Designing control cabinets that save as much space as possible can be a challenge for plant operators working in fieldbus-based automation. Fieldbus installations help optimize space in electrical cabinets, since intermediate wiring is not required, and each field cable supplied from the cabinet connects up to 20 field devices to the control technology. The number of segments that can be installed per control point cabinet plays a key role in planning, because more segments per cabinet means fewer cabinets in the supply room and significant cost savings during construction. These factors contribute to savings for investors, planners, and plant operators. In order to achieve this goal, three factors have to be taken into account:
Many of today’s process automation applications depend on fieldbus technology because of its efficiency in digital bilateral communication. Fieldbus devices can communicate standard process values to the plant operator and the DCS; however, they also have the ability to provide additional information such as operating hours, process temperature, and status bytes for condition monitoring. This wide range of measurements allows plant operators to perform preventative maintenance, recognize field device faults, and predict outages to reduce downtime and increase availability.
"The elephant in the room" – with this metaphorical idiom, James Powell, Senior Product Specialist Industrial Communications at Siemens, describes in his blog post 'Is Profibus or 4-20mA More Accurate?' in detail the issues with 4 mA ... 20 mA signal quality that everyone is aware of, but nobody wants to talk about.
...and, the goose!
As I was reading John Rezabek's recent article "Can Improved Physical Layer Diagnostics Save Christmas Dinner?", a few thoughts came to mind.
John pointed out that keeping the installation — junction boxes, instrument housings — sealed from moisture ingress is one of the big challenges for both fieldbus and 4 mA … 20 mA installations.
Recently, ControlGlobal.com featured an article by John Rezabek: Why Industrial Couplers Aren't Commodities?