Corrective Maintenance: Ally or Villain?

According to the NBR-5462 Standard, Corrective Maintenance is the maintenance carried out after a breakdown has occurred, aimed at putting an item back in conditions to perform a required function, that is, to correct a defect or failure.

It represents the first paradigm in the history of Industrial Maintenance, when there was no other maintenance methodology than letting a machine run until failure.

TYPES OF CORRECTIVE MAINTENANCE

To understand the types of Corrective Maintenance, it is necessary to define two distinct maintenance philosophies: proactive and reactive.

Reactive maintenance is the philosophy of operating up to breakdown and its main activities are performed only after the failure.

Proactive maintenance seeks to anticipate failure, and its main activities are prevention, detection, and elimination of root causes.

Even when the methodology adopted for a given piece of equipment is proactive, it is still susceptible to unforeseen failures.

As this equipment is probably classified at a higher criticality level, these failures require immediate treatment, requiring the application of Corrective Maintenance.

With these understandings, such methodology can be divided into three types:

• Reactive Corrective Maintenance: the result of a maintenance plan that foresees interventions only when the equipment fails. It is already expected that the breakdown will occur at some point.

An everyday example are light bulbs, which we let operate until they burn out.

When this occurs, we perform Reactive Corrective Maintenance by replacing the bulb. In industry, for example, we have a pump for lifting water for a non-critical process that operates until it loses performance due to its impeller’s erosion.

The maintenance plan predicts having a rotor in stock that is fit to replace the one that failed, so the pump is stopped for Reactive Corrective Maintenance until normal performance is regained.

• Planned Corrective Maintenance: part of a proactive maintenance plan, in which Corrective Maintenance is a result of Preventive or Predictive Maintenance.

Planned Corrective Maintenance is performed to correct defects and prevent breakdowns.

Following the example of the hydraulic pump, but used in a critical process (such as the feeding of a boiler), a Preventive Maintenance plan can schedule the shutdown for Corrective Maintenance of the rotor within fixed periods of operation; or a Predictive Maintenance plan can detect the defect in its incipient phase, prognosticate the failure, and determine when Corrective Maintenance should be done.

• Non-Planned Corrective Maintenance: it also has a reactive character, because it comes into action when the failure occurs randomly, in an equipment submitted to proactive maintenance.

The failure is not expected and its occurrence affects the production and maintenance plans, which makes it an emergency. Its effect is further enhanced when the maintenance plan works with reduced stocks of replacement components, something very common in proactive maintenance.

So this type of Corrective Maintenance is costly, affects safety, quality and reliability. Therefore, it is the only type of maintenance that we want to avoid under any circumstances.

A typical example of Unplanned Corrective Maintenance is that performed on a conveyor belt suffering from overheating due to blocked rollers after a period of undetected bearing wear.

In this case, it should be urgently stopped for correction.

WHEN TO APPLY REACTIVE CORRECTIVE MAINTENANCE?

The use of Reactive Corrective Maintenance can be justified for machines with the following characteristics:

• Low criticality;
• Low defect frequency;
• Low cost of repair of catastrophic failures.

The Figure below compares the repair and application costs of three different maintenance methodologies: Corrective, Preventive, and Predictive.

Reactive Corrective Maintenance has the highest repair cost, because failures are usually catastrophic and require complete component replacement.

On the other hand, it has the lowest application cost, because maintenance activities are simple, little instrumented, and fast.

The ideal maintenance strategy is one that can apply all these different methodologies in a way that suits the nature of each piece of equipment, achieving efficient results.

ADVANTAGES OF REACTIVE MAINTENANCE FOR YOUR COMPANY

We live in a highly competitive market scenario, so in order to stand out from the competition, it is necessary to always seek the best practices.

Since Unplanned Corrective Maintenance is always unwanted and Planned Corrective Maintenance is part of a more complex maintenance system, we seek to explore how Reactive Corrective Maintenance can be used as an ally to your company.

Let’s start by listing the main advantages of this methodology:

• Decreased maintenance costs;
• Allows the maintenance team to focus its resources on critical equipment;
• It can be used as the starting point for the implementation of a Maintenance System.

DISADVANTAGES OF REACTIVE CORRECTIVE MAINTENANCE

Due to its high level of uncertainty, Reactive Corrective Maintenance has some disadvantages that must be considered in the maintenance plan:

• Determining the most appropriate type of maintenance for a piece of equipment is in itself a great challenge, so Reactive Maintenance poses many unknown risks;
• Causes production stoppage;
• Usually demands a stock of spare parts;
• Can have a high maintenance cost when it requires outsourced teams and urgent procurement of out-of-stock parts;
• Repair costs are even higher in the infant mortality and wear phases of the machine’s life.

