Listen in: Fieldbus Foundation demonstrates safety protocol
If you like fieldbus architecture for control, it's coming for safety too.
In mid-May, the Fieldbus Foundation (FF) unveiled a group of demonstration projects that provide proof of concept for its new safety instrumented functions. While the concept is exciting, it’s important to keep the reality in perspective. ( Click here to hear comments from Bill Tatum , marketing manager for FF. Timing: 1 minute.)
First, a bit of history: This demonstration is the latest step in a process that began in 2002 when FF launched its larger safety project. Progress moved along and reached a major milestone in December 2005, when TÜV Rheinland Industrie Service GmbH granted type approval for the FF safety instrumented system (SIS) protocol specifications. The foundation’s SIS protocol specification is suitable to fulfill safety integrity level (SIL) requirements of the IEC 61508 standard up to and including SIL 3.
With the TÜV type approval, FF technology has been extended to provide a comprehensive solution for safety instrumented functions (SIFs) in a wide range of industrial plant applications. The specifications enable manufacturers to build FF enabled devices in compliance with IEC 61508. Third-party test agencies such as TÜV will then certify that these devices are suitable for use in safety instrumented systems. As the number of approved devices grows, end users will be able to choose devices meeting the requirements of IEC 61511 from multiple suppliers, instead of being restricted to those designed specifically for a proprietary safety system platform.
What all this means in the most basic terms is that TÜV is satisfied that the protocol, as it is being developed, is capable of delivering messages within a control platform reliably enough that safety functions can depend on it and still offer sufficient protection. The protocol itself will be completed by the end of the year, according to the foundation. The demonstrations shown or discussed at the event were purpose-built bench-top prototypes using devices from a variety of suppliers in an effort to demonstrate interoperability. So far, there are no actual plant installations on any scale. Nonetheless, the demonstrations worked and proved all the critical functions that they set out to do.
So what does this mean? In a nutshell, when the protocol is implemented, it will allow you to install your safety instrumented systems using a fieldbus rather than hard wiring. This will help you enjoy all the benefits of fieldbus architecture, including wiring savings, improved diagnostic capabilities, shorter commissioning times, etc. ( Read an article from Control Engineering’s March 2008 issue to review fieldbus technology for process industries.) If you like FF H1 for your control systems, you’ll love FF SIF for all the same reasons. However, much has to happen before you will be able to realize those benefits.
Much of what FF is trying to do at this point is promote interest among the companies that will have to choose to adopt the platform and manufacture equipment to work within it. Unless there is a wide enough variety of instrumentation, logic solvers, and ancillary equipment to fill your needs, the protocol itself does not help. Supplier companies won’t make the hardware until they are convinced enough users will embrace the protocol and buy related equipment. This chicken-and-egg dilemma is an unfortunate but normal part of many new technology introductions.
Others have been down this safety-on-fieldbus trail before with mixed success. AS-Interface has safety functions that have been used widely for bit-level equipment, primarily in discrete manufacturing. ProfiSafe has also been available for several years. It has been adopted extensively in discrete applications, however it has never made much progress in process industries. So far, there is only a handful of certified instrumentation devices and little activity in that direction.
FF may be able to promote this more successfully, but adoption will surely take a while. A Shell Global Solutions representative said that he doesn’t anticipate any actual in-plant experiments until 2011. Other end users suggested that timeline may be a bit aggressive. In any case, wider deployments of this technology could easily be five years away. Process industries are conservative by nature, as slow adoption of fieldbus technology for regular control functions has shown. Safety is another matter that tends to be even more conservative.
Dave Glanzer, director of technology development for FF was a presenter in a Control Engineering Webcast on process safety , which is available for listening on demand.
—Peter Welander, process industries editor, PWelander@cfemedia.com ,
Process & Advanced Control Monthly
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