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

24 Guidelines for Tricon ControllersSafety-Critical ModulesIt is recommended that only the following modules be used for safety-criticalapplications:• Main Processor Modules, all models• Communication Modules, all models• Digital Input Modules, all models• Digital Output Modules, all models• Analog Input Modules, all models• Analog Output Module, Model #3805 only• Pulse Totalizer Input ModuleThe Relay Output Module is recommended for non-safety-critical points only.Safety-ShutdownA safety application should include a network that initiates a safe shutdown of theprocess being controlled when a controller operates in a degraded mode for aspecified maximum time.The Triconex Library provides two function blocks to simplify programming asafety-shutdown application: TR_SHUTDOWN and TR_CRITICAL_IO. To seethe Structured Text code for these function blocks, see Appendix A, “Peer-to-PeerCommunication.” For more information on safety-shutdown networks, see section“Sample Safety-Shutdown Programs” on page 55.Response Time and Scan TimeScan time must be set below 50% of the required response time. If scan time isgreater than 50%, an alarm should be available.Disabled Points AlarmA project should not contain disabled points unless there is a specific reason fordisabling them, such as initial testing. An alarm should be available to alert theoperator that a point is disabled.Tricon Safety Considerations Guide