What is Corrective Maintenance?
Corrective maintenance is the process of restoring assets after unplanned downtime. It includes troubleshooting, disassembling, readjusting, repairing, replacing, and realigning equipment. The term may also refer to unplanned software maintenance.
Have you ever fixed a broken dryer, washing machine, or dishwasher? If so, you have engaged in corrective maintenance.
In his book, Logistics Engineering and Management, Benjamin S. Blanchard defines corrective maintenance as unscheduled actions that are initiated by failure (both real and perceived) and is intended to restore a system to required levels of performance. The only difference between home appliance corrective maintenance and industrial corrective maintenance is that the latter may delve more deeply into investigating root causes, cost analysis, and reducing the likelihood of future equipment failure.
Types of Corrective Maintenance
This type of maintenance can be categorized in several different ways. However, most organizations divide the practice into five classifications. Here’s how the U.S. Army’s Engineering Design Handbook: Maintenance Engineering Techniques breaks down the types of corrective maintenance:
- Fail Repair: Restoring a failed asset to its operational state.
- Overhaul: Restoring an asset to its complete service state as outlined by maintenance serviceability standards. Here assets are only inspected and repaired as appropriate.
- Salvage: Disposing nonrepairable materials and utilizing salvaged materials from irreparable assets.
- Servicing: Fixing after corrective action is taken. For example, welding or refilling crankcases after engine repairs.
- Rebuild: Restoring an asset as closely as possible to original standards in terms of performance, appearance, and life expectancy. Rebuilds involve disassembling the parts, examining them, repairing worn-out components, and replacing unserviceable ones in line with original specifications and manufacturing tolerances. Reassembled assets are then tested to ensure they match original production requirements.
These five categories are commonly divided into two parent classes: Unscheduled (immediate) corrective maintenance and Planned (deferred) corrective maintenance:
- Unscheduled corrective maintenance refers to repair actions that are taken immediately after an asset fails. . These failures are considered critical and corrective actions are needed without delay.
- Planned corrective maintenance refers to repair actions that are needed but can be deferred to a later date. This can be due to a limited budget, time, or staff. Some maintenance actions also require more technical services which the company may need to outsource.
From here, planned corrective maintenance is sometimes further broken down into two groups:
● Run-to-Failure Maintenance: In this case, an asset is permitted to run until it breaks down, at which point it is repaired or replaced. The strategy is only suitable for redundant systems and non-critical assets that are easily repairable and replaceable.
● Preventive Maintenance (as part of Condition-Based Maintenance (CBM) ): Equipment problems are identified during preventive and condition-based maintenance inspections.
How Corrective Maintenances Decreases Equipment Failure?
Timely corrective maintenance identifies asset problems before equipment failure occurs. Whether planned or unscheduled, it catches issues before they lead to downtime and unnecessary costs. For example, you can replace worn-out brake pads before they affect the rotors. By replacing the worn-out brake pads (correcting the problem), you keep the rotor from breaking down and needing to ground the vehicle (downtime).
Based on your maintenance management plan, your maintenance team will initiate corrective maintenance when they notice that an asset is about to break down or the condition of a given component will affect the overall performance of an asset. Repairs and restoration can be done before downtime occurs. This helps minimize equipment failure. Unfortunately, unscheduled corrective maintenance can halt production lines and cause service interruptions. However, the downtime for correction is minimal compared to total equipment failure. Unscheduled corrective maintenance interruptions are intended to restore assets to optimal performance before failure.
What Are the Advantages?
Corrective maintenance provides many benefits when correctly executed. It’s advantages include:
- Reduced Need for Planning: It requires less planning compared to preventive maintenance and CBM.
- Enhanced Simplicity: Due to its nature need-based, maintenance teams can focus on other tasks until a breakdown occurs. The process is also simple and doesn’t require complex tools to identify faults before they occur.
- Increased Cost Efficiency for Non-critical Assets: Instead of spending resources on creating a PM plan for non-critical assets, corrective maintenance allows you to save money by undertaking upkeep only when needed.
While not as full proof as a strictly PM plan, the strategic combination of corrective maintenance and preventive maintenance can improve workplace safety, extend the lifespan of assets, and optimize resource planning.
What Are the Disadvantages?
Like anything else, this type of maintenance has its downsides. Some of these include:
- Increased Unpredictability: The strategy can lead to a backlog of work orders. You never know when issues will arise. Not knowing when you will need technicians and specific parts increases uncertainty.
- Increased Cost of Maintenance: When exclusively practiced outside of an overarching preventive maintenance strategy, deteriorating equipment parts may not be found as quickly. This can cause increased costs associated with emergency maintenance (e.g. worker overtime, outsourced technicians, expedited shipping of inventory).