Finally, the best results are actually achieved when there is an optimal integration between Corrective Reactive Maintenance and proactive maintenance methodologies.

BEST PRACTICES FOR CORRECTIVE REACTIVE MAINTENANCE

To reach these results, one should be alert to Corrective Reactive Maintenance good practices. Make sure that your production is aligned with the following tips:

1. Corrective Reactive Maintenance doesn’t mean the absence of essencial periodical maintenance activities. The visual inspections and the lubrification inside the specifications should be included in any maintenance plan.
2. Keep a failure history that occurred in the equipment, since it’s an easy and low cost way to understand behavior, stock, identify critical failures and even estimate periods of some breaks occurrency.
3. According to the good practices stated in the World Class Manufacturing concept, planned maintenances should represent at least 90% of all maintenance activities and at least 90% of planned activities should be executed.
4. All of the interventions of the Corrective Maintenance should be excuted by well-qualified professionals. A poorly executed intervention can be the origin of other degradations that will evolve to a future break, increasing the repair costs and decreasing the efficiency of the maintenance plan.
5. If the frequency failures start to increase and the maintenance costs escalate, it should be re-evaluated if the Corrective Reactive Maintenance keeps being the best methodology for the case. Evolving to a more proactive maintenance concept could be more advantageous.

HOW TO EVOLVE TO PROACTIVE MAINTENANCE PARADIGMS

Depending on the maturity level of a company management systems, its maintenance programs could still be limited to the paradigm of Reactive Corrective Maintenance.

That is, it ends up being the only used methodology, even if it’s not the most advantageous.

This represents a great opportunity to start maturing the management system from the paradigm breaks in the maintenance programs.

The first step in breaking a paradigm is to make an assessment of the losses associated with Reactive Corrective Maintenance.

Then ask yourself:

• How much production, quality, safety level, time and money is your company losing directly and indirectly due to unplanned machine downtime?
• What will be the return on investment in a more effective maintenance system?

The answer to thesee questions may be surprising and influentiate decisions in management level.

It’s known that proactive maintenance paradigms significantly decrease losses in several sectors of a company.

However, it’s easy to reach the conclusion that the evolution of the maintenance paradigm is necessary.

As in all the cases of change in management level, the true challenge is to convince the whole company to engage in this evolution.

Therefore, we already gave tips on how to convince your manager that maintenance costs are investments and not expenses and how to engage all the complany in this activity.

Now, with an engaged team, the maintenance plan involving proactivge and reactive methodologies should be created, making decisions about which equipments will remain under Corrective Reactive Maintenance and which will migrate to Preventive/Predictive Maintenance.

A projected tool to support these decisions is the ABC method, which classifies machines according to their criticality level.

For critical machines, it is often justified to apply Predictive Maintenance based on continuous monitoring of their condition, which allows tracing the operation patterns of the asset and quickly detecting anomalies and diagnosing defects in time to plan maintenance activities.

One of the most effective ways to trace these patterns is by measuring vibration and temperature data from specific machine components.

The need to instrument the maintenance activities immediately brings two concerns for the manager used to Reactive Corrective Maintenance: the high initial investment and the need to train the team to analyze the generated data.

Fortunately, Industry 4.0-oriented technologies open up a range of possibilities for overcoming these two challenges.

As for the initial investment, IoT technologies, the Internet of Things, also identified as Industry 4.0, have sensing solutions for monitoring the health of machine components in a simple and affordable way.

At the same time, these technologies have telemetry capability, i.e., they measure vibration and temperature data and transmit them remotely, without the need for sensor cabling.

The data can be stored by cloud computing and accessed on an online platform from anywhere in the world.

Thus, a company with a maturing maintenance system, still without vibration and temperature data analysts, can easily outsource the work of monitoring the data and diagnosing defects.

This concept is known as Remote Monitoring and Diagnostics, in which analysts do not need to go into the field to collect data, which is acquired and monitored in real time for anomalies.

MAINTENANCE STRATEGY FOR YOUR INDUSTRY

The Dynamox Solution is a powerful predictive maintenance tool that acts to increase machinery availability and decrease corrective reactive maintenance actions.

The Solution has a data logger with sensors to monitor the vibration and heating condition of machines and components.

In addition to monitoring the failure trend, it allows alerts to be set and remote diagnosis to be assisted by an engineer specialized in vibration analysis.

All so that maintenance interventions can be planned assertively.

Learn more about the complete Solution and how Dynamox can help your maintenance planning and strategy.