April 17, 2014
ABB’s new safety PLC has provided the platform for Sandvik Materials Technology to add zoned safety guarding to a large cold-rolling mill at its Sandviken plant in Sweden. The mill is a key part of the production line for precision strip steel at the plant.
Safety PLC modules from ABB’s AC500-S PLC have been added to the machine control system of the 65-ft.-long mill. The networked architecture uses the PROFIsafe protocol over PROFINET® to provide independent control of six separate safety zones. The zoned arrangement means that parts of the machine can remain operational while an operator gains safe access to some other zone, where safety is assured by disabling power.
About 50 safety PLC I/O channels are employed to link to gate switch and light curtain guarding and emergency-stop buttons. The I/O also monitors pressure switches to sense that hydraulic power is disabled so that maintenance can take place and controls power supplies to the motor drives. With the PLC, Sandvik can use floating point numbers, which simplified the safety programming required for this project for tasks such as calculating speed.