Many Benefits, No Magic Bus, in Networking Trenches

KEY WORDS

Networks and communication

Fieldbus

Device-level networks

Sensor/actuator-level networks

Local area networks

PC-based control

Sidebars: Profibus Interbus Foundation fieldbus AS-Interface Online DeviceNet

Is industrial Ethernet going to eat everyone’s lunch? Maybe tomorrow, but not today. Though some initial Ethernet applications and solutions are underway, most users and manufacturers still seem like they’re too busy enjoying the savings and efficiencies gained from adopting more established networking protocols. The following stories contain updates on several established network protocols and users’ recent experience using them in applications.

Profibus assists PC-based lumber mill control

Engineers seeking to upgrade 10-year-old control systems at Rayonier’s three Georgia-based lumber mills found their existing PLC-based systems didn’t support open architectures, introduced system slowdowns, and couldn’t be improved to meet present requirements. To cut downtime, simplify system programming, and increase mill output, they decided to install a PC-based system running Think & Do (Ann Arbor, Mich.) software and Profibus links, I/O devices, drives, and operator interfaces.

To maximize lumber yield, each log is laser scanned and profiled for a “best fit” cutting and trimming solution. This operation—as well as conveying, stripping, edging, sorting, stacking, kiln drying, planing, and trimming—are all controlled and automated by PCs at approximately 20 logs per minute. Each kiln has 21 thermocouples and the control system for the six kilns at Rayonier’s mill in Swainsboro, Ga., includes 68 of Toshiba International Inc.’s (Houston, Tex.) variable frequency drives and approximately 3,000 Profibus I/O points.

Due to the importance of having boiler and kiln controls operate continuously, Rayonier implemented a dual master system with two PCs running identical programs and tied them to the same Profibus network. The PCs exchange process data over an Ethernet link, which allows the standby to take over if the primary PC fails. Rayonier uses a version of Canary Labs’ (Martinsburg, Pa.) trend analysis software specifically designed to work with the Think & Do database.

The new control system includes four Pentium PCs running Think & Do software on Windows NT and more than 10,000 data points. Operator information is available throughout the plant with 18 networked operator interface panels. Production data are extracted from three PCs networked to the Think & Do master station. All control panels are networked via Profibus.

“Operational improvements include near instantaneous machine synchronization made possible by a scan time of 14 msec with 10,000 data points,” says Jon MacArthur, Rayonier’s process control engineer. “In addition, setup time was reduced from two hours to less than five minutes. Since setup has to be performed every morning, this made a tremendous positive impact on production capacity. Profibus also allows us to identify defective sensors and devices in minutes rather than hours, further reducing downtime and lost profits.”

Cutting freeze dryer installation time with Interbus

Increasingly global markets, a need to reduce installation costs, and reliability concerns recently spurred BOC Edwards Pharmaceutical Systems (Tonawanda, N.Y.) to find a bus protocol for its commercial grade pharmaceutical freeze dryers. Used primarily by pharmaceutical manufacturers to preserve antibiotics, vaccines, and blood fractions, these freeze dryers sometimes process up to $1 million worth of product. BOC Edwards installed Interbus because of its increased flexibility in communicating with a variety of PLCs, including Siemens, Allen-Bradley, Modicon and Mitsubishi.

“As an international supplier of custom-built equipment, we’re driven by the type of PLCs our customers use. After examining various systems, we settled on the Interbus protocol as the most universal,” says Ivan Lanaway, BOC Edwards’ engineering manager.

BOC Edwards installed Interbus in its medium-sized Lyomax 11 freeze dryer, which consists of a series of skids for the process chamber, condenser, refrigeration unit, and control cabinet with an Allen-Bradley PLC-530. Interbus serves as the interface between the PLC—via an interface module—and 300 I/O points that monitor limit switches, temperature switches, and pressure switches.

