Spread the Word: Justify Investment in Fieldbus

KEYWORDS

Networks and communications

Process and advanced control

Automation investment

Fieldbus

Open architecture

Sidebars: Integrated fieldbus alleviates solvent recovery bottleneck To justify a fieldbus network Refinery retrofitted in six weeks with Foundation fieldbus, PlantWeb Overall Equipment Effectiveness Clients ask OEM to add distributed I/O devices on DeviceNet to plastics system ONLINE

One or two cables are better than bundles of 20 or 200. End of story. Okay, not end of story. More like beginning of story. Because belief in useful change logically carries the responsibility of making it happen, when one or more users become convinced of a fieldbus’ advantages, they must also champion its evaluation and implementation.

Confronting tradition

The problem is that a few fieldbus converts typically face an established hierarchy of skeptical colleagues and managers, who are extremely reluctant to alter traditional control and automation methods. Resistance to fieldbus and digital industrial networks is also fueled by the economic reality that hardware’s greater volume and revenues give it added staying power in the market.

The fact that fieldbuses-such as the Profibus Trade Organization’s (PTO, Scottsdale, Ariz.) Profibus, Open DeviceNet Vendors Association’s (ODVA, Boca Raton, Fla.) DeviceNet, and the Fieldbus Foundation’s (Austin, Tex.) FOUNDATION fieldbus-require so much less hardwiring than traditional controls and networks also makes them seem less tangible and, hence, less capable in the minds of many technical professionals. Even the potential double-digit percentage savings in material and labor that fieldbus can achieve appear to be an obstacle to its acceptance, because improvements of more than a few percent tend to seem unreal to many engineers.

However, the countervailing and always growing economic pressure for more manufacturing efficiency is making the advantages of fieldbus more difficult to ignore. Many converts are chipping away at official resistance with specific technological evaluations, savings data and diagnostic improvements that are fueling consistent increases in fieldbus-enabled applications.

Shared language, learning

Besides demonstrating all of fieldbus’ concrete benefits, its advocates also must do something that many engineers don’t like to do-become comfortable with thinking beyond the plant floor and the immediate operations and maintenance needs of their application.

To successfully pitch a fieldbus system, or secure investment in any capital project, its supporters must understand the organization’s decision-making process and all the layers involved, says Rob McKeel, vp, GE Cisco Industrial Networks (Charlottesville, N.C.). Engineers must also become familiar with management’s objectives and overall business goals, so they can calculate return on investment (ROI) of a proposed fieldbus system and how it would fit into an application’s lifecycle.

Tom Wallace, PlantWeb marketing manager, Emerson Process Management (Eden Prairie, Minn.), adds that fieldbus supporters must simply try to speak the language of whomever they’re trying to persuade, whether that terminology is based on finance, operations, management or engineering.

‘The most important starting points are determining where you and your organization really are; where you want to be; and how to get there,’ he says. ‘This is where our Overall Equipment Effectiveness (OEE) benchmarking method can help (see sidebar).’

OEE examines a company’s basic goals; its application’s running time; time of production on specification; actual versus theoretical throughput; and other data about what is being produced at what quality and cost. Mr. Wallace says it’s not unusual for a continuous process plant or application to find it has an OEE of 60% to 75%, compared to international best practices of 95%.

‘Jaws drop when people see these numbers, which sets the groundwork for really changing some minds and making significant improvements,’ says Mr. Wallace. ‘In some ways, persuading the human element is more important and difficult than implementing new technologies.

Wiring, labor savings

The best known, and most-often disputed, advantage of implementing fieldbus is that it can save 20-40% or more on materials and labor over traditional hardwired systems.

‘Thirty-two I/O devices used to mean 32 wires. Now, you can have a single cable, which means reduced wiring and terminations; fewer bad connections and places for failures to occur; and easier troubleshooting,’ says Mr. McKeel. He adds that GE Cisco often helps users walk through their existing applications, so they can see the cost of what they’ve done before, and better appreciate potential improvements using fieldbus.

Dave Quebbmann, marketing manager, Omron Electronics LLC (Schaumburg, Ill.), adds that users installing twisted-pair fieldbus in material handling/conveyor applications generate savings of 50-60% or more over hardwiring. ‘Sure, there’s some fear factor. We’ve all heard horror stories about lacking interoperability after buying many components from different vendors, and that the best-in-class model can fail when everything has to work together,’ says Mr. Quebbmann. ‘The solution is do some research; gain some experience by building a prototype system; and then see what fieldbus works best for your application.’

Critics say fieldbus has higher up-front and more hidden expenses; not that much less required wiring; and fewer capabilities and less reliability than its supporters will admit. Supporters say the critics usually aren’t implementing the most appropriate fieldbus or aren’t installing it correctly.

