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I have been all over the world in the past 24 months to visit many different maintenance and reliability professionals. Many of them are kind enough to show me some details about the maintenance and reliability programs they are involved in.

We usually talk about planned and unplanned work and the topic of corrective maintenance usually arises.

When I ask for the definition of corrective maintenance - I get as many different answers as people I speak with.

Can someone in the forum please tell me if there is a proper definition of corrective maintenance and what it is?

Links are OK but I prefer to have the discussion right here.

Terry O

Replies sorted oldest to newest

Wowza Terry. Looking for the "perfect and right" definition is always a daunting task. That's probably why dictionary.com lists so many different definitions for so many different words. The two I like most for the word "corrective" are: 1) tending or intended to correct or counteract or restore to a normal condition (cited from Wordnet), and 2) counteracting or modifying what is malfunctioning, undesirable, or injurious (cited from American Heritage Stedman's Medical Dictionary). Also, the word "corrective" has quite a few synonyms if you look it up in a thesaurus. The one I like the most is "punitive". Anyone out there partake in punitive maintenance?
H
Terry - this topic was touched on by a thread originated by Jim Maslach on 12 July 2005. Here's an exerpt from Vee I will include which I think does it justice (hope you don't mind Vee):
quote:
Josh, Daryl,

I notice that the term failure itself is being interpreted, in my view, loosely. In RCM terms, Functional Failure is failure. So one can 'catch' functional failure if there is an incipiency condition. In this case degradation has already commenced and we are past the point of incipiency.

The bigger problem lies with the definition of Corrective Maintenance (CM). In my view, CM is any work done after initiation of failure, i.e. we have gone past the incipiency point. The initiation may be by condition monitoring or inspection by operators, inspectors, maintainers, managers. The repair or restoration may be done before or after Functional Failure based on the consequences we expect. CM also includes any rework after an earlier unsuccessful PM or CM activity.

In the case of Breakdown Maintenance (BM), we did not know of the impending failure, whether or not there was an incipiency condition. Generally, when you do an RCM, several on-failure tasks will be identified, these are BMs. CM means that we knew of the impending failure; we may choose to do the restoration before or after functional failure, depending on consequences. The knowledge may be by condition monitoring (by instruments, observations by operators, inspectors, maintainers, managers etc.).

Josh, in the four cases, the question you should ask is whether the failures were evident, and I think based on your statement that the answer is yes. Next is there an incipiency condition and can we measure it, again I think it is yes. If you chose to measure it and trend it, you have an on-condition task in your CMMS. Any action to 'catch' the functional failure and take corrective action to rectify it becomes a CM task. If you choose not to measure it, it is a BM task. In the four cases you describe, an operator or inspector has measured it (by visual or other senses), so it is CM.

The real problem seems to be one of managing performance indicators rather than managing performance. This is a common disease in many companies, especially prevalent when people get rewarded by KPIs that are defined without careful thought. Your rotating and static engineers should be encouraged to focus on eliminating breakdowns, trips and failures that cause harm, to HSE, asset value and profitability. But this is another subject, so let me stop here.

V.Narayan (Vee)

Regards.

V.Narayan (Vee)
Author of Effective Maintenance Management: Risk and Reliability Strategies for Optimizing Performance, Industrial Press, ISBN 0-8311-3178-0
RM
Just as an additional - I have been struggling for quite some time on the whole concept of corrective maintenance and what it is. It bugs me - however to reflect on Vee's definition has helped and I think the important thing is whatever def. you decide upon stick with it - it may not be the same globally and we may never have a global agreement on what it should be but if you are measuring it make sure you keep it the same within your four walls otherwise you will get into all sorts of strife.

I like the idea that it is an action initiated due to a measured/observed condition whether before or after functional failure.

Mike.
RM
Terry and All,


I have been teaching several plants and I often times here this word also Corrective Maintenance" and it spells different meanings for different types of plants.

From the book of Tokutaro Suzuki, Senior Consultant from JIPM, TPM in Process Industries, he defined page 149

Corrective Maintenance improves equipment and its components so that preventive maintenance can be carried out reliability. Equipment with design weaknesses must be carried out.

My understanding regarding Suzuki's definition is that from TPM's point of view corrective maintenance is also the same as proactive maintenance. However in other plants such as power plants, they termed corrective maintenance as doing repair works after a breakdown or failure had occured making it reactive in nature.

