Foundation Fieldbus is an all-digital, serial, two-way communications system that serves as a local area network (LAN) for factory/plant instrumentation and control devices.
The fieldbus environment is the base level group of the digital networks in the hierarchy of plant networks. Foundation Fieldbus is used in both process and manufacturing automation applications and has a built-in capability to distribute the control application across the network.
Unlike proprietary network protocols, Foundation Fieldbus is neither owned by any individual company, nor regulated by a single nation or standards body. The technology is controlled by the Fieldbus Foundation, a non-profit organisation made up of many of the world's leading control and instrumentation suppliers - and end users.
While Foundation Fieldbus retains many of the desirable features of the 4 to 20 mA analog system, such as a standardised physical interface to the wire, bus-powered devices on a single wire, and intrinsic safety options, it offers a host of additional benefits to users. This article highlights the advantages of this bus system.
Device interoperability
With interoperability, one fieldbus device can be replaced by a similar device with added functionality from a different supplier on the same fieldbus network while maintaining specified operations. This permits users to 'mix and match' field devices and host systems from various suppliers. Individual fieldbus devices can also transmit and receive multivariable information, and communicate directly with each other over a common fieldbus, allowing new devices to be added to the fieldbus without disrupting active control.
Enhanced process data
Multiple variables from each device can be brought into the plant control system for archival, trend analysis, process optimisation studies, and report generation. This access to accurate, high-resolution data enables processes to be fine-tuned for better manufacturing throughput and reduced plant downtime. These efficiencies add up to higher plant performance and profitability.
Expanded view of the process
Modern fieldbus devices, with powerful, microprocessor-based communications capabilities, permit process errors to be recognised faster, and with greater certainty. As a result, plant operators are notified of abnormal conditions or the need for preventive maintenance, and can make better production decisions. Problems that detract from operating efficiency are more quickly corrected, enabling yields to go up while raw material costs and regulatory problems decrease.
Improved plant safety
Fieldbus technology helps manufacturing plants keep up with increasingly stringent safety requirements. By providing operators with earlier notification and warning of pending and current hazardous conditions, fieldbus allows for corrective action before an unplanned shutdown. Enhanced plant diagnostic capabilities also reduce the need for frequent access to hazardous areas, thus minimising the risks to field personnel.
Easier predictive maintenance
Enhanced device diagnostics capabilities make it possible to monitor and record such conditions as valve wear and transmitter fouling. Plant personnel are able to perform predictive maintenance without waiting for a scheduled shutdown, thus avoiding or reducing downtime.
Reduced wiring and maintenance costs
Foundation Fieldbus' use of existing wiring and multidrop connections provides significant savings in network installation costs. This includes reductions in intrinsic safety barrier termination and cable costs, particularly in areas where wiring is already in place.
Additional cost savings can be achieved through the decreased time required for construction and start-up, as well as simplified programming of control and logic functions using software control blocks built into fieldbus devices. More information on this subject is available from the Foundation Fieldbus site ( www.fieldbus.org).
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