Maintenance and Reliability Best Practices. Ramesh Gulati
be applied to the assets.
• It determines and ensures that the optimum level of spare parts is stocked for highly critical assets.
• It provides input into the capital program so that highly critical assets are given a higher priority for upgrade or replacement.
• It guides reliability/maintenance engineers and professionals so that they focus their reliability improvement efforts on the most “critical” assets.
A mitigation strategy should be established for various types of criticality to ensure the appropriate level and quality of maintenance performed on assets. Figure 4.8 shows an example of a mitigation strategy for a different level of criticality.
FIGURE 4.8 Example of Asset Criticality and Mitigation Plan
There is definitely nothing more wasteful than spending lots of time assessing the criticality of every asset in the organization, loading this information into the CMMS/EAM system, and then doing nothing with it.
Job Priority
Priority codes allow ranking of work orders to get work accomplished in order of importance. Too many organizations neglect the benefits of a clearly defined prioritization system. The organizational discipline that comes through communication, education, and management support is key to the correct usage of priority codes.
Many organizations have more than one prioritization system;however,most of them have been found to be ineffective. The drawbacks of not clearly defining the priorities include:
• Wasted maintenance labor hours on tasks of low relative importance
• Critical tasks being lost in the maintenance backlog
• Dissatisfied operations customers
• Lack of faith in the effectiveness of the maintenance delivery functions
A disciplined method of prioritization will eliminate tasks being done on a whim and instead allow work to proceed according to its true impact on the overall operations of the plant. It will also allow the maintenance delivery function to be executed in a far more effective manner.
Priority System Guidelines
The system needs to cater to the following requirements equally and provide a universal method of coding all works orders:
• Plant-wide asset priorities, allowing for better plant-wide utilization of resources
• Operations requirements
• Improvement projects
Accurate prioritization covers two distinct decision-making processes. These are:
• Asset criticality
• Impact of task or work to be done on the overall operations
The original priority of the work orders needs to be set by the originator of the work order and should be validated by the coordinator. The work originator is the most qualified to make an initial assessment of asset criticality and impact of the work. Lists of major assets and their criticality will help in decision making for final priority ranking.
All the plant assets should be assessed to establish a criticality number by a team of plant professionals who are familiar with the assets and the impact of their failure. Most of the CMMS/EAM systems have a field for entering each asset’s criticality number. Lower criticality items or areas will then be easier to recognize. The following criteria can be used to assign asset criticality and work impact (if not corrected), which can then be used to make an objective assessment of overall job priority:
Asset Criticality
| Criticality # | Description |
| 5 | Critical safety-related items and protective devices |
| 4 | Critical to continued production of primary product |
| 3 | Ancillary (support) system to main production process |
| 2 | Standby unit in a critical system |
| 1 | Other ancillary assets |
Work Impact, if Not Corrected
| Work Impact # | Description |
| 5 | Poses an immediate threat to safety of people and/or plant |
| 4 | Limits operations’ ability to meet its primary goals |
| 3 | Creates hazardous situations for people or machinery, although not an immediate threat |
| 2 | Will affect operations after some time, not immediately |
| 1 | Improves the efficiency of the operation process |
Work Priority = Asset Criticality × Work Impact
WO #1: Asset criticality of 5 and work impact of 4 gives an overall job priority of 20.
WO #2: Asset criticality of 4 and work impact of 4 gives an overall job priority of 16.
In this case, WO #1 will have a higher priority than WO #2. The combination of the criticality and the impact of the work can be cross-referenced to give relative weight to each task when compared with all other work.
Backlog Management
The combination of work classification and job priority allows an organization to make sense out of its maintenance backlog. A maintenance backlog is very simply the essential maintenance task to repair or prevent equipment failures that have not been completed yet. By classifying these maintenance tasks into different categories and then prioritizing within those categories, maintenance backlogs can be developed from an overall organizational perspective or within smaller organizational groups or categories (e.g., PM, CM).
Why manage your backlog at all? Why not just work whatever maintenance tasks come due? The more toward proactive maintenance that an organization moves, the more likely it is, at least in the beginning, that the organization will identify more maintenance tasks than can possibly be addressed within that immediate time period (typically that week). Therefore, to keep from addressing the low-priority tasks or the categories of work that will not have the largest impact on the overall reliability of the organization, a backlog management system must be developed. Then the most effective approach to the backlog management system requires appropriate work classification and priority.
A backlog of 4–6 weeks is an industry benchmark. For example,say a maintenance department/section has on average 10 technicians. Then we get
Average labor hours available/week =
10 × 40 = 400 labor hours
Therefore, this department should have a backlog of between
400 × 4 = 1,600 labor hours
and
400 × 6 = 2,400 labor hours
On average, the backlog should be about 2,000 labor hours.
The right amount of backlog ensures that all the employees have the right work to do with appropriate planning (planned work) and that they are not hunting for work or sitting idle.