System-level reliability requirements are not usually sufficient to scope the design effort. Consequently, "complex" products usually require allocating the system-level reliability requirements to lower levels.
When a product contains only a "few" parts, the allocation of reliability requirements may not be necessary or cost-effective. Functional complexity, parts count, and challenges to the state-of-the-art are some considerations in a typical allocation process. In some cases, the process is iterative. In other cases, the requirements can't be satisfied and trade-off discussions may be needed.
RAM Allocation Features
- Allocation process is approximate.
- Six basic allocation processes, or models.
RAM Allocation Uses
- Establish reliability goals for hardware and software at lower levels in the system hierarchy.
- Establish reliability requirements for supplied items.
- Identify the need for more reliable parts.
- Identify the need to simplify the design.
- Identify the need to derate some or all parts.
- Identify the need for redundancy.