Keywords: Safety Solutions, Industrial Networks, OMAC.
One of the most significant automation trends in recent years has been the transformation of machine safety technology from hard-wired, standalone components to sophisticated networked systems. Today, modern safety solutions link intelligent safety devices via open networks. Safety information is exchanged via safe protocols that implement measures to ensure the level of data integrity necessary to meet the requirements of international safety standards.
Unfortunately for industry users, parallel developments have resulted in a variety of incompatible solutions. However, an initiative is now under way to standardize a single safety protocol - openSAFETY - across the most popular Ethernet-based networks. This would be a far more difficult endeavor were it not for the backing of major end-users and the support of an industrial consortium. This ARC View takes a "behind-the-scenes" look at this initiative.
The Evolution of Networked Safety
In the last decade, converging safety standards paved the way for the development of integrated safety solutions in which components communicate with other intelligent devices via industrial networks. This results in a host of user benefits, including more flexible architectures, more information for diagnosing safety trips, and integration of both safety and non-safety devices in a single networked environment.
As Ethernet-based industrial networks grew in popularity, safety protocols were implemented and certified by each responsible network consortium. Currently, the most popular networks with safety protocols are Profinet (PROFIsafe), EtherNet/IP (CIP Safety), POWERLINK (openSAFETY), and EtherCAT (Safety over EtherCAT). The benefits of using networked safety include:
Elimination of rigid hard-wired systems,
Fast re-configuration of existing networks thanks to flexible topologies (devices can be added and subtracted easily),
Remote configuration and troubleshooting of networked safety devices,
Access to device status data for fast diagnostics (useful for analyzing nuisance trips)
The openSAFETY Initiative
The openSAFETY protocol was originally developed for Ethernet POWERLINK by the Ethernet POWERLINK Standardization Group (EPSG). After several key customers expressed interest in interfacing with other safety PLCs, EPSG launched the current initiative to extend openSAFETY to other industrial Ethernet networks, including Profinet, EtherNet/IP, Modbus TCP, and Sercos III. EPSG specified the proof-of-concept tests while member companies B&R and Schneider Electric conducted lab tests.
To implement openSAFETY on other networks, the EPSG takes advantage of the fact that most networks support a layered network model, defining distinct layers of interaction. The openSAFETY application layer encapsulates safety messages over a network in a network-agnostic fashion. This enables complete independence from the underlying transport layer, allowing a common application to utilize a variety of networks.
End Users See Benefits of a Single Safety Protocol
While safety protocols allow for seamless device-to-device communication of critical safety information, many end users still face a real-world dilemma. Despite efforts to standardize industrial automation architectures across multiple plants, many plants still use several brands of incompatible systems, often deployed in the same plant or even on the same line. While information from different systems can be shared via open standards like OPC, differing safety protocols prevent a fast and secure way of exchanging safety-related information among different devices.
Nestlé S.A., a leading food & beverage producer, has identified key benefits of using a single safety protocol and is actively investigating the openSAFETY initiative. For Nestlé, these benefits include improving overall line safety and overall equipment effectiveness (OEE) due to better management of safety events at the line level. According to the company, the safety protocol doesn't have to be implemented down to the device level; it is sufficient for machine and line controllers to understand and react to a single protocol across a standard Ethernet TCP/IP network regardless of the type or brand of controller in use.
According to Nestlé, the lack of a common, machine-to-machine safety protocol reduces the value of having an integrated line. All machines on the line need to be able to react to a safety event, no matter where it occurs. For example, depending on the severity of a safety event, other machines in the line may be shut down or placed in a suspended state for a faster restart (heater bars remain on, axes remain synchronized, etc.). The key here is to strike a balance between energy consumption and restart efficiency, while maintaining safe conditions for the machines and operators. By using just a single safety protocol, Nestlé expects to improve operator safety, machine safety and OEE.
Besides Nestlé, a variety of other end users are investigating the openSAFETY initiative. These include Pactiv, an American food-packaging provider, and Rügenwalder Mühle, a German process meat producer. Other food & beverage producers like Kraft Foods, Pepsico, Arla Foods, and M&M Mars are also taking a closer look at the potential benefits of the technology.
OMAC and PackSafety
The Organization for Machine Automation and Control (OMAC) is an industrial consortium that defines hardware-independent guidelines for open control in packaging machines and machine tools. OMAC's various workgroups define requirements and issue guidelines ranging from tag and state naming conventions to machine connectivity.
Last year, OMAC founded the PackSafety committee and charged it with the task of identifying safety requirements that can be turned into OMAC guidelines for machine builders. Fabrice Bertin, a Nestlé employee, chairs the workgroup, which includes representatives from other large end-users, such as Pepsico, as well as several machine builders.
In early 2012, the PackSafety committee defined two primary goals: 1) maximize safe operational efficiency through the use of the latest safety technology, and 2) reduce line integration effort by providing safety interface definitions. The committee also set milestones that foresee the release of a first draft specification by the end of 2012. A top priority is likely to be the evaluation of a single safety protocol.
The Politics of Safety
As the fieldbus wars of the past have demonstrated, while industrial consortia provide real benefits through open technologies, they are still driven by commercial interests. openSAFETY is no exception. It won't be easy to convince automation suppliers to add support for an additional safety protocol to key products. On the other hand, these same suppliers tend to be good listeners when it comes to the demands of large, global accounts backed up by industry standards or guidelines. For its part, EPSG says it's prepared to help automation suppliers when they are ready to make the move. This support aims to reduce the cost and effort needed to implement openSAFETY by requiring no license fees (open source), eliminating legal hurdles (no contract to be signed), and providing technical elements (available TÜV certified stack for openSAFETY master and slave). But to make this happen, the burden is on the large end-users to convince their traditional controls suppliers support this new standard.
In many respects, the openSAFETY initiative represents a challenge to the automation industry. While the automation industry boasts about open technologies, ours are not nearly as open and ubiquitous as those enjoyed in the IT world. With so many flavors of industrial networks to choose from, deciding on a single, ubiquitous safety protocol for all networks may be a step in the direction of true openness.
All signed-in ARC Advisory Group clients can view the complete report in pdf format at this Link
If you would like to buy this report or obtain information about how to become a client, please Request ARC Info