Failsafe systems gain the flexibility of the PLC approach

Failsafe systems, which control potentially hazardous operations to ensure they are shut down if faults occur, have in the past traditionally been hard-wired installations. But there are serious drawbacks to the hard-wiring approach-an inherent inflexibility, and lack of data communications facilities, to name but two. These are prompting a growing move towards using specialised systems based on programmable logic controllers (PLCs) that are tailor-made for failsafe applications. The author considers how Newfield Automation has developed and installed a range of failsafe applications using PLCs since the company was founded in 1989. Its systems are based on the Siemens Simatic S5-115F PLCs, which are high-integrity units tailored for failsafe applications.<>