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8 Essential Indicators for Maintenance Management

Indicators are one of the main ways of measuring maintenance results. After all, what is not measured, is not managed.

They are very important for maintenance managers because of the work routine, teams, processes and equipment can be analyzed with their help. Do you know if your equipment and facilities are ready to handle the job?

Basically it is possible to measure any activity that generates numbers or values ​​under maintenance. The question is to find out which are the most important performance indicators so as not to waste time following those that are not very relevant. Below is a list of the main maintenance indicators.

  • MTBF: Mean time between failures
  • MTTR: ​​Average time to repair
  • Availability
  • Reliability
  • Backlog
  • CMF: Maintenance Cost on Billing
  • CPMV: Maintenance cost over replacement value
  • Distribution by types of maintenance

1st indicator – MTBF: Mean Time Between Failures

MTBF or mean time between failures is one of the most important indicators for the maintenance sector. It consists of measuring the total average time of good functioning between the failures of a reparable equipment, becoming a great tool to measure the reliability of the machine.

The most efficient way to manage this indicator is to apply it to each piece of equipment. Thus, actions can be applied individually, facilitating actions. Also taking into account that each piece of equipment will have a different life cycle. (In this other article we explain better the typical behavior of a machine)

To exemplify, imagine that during a certain period the electric motor of a factory operated 140 hours until it failed, then another 190 hours and finally 215 hours. In this case the MTBF will be:

Once the average time from one failure to another has been identified, we are able to identify the frequency with which we must place our preventive maintenance activities and inspections within the PCM. It is recommended to calculate 70% of the average failure time to perform this inspection. That is, if the electric motor has an MTBF of 181.6 hours, every 127.1 hours (181.6 x 0.7) the inspection on this equipment must be performed.

Logically, the higher the MTBF the better, since the equipment is taking longer to fail, that is, you managed to obtain a lower frequency of breaks.

MAIN MISTAKES MADE:

  • Add the MTBF of all equipment to find the global average
  • Calculate MTBF on irreparable equipment
  • Reset MTBF every month (add it

Currently, there are some predictive maintenance software that can, through the analysis of equipment vibration and temperature, estimate when the equipment will break and automatically create job orders to solve this problem, so the analysis is no longer manual and in spreadsheets and happens to be digital and in real time. Considerably increasing the accuracy of the results for decision making and drastically reducing the response time.

2nd indicator – MTTR: ​​Mean Time To Repair

This indicator is closely associated with maintainability, that is, the ease that a maintenance team finds in replacing equipment in conditions to perform its functions after a failure. Among other words, this KPI indicates the average time to repair.

Unlike MTBF, MTTR is a smaller / better indicator, that is, we must work to keep it low.

When adding it to the electric motor example, suppose that during the same period the maintenance team took to put the electric motor back into operation in each of the situations:

Failure 1: 9 hours

Failure 2: 15 hours

Failure 3: 12 hours

In that case the MTTR will be:

With this, we are able to measure what is the loss of profit, or better, how much the company fails to earn when this equipment breaks. If we hypothetically consider that such machinery generates R $ 5,000 per hour, the loss of this company with the failure of this equipment will be around R $ 60,000 (5,000 x 12).

MAIN MISTAKES MADE:

  • There is no ideal value and reference for MTTR
  • Requiring maintenance teams to maintain a low MTTR can mislead them.

Much better than keeping MTTR low, is to avoid breakage. The maintenance manager must encourage his teams to use predictive and sensitive maintenance techniques that assess the health condition of the machines, identifying the “symptoms” in real time so that the asset does not lose its performance to the point of reaching a critical situation of failure.

Indicators 3 and 4 – Calculating the availability and reliability of assets

These two indicators are fundamental for Maintenance Planning and Control, it can be said that the main objective of the PCM is to guarantee and increase the availability and reliability of assets, optimizing productivity. So we decided to put them together.

Both are determined from MTBF AND MTTR. But before calculating them, let’s understand the meaning of each one according to the NBR 5462 standard:

Availability: the CAPACITY of an item to be able to perform a certain function at a given time or for a specified period of time.

Reliability: the PROBABILITY of an item to perform its function specified in the project, according to the operating conditions, in a specific interval of time.

The meaning is similar, right? Let’s try to exemplify better. Equipment availability is the percentage at which the asset has remained available over a given period. Reliability, on the other hand, will be the probability that an equipment will remain available in a given period.

Want to understand how it’s calculated? The availability formula is given by:

That is, if we take the example of the electric motor (MTBF = 181.6 and MTTR = 12) the inherent availability of the equipment was 93.8%. That is to say, in the period used in the example, the engine normally operated about 93.8% of the time it was on. World-class standards determine that good availability is above 90%. That is, in this case the equipment is within the world standards.

What if we wanted to calculate the probability of the engine running in perfect condition for the next week? In this case the reliability calculation would be:

If we apply the formula for the electric motor (MTBF = 181.6) we can know that for the next 7 days (168 hours) the reliability of this equipment, that is, the probability of it operating normally without fail, would be 39.69%. See below:

MAIN MISTAKES MADE

  • Indication of reliability without a period of time

Wrong: The reliability of this centrifuge is 85.4% – what is the period?

