More on Foundation Fieldbus and HART

by | Dec 11, 2013 | Control & Safety Systems

I wanted to bring visibility to several recent comments from an earlier post, Major Difference between Foundation Fieldbus and HART Protocols. Here’s the summation thought from the first comment:

…With one software package, and as put above with HART pass-through, you can document EVERY HART instrument on site, and THEN with Plantweb, monitor the lot and see is there are problems, nip them in the bud before they become a problem. EG blocked impulse line on a DP flowmeter. How many weeks or months can go by with this problem, it takes an astute operator to pick it up.

Emerson’s Dan Daugherty, whom you may recall from earlier posts on digital communications added:

Emerson's Dan DaughertyI kind of see it as something similar to the transition between using a typewriter v using a computer and printer in terms of adoption attitudes. I remember a lot of people had typewriters and the idea of having to set up and learn a computer with its ever changing software revisions seemed unnecessarily onerous. But a new generation came along knowing nothing of typewriters and is completely at home and at ease using a computer to do what was once done with a typewriter… and more.

Techs and engineers who come out of technical schools these days are not afraid of FF. It has only gotten better, and it will only get better. The dinosaurs will retire and all of this will just be a story someday.

I cannot add to Jonas’ post. I would however offer my own pareto ordering of values over 4-20ma with HART:

  • at the DCS, a set of redundant communications cards offers extremely high reliability, saves space in cabinet by connecting to double or more of the number of I/O points as regular point-to-point I/O, can get all elements of a loop on one communication channel to increase the reliability, and provide superior control loop performance with low latency while off loading clock cycles from the main controller CPU.
  • it is inherently “electronic marshaling” because you can add I/O points without changing wires at the DCS, and you can put mixed signals on same comm link, and even better, ALL you have at the DCS is the comm wiring — NOT a pair for every signal.
  • less important because 4-20ma HART works pretty well, but still important is that the A/D and D/A conversions occur in the instrument rather than at the DCS. So just like HDTV, you get the whole signal without ANY added noise or you get none of it.

Frequent contributor Emerson’s Jonas Berge, who shared his thoughts in the original post, added this comment:

Emerson's Jonas BergeI personally think Dan explained it well above. Digital comes natural to some but not all. For example, downloading DD files to integrate HART, fieldbus, and PROFIBUS devices into a system is not that different from downloading songs and apps from iTunes.

The plant experience with FF varies greatly depending on the system used. Some DCS were introduced with FF but without any support by intelligent device management (IDM) software. They didn’t provide IDM support until 2010. On the other hand, DeltaV has had IDM software since the very beginning of fieldbus.

Some early FF projects were over-engineered with segment calculation for each individual bus instead of doing just a few worst case ‘typicals’ which is the standard practice today. Perhaps this was because FISCO and high power/energy trunk (HPT) barriers were not yet available back then. In the past we were also not yet as confident with fieldbus as we are today so we didn’t put as many loops per bus as we do now. Today implementation is a lot simpler.

Both the Fieldbus Foundation and Emerson have responded, and have spent the past few years improving usability.

Enhancements to the fieldbus standard includes error free download meaning download once without retries, Electronic Device Description Language (EDDL) with device level methods and views enabling task-based graphical device pages with user guidance instead of cryptic parameters scattered across blocks. NAMUR NE107 status signals for easy to understand device diagnostic alarm rationalization and routing. Backwards compatibility (COMPATIBILITY_REV) to make it easy to replace an old device with a newer version without loading new DD file or touching the system. And these enhancements continue making the work easier for the designers as well as the run & maintain organization:

DeltaV has been improved greatly over versions 9, 10, 11, and 12 with many new enhancements that make fieldbus easy to use. For example, version 9 (2006) function blocks in the H1 card for complex time-synchronized loops, greater function block capacity, enhanced EDDL (graphical device display); version 10 (2008) device replacement and commissioning (using only a screwdriver without touching software like 4-20 mA), and express download, and HPR 61a registration; version 11 (2010) integrated power in the H1 Card (eliminating the marshalling cabinet), EDDL device level access (dashboards), and HPR61b registration; version 12 (2013) NAMUR NE107 (prioritized device diagnostic alarms) and DD Update Manager (automatic DD download keeping the system up to date without manual DD downloads)

Emerson field devices are being released one by one conforming to fieldbus device profile version 6 (“ITK6”)

Foundation-Fieldbus-Usability-EnhancementsThe Fieldbus Foundation is just embarking on a second wave of enhancements have been announced known as “Project Gemstone“.

I personally agree that FF is the way of the future. All-digital; just like digital audio, digital photography, digital telephony, digital mail, digital television, digital video games, digital books, digital movies, digital payment, digital address book, digital maps, and even digital music instruments.

Fieldbus takes the place not only of 4-20 mA signals but also of on/off signals, so you can pull out astounding diagnostics not only from pressure transmitters but from all devices including on/off devices such as on/off valves and electric actuators etc.

Many plants did not know how to incorporate device diagnostics from their 4-20 mA/HART, FF, and PROFIBUS devices into daily maintenance and turnaround planning. However, now there is guidance in how to deploy intelligent device management (IDM) software and rewrite the work processes:

The ISA108 group is also doing work in this area.

Today with FF and PROFIBUS you can monitor diagnostics not only in instruments, but also gas chromatographs, electric actuators / motor operated valves (MOV), tank gauging systems, variable speed drives, and motor starters etc.

PlantWeb Alerts was indeed a breakthrough technology. It has now evolved into the NAMUR NE107 standard.

You can connect and interact with Dan, Jonas and many other participants in the DeltaV track of the Emerson Exchange 365 community.

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