How do remote I/O and fieldbus compare?

In this short article, we highlight some of the statements made in the "Fieldbus and Remote I/O System comparison" report. And if they pique your interest, you can visit the Pepperl + Fuchs website and download the 36 page compendium

At the 2001 Interkama exhibition, the "Fieldbus and Remote I/O System Comparison" (FuRIOS) study was initiated by Aventis, Infraserve, IGR and a group of suppliers to see if fieldbus offered significant savings over remote I/O systems when applied to a "real plant". The real plant in question was the Aventis Pharma (D712), that had been planned and built utilising Remote I/O.

If you visit the Pepperl+Fuchs website www.fieldconnex.info, you can download the 36 page FuRIOS compendium that comprises the FuRIOS study, with associated articles and presentations. In the words of Prof. Dr.-Ing Birgit Vogel-Heuser, "This compendium provides you, as a reader and user, with all the results of this supplier-independent study in detail."

In comparing the remote I/O system already installed on D712, and a comparable fieldbus system, no changes were made to the requirement that would facilitate or obstruct the comparison, and wherever possible use of the same field devices, or those with similar characteristics were used. Therefore the comparison was a 1:1 reflection of the plant using remote I/O, and a comment from the study said: "if used properly, fieldbus technology will lead to further cost savings and increased benefits from those already seen."

Added expense The solution for the fieldbus system was to use a trunk designed in the ignition class "increased safety" Ex e, while the designated connection to the field devices via a fieldbus barrier have the ignition class "intrinsically safe" Ex i. A comment about this design stated: "A rough estimate indicated that if the fieldbus lines had been totally intrinsically safe, then the fieldbus solution would have been considerably more expensive than the solution with remote I/O". The study thought this statement was so important that they repeated it by saying: "The Fieldbus solution would not have been economically feasible without the fieldbus barriers!"

The study highlights in great detail the costs for all relevant aspects of the project, and the financial implication was a saving of 3.6% when using the fieldbus system, and statements made were that this was a very conservative estimate.

The opening statement summarises the study by saying: "In contrast to the remote I/O systems, which have reached a wide market penetration within a few years, the technically superior fieldbus does not see a market breakthrough, yet it is frequently said that remote I/O systems are often seen as an interim solution. The result of the study is that the fieldbus is superior to remote I/O in many aspects: it brings further savings in investments, accelerates project execution and startup and so provides the migration to a new technological platform that enables the development of innovative and attractive instruments."

Pepperl + Fuchs

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