Maintenance strateges have different terms :

Reactive Maintenance : Also termed as Run to Fail, Run to Destruction, Breakdown Maintenance, Unplanned Maintenance, Band-Aid Maintenance, Firefighting Maintenance, Stop the Bleeding Maintenance, Mc Guyver Maintenance, No schedule maintenance (RCM Term), Unscheduled Outage, etc.

Preventive Maintenance - Also termed as, Calendar-Based, Scheduled Maintenance, Time-Based Maintenance, Stroke Based Maintenance, Scheduled Discard, Schedule Restoration, Scheduled Outage and Corrective Maintenance for some industries

Predictive Maintenance also termed as Condition-Based Maintenance, Reliability-Based Maitenance, On-Condition Tasks, Equipment Diagnostic Monitoring, Diagnostic Techniques, Non-destructive Testing etc.

Proactive Maintenance - Modification, Redesign, Maintenance Prevention, Equipment improvement

The way my understanding lies, there is no standard understanding of what corrective maintenance is, it can be proactive or reactive.


My Warm Regards,
RM
I'd like to see corrective maintenance split into two categories- planned and unplanned. Planned corrective maintenance indicates the work was performed before a breakdown occurred and unplanned indicates work was performed because a breakdown occurred.

It would be great to have a bucket for work performed because a PM discovered a deficiency, that would be planned CM work.

CMP and CMU would give better definition of how your PM program is working. More CMPs and less CMUs means the program is working. Less CMPs and more CMUs means the program needs development.
RM
Terry and others,

To correct something, we must already know that it is not performing as desired. That it is not performing can only be known if we 'measure' by sight, touch, smell or hearing (by human senses or with instruments) and we have an established set of performance standards. Prior knowledge is an essential element in determining whether it is corrective or otherwise.
In contrast, 'Preventive' work is anticipatory, using design calculations,historical evidence, expert opinion or probabilistic predictions.
Breakdown work may be based on predicting condition (when it is Corrective Maintenance or CM that has such low consequences that we allow it to run to failure), or because we had no prior knowledge of the condition. Thus Breakdown work may be 'planned' (when we decide to allow an item to run to failure) or unplanned,where we had no prior knowledge at all. I think Wally was referring to this aspect of BM in his post and I support his view.
In this context, I like to think along the following lines - If a machine is not functioning, is it because:
1. We stopped it while it was running OK? That is PM, a planned activity.
2. We measured it to confirm possible loss of function? That is Condition Monitoring, a planned activity. If we can predict failure and intervene before that happens, it is CM. If we intervene after failure, it is a planned BM.
3. The machine stopped itself? Then it is unplanned BM.
Mike makes a good point: once you agree on a definition, stick to it and don't keep changing it.
RM
In CMMS, we may use:

Breakdown Maintenance (BD) for unplanned total functional failure or planned run to failure. So it's important to distinguish them in maintenance activity type field.

Corrective maintenance (CM) for normailizing partial functional failure ad-hocly and not found during PM.

Corrective/preventive maintenance (CP) for normalizing partial functional failure found during preventive maintenance (PM). CP can indicate how efective the PM and its doer in detecting failures.

How about corrective jobs found during daily walkarounds? If the daily walkaround is scheduled in CMMS, it's CP but if not scheduled in CMMS, it's CM.

How about corrective jobs for abnormalities found by operators? It's CM!
RM
Posted on behalf of Mac Smith

We use the following definition of preventive maintenance (PM):

Preventive maintenance is the performance of inspection and/or servicing tasks that have been preplanned (i.e., scheduled) for accomplishment at specific points in time to retain the functional capabilities of operating equipment or systems.

