Protecting Plant Assets with Industrial Safety Networks
EP Editorial Staff | February 21, 2014
Revolutionary technologies safeguard your plant assets and everything associated with their performance. How much do you know about them?
By Jane Alexander, Deputy Editor
Most end-users would rather not deal with the costly damages to people, property and environment that can come from running equipment without reliable, integrated safety features.
That said, what do you really know about the systems your operations count on to stop, shut off or shutdown machinery and/or processes in case of emergencies? If you’re not already familiar with them, the capabilities of today’s state-of-the-art industrial safety networks might surprise you.
The good news for plant managers is that safety and productivity no longer need to be viewed as mutually exclusive: The pursuit of those goals has been linked not just by advancements in safety networks themselves, but in the protocols that enable them. Deployment of these cutting-edge technologies can provide significant benefits for an enterprise. Consider the following:
Developed by PROFIBUS & PROFINET International (PI), IEC 61508-compliant PROFIsafe has become an international standard (IEC 61784-3-3). The technology is suited for use in all sectors of discrete manufacturing and process automation where, according to PI, independent of the communication method, it provides cost-effective and flexible functional safety. PROFIsafe covers the entire communication path—from the sensor over the network to the controller—and integrates safety and standard communication on one cable.
PI uses the term “threefold quantum leap” in describing PROFIsafe’s introduction into plants:
- Moving from safety-related relay logic to safe programmable logic
- Moving from multi-wire to functional safe serial communication
- Moving from isolated to cooperating safety-related devices
That leap has translated into returns that go well beyond reduced wiring and associated costs: A range of PROFIsafe-supported products from different manufacturers enable easy, cost-effective system configuration. Training, documentation and maintenance are required for just one bus technology. Standard and safety-related applications can be programmed with a single tool and certified function blocks. The technology offers considerable flexibility in configurations, replacements of existing relay technology and installation retrofits.
For an example of the PROFIsafe value proposition,
PI North America’s Executive Director Michael J. Bryant points to the noteworthy and widely reported success of KUKA Flexible Production Systems, a producer of automated/robotic production systems for car bodies and chassis. Several years ago, as it worked to become a Tier I supplier to Chrysler, KUKA needed to design a body shop based on the DBOOM (Design, Build, Own, Operate and Maintain) philosophy. Part of that project involved overcoming drawbacks in traditional automotive-market machine-safety systems, among them remote emergency-stop buttons and safety-gate switches, redundant relays and extensive, complicated, redundantly hard-wired circuitry. Knowing there had to be a better alternative, KUKA turned to a PROFIBUS-based processor that communicates to all field components, including safety devices, via an inexpensive two-wire cable. Leveraging this PROFIsafe-enabled technology, the company was able to combine machine safety and standard machine control on a single field bus—a move that reduced machine-safety components by 85%, while increasing machine safety.
Common Industrial Protocol (CIP) and its network adaptations EtherNet/IP, DeviceNet, CompoNet and ControlNet reflect the core technology and interest of the Open DeviceNet Vendors Association (ODVA). Since its founding in 1995, the association has released a number of network extensions that incorporate “future-proof” CIP technology, including CIP Safety. The first CIP Safety protocol (for DeviceNet) was introduced in 2005. CIP Safety for EtherNet/IP was rolled out in 2006. (Developed by Rockwell Automation for use in manufacturing-related automation applications, EtherNet/IP had been launched in 2001.)
CIP Safety lets safety devices coexist with standard control devices on the same CIP Network—with or without a Safety PLC. In this environment, safety sensors can operate alongside variable speed drives, safety controllers with standard PLCs and proximity switches. That means, regardless of what combination of devices is used, the integrity of the safety control loop can’t be affected by any of the standard control devices.
By allowing a plant to automate safety through the same network it uses for standard control, CIP Safety provides a number of benefits. Certified for Safety Integrity Level (SIL) 3 according to IEC 61508, the end-to-end CIP Safety protocol makes end nodes responsible for ensuring safety (as opposed to bridges, routers or intermediate nodes). ODVA says this design “ensures that standard, easy-to-configure communication devices can be used in place of costly, maintenance-intensive safety-certified gateways, thus reducing installation, training, and maintenance time.” Scalable integration of multiple network-safety segments results in shorter loop closure times and tighter safety exclusion zones.
ODVA announced in late 2013 that future editions of the CIP Safety Specification would include services for safe motion applications. As a result, users will be able to deploy networked motion-control systems through EtherNet/IP and Sercos III in applications that require functions like safe torque-off and safety-limited positioning.