Stalled and restarted international standards efforts in recent years, principally IEC 61158, promised one unified fieldbus standard. However, proprietary interests succeeded in derailing and diluting it into an all-inclusive, eight-part document that provides little clear guidance. This means users or their system integrators must still research and evaluate fieldbuses; determine which one is most appropriate and useful; and add up the savings for their individual applications.

Besides the usual suppliers and trade organization, several academic institutions provide training and labs for side-by-side fieldbus testing, which can help end-users evaluate and configure networks. These sites include: Lee College’s Center for Digital and Fieldbus Education (Baytown, Tex.); Southern Alberta Institute of Technology (SAIT, Calgary, Alberta, Canada) and Singapore Polytechnic Institute.

However, pressed for time, many users simply pick a fieldbus supplier based on their application’s existing equipment. This can deliver needed capabilities quickly, though it may limit choices that might have been more useful in the long run.

Modularity, expandability

Though disputes may rage over its initial material and labor savings, there appears to be less debate whether fieldbus can generate significant savings related to improved, proactive maintenance and easier expansion as future needs arise.

‘In an area where a machine builder is going for a modular arrangement, fieldbus allows quicker disconnects, easier wiring, and other benefits when equipment is being disassembled and reinstalled,’ says Mr. Quebbmann.

More, better data

Perhaps the least famous force driving adoption of fieldbus is that many field devices have increasing amounts of added intelligence. To capitalize on the resulting data, users need fieldbuses deliver information to operators or software systems, says GE Cisco’s Mr. McKeel.

Besides tracking process status and health, and providing data on locations and types of problems, fieldbuses also can deliver device-based data that help prioritize maintenance jobs. For example, instead of routinely pulling and diagnosing valves, which may catch them before maintenance is needed, or after performance degrades significantly, users can now replace valves by using data from the devices themselves, which can greatly reduce costs and downtime.

To make fieldbus more real to potential users, most suppliers will gladly demonstrate sample solutions onsite and even help clients build fieldbus tests for their individual applications. For example, GE Cisco has a demonstration room with numerous base systems that walk users through a variety of vertical market applications, and also partners with customers to build pilot projects in their facilities.

Besides seeking all stakeholders’ input at the fact-gathering stage, Mr. McKeel adds they should also be involved at the technology evaluation and test stages, so a consensus can be formed on the best fieldbus solution.

‘There’s always a learning curve,’ says Mr. McKeel, ‘but, once people get used to a new technology, they’ll wonder how they ever got along without it.’

Comments? E-mail jmontague@cahners.com .

Integrated fieldbus alleviates solvent recovery bottleneck

To help monitor and control a new solvent recovery mixer, Janan Van Fossan, electrical and instrumentation specialist, Rütgers Organics Corp. (Augusta, Ga.), spent months researching available fieldbuses to help reduce wiring to transmitters and valves on the mixer’s hot oil system.

He polled other manufacturers, conducted online and literature searches, and then invited several suppliers onsite, borrowed some equipment for a month, and ran them on a desktop-based test bench he built using applicable interface cards. ‘I explained to the reps that I wanted to see if their solutions could function with my process without actually connecting to it, and every one was glad to help,’ says Mr. Van Fossan.

Rütgers Organics is a 20-year-old contract chemical manufacturer that annually produces 750,000 pounds of specialty bulk solids for agricultural, pharmaceutical and other customers.

Mr. Van Fossan’s small team eventually settled on a network topology that included an Ethernet backbone, Profibus-PA and -DP for its field devices, and AS-i for binary devices. They also opted for Siemens Energy & Automation’s (Alpharetta, Ga.) Simatic PCS 7 control system.

‘Siemens had the best control system flexibility for us. For example, they had the high-speed communications we needed between our PLCs and remote controllers,’ says Mr. Van Fossan. ‘We were also able to minimize distance over AS-i by installing Profibus DP with an AS-i gateway closer to the field. We had dramatic savings in wire, terminations and labeling, as well as in all the hours formerly needed to install them.’

The new fieldbus also fulfilled Rütgers’ requirement for quick changes to its equipment to complete orders. Its quick reconfiguration capabilities are also helping the recovery system solve its previous bottleneck by reducing processing time by 12-14 hours.

Material, installation and configuration savings totaled $25,000, which represented combined savings of 60% in labor and 50% in materials over traditional hardwiring, says Mr. Van Fossan. ‘We found that we were able install a new control system for less than it would have cost to upgrade our existing system.’

