What is MTBF?

To start with, MTBF or by its full name - Mean Time Between Failures is a quite important measurement in preventive maintenance.

If you’ve ever managed various devices or any kind of equipment, you probably faced the fact that there is no perfect system. As time goes on, machines might stop working, parts fail and unexpected downtime happens when you least want it, or expect it. This is where MTBF can help you and make your life easier.

MTBF measures how long (on average)a piece of equipment runs before it experiences a failure. Think of it as the “trust score” of your machinery: the higher the MTBF, the more reliable the system is likely to be.

It’s important to remember that MTBF will not predict the exact moment something will break. It will rather provide you with statistical data. With this data, you can optimize your maintenance process and operations. Additionally, you can make decisions with more confidence.

For better understanding, let’s take a look at one example. A ship’s main generator has an MTBF of 2,000 hours. Will it stop working after exactly 2000 hours? We don’t know that. But we know that around that time we should do the inspection, maybe replace the spare parts. We know that we have to allocate the team for that. That we have to order those spare parts. Now you see the way this leads?

MTBF should be your tool that helps businesses like yours save time, reduce costs and minimize unexpected downtime.

How to Calculate MTBF

Let's try to calculate MTFB. MTBF calculates the average time a piece of equipment runs before it fails. In formula form, it looks like this:

MTBF=Total Operational Time / Number of Failures

Going back to our ship example. During the last year, the main generator on a vessel has been running for a total of 10,000 hours. We’ve noticed it failed five times during that year. To calculate the MTBF, we divide the total operating hours by the number of failures:

MTBF=10000 hours / 5 failures=2,000 hours

So, on average, the generator runs for about 2,000 hours between failures.

A few things to keep in mind:

• MTBF gives you the average number, not the precise one. Some failures may occur sooner, while others may happen much later than the calculated MTBF. The number helps you plan and prepare.
• If you know your MTBF, you can schedule inspections, order spare parts and allocate the team on time.
• Good records are key. Accurate operational logs and failure reports make MTBF calculations meaningful. Without reliable data, the number becomes less useful.
• MTBF is like a weather forecast for your equipment. It doesn’t tell you the exact minute a storm will hit, but it tells you to pack your umbrella.

Common Problems and Challenges in MTBF Calculation

MTBF is a powerful tool, but like any other tool it is not perfect. Here are some common bumps in the road when using MTBF:

1. Failures aren’t always random.
MTBF works on the idea that failures happen randomly, but anyone who’s worked on a ship knows that’s rarely true. Sometimes a part just breaks down faster. Maybe the air is too salty or the engine has been working overtime. One engine might fail sooner than another just because it’s near a slightly leaky pipe. That means MTBF can only give you a rough idea — it’s a guide, not a guarantee.

2. Bad or incomplete data.
Pure MTBF is nothing, unless you store and keep data. You should keep track of when and why failure happened, and how often. If you skip some data, you will most likely get a wrong picture. Think of it like trying to figure out your average speed on a road trip when you forgot to start the odometer a few times. The number just won’t make sense.

3. Small sample sizes.
If a piece of equipment hasn’t been used much yet, calculating MTBF can be tricky. One early failure can make the MTBF look awful, even if the system is actually quite reliable. The more hours and failures you record, the more accurate the number becomes.

4. MTBF doesn’t account for human factors.
MTBF can not predict human factors. We’ve seen that sometimes the engineer forgets one step in installation or during the routine check. Despite that, MTBF is still there to help, by remaining us to keep good habits, teach a team and double check the work.

MTBF vs MTTF vs MTTR

If you are working in any maintenance intrustry, you know there are other terms, beside MTBF, such as MTTF and MTTR. We will now explain each of these and compere them for better understanding.

MTBF (Mean Time Between Failures)
This is the main topic of this blog. MTBF is just the average time your equipment runs before it needs a little care. It’s the number that helps you decide when to check in on it, when to stock spare parts and when to call the crew for maintenance.

MTTF (Mean Time To Failure)
MTTF is close to MTBF but has a small difference. It usually applies to items you don’t repair, you replace them once they fail. Examples include cabin light bulbs or sensors. MTTF gives you an idea of how long these parts are expected to last before they give out.

MTTR (Mean Time To Repair)
MTTR is simply about how long it takes you to get something running again once it breaks down. While MTBF and MTTF talk about how long equipment usually keeps going, MTTR looks at the downtime: the hours between “it stopped” and “it’s back in service.”

Picture this: the ship’s generator suddenly shuts down mid-voyage. MTTR that tells you how long the crew will likely spend troubleshooting, replacing parts and bringing it back to life. The exact time can vary but having an MTTR figure helps you plan ahead and avoid disruptions.

Quick Comparison Table

To sum up: All these measurements together give you the full picture of reliability. MTBF and MTTF tell you how long things keep working, while MTTR tells you how long you’ll be stuck when they don’t.

Benefits of MTBF - main helper in Preventive Maintenance

MTBF real value comes when you start using it in your daily operations. This is not just a number, but a tool that can help you optimize business and save money.

1. Smarter Maintenance Planning
Preventive maintenance is basically giving your equipment some regular TLC. You check it, service it, and make sure everything’s in good shape so it doesn’t suddenly quit on you. If you know the MTBF, you will have a better idea when to do the service and inspection. .

2. Reducing Downtime
Breakdowns at sea are never fun. If you are regularly tracking your MTBF you will be prepared and probably avoid surprises. If your team is ready and spare parts are available, downtime should be increased, a lot.

3. Improving Reliability
Over time, MTBF shows you which equipment is strong and which isn’t. Maybe one type of pump keeps failing while another keeps humming along. Those numbers tell you where to invest, which suppliers to trust and where to be extra careful.

4. Managing Risk
MTBF data enhances broader risk assessment efforts. It provides concrete numbers to support risk analysis and decision-making. Risk managers can use MTBF to:

• Quantify the likelihood of equipment failures
• Estimate the financial impact of potential downtime
• Prioritize risk mitigation efforts