The Three Types of MaintenanceCorrective Maintenance. Corrective maintenance is what to do when something breaks; it's better known as repairs. Preventive maintenance tries to spread costs by planning activities on a regular basis. Simplify preventive maintenance, schedule work orders and track inventory That's one of the answers.
Another is that new technologies make new strategies possible. When new technology gives us a new ability, we can leverage it in a new strategy. For condition-based maintenance and predictive maintenance, for example, sensors mounted on your assets and equipment capture a constant stream of data that you can use to help determine when to schedule upcoming inspections and maintenance tasks. Here, you use a program of inspections and tasks to find and fix small problems before they have a chance to become major problems.
Preventive maintenance is basically the idea behind the old saying that “An ounce of prevention is worth more than a pound of cure. One way to understand the benefits of preventive maintenance is to analyze all the problems that are avoided. Default maintenance is simply following the manufacturer's recommendations for maintenance, including when to perform inspections and maintenance. Basically, it's the same as condition-based maintenance, except that the data is analyzed to make accurate predictions about future failures.
You now have the same condition-based maintenance costs, plus the additional cost of even more sophisticated software that requires even more specialized training for your staff. For assets that don't fit either of these descriptions, it probably makes more sense to use preventive maintenance. As with many other strategies, you don't have to make a difficult decision between strictly one or the other. When an asset is newer, you can use default maintenance.
Later, when you have created a maintenance and repair history, you can begin to adjust the schedule to best suit your specific situation. Choosing the right maintenance strategy starts with understanding your options, benefits, and drawbacks. Execution to failure tends to get a bad reputation, but for a specific asset class and equipment, it's the best option. Use when things are difficult or impossible to maintain, cheap to carry in inventory, easy to replace, or not essential to your operations.
Preventive maintenance helps you find problems ahead of time when scheduling inspections and tasks. It also saves you money and frustration because you can plan everything in advance. For default maintenance, everything is basically the same as with preventive maintenance, except that it follows a schedule set by the manufacturer, not by your department. Condition-based and predictive by relying on sensors and special software to collect and analyze data from sensors installed directly on or near your assets.
For conditions, the software looks for readings outside the preset parameters. For predictive purposes, the software analyzes the data to predict future failures long before they begin to develop. In the end, there is no one and only perfect strategy for all time. You need to choose the combination that works best for your assets, adjust your focus as your assets age and your department collects data.
Preventive maintenance aims to detect and fix problems before they occur. It is usually carried out in the form of regular inspections, which usually occur several times a year. The main benefit of preventive maintenance is that it can eliminate unplanned downtime, since the ideal is to detect problems before they occur. Condition-based maintenance is sometimes considered a more advanced alternative to preventive maintenance.
Instead of being inspected according to a schedule, machines and systems are carefully observed for changes that may indicate imminent failure. A Proven Approach to Reduce Downtime by 90%. With our online training, your team can access first-class training wherever they are. Do you want to see what you can achieve with our support? Read success stories and testimonials from customers around the world.
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Across the industry, many definitions are used when it comes to the different types of maintenance. It can quickly get confusing when people talk about preventive maintenance, condition-based maintenance, or predictive maintenance, but they actually have something else in mind than you. Some people are very enthusiastic about these definitions and may spend a lot of time, for example, disagreeing with what preventive maintenance is and what is not. Let's not do that, instead, I'll give you my vision of the different types of maintenance and, most importantly, when to use them.
For example, when to use condition-based maintenance. However, since I am often asked questions about the different types of maintenance, I decided to give a quick summary of the types of maintenance. There are 9 types of maintenance divided between preventive maintenance and corrective maintenance. Instead, download The Types of Maintenance Tool Kit and learn what type of maintenance to use and when.
When people talk about preventive maintenance (or preventive maintenance), they generally refer to what is best described as time-based maintenance (TBM). Time-based maintenance is basically a type of maintenance that is performed at regular intervals while the equipment continues to operate in order to prevent failures or reduce the likelihood of failure. In the following paragraphs, I'll explore each of these types of maintenance in more detail, including when you should consider using them. Risk-based maintenance (RBM) is when you use a risk assessment methodology to allocate your scarce maintenance resources to those assets that carry the greatest risk in the event of failure (remembering that %3D probability x consequence risk).
