Reliability Allocation is a method of apportioning a system target reliability amongst sub-systems and components. It is a useful tool at design stage for determining the required reliability of equipment to achieve a given system reliability target.

Using Reliability Allocation

During the design phase of a product, it is often required to evaluate the reliability of the system. The question of how to meet a reliability goal for the system arises. Reliability Allocation can be used to set reliability goals for individual subsystems so that this goal is met. The simplest method is simply to distribute the reliability goal equally among all subsystems.

However, this rarely gives the best distribution of reliability objectives for all subsystems. It is better to allocate reliability values between the subsystems based on complexity, criticality, achievable reliability, or other factors that are deemed appropriate.

The Allocation module within Reliability Workbench supplies the user with six methods for assigning subsystem reliability values:

• Non-restricted equal allocation
• Non-restricted graded allocation
• Non-restricted proportional allocation
• Non-restricted redundancy proportional allocation
• Non-restricted reliability re-allocation
• Restricted direct research allocation

Inside the module, a system hierarchy can be constructed where sub-systems may be broken down further to component level, allowing a complete system allocation model.

Below is a screenshot showing the Failure rate allocation apportioned between various blocks: