versions for use on cranes and specialized applications, as well as in packaged versions for use in lighter-duty crane applications, and on I-beams, jib cranes, and gantries.
The accompanying selection table lists crane manufacturers and the equipment they supply. Literature from hoist manufacturers is reviewed in our Special Catalogs section.
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|Publication:||Modern Materials Handling|
|Article Type:||Buyers Guide|
|Date:||Jul 1, 1994|
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