Corrective maintenance tasks can be either planned or unplanned and occur for three different reasons:
- When condition monitoring highlights an issue
- When a potential fault is detected through routine inspection
- When a piece of equipment breaks down
Corrective maintenance is often unavoidable, with maintenance teams having to respond to equipment breakdown or failure. However, it can be a bad idea to rely solely on corrective maintenance over other types of maintenance such as preventive maintenance.
Corrective maintenance is fine for when an asset can be easily repaired or replaced and parts are freely available but, in some instances, it can lead to unexpected and costly downtimes. Experts tend to agree that 80% of your maintenance should be preventive and just 20% corrective.
Types of corrective maintenance task can be placed into different categories. For example, the United States Army uses five categories of corrective maintenance in their Engineering Design Handbook: Maintenance Engineering Techniques:
- Fail Repair - Restoring a failed asset to an operational state
- Overhaul – Fully restoring an asset to its service state as outlined by maintenance standards
- Salvage – Disposing of parts that cannot be repaired and replacing them with salvaged parts from unrepairable assets
- Servicing – Final fixes following larger corrective actions
- Rebuild – Disassembling parts and replacing worn components in line with original standards and specifications
Each of these five categories of corrective maintenance task can either be scheduled or unscheduled.
Unscheduled (or unplanned maintenance) refers to repairs that are done immediately, while scheduled (or planned corrective maintenance) are those tasks that can be deferred until a later date. This delay can take account of budgets, time constraints, or staffing.
Scheduled / Planned Maintenance
Planned maintenance can fall into two groups; run-to-failure maintenance and preventive maintenance. Run-to-failure is where an asset is allowed to run until it breaks, at which point it is repaired or replaced. This type of corrective maintenance strategy is only suitable for non-critical or redundant systems that are easy to replace or repair. Preventive planned maintenance, which is often performed as part of condition-based maintenance, is where problems are identified and addressed during maintenance inspections.
Unscheduled / Unplanned Maintenance
Corrective maintenance is unplanned either when a breakdown occurs unexpectedly. This can be because no maintenance plan was in place, or because an asset fails before its scheduled inspection or maintenance action.
Corrective maintenance can offer a range of advantages when used as part of a broader maintenance programme. These advantages include:
- Reduced Planning: Corrective maintenance requires less planning than preventive maintenance, even when scheduling repairs
- Simple Process: Corrective maintenance is a simple process that is need-based, allowing maintenance teams to focus on other areas until required
- Lower Short-Term Costs: This type of maintenance can be more cost-effective in the short term as work is only done when needed. This is true for simple repairs or replacements, such as a blown lightbulb that can be fixed quickly without the time and expense of a preventive maintenance plan
- Improved Resource Planning: If corrective maintenance work orders are prioritised and scheduled they can allow for labour and financial resources to be optimised. This can lead to fewer service interruptions as maintenance teams can resolve problems before production is impacted or services are interrupted
- Reduced Downtime: If a maintenance technician notices a worn component while performing routine maintenance, a corrective action can reduce the chance of later downtime due to failure
- Extended Asset Lifetime: Corrective maintenance can extend the lifetime of critical assets if parts are repaired or replaced before they impact other parts of a machine
Despite the advantages of corrective maintenance, there are also some disadvantages with this method, especially where there is no supporting preventive maintenance strategy. These disadvantages include:
- Higher Long-Term Maintenance Costs: Simply running assets until they break can lead to higher long-term maintenance costs as the condition of equipment deteriorates before problems are discovered. This can lead to other components being affected and more parts requiring repair or replacement along with the associated labour costs
- Safety Issues: Pressure to reduce unexpected maintenance costs can also create safety issues as repair work may be rushed and not completed correctly. Also, running a machine until it breaks can cause potential hazards for staff using the machine
- Unpredictable: The biggest single disadvantage is the unpredictable nature of corrective maintenance. If an asset unexpectedly fails, it can cause disruption to other maintenance work as well as unforeseen downtime. Maintenance can be slow and expensive, as the cause of the failure needs to be located and spare parts ordered to effect a repair. Because of the reactive nature of corrective maintenance, equipment is not maximised and production can drop. Unpredictability is not a problem in the case of small repairs (such as replacing a blown lightbulb), but can be a problem with larger failures. This can be prevented with a more proactive and predictive maintenance strategy.