The word "preplanned" is the key element in developing a proactive maintenance mode and culture. In fact, this now provides us with a very clear and concise way to define corrective maintenance (CM):

Corrective maintenance is the performance of unplanned (i.e., unexpected) maintenance tasks to restore the functional capabilities of failed or malfunctioning equipment or systems.As viewed by the authors, the entire world of maintenance activity is fully encompassed in these two definitions.
RM
Rolly,
In my view, there is nothing inherently good or bad about Corrective Maintenance. It is simply a type of maintenance.
All of the maintenance work we do must address the risks to the organization. These risks may affect Health, Safety, Environment, Profitability, Asset Life or Reputation. We choose our maintenance strategies to match the risk of failure (i.e probability and consequence). We can permit failures whose risks are low, i.e. run-to-failure or breakdown, because the combined risk of failure and adverse profitability is the lowest we can get. When risks are high, we opt for age-based (i.e time, cycles, starts etc) PM or condition-based (i.e PdM) strategies, depending on the failure distributions, or shape of the probability density curve. And if we cannot find a suitable task for high-risk failures, we have to redesign the process, equipment or retrain the people involved.
In my view, we should move away from any dogma, when it comes to deciding on maintenance strategies and stick to the science that applies to maintenance.
RM
Dear Vee,

I agree totally with your thoughts, however, there is really no universal standard for maintenance task and the terms used vary from one type of industry to another. My views are based on my experience in what industry termed their tasks although they offered the same meaning. Even RCM use the word No Scheduled Maintenance instead of the most common Run To Fail which most industries know. When I work with the mining firm, the maintenance craftspeople use the term Run To Destruction and not Run to Fail.

For TPM practicioners mostly those who have achieved JIPM awards level, they use the term corrective maintenance as performing modification and improvements.

When I was consulting with some power plants here in our country, they used they term scheduled and unscheduled outage in which later on learned that unscheduled outage refers to corrective maintenance irregardless of the consequences whether of high or low risk.

I apologize for sounding dogmatic but I am only basing these on the different terms industy use. Even John Moubray used different terms designating the same meaning :

No scheduled maintenance - means run to fail

Scheduled discard and restoration - Preventive Maintenance

On-Condition Tasks - Means Condition-Based Maintenance also with the inclusion of using human senses to detect potential failures.

By the way, have you completed writing your book ? And is it already out in the market ?

My Warm Regards,
RM
Rolly,
I am not sure if I am acting within the rules of the forum while answering your question. At the risk of getting a slap on the wrist, here goes:
My second book written with M.C.Das and J.Wardhaugh "100 Years of Maintenance: Practical Lessons from Three Lifetimes" # ISBN-10: 0831133236 and # ISBN-13: 978-0831133238 was completed about 4 weeks ago and is due for release in the next few weeks. You can see details on the Industrial Press or Amazon websites. I am happy to tell you that it has a Foreword by Charles Latino,one of our Reliability Greats and a Guru, and reviews by Brad Peterson, President of the SAMI Corporation and Joel Leonard, the Maintenance Evangelist.
RM
From the Reliability Centered Maintenance Project Manager's Guide (PDF)

To avoid confusion between terms and phrases used in other contexts within the fields of Maintenance and Reliability (M & R) the following notes are provided. Note 1: Corrective maintenance in the context of the metrics included in the RCM Scorecard refers to unplanned (unexpected or reactive) maintenance to restore the functional capabilities of an asset. It includes repeat maintenance required because initial attempt(s) at repair were not successful for any reason. It does not include maintenance that results from preventive or predictive (PM and on condition or condition directed, or PdM) tasks, which can be anticipated, pre-planned and scheduled. Corrective maintenance is a subset of Emergency/Demand Maintenance.

Note 2: Corrective maintenance in the Total Productive Maintenance (TPM) sense refers to actions taken to modify the asset to improve its performance. The labor hours and material costs for these improvements (as well as those that improve asset maintainability) should be categorized separately and not be included as part of any metric associated with the RCM Scorecard, unless the recommendation of a design improvement results from RCM analysis on an asset.
RM
Hello Vee,

Congratulations on your new book. Hope I can purchase it directly from you, someday maybe early dec or end nov. 2007. Highly appreciate some signature and brief note on your book. I'll email you personally regarding this matter. I know this is not the venue for promoting.

Charles Latino is a very reputable and respectable person when it comes to reliability and root cause. I learned from Bob Nelms that he (Charles) was his boss way way back ago.

In behalf of the people from the far east, your continuous contribution to reliability and risk management is highly appreciated.


My Warm Regards,
RM
On 11/01/2007 Maintenance Tips published the following:

Preventive Maintenance (PM) Tip
Is it Preventive Maintenance (PM) or Corrective Maintenance (CM)?

A dominant area of confusion about Preventive Maintenance (PM) versus Corrective Maintenance (CM) occurs when a scheduled task reveals unacceptable equipment deterioration.

