Ensuring that a power or steam generation unit will trip when required in compliancewith NFPA-85 Boiler and Combustion Systems Hazards Code and/or an OEM specifiedtrip condition is present should always be a major concern for design and implementationengineers. Of equal concern is preventing unnecessary unit trips or load reductions whichnot only reduce plant production but can also lead to excessive equipment degradation.In either case it is necessary to have the highest possible level of confidence that theprocess signals within the control system are reliable and accurate. Traditionally, powergeneration plants have relied on hardwired 4-20mA signals to achieve this level ofconfidence. However, with the introduction of FOUNDATION Fieldbus to the power andother industries, the question has arisen regarding its usage for critical signals thatdetermine the trip conditions.With on board device diagnostics, FOUNDATION Fieldbus provides operators with alertsto off normal device conditions such as plugged impulse lines or improper valve positionthat could result in bad or incorrect signals that have the potential to result in either aspurious trip or misreading conditions that should result in a unit trip. This paper
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