Fieldbus There Are Many Good Reasons to Get Going and Apply Fieldbus in Your Process Plant

Editor: Dr. Jörg Kempf

Most fieldbus novices feel edgy about their decision and understandably so. Getting a new technology to work right the first time is a task associated with perceived risk. Taking this risk out of the equation and getting the plant on the way requires change. A few concepts have proven true to get it right the first time.

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The control room cabinet: Each plug-in module powers and connects up to 32 field instruments to the DCS. (Picture: Pepperl+Fuchs)
The control room cabinet: Each plug-in module powers and connects up to 32 field instruments to the DCS. (Picture: Pepperl+Fuchs)

Fieldbus systems are often employed in process plants, particularly where hazardous areas exist. Fieldbus is today’s data highway for connecting the Distributed Control System (DCS) to the field instruments. Prevalent in today’s process plants are Foundation fieldbus H1 and Profibus PA.

Fieldbus systems are employed because they offer or enable:

  • remote access to field instrumentation for configuration and diagnostic information;
  • digital and thus precise transmission of measurements unsusceptible to drift;
  • long cable distances;
  • explosion protection in hazardous areas up to Zone 0/Div. 1;
  • all-in-one instruments with multiple variables e.g.: for temperature, pressure, volume, or mass.

Fieldbus is the operator’s darling, as it leads to substantial savings in Operating Expenditure (OpEx) when applied properly. Fieldbus helps through:

  • precise measurements for exact and drift free control loops;
  • remote fault diagnostics for pointed and planned action;
  • reduced number of trips to the field for fault finding and maintenance.

All the above lead to extended maintenance cycles at reduced costs. The main reason is that fieldbus instruments provide extensive diagnostic information. And now the fieldbus itself can be monitored for its quality at a reasonable cost. This allows plant operators to switch from reactive or scheduled maintenance to proactive and need-based plant upkeep.

The Practitioners Voice — Example 1

Once, an operator running a batch process deliberately overrode the temperature warnings from a motor finishing and thus saving the batch worth € 250 000 and burning up a motor costing € 400. Maintenance teams were informed and prepared themselves. Replacement and repair work took place while the plant was reconfigured for the next batch. This is informed decision making — enabled through fieldbus.