Technology Update: Integrated safety helps control system design
Advancing technologies and industry standards have made single-system platforms for safety and standard control easier and more cost-effective to design, implement, and maintain. Automation designers use recent technology advancements to deliver greater flexibility in how they implement safety systems to help streamline costs and improve productivity. Advice follows.
Tim Roback, Rockwell Automation
Single-system platforms for safety and standard control have become easier and more cost-effective than ever to design, implement and maintain, spurred by advancing technology and changes in industry standards. Automation designers use recent technology advancements to deliver greater flexibility in how they 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 nonsafety functions, the better the opportunity to minimize equipment redundancies, improve productivity, and minimize costs. Hardware costs can be decreased because standard and safety portions of the application can share system components.
Along with eliminating the need for a separate safety controller, integrated safety systems also use one programming software package. That 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.
One development environment also helps eliminate expensive redevelopment. For example, if a control engineer needs to scale from one line to three, the engineer just needs to port the necessary application from one to the next. Fewer components also mean smaller panel enclosures, saving money on control cabinets and floor space.
Network protocol for safety
CIP Safety, a network extension, helped integrate safety and standard control systems while enabling the seamless transport of data across multiple plant-floor physical networks. The Common Industrial Protocol (CIP), an application protocol for industrial networking, is independent of the physical network. The CIP protocol provides a set of common services for control, configuration, collection and sharing across CIP networks: DeviceNet, ControlNet, and EtherNet/IP.
In the past, 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 one network and share data between the safety and standard applications. This enables engineers to perform “zone control,” for example, where one zone of the machine is brought to a safe state while other zones continue to operate.
Unlike conventional systems, the integration of 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 gateways between each network. Before the development of safety networks, engineers often had to use smaller systems or minimize performance requirements since it was difficult to hard-wire interlocks and relay-based safety logic into a complete automation system. Now engineers can integrate devices on common physical network segments and allow safety and standard information to flow between devices and controllers.
Integrated safety can leverage benefits of a common control platform and provide a more compact, scalable form factor. This gives 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. (Sidebar provides an example of enabling technology.)
Integrated safety also offers the advantages of a common programming environment, which helps reduce design, configuration, startup, and maintenance time and costs. With one software program to manage 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 Revesby, Australia, aluminum can production plant. Previously, standard controllers on the plant’s 11 bodymaker and trimming machines were interlocked with a separate hard-wired safety control system. Now 11 individual integrated safety controllers manage them.
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. A combined 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 significant time. In addition, with the integrated control architecture already set up, developing and expanding the system is easier.
Control consistency, security
New software tools, such as high-integrity add-on instructions (AOIs), contribute to more accurate and efficient safety system designs. AOIs encapsulate code capable of being pre-validated modules and easily reused. This promotes consistency between projects, helps simplify debugging and troubleshooting, and minimizes the risk of coding errors. AOIs have a signature feature to help designers protect data from being accidentally or intentionally altered. The signature feature lets them know if an AOI definition has been modified. Revision control is critical in highly regulated industries where manufacturers need to maintain consistency to meet regulatory requirements and protect intellectual property.
More options and more flexibility to apply safety technology are expected 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 a concurrent and more natural part of the design process. These innovations will help keep personnel and machines safer while boosting the bottom line.
Safety PAC integrate drive, motion, sequential control
An example technology that integrates safety functions is the new Allen-Bradley Compact GuardLogix programmable automation controller (PAC) from Rockwell Automation. The compact controller integrates machine control functions: drive, motion, and high-speed sequential control with SIL2 and SIL3 (safety integrity level) functions. Ideal for midrange applications, the multidiscipline controller offers designers safety functionality previously found only in larger integrated systems.
Tim Roback is marketing manager, safety systems, control and visualization, Rockwell Automation; edited by Mark T. Hoske, Control Engineering, www.controleng.com, CFE Media.
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