Safety Considerations Guide, Tricon v9.0 - Tuv-fs.com

30 Guidelines for Tricon Controllers• Maintenance instructions outlined in the Tricon Planning & InstallationGuide should be followed.• If degradation to dual mode occurs, continued operation without repairshould be limited to 1500 hours (two months).• If degradation to single mode occurs, continued operation without repairshould be limited to one hour.• The GATENB function allows external hosts to write selected aliasedvariables even when the remote mode is false. A network using theGATENB function should be thoroughly validated to ensure that only theintended aliased variable range is used.Additional Fire and Gas GuidelinesProject Change and Control• Analog input cards with current loop terminations should be used to readdigital inputs. Opens and shorts in the wiring to the field devices should bedetectable. The Triconex library function, LINEMNTR, should be used tosimplify program development.• A controller should be powered by two independent sources.• If outputs are normally de-energized, a Supervised Digital Output Moduleshould be used to verify proper connection to the final control element andto check the load and the wiring for potential shorts.• If degradation to dual mode or single mode occurs, repairs should be timelyand limits for maximum time in degraded mode should not be imposed toensure maximum availability.A change to a project, however minor, should comply with the guidelines of yourorganization’s change control committee. The following steps are recommended:1 Generate a change request defining all changes and reasons for changes, thenobtain approval for the changes from the Safety Change Control Committee(SCCC).2 Develop a specification for changes, including a test specification, then obtainapproval for the specification from the SCCC.3 Make the appropriate changes to the project, including those related to design,operation, or maintenance documentation.Tricon Safety Considerations Guide