Throughput Analysis

Throughput is the amount of output that can be processed in a given period of time. To understand system throughput, consider this example: Assume that each component in the system processes (or makes) something while operating. The RBD shown next contains two components in series, each processing/producing 10 and 20 items per unit time (for explanation purposes, we will call that “ipu”) respectively.

In this case, the system configuration is not only the system's reliability-wise configuration but also its production/processing sequence. In other words, the first component processes/produces 10 ipu and the second component can process/produce up to 20 ipu. However, a block can only process/produce items it receives from the blocks before it. Therefore, the second component in this case is only receiving 10 ipu from the block before it. If we assume that neither component can fail, then the maximum items processed from this configuration would be 10 ipu. If the system were to operate for 100 time units, then the throughput of this system would be 1,000 items, or (100 x 10).

Throughput analysis can be performed for simulation RBDs in BlockSim. Results are available at the block and system levels, taking into account the reliability and maintenance properties of the blocks and the system. In order to perform throughput analysis, you must specify throughput properties in the Block Properties window for the relevant blocks and select the Run Throughput Simulation option on the Analysis Settings page of the diagram's control panel.

Note: While throughput analysis is not available for fault trees, fault trees may be used as subdiagrams for simulation RBDs. To perform throughput analysis in this case, you would define throughput properties for the subdiagram in the Block Properties window for the subdiagram block. In simulation, the fault tree is simulated and determined to be up or down. If it is down, no throughput is passed to the next block in the RBD; if it is up, then the throughput properties defined for the subdiagram block determine the amount of throughput passed to the next block.

In many real-world cases, throughput can change over time (i.e., throughput through a component is not a constant, but a function of time). You can model variable throughput using phase diagrams.

The ReliaWiki resource portal has more information on throughput analysis at: http://www.ReliaWiki.org/index.php/Additional_Analyses#Throughput_Analysis.