- Safety Concerns: It’s not uncommon for maintenance technicians to rush through standard operating procedures (SOPs) in an attempt to quickly bring important assets back to life. Unfortunately, such hastiness can lead to unsafe work environments.
Advantages vs. Disadvantages of Corrective Maintenance
|Reduces need for planning||Increases unpredictability|
|Simple process that is not resource-intensive||Safety concerns if maintenance is hurried|
|Cost-effective for non-critical assets||Increases cost of maintenance for critical assets|
|Improves workplace safety when used together with preventive maintenance||Increases downtime in event of serious problems|
Examples of Corrective Maintenance
Here are a few scenarios when this type of maintenance is used:
- Example of Unscheduled Corrective Maintenance: Water companies periodically deal with hard water residue build-up in their pipes. This common occurrence increases water pressure, leading to burst pipes if left unremedied. For this reason, water companies must immediately replace burst pipes upon identification to avoid large financial losses.
- Example of Scheduled Corrective Maintenance: It’s a known fact that dusty HVAC filters negatively affect unit efficiency over time. For this reason, facilities often replace air filters monthly.
Other examples include replacing a faulty part on a production line after a breakdown, replacing a clogged nozzle head that is stopping lubricant from flowing, and repairing road sign damage after a major storm. Frankly, the examples are endless!
Frequently Asked Questions
What is the difference between corrective and preventive maintenance management?
Due to the overlapping nature of the terms, it’s not unusual for folks to confuse planned corrective maintenance with preventive maintenance (PM). However, there are some clear distinctions between the two maintenance strategies.
Most notably, the former focuses on dealing with problems after they occur. Alternatively, PM focuses on reducing the likelihood of problems ever occurring. This means that corrective maintenance is performed at random intervals, while preventive maintenance is conducted at regular intervals with active inspection measures in place.
What is the ideal corrective maintenance vs preventive maintenance ratio?
Finding the right balance between corrective maintenance and preventive maintenance can be tricky. John Day, operational manager at Alumax of South Carolina, answers this persistent question with the The 6–to-1 Maintenance Philosophy. The philosophy dictates that for every six PM tasks a company performs, it may need to complete one corrective task.
This ratio ensures that equipment issues that cannot be predicted with preventive maintenance are handled with planned corrective actions before excessive downtime can occur. While the 6-to-1 Maintenance Philosophy provides a useful benchmark for equipment service planning, every organization is unique. Nothing substitutes for conducting a thorough asset inventory, tracking individual asset behavior, and fine-tuning a customized preventive maintenance strategy.
What is planned corrective maintenance?
As previously mentioned, the maintenance can either be planned or unscheduled. Unscheduled corrective maintenance refers to actions that are taken immediately after asset failure occurs. In such instances, the failure is considered critical, and corrective action is needed without delay.
Planned corrective maintenance, however, refers to actions that are needed but can be deferred to a later date without harm. Deferred maintenance can happen due to limited resources in terms of budget, time, or staff. Certain maintenance tasks might also be backlogged because they require outsourced specialty services. Planned corrective maintenance takes place in two forms:
- Run-to-Failure Maintenance Strategy: Here, an asset will be allowed to run until it breaks down. Only then will it be repaired or replaced. The strategy is suitable only for redundant systems and non-critical assets that the company can easily replace or repair cheaply.
- Planned Corrective Maintenance (part of CBM or preventive maintenance): In this instance, problems identified during preventive and condition-based maintenance inspections are scheduled for maintenance actions.
When Should You Use Corrective Maintenance?
This type of maintenance is best used in conjunction with a comprehensive PM program. Experts recommend only relying on corrective maintenance when absolutely necessary. Your reliance on it will depend on a number of factors such as how critical certain assets are to daily operations, the cost of downtime for these assets, and how easily swappable the pieces are in the event of a problem. When in doubt, follow the 80/20 rule: direct 80 percent of your effort toward preventive PM and 20 percent of your attention toward corrective maintenance.
Utilizing the right Computerized Maintenance Management Software (CMMS) can help organize, optimize, and personalize your strategy. The more asset data your facility accumulates, the easier it is to make cost-effective service decisions.
Corrective maintenance requires companies to invest in sufficient manpower and resources to enable them to handle equipment problems when they arise. Organizations can avoid major unplanned downtimes—and extend asset life spans— by pairing both unplanned and planned repair actions with realistic preventive maintenance programs. Aim for an 80 percent preventive maintenance to 20 percent corrective maintenance ratio when planning programs.