As a result, equipment that has a higher risk and a very high failure consequence would be subject to more frequent maintenance and inspection. Low-risk equipment can be maintained at a much lower frequency and, possibly, with a much smaller scope of work. When you implement a risk-based maintenance process effectively, you should have reduced the total risk of failure throughout the plant in the most cost-effective way. Risk-based maintenance is essentially preventive maintenance in which the frequency and scope of maintenance activities are continuously optimized based on the results of tests or inspections and a thorough risk assessment.
Examples of risk-based maintenance would be risk-based inspection applied to static equipment such as vessels and piping or even pressure relief valves. Troubleshooting Maintenance tasks are designed to detect hidden faults that are often associated with protection functions. Think about pressure safety valves, disconnect transmitters, and the like. This type of equipment will not need to work until something else has failed.
This means that, under normal operating conditions, you will not know if this equipment is still working,. And since these flaws are hidden, you'll need to find them before you can trust that computer to protect you. It is important to realize that fault detection maintenance tasks do not prevent faults, but simply detect them. And once detected, you'll have to repair the fault you found.
Fault finding Maintenance is carried out at fixed time intervals, usually derived from legislation or risk-based approaches. Therefore, condition-based maintenance as a strategy seeks physical evidence that a failure is occurring or is about to occur. Thinking of CBM in this way shows its broader applications outside of condition monitoring techniques, often only associated with rotating equipment. The curve shows that as a fault begins to manifest, the equipment deteriorates to the point where it can be detected (point “P”).
If the fault is not detected or mitigated, it continues until a functional failure occurs (point “F). The time interval between P and F, commonly referred to as the P-F interval, is the window of opportunity during which an inspection can detect impending failure and give you time to address it. It is important to note that CBM as a maintenance strategy does not reduce the likelihood of failure through service life renewal, but rather aims to intervene before the failure occurs, with the premise that this is more economical and should have less impact on availability. A general rule of thumb is that the interval between CBM tasks should be half or one third of the P-F interval.
How much more effective the CBM is above fault maintenance depends on the duration of the P-F interval. With many caveats, rectification can be planned, materials and resources can be mobilized, and breakdowns avoided (although production is still stopped for the duration of maintenance). When the P-F interval is only a few days, the resulting organizational and workplace actions are much like a breakdown, and the value of CBM is largely lost. For CBM to be effective as a strategy, early intervention is essential.
This requires an efficient and effective process for data collection, data analysis, decision-making and, ultimately, intervention. For failure modes where the P-F interval shows great variability, condition monitoring is not an effective strategy. If you're interested in learning more about how to better manage failure modes, don't forget to check out my article Reliability-Focused Maintenance: 9 Principles of Modern Maintenance. Until recently, when talking about predictive maintenance (PDM), this was essentially synonymous with condition-based maintenance.
But with the advent of Artificial Intelligence, the much lower costs of equipment sensors (IIoT) and machine learning, there is a clear difference between predictive maintenance (PDM) and condition-based maintenance (CBM), at least in my opinion. I see predictive maintenance as an extension, a more advanced approach to CBM, in which we potentially use many process parameters obtained from in-line sensors to determine if our equipment is moving away from stable operating conditions and if it is heading towards a fault. The central idea here is to predict when the failure will occur and then determine the right time for maintenance intervention. There are many (very large) companies that are actively moving in this space and, without a doubt, it is an exciting and fast part of our discipline as maintenance professionals &.
However, I continue to believe that even the most advanced predictive maintenance approaches should be backed by sound principles of reliability and understanding. And I also think that using a predictive maintenance (execution to failure) or corrective maintenance strategy only restores the function of an element after it has been allowed to fail. It is based on the assumption that non-compliance is acceptable (i.e. No significant impact on safety or the environment) and that preventing failures is not economical or not possible.
In addition to being the result of a deliberate run-to-failure strategy, corrective maintenance is also the result of unplanned failures that were not prevented by preventive maintenance. A run-to-failure strategy can be effectively used for general area lighting, intelligent process instrumentation (no trigger functionality), etc. When the consequence of the failure is limited and you would not need an urgent repair. When choosing corrective maintenance as a strategy, it is essential to ensure that the failure modes considered do not have the potential to become emergency maintenance.
