The more designers can integrate the safety functions of a control system with non-safety functions, the better the opportunity to minimise equipment redundancies, improve productivity and minimise costs. Hardware costs can be reduced because standard and safety portions of the application can share system components.
Economic factors – the aim to increase the bottom line without compromising safety – are driving the evolution of safety systems from older hard-wired solutions to contemporary networked integrated configurations.
Without the need for a separate safety controller, integrated safety systems use a single programming software package.
This eliminates the need to write and coordinate multiple programs on different controllers, simplifying software development and reducing training and support costs.
A single development environment also reduces the risk of 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.
Integration via CIP Safety
Historically, seamless communication was nearly impossible because no single network could integrate safety and standard control systems while also enabling the seamless transport of data across multiple plant-floor physical networks.
The introduction of the Common Industrial Protocol (CIP) – an application protocol for industrial networking that is independent of the physical network – was an important step in the evolution of integrated safety.
The CIP protocol provides a set of common services for control, configuration, collection and sharing across all of the CIP networks – DeviceNet, ControlNet and EtherNet/IP.
In the past, a safety risk 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 share data between the two types of applications.
This enables engineers, for example, to perform zone control where one zone of the machine is brought to a safe state while other zones 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 the human-machine interface (HMI).
With the insight provided by the integrated system, plant personnel can respond quickly to return the machine to full production.
CIP Safety also minimises the installation of 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 because it was difficult to hard-wire interlocks and relay-based safety logic into a complete automation system.
Engineers are now able to integrate their devices on common physical network segments and allow 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 gives users more design flexibility, allowing them to apply integrated safety functionality across a broader range of applications, including many midrange applications in which a larger controller previously would have been excessive or cost-prohibitive.
The new Allen-Bradley Compact GuardLogix programmable automation controller (PAC) from Rockwell Automation performs all machine control functions – including drive, motion and high-speed sequential control – while simultaneously executing SIL 2 and SIL 3 safety functions. Developed 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 the time and costs of design, configuration, start-up, and maintenance. With a single software program managing both safety and standard functionality, engineers no longer need to manually separate 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. The original separate hard-wired standard controllers on the plant’s 11 body-maker and trimming machines were replaced with 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 significant time.
With the integrated control architecture already in place, developing and expanding the system is much easier.
Improved control and 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 that can be pre-validated modules and 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 data from being altered accidentally or intentionally. 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 points to 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. In turn, these innovations will help keep workers and machines safer while boosting profits.
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