Meiden drives keep concrete blocks moving

Edited by the Engineeringtalk editorial team Jul 3, 2000

In re-engineering of the drive system in a system for handling palletised concrete blocks, system builder Emmas opted for two Meiden VT210SA variable speed drives and two 7.5kW motors

Twelve years ago Aggregate Industries installed an electro-hydraulic driven 'Pallet Transporter car' for handling palletised concrete blocks.

That drive system has now been replaced by an all electric one that provides easier control, greater reliability, energy savings and increased efficiency.

The Pallet Transporter car comprises two vehicles, one of which is carried piggy-back by the other.

In operation, the main vehicle travels along rails to positions adjacent and at right angles to either one of 25 kilns or stations for collecting wet blocks/depositing dry ones.

Aligned to these stations, the piggy backed Pallet Finger car moves off its Transfer car to either collect or deposit loads.

With the original electro-hydraulic system, each vehicle was powered by a 7.5kW electric motor mounted on an hydraulic pump driving through a gearbox.

Although considered the ideal solution at that time, its age, declining efficiency and increasing maintenance demands necessitated re-engineering of the drive system.

System builder Emmas, who had worked on the system previously, was given the project.

Their solution was a closed-loop, PLC controlled package employing two Meiden VT210SA variable speed drives and two 7.5kW motors (one axle mounted giving direct drive for the Transfer Car), providing a speed range of 30:1.

The result is a turnkey, fully automated, maintenance free system with dynamic braking and high starting torque that was easy to set up using the drives' auto tune function.

The operating routines programmed into the drives also means automatic motor control for the various duties at each station, plus easy switching between handling routines when required.

Also, the motors do not need to be running continuously as with the hydraulic system, making valuable energy savings.

In addition, because of the control provided by the Meiden drives, positioning at docking stations is more precise, eliminating the need for a position correcting mechanism required with the previous arrangement.

The reliability and consistency of the new all electric system has boosted production by more than 10%, to 8,000t/day of concrete blocks, and has not needed attention since Christmas 1999, when it was commissioned.

"The new closed-loop electric drive package from EMMAS has given us continuous, uninterrupted operation", says Martin Parsons, Factory Manger, Aggregate Industries.

"The motor control provided by the Meiden variable speed drives", he added, "is essential to the system's success, providing both reliability and flexibility, ensuring our production demands are met." The Pallet Transporter car, handling 540 blocks on each lift, is used to transport wet blocks to the kilns, each of which accepts nine drops of the ten tier palletised loads.

After curing, the blocks are then taken by the car to an unloading station from where the blocks are taken to a packing station to be automatically stacked onto pallets, initially for yard storage and then shipping.