You see, if you adopt run-to-failure equipment, that once it has failed, it must be restored immediately to have your organization doomed to a reactive maintenance environment. A reactive maintenance environment isn't where you want to be. It's more expensive, less efficient and less secure. Therefore, while a strategy of running towards failure may be a good option, make sure you decide wisely.
Emergency maintenance often results in longer equipment outages and a greater impact on production. Therefore, when making a request for corrective maintenance work, it is essential that you properly prioritize it to ensure that, as much as possible, you postpone the work request and give your team the time to plan and schedule the work correctly. If you want to read more about prioritizing corrective maintenance, check out the article You'll Fail Without Planning & Scheduling. Emergency maintenance is corrective maintenance that is so urgent that it falls into your weekly frozen program (you have one, right?).
It disrupts their plans and schedules and usually disorganizes everything. Some people thrive in this type of environment and are often heralded as heroes when they have worked 16 hours non-stop to bring production back online. But when it comes to the Path to Reliability, it's a dead end. Therefore, emergency maintenance is the only type of maintenance that we really want to avoid as much as possible.
In fact, world-class organizations ensure that less than 2% of their total maintenance is emergency maintenance. How much emergency maintenance do you have? An efficient and effective preventive maintenance program will have a combination of all of these different types of maintenance. In the rest of the article, I want to answer some of the most frequently asked questions (FAQ) I receive from readers or email subscribers. In my opinion, they are not the same.
Planning refers to the maintenance planning & scheduling process, so maintenance planning is preparing the maintenance job to be ready to run. Whereas preventive maintenance is maintenance that has been identified to prevent or mitigate a failure mode. Therefore, in my opinion, planned maintenance is maintenance that has gone through the planning process and that has been properly prepared with all the steps of the work, labor, parts and tools identified and organized. All preventive maintenance must be planned maintenance, as it has been identified in advance and there is no reason why it should not go through the normal maintenance planning process &.
The opposite of planned maintenance is unplanned maintenance, which has not been properly prepared and is planned in the plan as the work is done. This is very inefficient and something you should avoid at all costs. The only time you need to perform unplanned maintenance is when you have a high priority work request that comes in and is so urgent that it enters the frozen weekly schedule to complete the work without going through the normal planning process &. I refer to this as emergency maintenance.
The above table of maintenance types does not include stand-alone maintenance or autonomous care (also known as front-line maintenance in other organizations). CLAIR's activities (cleaning, lubricating, adjusting, inspecting and repairing) performed under Autonomous Care are essentially a combination of the above strategies, but performed most often by frontline personnel. This is an interesting question and, in general terms, unplanned corrective maintenance ie. Emergency maintenance is the most expensive to perform.
This is because this type of maintenance does not go through the scheduling process of full maintenance planning & because it is very urgent and is simply planned on the fly. This means that when you run emergency maintenance, you typically have very low efficiency and additional time is wasted searching for materials, organizing access to equipment, waiting for other operations, etc. Another common problem with emergency maintenance is that parts and services are often expedited to arrive faster and higher costs are incurred to achieve this. In general, preventing a failure is simply much cheaper and safer than letting the equipment fail.
In addition, preventive maintenance would have a much smaller impact on production than fault maintenance (ie,. However, there are cases where a deliberate run-to-fail maintenance strategy is the right thing to do. A good example would be something like general area lighting in an industrial plant, where you'll simply wait until you have a number of lights that have failed and then replace them. Trying to replace these lights before they fail would be a waste of money because we can't accurately predict when the bulbs will fail.
And because the consequence is low, we can simply accept that general lighting fails. Predictive maintenance is really a type of preventive maintenance, since both see that you perform maintenance before the failure occurs. However, the problem is that most people think of traditional time-based maintenance when talking about preventive maintenance. So, from that perspective, what is better? Nor.
You must select the correct type of maintenance based on the failure mode you are trying to manage and its characteristics. If you have a failure mode that is random in nature, you'll want to opt for a predictive or condition-based maintenance task so you can see the potential failure approaching and take action before the failure occurs. However, if you have a failure mode that is clearly age-related or where a condition-based task is simply not economical, then you would use a time-based maintenance task. Changing lubricating oil in a turbine with thousands of liters of oil is often best done under conditions to ensure maximum oil life.
