# ERAU Mean Time Between Failures MTBF And Maintenance Costs

As you have learned from your reading, knowing when a part or system will fail is important for a company. Mean time between failures (MTBF) is the expected time between failures of a part, process or system and is a common matrix for a firm to use to understand how often a failure will occur.

Assume that you are the manager of a production line and are responsible for keeping the machines running 24 hours per day, 365 days per year. When a machine breaks it must be repaired and put back onto operation as soon as possible. The problem is that your machines are always breaking down, and you really do not have a good understanding of how often a machine breaks down.

Complete the steps in each section and then submit your assignment for grading. Submit one spreadsheet containing a tab for each step.

### Step 1: Calculate the MTBF

You decide to run a test to determine the mean time between failures. During the test, you start with 10 operational machines on your production line producing widgets. You record breakdowns during a 100-hour observation period in which two of the machines broke down. One at 35 hours into the test and the other at 50 hours into the test.

Use Excel and the data you collected to calculate the MTBF of your machines.

### Step 2: Calculate the Expected Breakdown Maintenance Costs

After collecting and analyzing the MTBF data you were surprised at how often your machines really broke down. At your last company you remember that they had a service firm that would come in and perform preventive maintenance (PM) on your machines and you wonder if this would be an option to reduce breakdowns. However, before you go to your boss to pitch the idea you want to see if using an outside PM firm would reduce your cost.

So you do some research on the cost and run another study on the number of breakdowns of your machines. You run the study for one year and create a chart containing the number of breakdowns and the number of months that breakdowns occurred.

Number of Breakdowns Number of Months that Breakdowns Occurred
0 0
1 9
2 7
3 5

You also do some research on breakdown cost and find that the average cost of a breakdown to your firm is \$350. You find a service firm and request a price quote from them. The PM service firm costs \$200 per month, but they tell you that you can still expect on average of 2 breakdowns per month even with the PM service.

Use Excel and the data to calculate the expected breakdown maintenance cost versus hiring the PM firm to service your machines.

### Step 3: Recommend and Submit

On a third tab of your spreadsheet, indicate which of the options you will recommend to your boss – hire the firm or continue dealing with the breakdowns at the current rate?

Submit one spreadsheet containing a tab for each step. Save your assignment using a naming convention that includes your first and last name and the activity number (or description). Do not add punctuation or special characters.

Review the Problems Rubric for detailed grading information.