By using Interbus ST modules with BK interfaces distributed at convenient key points, BOC Edwards reduced hardwiring in its freeze dryers by eliminating cumbersome parallel wiring and wiring looms. “We estimate that with Interbus we will now save one week of work during installation. We have already saved one day during our in-plant test process. In addition, with less wiring, we can anticipate a reduction in the amount of wiring errors,” adds Mr. Lanaway.

Foundation fieldbus aids lubricant batch processing

It’s easier to look up a recipe than it is to buy new pots and pans every time you cook. For instance, when Petrolube Co. (Saline, Mich.) decided to build a new plant, it also chose to install Fisher-Rosemount Systems’ (Austin, Tex.) DeltaV control system in conjunction with S88 standard batch methodology from ISA, the international society for instrumentation and control (Research Triangle Park, N.C.). The firm previously used a partially manual control system in its old plant to make industrial lubricants and dry-powder lubricants for wire drawing.

“S88 is helping Petrolube implement a powerful, flexible batching system. This will allow the company to simply assign a new recipe when it needs to mix and match equipment,” says Steve Gwizdala, sales engineer for control systems, Michigan Instrumentation and Controls (Plymouth, Mich.), which represents Fisher-Rosemount and is helping Petrolube install its new system. “This requires some added pipes and valves at the beginning, but it’s much easier to reconfigure later.”

The FOUNDATION fieldbus portion of Petrolube’s plant includes 1,200 I/O points and devices, which include 100 analog devices. The system also includes almost 100 FOUNDATION fieldbus-compliant devices. FOUNDATION fieldbus allows the plant’s managers to monitor status and maintain the health of each device via online connection to workstations. Besides allowing device checks prior to field searches, DeltaV also recognizes FOUNDATION fieldbus devices when they’re first plugged in, which eases start up, parameter checking, and commissioning tasks.

“During system wring out, this type of recognition lets you know the right device is hooked up to the system, that it’s in the right place, and that it’s performing the right function,” says Mr. Gwizdala. “There’s also a huge wire savings. This particular system can put 16 devices on a pair of wires, while the FOUNDATION fieldbus protocol allows 32 devices on one wire pair. So, instead of having 100 pairs of wires in a system, we may just have six pairs, which is a lot easier to troubleshoot.”

Another fieldbus used at Petrolube’s new plant is Actuator Sensor-Interface (AS-i), which is being used to control 180 devices, such as on/off valves, peripheral pressure switches, and level switches. Mr. Gwizdala says these AS-i bit bus devices, and the 100 FOUNDATION fieldbus devices, will send a total of 40 wire pairs back to the control room, a substantial saving over the 280 pairs that a hardwired system would have required.

“It’s pretty incredible to start up a system like this because plug-in and commissioning that used to take hours can now take just a few minutes,” says Mr. Gwizdala. “Likewise, we were able to connect and commission our 180 AS-i devices in three days. Previously, a job like this could have taken weeks.”

DeviceNet dishes benefits for Corning

Fast, cost-effective installation, superior troubleshooting, and reduced wiring were the advantages DeviceNet focused on recently to help improve production efficiency at Corning Consumer Products Inc. (Corning, N.Y.). The company installed DeviceNet at its Pressware Plant, the world’s largest glass melting facility, which melts 500,000 pounds of glass daily in its tanks. DeviceNet’s easy installation allowed Corning to restart its line two days ahead of schedule, which translated to two extra days of production.

“Since we were able to start two days early, roughly 110,000 pieces of ware were realized because we chose DeviceNet. We wouldn’t have finished ahead of time without DeviceNet,” says Eric Snyder, Corning’s facility electrical engineer. “It actually reduced costs twice because we decreased production downtime and also saved on labor for electricians, who would otherwise have had to do the rewiring.”

The plant makes 127 million pieces of Corning’s well-known Corelle dinnerware per year, using a hub lamination process. Melted glass from the tanks is formed into 6-16 in.-wide sheets, compressed to a uniform thickness, and then molded and trimmed to specific patterns at a rate of 35-60 cuts per minute.

