One of the most basic maintainability requirements is that the system be easy to maintain by human personnel. Maintainability analysis of a system typically involves maintenance tasks that deal with the repair or removal and replacement of a part or subassembly. Maintenance tasks usually involve the disassembly, which is needed to access the target component, component repair or replacement and subsequent reassembly.
Thus, human factors analysis is performed to identify problems related to the interaction between maintenance personnel and the design model in performing each maintenance task. This analysis is used to verify that each required maintenance task, and its associated motions and manipulations,
can be performed by humans. It deals more with the qualitative requirements than the quantitative requirements. Also, it is extremely important, that this
analysis be done while the product is still in the early design stages, i.e., before any "metal is bent."
Human factors problems may involve the limited strength of maintenance personnel, limited or no work clearance required to carry out the task, i.e., accessibility problems and problems related to visual requirements of the maintenance person performing the task. Thus, human factors analysis involves three major considerations:
- Strength analysis
- Accessibility analysis
- Visibility analysis
Strength analysis. This analysis is used to determine the feasibility of the disassembly and assembly sequences. Determine whether or not the maintenance person is able to carry out a maintenance activity that requires a certain level of human strength. That is, to evaluate the ability of the maintenance person to carry, lift, hold, twist, push, and pull objects in a standard body position (i.e., standing, bending, sitting, squatting, lying, etc.). Strength analysis can be one of the most important criteria for the evaluation of a maintenance task.
Accessibility analysis. This analysis is performed to identify design problems related to the inability of maintenance personnel to access the work area, i.e., to detect possible collisions during the maintenance activity.
Visibility analysis. For some maintenance activities it is important (e.g. for safety considerations) that the maintenance person be able to fully observe the work area.
In the past, human factors analyses were very time consuming. They required the construction of expensive physical mock-ups to perform the analysis and also, unfortunately, the analysis was not done until the final stages of design, when modifications were very costly. However, there are a variety of modern, animated, computer-aided-design (CAD) tools and new virtual reality techniques available to assist the maintainability engineer in
effectively and efficiently performing these analyses. Furthermore, when problems are discovered in the course of the human factors analysis, the proposed design modifications can be quickly verified for their effectiveness using these same tools and techniques.