For many folks, the subject of industrial safety brings forth visions of signs saying, “SAFETY GLASSES MUST BE WORN BEYOND THIS POINT.” That, and stern instructions to keep hands away from moving parts.

Important instructions, surely, but as static as some attitudes toward safety. In reality, industrial safety today, including in the packaging industry, is a dynamic and rapidly changing field whose trends and debates, though specific to the subject, mirror those that characterize automation as a whole.

Perhaps the most obvious change is in the topology of the safety system itself. Traditionally, production-line safety systems have deployed an array of devices, such as door interlock switches, sensors, safety relays and the like, with the intelligence for the safety system supplied by a programmable logic controller (PLC)—often a dedicated safety PLC. Today, however, automation vendors are imbuing servo-motor drives with intelligence, allowing these formerly dumb devices to handle new tasks, including safety logic.

Some have questioned the usefulness or relevance of this recent trend, but Brian Deal isn’t one of them. “There has been an ongoing debate regarding where exactly to locate a safety function,” acknowledges Deal, packaging market segment manager for automation supplier Schneider Electric, of Palatine, Ill. “However, safety inside the drive will become necessary because the drive, with its moving parts, is the main source of risk in a machine. And if a drive is able to monitor its own safety behavior, it is able to react faster to changing conditions.”

David Arens, food and packaging applications engineer at supplier Bosch Rexroth Corp., in Hoffman Estates, Ill., forcefully seconds that notion. “You can’t have a good handle on the operational condition of the machine unless all of the components can be ensured on their safe and reliable operation, so incorporating safety and/or safety monitoring into all of the devices on a machine is actually, in my opinion, a future critical path.”

Integrating safety functions into the drives, as well as other components, can not only boost safety but also have a positive impact on other aspects of machine operation as well. For instance, it may obviate the need for an external speed-monitoring device or for a contactor, which is a relatively large and costly device. Fewer components can mean less expense, a smaller space requirement, reduced wiring, faster installation, and easier monitoring and maintenance.

Beyond the specific example of the drive lie two factors: the functional safety concept and international standards, both of which are acting to push safety concerns and safety functionality deeper into the guts of the production system. First, the concept.

Functional safety is a holistic, or “end-to-end,” approach to safety. Traditionally, safety systems have been somewhat isolated from the automation system. They were implemented and controlled separately from the automation system, and the criteria for evaluating the safety level of equipment and systems tended to be limited to specific technical inputs. Functional safety, on the other hand, evaluates the safety of a system or piece of equipment in relation to a broader range of “real-world” inputs, including the operation of upstream and downstream systems, as well as likely operator errors and environmental disruptions.

The goal is two-fold: one, to improve the overall level of safety, and two, to improve the functional operation of the machine or system. In the past, equipment safety and productivity have been viewed as separate and generally competing goals; the concept of functional safety brings them together.

The role of standards

The question now becomes, how do you evaluate functional safety? You can’t just wing it; there must be standards. Fortunately, there are—IEC 61508, for starters. Developed by the International Electrotechnical Commission, this is a standard for the evaluation of functional safety of products, components and systems, covering electrical/electronic/programmable electronic (E/E/PE) safety-related systems, along with the assessment of the proper safety integrity levels (SILs).

Deriving from that is IEC 61800-5-2, a standard that allows the evaluation and quantification of safety for adjustable speed electrical power drives. The key here is that prior to the promulgation of these and related standards, there was a reluctance to accept electronic and programmable electronic components in safety related functions—just the sorts of components that are being increasingly used in every aspect of today’s packaging operations.  With the aid of the methodology provided by IEC 61800-5-2, this is changing.

The overarching standard in this regard is EN ISO 13849-1, promulgated by the International Organization for Standardization, which governs the safety of machinery and safety-related parts of control systems. (The EN in the standard stands ...