AADvance Safety Manual - Tuv-fs.com

Chapter 6 ChecklistsEngineering ChecklistsI/O Architecture ChecklistDescriptionHas the PST been specified ?What is the PST?Has the fault detection time for the system been specified ?What is the fault detection time?Is the safety-accuracy adequate for the application?Where the fault detection time is greater than the PST, does thesafety-related I/O configuration provide a fail-safe configuration?Yes/NoIf not, the system topology shall be discussed with the client toensure that the system implementation is safe.If a probability of failure on demand has been specified, has thisbeen met?Do the selected architectures provide solutions where there isno single power source or distribution point of failure that couldlead the system to fail to function safely when required?Have sensor fault conditions been taken into account?For each of the I/O signal types, do the I/O modules provide thecorrect characteristics and behaviour for the intended sensor oractuator (including minimum and maximum load requirements)?If not, have additional interfacing elements been included toensure that the effective signal is compatible with the selectedmodule type?Are the selected I/O module types compatible with the requiredI/O architecture?Has the allocation of signals to I/O modules and channelsconsidered each of the signals' function?Ensure that potential module and power group failures result ineither continued safety function or fail-safe operation.Do safety related inputs and outputs use only thoseconfigurations identified as safety relatedAre there any safety-related, normally de-energised outputs?If so have redundant power sources, power failure warning andline monitoring been provided?Document number 553630 Issue 7: February 2010 6-3