A year ago, an A-list group of automation users and equipment suppliers gathered in Amsterdam. Though there are many reasons for going to Amsterdam, these folks came to witness a demonstration of the Foundation Fieldbus Safety Instrumented Functions (FF-SIF) protocol at the Shell Global Solutions technology center. Promulgated by the Fieldbus Foundation, FF-SIF is an attempt to bring the advantages of fieldbus technology, with its nonproprietary two-way digital communication, to the process safety realm, facilitating a high degree of integration between process control and safety. Products for the demo were supplied by a host of vendors, including ABB, Emerson, Siemens and Yokogawa.

Among the many devices tested with the new protocol were Foundation Fieldbus-enabled safety valves with Partial Stroke Testing (PST) capability. PST is one of the key innovations in safety devices in recent years. Traditionally, shutdown valves have been operated by pneumatics or solenoids, and have had only two positions: open or closed. Because they were used so infrequently, they often became stuck, and troubleshooting or testing them was a time-consuming, manual operation.

The advent of valve positioners made partial-stroke testing, or checking the valve by moving it a small degree, feasible. Initially, these were too expensive for widespread use, but in the last decade, the cost of valve positioners has fallen dramatically, making their use not only feasible but highly affordable.

Other areas of focus included an array of pressure, level, temperature and diagnostic devices. Importantly, the demo also evaluated system integration capabilities with asset management and Basic Process Control System (BPCS) platforms.

Audun Gjerde, consultant, instrumentation and plant automation, of Shell Global Solutions, conducted the demonstration, and he liked what he saw. By employing FF-SIF, he said, “Shell expects enhanced diagnostics through a fully integrated asset management system. We also anticipate less testing of final elements, thanks to smart testing and diagnostics, as well as online testing and partial stroke testing. This will result in early detection of dangerous device failures—and fewer spurious trips.” Improved testing and diagnostics, he notes, should enable plants to run for longer periods of time without shutting down for testing.

New era?

The protocol has received approval from accrediting agency TÜV Anlagentechnik GmbH, and the Fieldbus Foundation confidently predicts that suppliers will be submitting FF-SIF compliant devices for TÜV approval this year, with many major end-users specifying FF-SIF systems for new projects by 2011. All of this is good news for FF-SIF backers, but beyond that, it’s also another indication of a major change underway in the world of safety systems.

To appreciate the extent of this change, it helps to step back a bit in time. Traditionally, safety was a stand-alone system, which meant different and roughly parallel human-machine interfaces (HMIs), configuration tools, communications, data and event historians, asset management and other requirements for a plant’s safety instrumented system (SIS) and BPCS. This separation was a requirement not only for process systems, such as those now being addressed with FF-SIF, but in the discrete manufacturing world as well.

“The safety solution was completely separate from the automation system,” says Dan Hornbeck, manager, safety business development, for vendor Rockwell Automation Inc., Milwaukee. “Also contributing to this reactive and separate approach were the limitations of safety technology, which often required machines to come to a full stop and be in a “safe state” for repair, maintenance or any time operator access was needed.” Because this downtime decreased productivity, operators and maintenance personnel often felt pressure to bypass the safety system, risking their own safety in the process.

“Such risks are no longer needed or acceptable, thanks to progressive, enforced global standards, significant technological innovation and risk management,” Hornbeck says.

These technological innovations have come in two forms. Some are device focused and driven by the growth of digital technology, such as PST and the “safety zones” that can be engineered into today’s production lines and equipment, and then managed independently, allowing maintenance without shutting down an entire system.

There have also been safety developments at the input/output (I/O) device level in discrete manufacturing. Consider the TwinSafe products from Beckhoff Automation LLC, Burnsville, Minn., which are designed to allow machine builders and end-users to create safety systems (e-stops, light curtains, safety doors, and other devices) using safe I/O terminals that can be used without a dedicated safety programmable logic controller (PLC).

The other involves advances in networking and communications technology, and has made possible a networked and integrated approach to safety. This development, notes Hornbeck, has been driven by the need for greater efficiency and lower ...