Process Flow Simulation Settings

To simulate a PFS diagram, choose Simulation > Simulation > Simulate or click the Simulate icon.

In the Process Flow Simulation window:

• Enter the Simulation End Time. Specify the time and the units of time used. Simulations begin at time = 0.
• In the Point Results Every field, specify the frequency at which the simulation will return results. For example, if you have entered 100 hours in the Simulation End Time field and you enter 10 hours in the Point Results Every field, the simulation will run from 0 to 100 hours and point results will be available at 10 hours, 20 hours, 30 hours and so on.
• Specify the Step Interval used in simulation. Process flow simulation is performed in time steps; the smaller the step size, the more accurate the simulation results will be, but the longer the simulation will take.
• Enter the Number of Simulations to be performed.

If you need your results to be repeatable, select the Use a Seed check box in the Advanced Options drop-down and enter a seed, which specifies a starting point from which the random numbers used in simulation will be generated. The same random numbers and, therefore, the same simulation results will be generated when the same seed value is used.

You can specify task types to exclude from the simulation, allowing you to create results and plots for a certain set of conditions. For example, you might exclude all preventive tasks to get a sense of how a corrective-only maintenance strategy differs from one incorporating preventive maintenance. To exclude task types, simply select the relevant check box(es) in the Comparative Options drop-down menu. You can exclude all corrective tasks, inspection tasks (not including the inspection portion of on condition tasks), preventive tasks and/or on condition tasks.  If any task type is selected for exclusion, a warning light will be displayed on the Comparative Options menu in this window. Additionally, the exclusion will be indicated in the PFS diagram plots and the General Summary results worksheet.

You can run simulations in multiple threads, which may improve performance and save time when simulating complex diagrams. The Number of Threads field in the Advanced Options drop-down allows you to specify the number of threads to use for simulation. In general, using twice as many threads as the number of cores in your computer is appropriate; a ratio of threads to cores greater than this 2:1 ratio is likely to degrade performance. To have the application automatically determine the number of cores in your system and set the number of threads accordingly, click the Calculate icon beside the Number of Threads field.

The number of threads you use affects repeatability of results. In order for your results to be repeatable, you must use the same number of threads and the same seed each time you simulate the diagram. When you are using multithreading, the seed that you specify in the Advanced Options drop-down is the seed for the first thread; seeds for additional threads are sequential (e.g., if you are using 3 threads and your starting seed is 7, the threads will use 7, 8 and 9 as the starting points for random number generation).

The same display options that apply for RBD and fault tree simulation are available for PFS diagram simulation.