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

General Guidelines 21• Under certain conditions, a PES may be run in a mode which allows anexternal computer or operator station to write to system attributes. This isnormally done by means of a communication link. The following guidelinesapply to writes of this type:– Serial communication should use Modbus or another approved protocolwith CRC checks.– Serial communication should not be allowed to write directly to outputpoints.– For information about writes to safety-related variables that result indisabling safety action, see section “Module Diagnostics” on page 43.• PID and other control algorithms should not be used for safety-relatedfunctions. Each control function should be checked to verify that it does notprovide a safety-related function.• An SIS PES should be wired and grounded according to the proceduresdefined by the manufacturer.Emergency Shutdown SystemsThe safe state of the plant should be a de-energized or low (0) state.For ESD functions, it is recommended that the hardware devices connected to PESoutputs should be made of fail-safe components or should have two separate,independent shutdown paths which are periodically inspected.Burner Management SystemsThe safe state of the plant should be a de-energized or low (0) state.When a safety system is required to conform with the DIN 0116 standard forelectrical equipment in furnaces, PES throughput time should ensure that a safeshutdown can be performed within one second after a problem in the process isdetected.Chapter 2Application Guidelines