There are several subtle differences in the types of corrective maintenance that can be done. Examples of corrective maintenance can demonstrate these differences, for example:
Run-to-Fail Corrective Maintenance
An example of this type of corrective maintenance includes lightbulbs and other non-essential and easily replaced components. In such cases, a stock of replacements can be kept on site and fitted when the last one fails.
Planned Corrective Maintenance
This type of maintenance often goes hand-in-hand with preventive maintenance routines. For example, you may have a production line conveyor belt that is inspected for wear on a regular basis. An inspection highlights that some bearings need replacing and so a corrective maintenance order is scheduled. Alternatively, a technician could respond to one problem, such as a misfiring engine and discover another problem like a clogged filter. A planned corrective maintenance request can then be filed to clean or replace the filter. This type of maintenance still deals with unexpected breakdowns and failure, but the repair and replacement work can be planned for or highlighted as potentially necessary through inspection.
Unplanned Corrective Maintenance
Unplanned corrective maintenance usually occurs when there is no set preventive maintenance plan in place. For example, you may have a trolley or forklift that is not inspected, but breaks down. Fixing such an item is unplanned corrective maintenance. Other examples include burst water pipes that need replacing quickly. However, unplanned maintenance can happen even when a maintenance plan is in place. For example, if you have a machine that needs inspection after every 100 hours of use, yet it breaks down after just 80 hours, you would need to perform an unplanned emergency repair. Unplanned maintenance often requires an immediate remedy but wasn’t part of a plan to let the component fail, as with run-to-fail maintenance.
Corrective maintenance is important as it allows a facility to return to full efficiency following an equipment failure. Maintenance tasks involve the replacement or repair of items after they have failed and can be prioritised according to how critical they are. This priority includes factors relating to safety as well as production and downtimes.
Unscheduled corrective maintenance tasks can slow production lines, but usually the downtime associated with these corrective tasks is low in comparison to a total equipment failure. Performing these corrective actions in a timely manner should restore your asset to full working order as quickly as possible.
Corrective maintenance can also take place before an item fails completely. Noticing wear and replacing components before they break can prevent unnecessary costs and downtime. These tasks can be scheduled according to how critical they are, helping to minimise equipment failure.
Corrective maintenance is often unavoidable and will include unforeseen costs by its very nature. However, in the short term, corrective maintenance can actually save money.
This type of maintenance doesn’t use many resources in regards to tools, time, technology or expertise. Deliberately letting something run to failure or not implementing a predictive maintenance plan is fine for less-critical, inexpensive, readily available and easy to replace parts. However, it is inefficient as a general working practice and can lead to greater expense if one failure leads to other parts failing and an eventual catastrophic failure of the whole asset. Such serious problems can lead to long periods of downtime, expensive repairs or even the need to replace an entire piece of equipment. All of these factors can quickly cause costs to increase dramatically.
In addition, corrective maintenance does not tend to take account of the causes of a problem, which could lead to repeated failures of subsequent replacement parts and the associated repair and replacement costs.
Corrective maintenance is something that all facilities have to contend with, yet it needn’t be a costly process. While it is fine to let some inexpensive and easily-replaced, non-critical parts run to failure, there is still a level of preparation required in ensuring replacements are available in stock as well as someone who can fit them.
To get the most from corrective maintenance it is best to couple it with preventive maintenance duties so that employees can report any problems. This will allow for maintenance to be planned for a suitable time, before critical failure strikes.
Critical, unplanned, corrective maintenance can be expensive, in terms of both labour costs and downtimes, so maximising planned corrective maintenance to keep your assets running at maximum efficiency is worth the effort in the long term.
Related Frequently Asked Questions (FAQs)