According to process-industry-focused Fieldbus Foundation, its open, nonproprietary FOUNDATION architecture provides a protocol for control and instrumentation systems in which each device has its own “intelligence” and communicates via an all-digital, serial, two-way system. Not only can this type of platform help end-users cut capital and operating costs, as demonstrated by FOUNDATION for Safety Instrumented Functions (FF-SIF), it’s also suited to advancing safety. Meeting the requirements of IEC 51508 up to, and including, SIL 3, FF-SIF offers advanced diagnostic capabilities in a reduced footprint, at a reduced installed cost—things that process-industry end-users have told the Fieldbus Foundation they need.
Discussing those needs, Larry O’Brien, Marketing Director of the Fieldbus Foundation, explains most process safety systems fail because of the valve or device in the safety instrumented system. The value of digital process-safety networks, he says, is that they provide advanced diagnostics immediately.
O’Brien also highlights the advantages of the reduced fieldbus-system footprint: “It takes up less room in the control house.“ This can be quite an issue, he says, for operations that need to modernize their safety systems—especially if they don’t have enough existing rack room to keep an old system running while a new one is being installed.
FF-SIF technology has gone through substantial beta testing since its introduction several years ago—and is expected to show up in the marketplace soon. Its technical specifications now include support for FOUNDATION fieldbus H1 (31.25 bit/s) dual-mode devices employing powerful field-diagnostics capabilities. Translation: Instrumentation manufacturers can bring new safety products to market without having to design two entirely different devices. Developers can implement H1 devices with SIF features activated or de-activated. More important, end-user operations will only need to stock one type of product for use as either a process device or a safety device. MT&AP
PROFIBUS and PROFINET International (PI) is responsible for PROFIBUS and PROFINET, two important enabling technologies in automation. Its global network of more than 1400 member companies includes vendors, developers, system integrators and end-users with a common interest in promoting, supporting and using PROFIBUS and PROFINET. For more details, visit www.profibus.com or
www.us.profinet.com. (While you’re there, consider downloading the PROFINEWS App for iPhones, iPads and Android devices.) And if you enjoy learning about technologies via video presentations, check out the following:
The Open DeviceNet Vendors Association (ODVA) is made up of members from the world’s automation companies. Its focus is on advancing open, interoperable information and communication technologies in industrial automation and contributing to sustainability and prosperity of the global community by transforming the model for information and communication technology in the industrial ecosystem. ODVA embraces adoption, wherever possible, of commercial-off-the-shelf (COTS) and standard, unmodified Internet and Ethernet technologies. According to the association, that’s a principle exemplified by EtherNet/IP. For more information, visit www.odva.org.
The Fieldbus Foundation is a global not-for-profit corporation supported by leading process end-users and automation companies. Within the Foundation, members work together to develop an automation infrastructure that provides process integrity, business intelligence and open scalable integration in a managed environment. According to the organization, its technology provides end-users with the “Freedom to Choose” best-in-class, interoperable control products from their suppliers of choice and the “Power to Integrate” control systems, subsystems and devices across the plant enterprise.” For more information, visit www.fieldbus.org.
The HART Communication Foundation is the technology owner and standards-setting body for the HART Communication Protocol. Celebrating 20 years of serving the process industry and its 300+ member companies, the Foundation, instrumentation manufacturers and users around the globe continue to use this technology, making it the world’s most used field communication protocol in the industry. Membership is open to suppliers and users who are interested in the use of HART technology. For more information,
A Matter of Opinion: HART in Safety Networks?
HART (Highway Addressable Remote Transducer) Protocol is a global standard for bi-directional communication of digital information between intelligent field instruments and host systems via analog signals or wireless. A host can be any software application from a technician’s handheld device or laptop, to a plant’s process-control, asset-management, safety or other system, using any control platform.
As the technology’s owner, standards-setting body and central authority, the HART Communication Foundation supports the protocol worldwide and ensures that both the original and WirelessHART versions of it remain open and free for use by the industry.According to the Foundation, most automation networks in operation around the world today are based on traditional 4-20mA analog wiring. Given that fact, it’s easy to see why the analog-based HART protocol has such a massive footprint in industry. Assessing its penetration in industrial safety networks is more complex.
Chuck Micallef, the Foundation’s Director of Marketing, says its members report the majority of instrumentation shipped in the past 5-10 years as being HART-enabled. “We’ve also been told,” he says, “that the majority of safety systems sold over the past 5-10 years have offered HART capability and that many customers have selected it and are using it.”
As for why all customers don’t opt to use HART diagnostics with their safety systems, Micallef suggests that host or control/safety systems might be the limiting factor (in light of the large installed populations of those systems that aren’t HART-enabled). Still, he notes, several suppliers offer alarm monitors and converters that allow leveraging of HART diagnostics while connected to a “non-smart” host.
Micallef says the Foundation is in the early states of investigating how intelligent-device information delivered to a safety system through HART protocol can add more value to the Safety Application, device SIL rating or other certifications or validations. “It’s possible,” he concludes, “that the information from the smart instruments currently attached to a safety system can indeed help with the safety requirements.” If you have an opinion on the matter, email Micallef at: email@example.com.