Retrofitting with DeviceNet enabled the high-volume line to maintain this precision, while simplifying and eliminating much of its previous hardwiring, which also reduced installation and maintenance time. “With DeviceNet, our installation required only one cable. If we hardwired the system, we would have had to sort through multiple existing wires, locate the spares, and terminate everything individually,” says Mr. Snyder, who also integrated four previous operator panels into one containing all switches for the entire forming process. The new system connects a DeviceNet fieldbus coupler to a DeviceNet master card and five ac drives.

Profibus

Level: Field, device/actuator

Speed: Profibus DP provides 9 kbps to 12 Mbps using RS-485 transmission technology; Profibus PA delivers 31.25 kbps using IEC 1158-2 technology

Network size: 200 m at 1,500 kbps, up to 1.2 km at 93.75 kbps, also repeater extendable.

Installed base: 3 million nodes in 300,000 applications

Organizations/developers: Profibus Trade Organization

Website:

Outlook: For applications worldwide, including DCSs, PC-based control, and PLC systems combined, a recent Venture Development Corp. (Natick, Mass.) report states the largest share of distributed/remote I/O shipments in 1998 interfaced to the Profibus DP network, and that it is expected to remain the most used through 2003.

Interbus

Level: Device/actuator, sensor

Speed: 500 kbps

Network size: Communication to 4,096 I/O points across 512 devices over 8 miles of cable through 16 network levels in 16 msec.

Installed base: 3.5 million nodes

Organizations/developers: Interbus Club, Phoenix Contact

Websites:

Outlook: U.S. sales increased 24% and chip sales increased three-fold in 1999 compared to 1998. Worldwide node growth was 36% in 1999. It is supported by more than 1,000 third-party I/O device manufacturers and 600 Interbus Club member firms worldwide.

Foundation fieldbus

Level: Field

Speed: H1 at 31.25 kbps, high-speed Ethernet at 100 Mbps

Network size: N/A

Installed base: Results of a member survey announced in December 1999 indicate that approximately 800 Foundation fieldbus-compliant systems are on-order or installed on six continents and that more than 30,000 compliant devices are presently in service.

Organization/developers: Fieldbus Foundation

Website:

Outlook: More than 40 Foundation fieldbus products are now registered, with an additional 70 devices scheduled for registration testing by June 1, 2000. Delivery of the foundation’s High-Speed Ethernet (HSE) technology during 2000 is expected to drive explosive growth of Foundation fieldbus across traditional boundaries.

AS-Interface

Level: Sensor/device

Speed: 167 kbps

Network size: 31 slave devices over 100 meters, 300 m with repeater; 62 slaves using AS-i version 2.1 with “A/B addressing,” though cycle time is doubled to 10 msec.

Installed base: More than 600 available products and more than 1 million field devices installed worldwide.

Organization/developers: AS-Interface Trade Organization

Website:

Outlook: Though designed for low-level binary devices, compatibility to higher-level networks is made possible with gateways developed for Profibus, Interbus, DeviceNet, CAN, SDS, Modbus, Modbus+, RS-232, RS-422, and RS-485. Recently accepted as an international standard under EN 50295.

Online

For additional coverage of network applications, including industrial Ethernet, visit

Gigabit Ethernet Alliance

IAONA

Industrial Ethernet Association

Schneider Electric’s Automation Business

Wago

Omron

DeviceNet

Levels: Device/actuator, sensor

Speed: 125 kbps at 500 m, 250 kbps at 250 m, and 500 kbps at 100 m

Network size: Up to 64 nodes

Installed base: DeviceNet uses Controller Area Network (CAN) chips of which 40 million were expected to ship in 1999

Organizations/developers: Open DeviceNet Vendors Association, Rockwell Automation

Website:

Outlook: Signs up 300 member organizations in four years by April 1999, forms 17 special interest groups, and creates membership category for distributors. European Committee for Electrotechnical Standardization (CENELEC) officially adopts DeviceNet as a European Standard to be known as EN 50325 or “Industrial communications subsystem based on ISO 11898 (CAN) for controller-device interfaces.”

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