3. DESCRIPTION OF PROGRAM OR FUNCTION
AVPROG is a large-scale simulation program used to estimate steady-state availability of a system, typically a large production unit. The system is modeled as a success logic flow block diagram of equipment affecting the production output. AVPROG simulates system operation over a specified time period using Monte Carlo techniques. System components are failed and restarted using numerous types of distributions that are available. Among the distributions available are the exponential and the lognormal. AVPROG computes availability based on averages from a number of simulation cases (batches) for the specified production time interval. It also ranks unavailability contributors to permit investigation of design modifications that have the greatest impact on availability.
Input to AVPROG consists of system geometry (as defined on logic diagrams), mean time between failures, mean time to restore (MTTR), and mean plant delta (MPD) for each logic block. MTTR is defined to include access time, equipment preparation time, actual replace time, cleanup time, and time to restore the equipment and associated subsystem to normal operation. MPD is defined as additional time to restore full production after theequipment in the logic block has been restored.