Spurred by advancing technology and changes in industry standards, single-system platforms for safety and standard control have become easier and more cost-effective than ever to design, implement and maintain. Recent technical improvements now provide automation designers greater flexibility in how they can implement safety systems to help streamline costs and improve productivity.
Economic factors – namely the aim to increase the bottom line without losing sight of safety – are driving the evolution of safety systems, from older hardwired, to networked, to contemporary integrated configurations. The more designers can integrate the innovative safety functions of a control system with non-safety functions, the better the opportunity to minimise equipment redundancies, improve productivity and minimise costs. Sharing system components between an application’s standard and safety portions helps decrease hardware costs.
Along with eliminating the need for a separate safety controller, integrated safety systems also use a single programming software package. This can eliminate the need to write and coordinate multiple programs on different controllers, which in turn can simplify application programming and help reduce training and support costs.
In addition, a single development environment helps eliminate expensive redevelopment. For example, if a control engineer needs to scale from one line to three, it’s as simple as porting the necessary application from one to the next. Fewer components also mean smaller panel enclosures, saving money on control cabinets and floor space.
CIP safety allows integration
Another important step in the evolution of integrated safety occurred with the introduction of CIP (common industrial protocol) safety. In the past, seamless communication was nearly impossible because no single network was able to integrate safety and standard control systems while also enabling the seamless transport of data across multiple plant-floor physical networks. With the CIP (an application protocol for industrial networking that is independent of the physical network) this changed. The CIP protocol provides a set of common services for control, configuration, collection and sharing across all CIP networks, DeviceNet, ControlNet and Ethernet/IP.
Previously, a safety event in one section of a machine could result in the entire machine shutting down because the standard system had limited knowledge of the safety event. CIP safety allows the control and safety systems to coexist on the same network and to share data between the safety and standard applications. This enables engineers to perform ‘zone control,’ where one zone of the machine is brought to a safe state while the others continue to operate.
Unlike conventional systems, the integration of the safety and standard control systems provides operators and maintenance personnel with visibility to all machine events – including safety events – via the machine or system HMI. With the knowledge and insight provided by the integrated system, plant personnel can respond quickly to return the machine to full production.
CIP safety also helps eliminate the need to install expensive and difficult-to-maintain gateways between each network. Before the development of safety networks, engineers often had to use smaller systems or minimise their performance requirements since it was difficult to hard-wire interlocks and relay-based safety logic into a complete automation system. Now these devices can be integrated on common physical network segments, allowing safety and standard information to flow between devices and controllers.
Next generation safety control
Recent developments in integrated safety involve leveraging the benefits of a common control platform and extending them into a more compact, scalable form factor. This provides users more design flexibility, allowing them to apply integrated safety functionality across a broader range of applications, including many midrange applications where a larger controller previously would have been excessive or cost-prohibitive.
According to Rockwell a case in point is its new Allen-Bradley Compact GuardLogix programmable automation controller (PAC). This compact controller offers integration by performing all machine control functions – including drive, motion and high-speed sequential control – while simultaneously executing SIL 2 and SIL 3 safety functions. Ideal for midrange applications, the multidiscipline controller offers designers safety functionality previously found only in larger integrated systems.
Integrated safety also offers the advantages of a common programming environment, which helps reduce design, configuration, start-up and maintenance time and costs. With a single software program managing both safety and standard functionality, engineers no longer need to manually manage the separation of standard and safety memory or worry about partitioning logic to isolate safety.
More streamlined designs
These design productivity benefits led Amcor, a global packaging manufacturer; to implement a new integrated safety solution at its aluminium can production plant in Australia. Initially, standard controllers on the plant’s 11 body maker and trimming machines were interlocked with a separate hard-wired safety control system. Now they are managed by 11 individual, integrated safety controllers.
An Ethernet/IP connection provides interlocking between machines and links the integrated safety controllers to the factory’s supervisory control and data acquisition (scada) system. The combination of distributed I/O and a CIP safety network helped reduce site installation and wiring time.
The integrated development environment allowed engineers to develop the standard and safety control system code concurrently, which saved a significant amount of time. In addition, with the integrated control architecture already set up, developing and expanding the system is much easier.
Improved control, consistency
New software tools, such as high-integrity add-on instructions (AOIs), are contributing to even more accurate and efficient safety system designs. AOIs encapsulate code for common routines into pre-validated modules that can be easily reused. This promotes consistency between projects, helps simplify debugging and troubleshooting, and minimises the risk of coding errors.
These high-integrity AOIs employ a signature feature to help designers protect their data from being accidentally or intentionally altered. The signature feature lets them know whether an AOI definition has been modified. This revision control capability is critical in highly regulated industries where manufacturers need to maintain consistency to meet regulatory requirements and protect intellectual property.
The future of integrated safety suggests more options and more flexibility to apply safety technology to meet specific needs. As safety and standard components continue to become more seamlessly integrated into control system designs, implementing safety will no longer be a separate discipline, but rather a concurrent and more natural part of the design process. These innovations in turn will help keep personnel and machines safer, while boosting the bottom line.
For more information contact Jeff Sandison, Rockwell Automation, +27 (0)11 654 9700, [email protected], www.rockwellautomation.co.za
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