When Cleveland-based BP Chemicals Inc. decided to build a 1, 4-butanediol (BDO) plant in Lima, Ohio, managers wanted the plant to achieve high reliability without the complexity and redundancy of a traditional process control system. “In designing the BDO plant, we wanted to avoid older analog communications,” says John Rezabek, controls specialist at the Lima complex. “An analog system would reduce our design flexibility, inflate life-cycle costs and complicate upgrades.”

Plant managers are gaining a wide range of paybacks from fieldbus networks. They are seeing gains through easy initial set-up, better preventive maintenance techniques, improved asset management, quick reconfiguration and simplified upgrades. The net result of fieldbus networking can be counted in dollars through fewer shutdowns and longer-lasting equipment.

Warnings and safety

The fieldbus network can now behave as a system that tells operators the condition of the devices. “Engineers who work with fieldbuses work with a block of data that tells them when something is wrong,” says John Yingst, product manager of fieldbus systems at vendor Honeywell Process Control, in Phoenix. “That’s the low-hanging fruit because it’s built into the device. That’s the first piece of value in diagnostics—the device telling you the condition of the device.”

The smart network can send warnings of a potential device failure before the failure occurs, so preventive actions can be taken to avoid a costly shutdown. “The drives can now report back—not just a fault or warning, but the condition before a fault so you get a warning before it fails,” says Steve Boren, regional application engineer from the Low Voltage Drives group at automation vendor ABB, in Warminster, Pa. “Then the drive can be reset before something catastrophic happens.”

Another advantage of the fieldbus network is that a number of functions can be tied
together into one control platform, including safety. “You can take automation capabilities that had been separate and put them into one system,” says Harry Forbes, senior analyst at ARC
Advisory Group Inc., in Dedham, Mass. “In the past, the regulator, motion and safety
functions were separate. You used to have to integrate them yourself. Now they’re converged in the automation controller.”

A network that combines programmable logic controllers (PLCs) and safety devices gives the operator enough information to determine whether a safety shutdown is really necessary. This can stop some costly shutdowns due to faulty safety devices. “When the safety devices and the input/output (I/O) devices are on the same control network, you can evaluate two pieces of information to see if the information is correct,” says Helge Hornis, intelligent systems manager at vendor Pepper+Fuchs, in Twinsburg, Ohio. “When you can see the PLC data and the safety data, your diagnostic capability is enhanced and you can determine whether a shutdown is really required.”

This information coming from the devices lets operators improve the efficiency of the plant. “The fieldbus allows for minor changes, to improve how the machine is working,” says Tim Black, device integration manager at Wonderware, another automation vendor based in Lake Forest, Calif.

Maintenance is another area in which plants are taking savings due to the diagnostic capabilities of fieldbus networks. Devices have become more intelligent and can actually report back on their true condition through the network. The savings come from not shutting down for routine maintenance if that maintenance is not required. Savings also come when you can replace a device that is on its way to failure.

Real-time data coming through ...