So actions are taken to repair/restore the full functionality before an unexpected operational impact can occur. Is the repair/restore action preventive or corrective?

If the purpose of the PM task is to perform actions that will retain functional capabilities, then the answer is essentially self evident "” the repair/restore action is preventive. Why? Because a proper structuring of the PM task will always include not only the search for equipment condition, but also the requirement to do something about it if the search uncovers a problem.

This search includes PM tasks that require inspection, monitoring parameters that detect failure onset, discovery of hidden failures and even restoration of equipment that was deliberately allowed to run to failure. Unfortunately, though, many CMMS programs will not allow the user to create or code a new work order to cover the emergent work as PM. This additional PM work can only be coded as CM. This inflates the cost of CM, and can lead management to question why CM costs are increasing even when their PM program had been recently improved.

Tip provided by Anthony "Mac" Smith, Author, RCM - Gateway to World Class Maintenance, Butterworth-Heinemann, ISBN-10: 075067461X
RM
ON 11/06/2007 we got this feedback about the Tip published in 11/01:

I would like to comment on Mr. Smiths earlier Preventive Maintenance (PM) Tip Is it Preventive Maintenance (PM) or Corrective Maintenance (CM)?

In the tip he makes the point that items found during the preventative maintenance are also preventative maintenance and should be coded as such. If not then the question comes why are you finding so much corrective maintenance.

I disagree with this. Preventative maintenance is the closet thing to standard work that the maintenance department has. With this type of work the cost and time to perform should be constant each time the work is performed. Otherwise how do you schedule. Yes an adequate PM is designed to find the deficiencies prior to failure and can be part of an effective program but the repairs to the equipment should be corrective (CM). If not then my question is why are your PM costs so out of control.

Most CMMS programs allow you to create your own coding system. I have created and used the PM-Repair code to show what we have found and fixed using the PM program. This along with PM costs and CM costs will show an effective program. The curve will show as PM costs go up the PM-Repair costs will peak and then decrease and the CM costs will decrease. The point at which the PM costs, PM-repairs and CM costs are at the minimum is the maximum you are going to get from the current PM program you are using. At that time only a change in the maintenance will cause a continual decrease.


Feedback provided by Clint Mileur
Maintenance Manager
JamesHardie Building Products
Peru IL
RM
Yes, to repair major defects found during PM will inflate the PM cost but not the minor defects. Therefore, the PM doers should decide whether to repair the defects straight away using the same PM work order, same work permit, same person, etc, or to rectify the defect later on using a corrective/preventive maintenance work order and another work permit etc.

Perhaps, as a rule of thumb, it's alright to rectify defects immediately if can be completed within 1 or 2 hours e.g. cleanliness, looseness, etc. Just add a small operations under the same work order in the CMMS to notify it has been done. But if the defect requires an overhaul after condition monitoring as an example, then a separate child work order should be raised.

Under Equipment basic care, I thought we encourage the problem finders to rectify the problems found right away, if possible instead waiting for or passing to another persons.
RM
Ramesh Gulati of ATA sent this in response:

Maintenance Work Classifications:

Maintenance can be classified in four major categories:

1. Preventive Maintenance (PM)
2. Predictive Maintenance (PdM) aka Condition Based Maintenance (CBM)
3. Corrective Maintenance (CM)
4. Capital Projects –Maintenance (CPM)

Maint. Work 1,2, and 4 have been defined and all of us understand it. However, corrective maintenance creates lot of confusion.

3. Corrective Maintenance (CM):
Asset repair resulting from PM & PdM actions or breakdown/failures.

Corrective Maintenance is repair of asset to bring it back to it's designed or an acceptable condition.


The CM work can be further classified in three:

a) CM – Scheduled :

The repair work discovered as a result of PM or PdM actions. This work should be or can be planned and scheduled.

b) CM - Run –to-Maintenance (RTM) :

If we have performed FMEA/RCM analysis on a specific asset/component and made decision to not to perform any PM/PdM but to let it run –to –maintenance (failure) because it's a cost effective strategy, then we will call this as CM-RTM. It's not a negative. This failure is by design. This is not a critical asset and should be repaired in scheduled manner.

