Elements of a Good Preventive Maintenance Program
If your preventive maintenance program does not have the right content, it will never generate the desired and possible results. If you haven’t updated the program in the past five years, it probably contains not only too much PM but also the wrong activities. A good PM program has 90% of all PM activities done as inspections while equipment is running.
Classical examples of wrong and excessive PM are those activities on V-Belt drives, couplings and many other components with safety guards. Many PM programs suggest weekly inspections of these components by maintenance and at every shift by operators. On top of that, a shutdown PM is also done. The fact is that the design of most guards makes on-the-run inspection of the components impossible, and it doesn’t make sense to inspect something that cannot be seen.
Many guards are big and heavy, so it can take two crafts people several hours to remove the guards, do the inspections and replace the guards during a shutdown. Even worse, if they find a problem on the component during the inspection and it has to be corrected before start up, this could lead to a prolonged shutdown and production losses.
A correctly designed guard allows for inspections on the run (see Figure 1). In a route based inspection program, each of these inspections takes an average of three minutes including walking time. If a problem is found during these inspections, a planned and scheduled corrective maintenance action will be done when the opportunity presents itself.
To decide the right content, you must understand three things:
- The consequence of component breakdown
- How failure can be detected
- How long before component breakdown can failure be detected
Consequence of a Breakdown
A breakdown is defined as the point in time when a component’s function ceases. The consequence of a breakdown can be prioritized in the following groups:
- Personal or environmental damage
- High costs for production lasses or maintenance to correct breakdown
- Preserve value
As a first step, we advise not to go into any elaborate and time-consuming evaluation to find the criticality of equipment; this can be done later. We use the following fast approach to evaluate criticality:
- What will happen if this equipment breaks down? For 90% of equipment the answer is given by reading the nameplate of equipment and understanding the process. If there is spare equipment, you can find out how fast the spare equipment can be started
- Ask operators. If you do not know the answer to the first question, you should ask an operator. That should take care of another 50% of the remaining questions.
- Consult process and instrumentation drawings. It is bad if the operator does not know the answer, but it also identifies a need for training. Together, we will look at a process and instrumentation drawing to learn what will happen if the equipment breaks down. This will answer most of the unanswered questions.
Using this screening process you only need to analyze what is important to analyze and you can save more than 90% of time as compared to processes suggested in Reliability Centered Maintenance and similar programs.
Using the above approach, the next step will be to set up the right PM for each component (Coupling, valve, cooler, etc.) of the equipment (e.g. Hydraulic system).
Documentation and Training
After you have selected the right PM procedure, you need to document the procedure. It is important to decide on the document format, because it should be used to train people and improve the procedure in the future. Remember, in this case we are talking about basic inspection methods, not predictive maintenance (PdM) methods such as vibration analysis and wear particle analysis.
It is easier AND safer to describe a method with pictures than words. The document also stands a better chance to be read and understood when it includes pictures. IDCON’s Condition Monitoring Standards books have 100 of the most common components documented in this type of format.
At bare minimum, you need to include “what”, “how”, and especially “WHY” an inspection should be done. It does take time to create these documents, but once you do, the document can be re-used for most all components of the same type, for example a coupling.
Frequencies and other values unique to the individual component will be described in the route list or in a hand held device. Do not make the mistake of assuming that crafts people or operators know how to inspect components.
In our experience, crafts people have been trained to do repairs and trouble shoot existing problems. Very few have been trained in inspections to discover problems before they are actually problems. Much of this training is a thought process; you need to teach people to think about inspections and anticipate latent problems.
At a minimum, training needs to include inspection methods for most common components and systems and a basic knowledge of instruments and tools such as high intensity lists, strobes, hand held IR instruments, optical tools and leak detectors.
It seldom works well to say, “PM is priority 1 and we will assign different people to do it as we see the need.” Or worse still, “Our team decides who will do inspections today.” Trying to do it this way almost guarantees the PM effort will fail.
Another common mistake is to assign the night shift to do PM when they have nothing else to do. The reason for having shift maintenance people is so they can respond to possible emergencies. If there are no emergencies, they are not needed on the shift and they can be moved to daytime work. The best results are always achieved when special people are assigned to do inspections on a full time basis.
Assigning dedicated inspection resources garners the following:
- The right people to do the inspections, including in or adjustments and repairs
- The right people trained for this unique work
- The ownership and interest for PM that is necessary for continuously updating and improving PM work.
- An easier situation to manage. It can be very tempting to pull the people who are supposed to do PM to do emergency work.
Wherever the assigned resources (PM inspectors) report to in your organizational structure, we advise they work very closely with the supervisor in the area where the inspections occur. They must report any findings and what they have inspected to the supervisor/area leader once or twice a day. When they have completed the route, they should do some of the repairs and adjustments that are the results of the inspections. This cuts back on administration and eases up the friction that can develop between PM inspectors and the crafts people who have to do all of the repairs.
It is also important that PM inspectors start all routes with an interview with the operators in the area; this not only improves communication but also the on-the-job training of operators. The ultimate goal should be to have the operators do the majority of PM inspections.
After you have decided the PM activity that needs to be done and the frequency you decide who should do it. The choices (in order of preference) are:
- Area Maintenance- Mechanical, Electrical, Instrumentation crafts person
- In house expert, for example Vibration Analysis or Wear Particle Analysis
- Outside expert, for example X-ray, Acoustic Emission