Solutions for SIS and Foundation Fieldbus

I’m lucky enough to receive a copy of Andrew Bond’s Industrial Automation Insider newsletter each month through an Emerson subscription agreement. Andrew covers the happenings among the automation suppliers and standards bodies. You can also find some of Andrew’s writings on the ControlGlobal.com site.

In the November 2008 newsletter, one item that caught some attention around here was this nugget:

…first TÜV-approved SIL3 Foundation fieldbus safety valve controller to appear on the market. The device delivers status changes automatically via Foundation fieldbus and incorporates real time alarm management eliminating the need for external wiring or I/O cards.

I have the privilege of working in the vicinity of two very knowledgeable people with respect to process safety, Riyaz Ali and Mike Boudreaux.

Riyaz notes that the Foundation SIF specifications are still under development. In a recent Fieldbus Foundation release, it quotes ARC’s Larry O’Brien:

It is very clear that end users want this technology and are striving to include FF-SIF systems in their project specifications. Many major end users will probably be specifying FF-SIF systems for their new projects starting in 2011.

A September 2008 ARC whitepaper, Foundation Fieldbus Safety Instrumented Functions Forge the Future of Process Safety, provides background on the Foundation SIF standard advancement and its current draft status. Mike and Riyaz were present at the successful May 2008 Foundation SIF end user demonstration project in Amsterdam, and Mike shared his experiences with me. Riyaz also shared that one of the function blocks, the SIF_DO block, will not be available from the Fieldbus Foundation until the first half of 2009.

Many automation suppliers are developing products based on the current Foundation SIF draft, including Emerson. I asked Riyaz about the current solution Emerson provides until the standard is ratified. Riyaz responded:

The current solution for use in a Foundation fieldbus SIS application is to use the DVC6000f PD instrument. Several hundred units have been supplied worldwide to process manufacturers where partial stroke test scripts are run from host systems, such as the DeltaV system and AMS Device Manager.

In this application, process manufacturers use a solenoid valve operated by a hardwired digital output from the SIS logic solver.

Riyaz expects that until process manufacturers have sufficient experience, they will continue to use an independent solenoid valve to take the SIS valve to the fail state, while at the same time using a DVC6000f PD for partial stroke diagnostics using Foundation fieldbus through the basic process control system (BPCS).

DeltaV and DeltaV SIS systems with DVC6000f PD and DVC6000 SIS
Mike notes that both the DeltaV and DeltaV SIS systems are capable of performing these safety instrumented function predictive diagnostics. The DeltaV system is being used to perform partial stroke testing with the DVC6000f PD using Foundation fieldbus communications. The DeltaV SIS system is being used to automate partial stroke testing with the DVC6000 SIS safety valve controller using HART communications. This additional diagnostic coverage assists process manufacturers with their IEC 61511 safety lifecycle efforts.

Using diagnostics enabled by Foundation fieldbus and HART communications, the DeltaV and DeltaV SIS systems with DVC6000 digital valve controllers can provide many of the benefits today that are promised by Foundation SIF in the future.

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Update: Next week is the Thanksgiving holidays in the U.S. and I’ll not be posting. We’ll be upgrading our version of Movable Type software. Wish us luck!

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