When a component failure occurs, it generally takes less time to replace the failed unit with a spare than it does to repair the failed unit. Therefore, the use of spares increases the availability of a system by decreasing downtime.

Spares pools are collections of spare components. You can assign a unique spares pool to each block in the diagram. Or, to have multiple blocks share the same spares pool, you can assign them the same collection.

You insert and define the spares pools to assign to blocks in the Project’s RBD Spares file. For more information, see RBD Spares Files. You then assign a block to a spares pool on the Spares page in its Calculation Properties window. For more information, see Block Calculation Properties.

The use of spares does not affect your system configuration but rather allows you to best determine how many spares to have on hand for system components. The results are a system with improved performance measures that minimize or maximize the specified goal.

To extend its advanced capabilities even further, the RBD module supports spares optimizations, which refers to calculating the optimal number of spares to have on hand for a component to achieve a specified system goal, considering various system-level constraints such as desired system capacity or availability. For example, you can optimize the number of spares needed to achieve a desired availability with a goal of minimizing either spare costs or system downtime. In such cases, optimization stops when the desired system availability is reached and the addition of more spares is no longer cost-effective.

Once you assign a block to a spares pool, you indicate whether you want to optimize the number of onsite and offsite spares on the Spares page in the block’s calculation properties. Additionally, you indicate whether you want to optimize the replenishment level for spares. For more information, see Calculating the Optimal Number of Spares for a Block.