To justify a fieldbus network

What users need to do

To start a fieldbus evaluation and implementation effort, there are several basic steps users must take:

Form an internal research and implementation group;

Involve personnel from all aspects of your organization;

Determine the specific needs of your application and goals of your overall business;

Research and evaluate available fieldbus technologies;

Try to select a company-wide fieldbus standard to aid uniformity;

Ask suppliers to demonstrate their fieldbus solutions onsite;

Implement fieldbus in a small, offline trial setting;

Arrange for applicable training and support;

Commission any new solution offline to minimize installation downtime; and

Continually reevaluate the fieldbus solution implemented

What users need to show

Reports or proposals seeking approval of a fieldbus project, or any capital expenditure, must show managers some crucial facts:

Calculate specific material, labor and other cost savings;

Demonstrate ease of installation, configuration, and maintenance;

Quantify improved quantity, quality, and accessibility of production data;

Calculate better capability, capacity, and throughput;

Show possible risks and how they’ve been mitigated;

Estimate reduced downtime and faster time-to-market;

Project expandability and aid to modularity; and

Relate to organization’s overall capital expenditures and core business goals.

Refinery retrofitted in six weeks with Foundation fieldbus, PlantWeb

Calcasieu Refining Co. (Lake Charles, La.) is reported to be the world’s first refinery controlled entirely by bus-connected intelligent-i.e. microprocessor-based-field instruments. The refinery achieved this distinction when it recently upgraded virtually all controls at its 22,000-barrels-per-day petroleum refinery from 25-year-old pneumatics and relay logic to Foundation fieldbus and Emerson Process Management’s PlantWeb architecture and Delta V process automation system. The automation system includes two atmospheric crude distillation units, a naphtha stabilizer, an 800,000-barrel tank farm, and a five-mile product pipeline.

Calcasieu officials add that the retrofit was performed more efficiently than would have been possible with a conventional DCS or PLC architecture. A 5,000-barrel-per-day crude unit was added simultaneously, without requiring additional operators. Operation and maintenance costs have already proven to be substantially less than with the refinery’s old system. These savings and an increase in operating capacity are already yielding a projected annual return of 80% on the project’s $1-million pricetag.

‘I had a contractor tell me this installation would take at least six months with an ordinary DCS and having to hardwire all the analog instruments,’ says Jody Verret, Calcasieu’s process and mechanical superintendent. ‘PlantWeb let us do it in about six weeks.’ Mr. Verret attributed most of this speed to Foundation fieldbus wiring and virtually automatic commissioning of intelligent instruments. ‘We had one worker on the console and one with a radio in the field running cable. It seemed like the guy on the console was able to calibrate and commission instruments over the network nearly as fast as the field guy could plug them in.’

Overall Equipment Effectiveness

First described by Seiichi Nakajima, founder of the Total Predictive Maintenance concept, the equation for Overall Equipment Effectiveness (OEE) can help identify areas for improvement and potential investment in manufacturing processes. It assesses incremental revenue opportunities, and allows benchmarking against similar or competitive processes. Using availability, productivity and quality definitions from Emerson Process Management’s online Operational Economic Efficiency (OEE) course, the basic equation is:

% OEE = (% Availability) x (% Productivity) x (% Quality)

% Availability = actual production time/possible production

% Productivity = actual production/optimum capacity

% Quality = product produced – scrap and rework/product produced

Clients ask OEM to add distributed I/O devices on DeviceNet to plastics system

Downtime simply is not allowed in the high-speed, low-profit margin plastics manufacturing field. To lessen this risk and cut installation and maintenance costs, a 40-year-old plastics material handling OEM, AEC Corp. (Wood Dale, Ill.), recently added distributed I/O devices on DeviceNet to its VacTrac Series VTC7/50D, which controls pneumatic conveying equipment used in extrusion and injection molding applications.

‘Developing an alternative to our traditional, chassis-based, local I/O points, we reduced the installation time of our conveying controls up to 50% or more,’ says Ron Newlun, AEC’s project manager. Hardwiring on a medium-sized plastics handling application typically costs $24,000. AEC had been interested in adding distributed I/O capabilities about 10 years before, but electrical spikes, noise and wiring problems, not to mention proprietary issues, prevented it.

More recently, AEC evaluated several fieldbuses, and found that DeviceNet provided the interoperability that VacTrac needed. Instead of running several wires to each molding press, hopper and vacuum pump, AEC can now run one cable, and plug VacTrac’s devices into it, which also aids troubleshooting, replacement and expansion. AEC uses Rockwell Automation’s Allen-Bradley KwikLink flat cable and its ArmorBlock MaXum I/O devices.

‘There are still some subtle differences and quirks, but we’re light years ahead of the all-proprietary situation we were in 10 years ago, because we now have multiple suppliers supporting a few common technologies,’ says Mr. Newlun. ‘We’re not in heaven yet, but we’re getting there.’

ONLINE

For an expanded version of this article, including more on each of the fieldbus applications included here, visit

For related reading, see:

Information about field testing sites, ‘Digital networks permit global integration, asset optimization,’ CE Today’s News, Dec. 6, 2001

‘Tailor a best-fit network,’ CE, Aug. ’01.

‘Time to Reinvest in Automation,’ CE, Feb. ’01 cover story

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