Rockwell Automation Inc. visited our offices yesterday and talked about how to tie safety in with standard automation systems. A critical point: safety is a main business driver. Why? Because an older safety system might completely shut down a machine during a safety incidence, whereas newer systems don't shut everything off. A lot of components go into the makeup of an automation system, including sensors, acturators, and power supplies. An efficient way to integrate safety into a system is building a sensor, for example, that works for safety as well as its usual function. The premise: if you have control of all the moving elements, you don't have to shut down the whole machine.
The best way to ensure safety is to design the automation system with safety in mind, upfront. Start with a risk assessment. The EN1050 standard covers principles of risk assessment asking such questions as, "How frequently is a worker exposed," and "What is the danger level?" Perform the assessment, then see what equipment is needed to eliminate issues.
Machine builders have more risk than they realize, often resulting in huge losses. Performing risk assessments are a good way to show you have followed good engineering practice.
So, what is it about the new technology that makes it easier to build in saftey? Compare old and new systems:
Sensor-specific relays PLCs
Monitoring via hard wiring into PLCs Monitoring via network connections
Fixed I/O Remote I/O via safety networking
Can use PLCs with light curtains