With the new system, the palletizers' control is done independently, although the signals can be displayed from old main PLCs and then the operator will see the information in the control screens by the same way, as he saw it in the past.

System description:

By the fact of being gas plants, all of the control's elements, backstops, PLCs, cards, are confined in antideflagration chests, and that is another problem because the space available for installing new elements is quite short.

The adopted solution was to installing the new elements over old remote cards, using special supports patterned for so. In this manner, digital inputs will keep cabled to the original cards and then this signals are displayed at the operator screen as always.

The new control system elements are:

• 1 cpu KT92 of ABB
• 4 digital input/output cards

The cabling of the chests was restyled using old and useless cable of old remotes cabling. It was done by this way because the cables were sealed and for recabling had been necessary to remove the seals, wire up and seal it again.

For the programming of control system, the old control program was adaptated, then, the operators way of working didn't change at all.