SMART CONTROL BRINGS AUTOMATED CRANES A STEP CLOSER
The UK's largest volume crane builder, Street Crane Company, is offering new control packages to enhance safety, efficiency, prolong service life and drive down the cost of ownership. Their new PLC based control options provide the flexibility to deliver control customisation at relatively low cost.
The UK's largest volume crane builder, Street Crane Company, is offering new control packages to enhance safety, efficiency, prolong service life and drive down the cost of ownership. Their new PLC based control options provide the flexibility to deliver control customisation at relatively low cost.
The new developments also introduce a degree of automation into operations that reduce training times and stress levels. A good example of this is Street's load sway prevention system (LSPS). This has just two sources of data input; the total length of rope, including the sling, and the operator speed command. Given this data the system calculates the required speed profile for each load to achieve zero swing. It delivers precise movement without the need for operator intervention.
LSPS is very user friendly because it responds to the user's commands, so they retain control, but the system optimises the resulting action. This means the operator concentrates on delivering the load without the burden of controlling sway. This makes crane movements quicker and more productive. The system has already been proven in a high volume automotive casting foundry. Other users include steel coil warehousing, aircraft component manufacture and galvanising facilities.
There are many industries where precise pickup and touch down of loads are vital to avoid damaging high value product. Aero engine manufacture/service is one such case and aluminium foil is another. Street has recently completed an innovative PLC based control package for one of Europe's largest foil producers. This uses two advanced coil handing cranes featuring a unique homing device for accurate load parking without damage to the delicate coils.
This is achieved by using reference data stored in the PLC to calculate a coil's horizontal and x, y position precisely from up to 100 predefined locations. The operator is in full control until the critical parking zone is reached. At this point the PLC takes full control and ensures a safe and gentle touch down.
These new cranes also have an unusual zone limiting system. Resident in the PLC, this system defines excluded areas of the bays where there are large items of plant. The crane therefore automatically routes the load around these objects to avoid collision.
The range of PLCs available make it possible to engineer special control options for simple to very complex applications. Many users will standardise on a particular PLC throughout their site and this generally presents few programming difficulties. Where a user requires an ability to swap out a faulty PLC, programming can be stored in the coprocessor to simplify maintenance.
Like other forms of computing hardware, the cost of PLCs is falling while their capability is increasing. Add to this, the ease of programming, simplicity of installation and straightforward maintenance, and you can see that modern EOTC's, offer radical solutions to the mechanical handling needs in high volume process driven manufacturing plants.
High-res photo for this text is on the web at www.ainsmag.co.uk/st165/3077st1a.htm
March 22, 2002
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