Frequently Asked Question
How does demand rate set to "based on demand rate" change the PFH calculation? For SIFs using sensors, logic solver, and final elements with HFT>0 (with redundancy), how will the high demand calculation for PFH account for changes in the manual proof tes
Last Updated 5 years ago
If you set the demand mode to 'based on demand rate' the tool will determine the demand mode based on proof test intervals and the demand rate you enter. This will determine if you are calculating PFH for high demand and continuous demand or PFDavg for low demand. The proof test interval will impact the detection frequency of failures within the redundant configuration. Using simplified equations: PFH = PFD/TI, Where TI = proof test interval. (Note PFD, not PFDavg). For a 1oo1 configuration: PFD = lambdaD*TI, therefore PFH = lambdaD. For 1oo2 configuration: PFD = (lambdaD * TI)^2, therefore PFH = lambdaD^2 * TI