Right: The reliability of this centrifuge is 85.4% in the next 400 hours

  • Use the formula above for irreparable equipment. For such items, the Weibull Analysis must be used.

5th indicator – Backlog

The backlog can be understood as the labor time required to perform all current services, which is the accumulation of activities pending completion. This indicator demonstrates the relationship between the demand for services and the ability to meet them.

We can associate the backlog, as the work load originating from the maintenance activities, among other words , it is the sum of the hourly load of services planned, scheduled, and now pending execution by the maintenance sector.

Since it is a time indicator, its calculation must be given in minutes, hours, days, weeks, months, etc. Let’s calculate.

The backlog graph is also of great importance for management decisions, there are basically six types of curves. Consider the vertical axis as Backlog values ​​and the horizontal axis as the months of the year.

Curve A: Stable, necessary analysis if it is at an acceptable value for decision making;

Curve B: Decreased service demand, it can generate idle staff due to the drop in services;

Curve C: Backlog with a constant upward trend, which can generate problems such as low quality of maintenance;

Curve D: Sudden ascent. It can occur when there is failure with a very quick execution time.

Curve E: Sharp drop. In this case there might have been a contraction of external services, internal mobilization for reduction, among others.

Curve F: Oscillation. It is usually justified in industries that have a strong seasonality characteristic, such as those related to agriculture.

MAIN MISTAKES MADE

Associating the backlog with “Activity in arrears” is a common mistake with this indicator, as it encompasses much more than that, this indicator refers to all the activities that need to be done, from urgent to normal day-to-day activities.

6th indicator – CMF: Maintenance Cost on Billing

Cost-related indicators are excellent evidence of the effect of maintenance on the company’s performance, which makes them a fierce weapon for the board. With them, it is possible to identify whether the maintenance sector is doing good financial management of resources.

The maintenance costs includes all expenses with related to

  • Personnel
  • Materials:
  • Hiring of external services
  • Depreciation
  • Loss of revenue

One of the main reasons for this highlight is that the cost of maintenance can directly impact product pricing, so if the company spends a lot on maintenance, the end price of the product will be higher affecting its competitiveness in the market.

The indicator that works best in this scenario is the CMF as it is a direct comparison between billing and the cost of maintenance. Observe the formula:

To demonstrate on a practical example, Imagine that a certain Textile industry had a total expenditure of R $ 1 million with maintenance in the last year. In the same period, the company had gross sales of R $ 25 million. Therefore, the CMF is 4%. But is it good or bad?

Once calculated, the best thing to do is to compare it with the average of the segment in which your company is operating. In this case, the average of the CMF for the Textile industry is 1%, that is, the company analyzed would be spending 4 times more than the average of the Brazilian textile industries. According to ABRAMAN, on average, 4% of companies’ revenues in Brazil are use in maintenance.

7th indicator – CPMV: Maintenance cost over replacement value

Another important financial indicator is the CPMV, as it is a way of analyzing the maintenance cost used for each piece of equipment and identifying whether it would be more advantageous to continue to keep the asset or purchase a new one. It is advisable to use this indicator for highly critical equipment

Its calculation is simple, but first we will understand what is the acronym ERV (Estimated Replacement Value). The Estimated Exchange Value, as the name itself refers, is the amount of capital that there needs to be paid  to purchase new equipment. Thus, the CPMV formula is given by:

For example, think that R $ 4,000 BRL was spent on the maintenance of an overhead crane. While the value of a new bridge would be R $ 190,000. Therefore, the CPMV is 2.10%.

The maximum acceptable value for this indicator is 6% over a period of one year, however this value may depend on an analysis of the equipment, in some cases 2.5% is enough. If we find a larger number, it means that it is more advantageous to buy new equipment than to keep the old one.

A more effective way to reduce maintenance costs is to change the dynamics of “break, repair”. That is, try to reduce the number of corrective maintenance to the maximum and use the power of the data to predict failures before they happen. THE cost of a predictive maintenance plan is infinitely less than the expenses of repairing  equipment and getting it back up and running. (The PF curve shows this dynamic very well, click here to learn more).

8th – Distribution by types of maintenance

This indicator reveals the percentage of the application of each type of maintenance being developed. Evidently, the type of installation or equipment can determine variations around these values. In general, the maintenance manager must keep the practises of unplanned corrective maintenance unplanned  up to 20%, and it is always good to restrict them to the maximum. Other practices do not require a close limit, in Brazil, preventive maintenance generally ranges between 30 to 40%. In global reliability standards, companies look for predictive maintenance as the largest percentage in distribution.

How can technology help your company to monitor indicators?

Technology, such as maintenance management software and machinery condition monitoring devices, has revolutionized the maintenance routine, replacing extensive spreadsheets, helping to collect and manage data from these indicators, making information more reliable and giving valuable insights about the reliability and availability of your equipment in real time.

If you want to know more about how Tractian is making the routine of maintenance managers more practical and intuitive, send a message to our team in the question balloon on the right or schedule a demonstration:

Schedule a demo

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Sobre o Autor:

Gabriel Lameirinhas

COO of TRACTIAN. Computer Engineer from University of Sao Paulo, Specialist in predictive and passionate about industrial maintenance.

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