Ready or not, Intelligent Safety Networks have arrived

Intelligent Safety Network technology is proven, tested and here today. New technical advances in automation hardware and software, as well as revised safety standards are driving implementation of intelligent and programmable safety solutions. In fact, much of the architecture for intelligent safety networking is already here.

By Ed Nabrotzky, Woodhead Industries, Inc. November 1, 2006

Intelligent Safety Network technology is proven, tested and here today. New technical advances in automation hardware and software, as well as revised safety standards are driving implementation of intelligent and programmable safety solutions. In fact, much of the architecture for intelligent safety networking is already here. For example, virtually all new automotive robot applications use industrial I/O networks such as DeviceNet, ControlNet, Profibus, Interbus, EtherNet/IP, etc. Market adoption of open networks is continuing.

Recognized as a powerful new business tool, ISNs have become one of the fastest growing segments of the industrial automation market. In addition to improving safety performance, limiting liability exposure and helping improve a company’s public image, ISNs also deliver hard benefits such as reducing manufacturing KPIs. Moreover, harmonization of international safety standards (such as IEC 61508 and EN 954) has produced easier to understand regulations for machine OEMs.

Implement early

As with the transition from hard-wired to soft-wired automation systems, ISN implementation will take time and require changes in traditional operating procedures. But at some point — probably sooner than later — the shift will gather momentum, and become inevitable for equipment and machinery suppliers. Implementing ISN technology now will make that inevitable shift smoother, more efficient and ultimately more profitable. If your company is not yet planning for ISN implementation, you are already behind the curve.

ISN technology has already been widely implemented in Europe and is gaining more traction in North America. The development of harmonized global standards for ISNs is well underway, which will help speed adoption and lower implementation costs. Developing countries such as China have not traditionally used the same safety standards as developed countries. However, they are likely to come under more pressure to implement ISNs as they do more export business and invest in the same advanced machinery used in developed countries.

Some companies have cut wiring costs by half while reducing the number of operators involved in safety operations by 75%. Area safety operations in a manufacturing plant can be scaled down to one or two operators who activate emergency switches that are run by the network, thus improving cost efficiency.

Putting ISNs to work

Now that leading vendors have either introduced or are developing platforms for Intelligent Safety Networks, many manufacturers in both discrete and process industries are considering making the transition. This means migrating from a traditional discrete PLC-based safety controller — in which every sensing device must be hard-wired to alarms or emergency stop devices, to the next-generation ISN technology — in which both safety and process control can operate on the same network.

With an ISN, those same devices, such as optical sensors, emergency push-buttons, floor mats and guarding switches, are integrated into the central network control cabling infrastructure. This eliminates the need for a separate safety controller and dramatically reduces the volume and related expense of copper wiring. In addition, ISNs provide intelligent monitoring and control of physical and machine hazards that can be more easily configured to shut down processes by zone, depending on the existing hazard, rather than shutting down an entire production line.

In a large automated material handling system, if a safety zone in the conveyor area is momentarily violated, only that portion of the system would close down and the upstream process is automatically adjusted. This gives workers enough time to rectify the problem and restart the conveyor before impacting processes downstream.

In robotic work cells and assembly lines, traditional safety systems require hard-wiring of multiple sensors (e.g., light-curtains and cages) in multiple places to provide emergency shut-off points in machine danger zones. The ISN system can be programmed more precisely to ‘know’ where machine danger zones are as it runs through its motion cycle. It also knows where people are situated and can react appropriately.

In transitioning to ISN technology, many users can actually take a phased implementation approach. To start, they can continue to use their existing safety sensors that are now networked into the central system. This produces the immediate benefit of reducing copper cabling materials and installation costs.

In the next phase, as the reliability and effectiveness of the centralized ISN is realized, plant engineers will find that some of the switches, fences, guards and emergency push-buttons can be eliminated, thus reducing the cost of installing and maintaining these physical safety devices. They will likely find that manpower and labor costs required to monitor safety throughout the production facility are significantly reduced.

Ultimately, they may also discover that integrating the ISN directly into the process control network results in increased production uptime, with fewer occurrences of unplanned downtime. Thus, it is in this final phase of implementation that the full return on the ISN investment can be realized.

Getting rid of separate networks

Separate controller and safety network architectures are becoming obsolete thanks to the emergence of dual-purpose safety controllers that handle both monitoring and control of safety and non-safety functions with a single CPU. ISNs are now available for motion control products without requiring external hardware.

ISN technology lets operators perform essential tasks such as inspecting, aligning, cleaning and changing out worn tools that previously could only be performed when electrical power was completely cut off from drive mechanisms. By allowing safe access to machinery with power still available, ISNs facilitate faster restarts, machine accuracy (due to elimination of repositioning), reduced brake wear and shorter machine downtime. As a result, overall machine efficiency can be improved, sometimes dramatically.

Documenting compliance with accepted industry safety practices becomes easier with ISNs, since electronic records are maintained by the system. Also, effective safety systems that allow easier access to machines by operators make it less likely that controls will be overridden by frustrated operators. ISNs help cut downtime by allowing operators to quickly troubleshoot machine stoppages — especially nuisance trips — and get production lines back up faster than with traditional hardwired safety systems.

One of the barriers to implementing ISNs — outdated safety standards — is in the process of being removed. For example, recent changes to NFPA 79 in the United States and IEC-60204 permit non-hardwired components to be used in emergency stop functions. These and other revised safety standards allow integration of ISNs into various drive mechanisms. This, in turn, allows manufacturers to design machines that continue to rotate at safe speeds while the operator is in the work area.