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

Guidelines for Tricon Controllers 29SIL3/AK6 GuidelinesFor SIL3/ AK6 applications, the following guidelines should be followed:• DIN V VDE 19250/AK6 applications that require continued operation afterdetecting an output failure must have a secondary means of operating theoutput. A secondary means may be an external group relay or a single pointon an independent output module that controls a group of outputs. If a relayis used, it should be checked at least every six months, manually orautomatically.• If non-approved modules are used, the inputs and outputs should be checkedto verify that they do not affect safety-critical functions of the controller.• Two modes control write operations from external hosts:– Remote Mode—When the keyswitch setting is REMOTE, externalhosts, such as Modbus master, DCS, etc., can write aliased data in thecontroller. When false, writes are prohibited.– Program Mode—When the keyswitch setting is PROGRAM, TriStationcan make program changes, including operations that modify thebehavior of the programs currently running. (For example, DownloadAll, Download Change, declaring variables, enabling/disablingvariables, changing values of variables and scan time, etc.)Remote mode and program mode are independent of each other. In safetyapplication, operation in these modes is not recommended. In other words,write operations to the controller from external hosts should be prohibited. Ifremote mode or program mode becomes true, the application programshould include the following safeguards:– When remote mode is true:• A program should turn on an alarm. For example, if using theTR_SHUTDOWN function block, the ALARM_REMOTE_ACCESSoutput could be used.• Aliased variables should be checked for adherence to the guidelinesdescribed in section “Maintenance Overrides” on page 32.– When program mode is true:• A program should turn on an alarm. For example, if using theTR_SHUTDOWN function block, theALARM_PROGRAMMING_PERMITTED output could be used.• Wiring and grounding procedures outlined in the Tricon Planning &Installation Guide should be followed.Chapter 2Application Guidelines