But, if it's just 50 liters of oil, the time and effort it takes to sample the oil and analyze it probably means it's not worth relying on the conditions and simply change that oil based on a fixed time or a fixed number of operating hours. What a great job you've done, thank you & it's still like this, although it may have 2 add-ons. First it's about corrective vs preventive men. As you say, they correspond to a decision, a strategy adopted or, as some books claim, an evolution from “reactive” to “proactive”.
The original maintainer, poor or unaware, would be in the reagent, enduring faults that need to be repaired. But it could be misleading in terms of sorting tasks. They do not represent a mathematical “partition” of all maintenance tasks. If you wanted to list all the maintenance tasks for a particular piece of equipment, you couldn't put 2 different lists.
For me, this is the cause of a lot of confusion in non-specialized minds. Some of the same tasks could be performed in corrective or preventive modes. For example, greasing of a door latch can be performed once the door stops working (it cannot or cannot be closed easily enough), i.e. In corrective mode, or when the door function is OK, or starts to be less easy to close (goes beyond point “p” of the p-f curve), i, e.
Another example would be the replacement of an automobile wheel, which can be done on a flat (broken) tire or before the tire wears too much. It's still exactly the same task, the same series of steps. Many tasks can be performed in exactly the same way, but under different circumstances. This is also true that, in some cases, the tasks will be somewhat different, because when a failure occurs, some additional damage could have occurred, which would lead to the need to perform other tasks when performing a repair.
This seems to be just a small detail, but it is enough to create confusion in terms of classification and logic for those who think that preventive and corrective would represent 2 distinct categories of the maintenance tasks listed in a manual (Unfortunately, many manuals make this mistake or this simplification). Thanks Ivan for your detailed answer. Great observation that the same task could be considered preventive or corrective depending on when the task is performed, that is,. I prefer to maintain the planned and unplanned distinction for (corrective) maintenance to identify those maintenance tasks that have not been planned ie.
They are prepared in advance and, therefore, are often a very urgent, inefficient and costly way to perform maintenance. This is what I call emergency maintenance. And then you've planned (that is, e. Preparation) corrective maintenance where we have had a failure, but we are still taking the time to plan the work for good efficiency.
Preventive maintenance should always be planned (i.e. Prepared) Every time we use preventive maintenance of the material and the drill rig to be actually used and prevent corrosion. The process gives us a good offshore drilling installation on platforms Thank you for this enlightening article. Could you help with the theoretical concepts of maintenance? Thanks Engr, Erik, It's such useful information, We apply preventive maintenance on 80% of our maintenance work Productivity is always high.
Mr. Hai, can I know what type and maintenance strategies are appropriate for building heritage? The strategies and types of maintenance you would use for building maintenance would depend on the failure modes you want to manage, in addition, of course, to legislative maintenance requirements. For example, you would use fault detection maintenance to test your building's smoke and fire detectors on a regular basis. But I would probably use deferred corrective maintenance for any lighting maintenance, that is,.
Turn the lights on until they fail and then replace them in a campaign once several lights fail. For an air conditioning system, you would probably use time-based maintenance to replace the filter elements. Hello, please, I want to know the different maintenance aids. Can you explain a little more what you refer to with various maintenance aids? I read your section it's very good and it's full of package.
My question is that some time manufacturers recommend that after a while (every 20000 hours we have to change the oil), but when we did our oil test analysis, we found that the oil is in good condition. So just suggest to me that we need to follow the manufacturer's instructions or we can run our equipment based on our analysis. Oil change work is too expensive. Interesting reading, some highlights and clear benefits of using preventive maintenance, although I think it requires more labor with more frequent checks, resulting in higher execution costs.
Excellent article, very interesting and educational Great knowledge, enlightening and knowledgeable article. A Safe Path to Safety and Cost Savings. Thank you for the articulated, well-thought-out and simplified process to achieve a high standard of safety and cost savings. PS: I'm not a big fan of the phrase proactive maintenance, since it seems pretty useless to me.
In my opinion, all MPs are proactive and, once they have accepted an execution to failure strategy, I would even consider the resulting CMs to be proactive, since they have made a deliberate decision to allow that failure to occur (i.e. I prefer to use the distinction between reactive and proactive more around the general maintenance culture rather than maintenance tasks. A proactive or reactive maintenance culture makes sense to me. If any errors are found during data collection or data reading, make work orders, it is called good corrective maintenance.
