Fieldbus and Safety Instrumented Systems-implementing Safety Instrumented Functions in Fieldbus


Miami Dec 19, 2011– There has been a lot of buzz lately about Safety Instrumented Systems utilizing Fieldbus technology, or rather having Fieldbus systems also have Safety Instrumented System functionality. As those of you in the process industries probably know, Safety Instrumented Systems are special automation and control systems that ensure that plants having hazardous processes will be adequately protected and can be shut down safely in case of any process upsets or untoward incidents. Safety Instrumented Systems protect people, assets and the environment, in case of unwanted deviations, failures of the main process control system or equipment and other undesirable and unplanned events. Safety Instrumented Systems (known as SIS for short) are also called by other names such as Safety Shutdown Systems, Emergency Shutdown Systems (ESD) and similar terms.

Till recently, the SIS and the main plant automation systems (also known as BPCS-Basic Process Control Systems, which could be DCS or PLC based systems) used to be completely separate systems. The hardware, software and programming of both systems (BPCS and SIS) used to be totally different, like chalk and cheese. Later on, we began to see the introduction of integrated BPCS-SIS systems, where the BPCS and SIS were not totally different, but shared some of the hardware, user interface, communications network, etc. Though the programming was similar, the SIS programming was kept secure and separate with the aid of special functions in software.

Now we are seeing an even more integrated approach, in Fieldbus systems. For example FOUNDATION Fieldbus (which is one of the many Fieldbus protocols in use today) has introduced special Safety Instrumented Functions, that could be implemented in FOUNDATION Fieldbus based systems. They call this FF-SIF and this concept was presented in the FOUNDATION Fieldbus general assemby held sometime back. It is being done in a pilot project in Saudi Aramco at their Dhahran site. FOUNDATION Fieldbus recently announced that updated device development solutions for its Foundation Fieldbus for Safety Instrumented Functions (FF-SIF) technology are available. The new release includes the FF-SIF Technical Specification, Foundation for SIF Interoperability Test Kit (SIF ITK), and DD Library.

As many of you know, Fieldbus technology is rapidly gaining ground in the process industries and if the FF-SIF concept is accepted by user industries, it will lend a new meaning to the word “integrated” BPCS-SIS. In fact the distinction will get blurred. What FF-SIF proposes is to have Safety Instrumented Function blocks that will be resident in the smart devices in the field (like a humble pressure transmitter for instance) and thus can be used to implement Safety functions.This means that plants who decide to implement Fieldbus even on a smaller scale can have the power of a Safety Instrumented System, without paying a steep price for creating a separate system, programming, wiring, etc,etc. All they have to do is to utilize the SIF blocks that will presumably be available.  Since the user industries main aim is to implement Safety functions in an effective manner, this seems to be a good deal for them.

If all this sounds like being too complicated, you need not worry. Simply download the Fieldbus training course from Abhisam Software that we hear is being released in Q1 of 2012 and you will be fine, fully updated and conversant with all this new technology.

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