Effective maintenance tasks for each equipment are crucial for maintenance management. Many resources are used to design the tasks in order to improve a plant’s reliability and productivity. However, the way we incorporate all tasks in work orders (WOs) and schedule them will determine the final efficiency of our preventive maintenance strategy.
To effectively schedule the WOs, we use different criteria to group them. Each group has pros and cons, and in practice we usually apply a combination of them to get the most of our resources and increase our department efficiency.
The main criteria to group WOs are:
1) By areas:
Manufacturing plants are always divided into functional or physical areas (production lines, process areas like packing, assembly, sterilization, filling, welding, and so on). One logic and efficient way to group the WOs is to perform the maintenance tasks for a specific area altogether.
The main advantage of this approach is that technicians have all the equipment closely positioned. In doing so, we save the translation time between one area to the next, which could be huge in some facilities. Furthermore, the proximity between equipment allows the technician to concentrate on his work and to avoid tedious tasks like packing the tools and transferring them to other places each time he finishes a WO.
2) By equipment:
sometimes it is best to group all the tasks, related to one equipment, that need to be done at the same time. This is especially useful for complex equipment that is time consuming to disassemble and access internal components. In order to maximize our work efficiency, we take the opportunity to perform all the necessary maintenance once the machine is opened and accessible.
Sometimes, depending on how long that time is, it is convenient to perform maintenance tasks that are scheduled for a later time to save the disassembling time. This decision must be based on this fact and also on the cost of the spares (if applicable), life cycle, available time, manpower, and so on.
One disadvantage could be lack of physical space, which would prevent multiple tasks from being performed at the same time. Other technicians from other specialties would have to wait to start working until their colleague finished. Usually when this happens, it is impossible to use that time to do other tasks resulting in delays for one or more technicians to begin their work. Furthermore, this would extend the time needed to finish the complete project. Thus, time frames and availability issues should be taken into account during the planning and scheduling phase.
3) By craft:
Since equipment have many systems, their preventive maintenance tasks must be performed by different technicians (mechanical, electrical, electronic, et al.). We can group the tasks belonging to a certain specialty skill so they can be performed together.
This will avoid the problem I mention before about waiting periods due to interference with other technicians. However, a WO should be carefully analyzed to detect combined tasks that need more than one craft. For instance, when a mechanical part needs replacing, it is necessary to remove part of the electrical installation, followed be the reinstallation and a test for functionality.
4) By frequency:
This is an obvious division because each task and WOs have individual frequency. To simplify, most common frequencies are usually daily, weekly, fortnightly, monthly, and so on. This is mostly to facilitate the control and make it more intuitive.
Nowadays, frequencies and WO generation are mostly controlled by Computerized Maintenance Management Software (CMMS), and we can use almost any frequency. However, it is still a good practice to use common frequencies to facilitate planning and scheduling work.
Another issue to consider in this point is the equipment’s availability, especially in fast paced 24/7 or 24/5 environments. The time windows to perform preventive maintenance could be very tight when work is being performed continuously with very few or even no breaks.
Of course, this criterion is always used in a combination with the others, since it is the one that tells us when it is necessary to do the job. Nevertheless, frequencies can be modified in order to take advantage of other aspects like the availability of time and space needed to perform tedious tasks for more complex equipment.
5) By specific activities:
Sometimes maintenance tasks can be grouped by activities particularly when they are simple, repetitive ones. This can be a special case of points 1 and 3. Typical examples of this are thermographic checks of electrical cabinets or motors, lubrication campaigns in specific areas, ultrasonic detection of compressed air leaks, just to name a few.
Special mention about CMMS
As I mentioned earlier, CMMS simplifies some aspects of WO generation and control, but it is crucial to understand that this software will only follow our indications. The competence of the software to perform as requested will be explained in a future post. Ultimately, the key factor is the dedication and skills of the engineers involved in the maintenance planning process that will determine the proper and efficient use of the resources. As the popular GIGO establishes, the CMMS will work according to the information we input, therefore Garbage In, Garbage out, no matter how sophisticated, expensive, or complex our software is.
In my opinion, the design of every task directly impacts the performance efficiency of our equipments. Specific maintenance tasks govern equipment reliability and amount of downtime. On the other hand, the efficient use of the maintenance department’s resources, the equipment as well as manpower, is affected by the arrangement of the WOs. For instance, poor group organization results in overuse and hinder the reliability of resources, which decreases the maintenance department’s efficiency.
We can do a remarkable job of designing the maintenance plans for equipment, studying manuals, gathering data, and employing models that fit any patterns of failure. If we fail in the scheduling phase, we can increase the number of pending WOs and negatively impact KPIs, such as PM Compliance and PM effectiveness.
What is your experience? Do you know other ways to group the WOs?
Are there specific criteria for your industry?
Have you found it difficult to group some WO efficiently?
Please add your comments below so everyone can learn more about this topic.
Thanks for reading!