Preventive maintenance (PM) is the foundation of every maintenance strategy — yet organizations continually skip taking a disciplined approach to developing a PM program. They will develop a few incomplete checklists or schedules and then move on to PdM (predictive maintenance), RCM (reliability-centred maintenance) or TPM (total productive maintenance). Soon they realize they do not have sufficient resources to properly execute their PdM, RCM or TPM programs.
Why? Because their current resources are too busy fire fighting to devote enough time to the more advanced strategy components. Without an effective PM program, the organization cannot transition from a reactive to a proactive environment.
An effective PM strategy focuses on the basics including good inspections, proper lubrication practices and proper fastening procedures. Studies have shown that over 50 percent of all equipment breakdowns have a root cause in the neglect of these basics. For example,
- Has your company ever experienced an equipment breakdown and when a root cause analysis was performed, the cause was an item that should have been found on a PM inspection that was completed less than a month ago?
- Have bearings ever failed at your company due to improper (too little or too much) lubrication?
- Have mechanical failures occurred because a fastener was not installed correctly (proper torque), began to loosen, created vibration which creates wear, and ultimately fails?
Rather than fix the PM checklists, train their employees in the basics and conduct completion inspections, companies move on to the next three-letter acronym, virtually guaranteeing less than optimum results for their future endeavours.
If the PM program is being developed or changed for existing equipment, the following steps should be followed:
1. Assemble all current program information
If there is an existing PM program, it is important to collect all of the existing information related to the program. This will include:
- All of the existing PM tasks
- Downtime history
- Work order history
- Production performance reports
- Design engineering specifications
This information should be compiled into a chronological order. This will provide the detail to plot the entire life cycle of the equipment. This ensures the equipment’s life cycle is understood so that the proper PM tasks can be specified.
2. Determine the PM task lists
Using the data that has been gathered to this point, the maintenance (and/or reliability) engineer and the maintenance planner for the equipment can begin developing the preventive maintenance tasks. Using this data, the proper blend of inspections, routine services, lubrication and basic adjustments can be determined.
3. Create the task details
In this step, the actual work to be performed is detailed. This will include a complete job plan for the PM tasks. This requires the planner to detail the skilled labor requirements, the spare parts required and any special tools or equipment that will be required. Once the plan is finalized, the time estimation should be specified for the PM task.
4. Set intervals
This step sets the frequency for performing the PM. Types of PM schedules include:
- Calendar based
- Usage based
- Condition based
Once the type of frequency is set, the PMs are ready to execute.
5. Monitor performance
Since a PM program is never finished, it is necessary periodically to review the PM program by comparing the PM’s to the failures of any equipment components. If changes are required, the PM program should be adjusted to mitigate the failures that are occurring.
Once the PM program is considered effective, it is still not finished. When predictive tools are applied by the company, the PM program will undergo further change, since the predictive tools will replace many of the pure inspection PM tasks. Additionally, when the company progresses to utilizing many of the reliability analysis tools (including Reliability Centered Maintenance), the PM program will again require modifications.
If the above steps are applied to the PM program, it can be effective reducing the amount of reactive maintenance to less than 20 percent of the total maintenance workload. Then companies can successfully move to higher-level maintenance strategies.