Process engineering: In the trenches of Fieldbus War II

Like the 20th Century’s Great Conflict, the first Fieldbus War never really ended. But what will the outcome be this time? This article from CONTROL makes an educated prediction on how the battle may turn out.

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The three organizations that use Device Description (DD) technology as the basis for the interoperability of their devices—HART Foundation, Fieldbus Foundation and Profibus Nutzerorganisation e.V. (PA component)—recently announced the release of EDDL (Elementary Device Description Language) Phase 1 as a means to provide users with a number of enhancements to the ability of their devices to represent more data intense information such as tables, graphs and images.

This is only one of the battlegrounds at present, since the bar on the fieldbus wars of the past has been raised to the next layer or two of the enterprise. The war is now taking place not only at the control level, layer 2, with the various flavors of Ethernet, it is also happening at the layer 2/layer 3 interface. This is where information available from data rich environments is being integrated into the asset management solutions being offered not only by each of the automation system suppliers but also the ”big guns” such as SAP.

One theatre of war identified by all the fieldbus organizations is some form of safety-bus. In the case of HART this is not a factor because HART information is superimposed on the analog signal and then stripped off for use in the maintenance area and/or for partial stroke testing, and is not actually used as part of the system itself. ISA-84, under the direction of Bob Adamski, has a subcommittee working the safety bus issue and is preparing a technical report on the generic requirements of a fieldbus safety solution.

Of course, in addition to the Big Three fieldbuses in the process industries, other fieldbuses, such as DeviceNet, Modbus, LONworks, AS-i and others, are not standing still either.
What will all these new features mean to the control landscape of the future, say around 2010? As we enter 2005 and hence, the middle of this decade, it is time to look into our crystal ball and make an educated prediction on how things will unfold so that you readers can take this into consideration as you plan your new facilities and future automation upgrades.

Let’s have a look at each of the above points in turn.

EDDL vs. FDT/DTM
Despite the fact that Phase 1 is a significant improvement over the present text-only representation supported by these protocols, EDDL Phase 1 is a beginning on which to build better platforms in the future. The analogy is that DDL is presently in the DOS days, EDDL Phase 1 is like Windows 3.2 and EDDL Phase 2 will be the Windows NT release. In the interim, end users will continue to use what they have and be innovative in how it is applied, including the use of work-arounds if necessary.

Its competition is FDT/DTM (Field Device Tool/Device Type Manager) from Europe. When asked for his thoughts on EDDL/FDT, Jim Sprague, a controls engineer with a major Middle East oil and gas producer/refiner responded, “We are counting on EDDL and FDT/DTM to fully deliver on Foundation Fieldbus’ (FF) promise of giving us ‘best in class’ instrument choice.” Sprague continued, “Our company is moving ahead strongly with FF use, but we still have to be careful about our instrument selection to make sure Host ‘Plug-Ins’ or ‘Snap-Ons’ are available to give us full access to instrument maintenance features and diagnostics. We look forward to the time when we can choose best in class FF instruments and just know we will get everything at the host.”

The EDDL-FDT/DTM conundrum is a small part of the battle to integrate the abundance of information available from a modern integrated digital control system and effectively use it to increase the bottom line. Many end users are taking advantage of the additional information to operate their facilities in a more reliable way using asset management or maintenance system solutions but, as indicated above, are experiencing difficulties getting all the parts to play nicely together.

Another end user in Northern Europe responded to my inquiry on the impact of EDDL by saying “The (host) manufacturer that supports full functionality of non-host devices will have an advantage in the market.”

This confirms that end users are not so much interested in the technology used to provide them the information they require, but rather the content of the information itself and hence the use of FDT/DTM to get that information if it is not available from fieldbus directly. FDT/DTM uses DD technology as the basis on which it enables the device manufacturer to represent the information in their device the way they wish, rather than how the host or maintenance system supplier thinks it should be done. Obviously, if the maintenance system supplier manufactures an end device, it is going to integrate it more tightly into its system than someone else’s product and hence the request or need for FDT/DTM to fill a void. Interestingly, some speculate that the EDDL enhancements were driven not so much by end users but the competition from FDT/DTM.

The FDT/DTM vs. EDDL battle is one of those Layer 2/3 battles mentioned earlier, in which it is once again North America and fieldbus led by Emerson Process Management vs. fortress Europe with ABB and Endress+Hauser at the helm. However, this battle seems more a tempest in a teapot because both groups are working to release an OPC-UA compatible version of their standard in two to three years and the entire system will be using the same technology as its backbone, thus making integration and any necessary work-arounds much easier.

The greatest risk of having another skirmish on this level of the enterprise is that if it is not soon resolved, and a way to store data on a host in a retrievable manner regardless of supplier is not found, a web-based solution using XML and HTML with perhaps a small web server will sneak in the back door and make the entire discussion moot.

EDDL and FDT/DTM are the tools with which to present the data required so as to make best use of the information in a modern control system. What is also required is a standard or series of standards to define the information itself and how to move it from one system to another. ISA’s S-95 is one group leading this effort as are the NAMUR and WIB groups in Europe. Fortunately, efforts are also underway to have these groups work together with member-led ISA as the global instrumentation, systems and automation society taking the role of catalyst in these activities.

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