It will give you good ammunition to have those discussions with managers and leaders stuck in old beliefs. I found all your articles very useful. Please keep up your good work and you're already making a big difference. Great “digestion in the field of maintenance Good participation Erick, on our site we classify the type of maintenance Proactive (PM, Pdm, Sca), maintenance and reactive maintenance (emergency), PM we implement based on, by recommended time base team, Pdm we implement by mapping critical equipment, Sca we implement by work request and inspection.
Thank you very much for the useful and very interesting topic on the type of maintenance. The following equations require a specific and detailed answer Excellent summary. I had implemented plant maintenance models in several organizations and supported them with work management tools. I have often faced discussions with maintenance managers about what their maintenance strategy is, and it is very frustrating that we have to start from the basics and move to a maintenance strategy or philosophy to respond to business or equipment requirements.
Thanks for the comment Eyadeh. For your research, how about analyzing how aviation maintenance & reliability practices can be incorporated into industries such as Oil & Gas? Good Erik, thank you very much, but can you suggest more topics for my research? I really appreciate your help. Would you help me with the right origination table for the oil company's maintenance? Greetings section A, Sghair Do you mean “organization chart”? If so, send me a more detailed message with a little more background for your question via the contact page and I will do my best to answer. I have a question about what restorative maintenance is in hardware and software.
I would suggest that restorative maintenance is restoring a function that has been degraded, which, in my opinion, would involve an age-related failure mode, for example,. After so many hours of service, a restored %3D component was refurbished. However, I'm not sure how it would work with the software. Where does that phrase come from? I will, thank you very much.
I don't think you can, fundamentally, predictive maintenance is the same as condition-based maintenance, since it aims to prevent or, at least, mitigate the effect of a failure before the failure occurs. As such, it is a type of preventive maintenance. You never stop providing a wealth of knowledge. Your document is well presented, easy to understand, and useful for implementation.
In our days of rapid returns on investment, modeling the success of others with proven strategies is an effective means of reaping the same rewards, but in a much faster time frame. I can't say enough about your contributions of time, effort, knowledge and experience to the world of engineering and maintaining reliability. For those who haven't found the Road To Reliability community, please do so. It'll be worth your time.
This is a very basic and very important knowledge. Until now, I use time-based maintenance for almost all the equipment under my responsibility. And I think I was wrong. Improper equipment maintenance will also affect safety, maintenance members, and others.
Changing the maintenance strategy is my next goal. I know the reference objectives for availability and OEE, if I were to analyze reliability, what measure and objective would I consider? There are quite a few ways to measure reliability as a performance metric, but I often recommend using uptime as a relatively simple metric that is easy to measure and understand. The desired uptime objective would depend on the equipment, the industry and what generates value for your company. Thanks Erik Mean Time Between Failure (MTBF) is one of the most widely recognized and yet least understood indicators in the world of maintenance and reliability.
Manufacturers Cite Reducing Maintenance Costs Is Easy. Just stop doing the work and the costs are gone. Most industrial plants will continue to operate longer than we believe failure modes and effects analysis (or FMEA for short) is widely used in many industries. Often in the design phase of new equipment.
I agree that in many companies trouble is a problem when it comes to maintenance, but I firmly believe that in those same companies maintenance teams do a great disservice by performing many maintenance tasks with no added value. I appreciate your great efforts and informative articles and I am interested in reliability (especially the RCM) and maintenance scheduling, so I ask you about planning preventive maintenance activities. But, in many people's minds, fault maintenance is urgent maintenance, maintenance that needs to be done right now. One thing people often get wrong about is thinking that reactive maintenance isn't really a strategy, since it doesn't involve any proactive maintenance planning.
Unlike other styles, default maintenance is performed using rules and suggestions created by the original manufacturer, rather than the maintenance team. If what I consider to be condition-based maintenance, you call predictive maintenance, that doesn't really matter. Preventive maintenance can be defined as “an equipment maintenance strategy based on replacing or restoring an asset at a fixed interval, regardless of its condition. An efficient and effective preventive maintenance program will have a combination of all of these different types of maintenance.
One of the main reasons predictive maintenance is so valuable is because it allows maintenance to be performed only when absolutely necessary, that is, just before equipment failure occurs. If you have resource constraints, you need to ensure that you have high productivity during execution (read my articles on maintenance planning, scheduling &) and that you don't waste your scarce resources on preventive maintenance tasks that add no value (read my article on the principles of modernity maintenance). . .