Design-in Maintainability

The words maintenance and maintainability are often used interchangeably.

Maintenance is the performance of fixing or replacing an asset. Maintainability is a designed-in parameter. As shown in the graph, by the time a machine is built, you’ve lost more than 95% of the possibility for life-cycle cost reductions. Maintainability needs to be implemented in the planning phase.

Statements from the Principles of Maintainability Design (B.S. Blanchard in NASA RCM Guide ) include:

• Great maintenance procedures cannot overcome poor equipment design.

• All parts and components are replaced eventually, so design for that time.

• Label key components, show flow direction, and provide decision-making information.

• Design systems so failures are obvious.

• Reduce the opportunity for human error during maintenance.

• Repair is mainly a human activity. Design maintenance tasks to fit human limitations.

• Design repair tasks, alignments, and adjustments for minimum tear down.

• Accessibility should enable easy access to maintenance points and largely reduce maintenance time.

I teach thirty categories for Design for Maintainability. A sampling of four categories that you should be considering are:

Standardization: Minimize the proliferation of parts, material (hoses, mechanical/electrical components, valves), tools, and processes/procedures. Have you eliminated the need for special tools? Are spare parts common coded to reduce excess spares? 

Accessibility: This defines the ease at which a component can be accessed for intended maintenance. Is the repair space large enough? Are reach distances adequate? Are guards or other interfering items easily and safely removed? Can parts that break frequently be easily removed?

Visual Aids: Good visual controls facilitate fast and accurate maintenance. Do you use bar coding on your assets and in your spare-parts storage? Are lubrication points identified (color coded and alpha-numeric) with type of lubricant, amount, and frequency? Are all maintenance points visually accessible from the side or end of machine and have line-of-sight inspection capability?

Troubleshooting: Is key information quickly available, such as pressure, amperage, fluid flow, component identification? Do you have self-checking features and/or built-in test capability? Can hydraulic, electrical, and other systems be easily traced throughout the machine? Are your engineers trained to include design-for-maintainability concepts into machinery and equipment designs? Do you have checklists on key items for areas such as routine maintenance, accessibility, and hydraulic/mechanical/electric system design? Are there DfM (Design for Maintainability) expectations written into your purchasing specifications, i.e., statements such as, “all hydraulic lines should be replaceable in 10 to 15 minutes.” 

Not designing in maintainability adds to MTBF. By spending a little more initially (versus cutting costs), how maintenance is performed can be significantly improved over the life of the asset.

There are numerous reliability and maintainability activities that should be done during the planning phase through the operating and maintaining-equipment phases. If you’re looking for checklists as they apply to the life cycle of machinery and equipment and actions to be followed, refer to the Reliability and Maintainability Guideline for Manufacturing Machinery and Equipment (SAE Order No. M-110.2). EP