( Water cooler, circuit board, electrical component, or a line replaceable unit etc. )

c) CM – Unscheduled (Run-to-Failure) :
aka failure repair = breakdown maintenance = reactive maintenance

This CM is failure or breakdown work. It's fixing of the asset after they fail. This work is also known as reactive. Most of the time this work will break the regular schedule to get it done.

Usually we have found that there is a big confusion when we try to mix maintenance work with how we respond to get it done e.g. Emergency work is really CM-Unscheduled or reactive which needed to be done now. In some organizations, breakdown work is called urgent maintenance but could be done within 48 hours.
RM
Roger Harris sent this response:

As a Maintenance Manager in a large automotive manufacturing plant, I faced this same problem and answered it by creating a new work type called PMO for PM Originated work. This did two things for our organization:

1) It allowed us to measure the effectiveness of our PM system by determining what percentage of our repairs were driven by the most qualified individuals (Maintenance Crafts Personnel) and;
2) Created a category of work management costs that could be directly compared to the cost of running to failure by considering downtime, cost of quality, and the added cost of repair that would be incurred by affecting other components or systems.

This requires the PM focus to be one of; clean, lubricate, and inspect, and allows for better scheduling of PM tasks by forecasting accurate equipment downtime associated to the PM routine.

This helps maintain the relationship with the equipment stakeholders by only having it down the time that you requested and agreed to as much as possible, and allows the mechanics to complete their scheduled work by not bogging them down into lengthy repairs.

This will help the entire organization see that the PM efforts are manageable and supportive of changing the culture from reactive to proactive.

This is also a mandatory mind set shift if you ever expect to reach the best in class goal for scheduling accuracy of 95%.

By closing the PM work order and creating a new PMO workorder the parts needed to repair could be ordered against this work type which separates the cost of repair and PM and properly identifies it as PM originated expenses. Not only does this accurately identifies cost it improves equipment downtime when it is possible to return the equipment to service and wait on the arrival of spares with the equipment running. Any good EAMS/CMMS software support consultant can help you configure your system to support this process. If your software or consultant is not capable, find a new one, otherwise you will never reach the full potential of your groups human capital, or clearly identify for management the true value of being proactive through preventive measures. Mr. Smiths points are accurate and valid, but there are solutions for these problems.

Roger Harris CMRP CPMM
Senior Business Consultant
Total Resource Management
MAXIMO & LAWSON Consultants
Cell: (502)664-7089
RM
One more reply came from Jeff Wahl:

I saw your Preventive Maintenance Tip in the Maintenance-Tips from Reliabilityweb newsletter today. You gave definitions for PM and CM. I have to ask if CM should be sub-divided into two categories, such as CMP and CMU. P and U divide the category into Planned and Unplanned Corrective Maintenance.


When a PM exposes CM work that needs performed, it shouldn't be in the same bucket as a CM that is initiated during operations, say. CMP could also be categorized as a PMC if that makes more sense.


Sincerely,
Jeff Wahl
RM
Hi Terrence,
You have created some good discussion here and I appreciate your concerns. Reading the replies of the group I find that there is need to go further into the discussion. What is the reason for trying to determine is work Corrective or Preventive? If the mission is to understand reliability performance one must consider anything that is performed to restore the equipment to acceptable design capacity as corrective. I say this because I view the corrective measure as a weakness in the reliability of the equipment and may indicate more tend and adjust is needed to operate. Measuring corrective this way will allow you to compare like type assets to determine which models have the lowest operating costs over the life of the asset. This will also support the purchasing department with information to make better purchasing decisions.
Similarly, I feel that understanding the maintenance department's proactive and reactive tendencies is a vital part of managing the maintenance department. So I view corrective planned maintenance as part of the planned maintenance program and view it as proactive in nature. Unplanned Corrective Work is viewed as a negative impact on both the reliability of the equipment and the operational efficiency and effectiveness of the maintenance department. Unplanned corrective work should be avoided unless otherwise planned for by identifying run to failure equipment. My question is what are you trying to understand by measuring corrective work routines? Maintenance Operational Performance, or Equipment Reliability scores? They are both part of the overall continuous improvement process and require specific training and EAMS/CMMS configuration planning. Getting at a clear understanding of these two issues are normally when I see the confusion mount about what is corrective maintenance. Thanks for starting this great discussion.
Kind Regards,
Roger Harris CMRP CPMM
RM