Ep 4: What is Condition Based Maintenance and How Do You Assign Task Intervals?April 13, 2022 April 19, 2022 / Published By
In this episode we explore what Condition Based Maintenance (CBM) is (aka On-Condition Maintenance). We’ll talk about :
– What CBM is
– The biggest trap you can fall into when implementing CBM
– And what governs how often you do a Condition Based Maintenance task.
As asset managers, we know that most Failure Modes occur randomly, and that can seem a little intimidating or maybe even a little scary, but it doesn’t have to be because that’s where Condition Based Maintenance can be very helpful. The whole point of Condition Based Maintenance is to detect a Potential Failure Condition and take action before failure occurs. That interval is called the P-F Interval and that is explained in this episode.
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Hi Everyone. And welcome to The Heart of Reliability, where we break Reliability down to the basics. Because after all, anything that’s not built on a firm foundation will eventually crumble. And that goes for Reliability, too.
I’m Nancy Regan. And welcome to episode four of The Heart of Reliability. Today, we are going to talk about Condition Based Maintenance, or CBM.
Another term to use is On-condition maintenance. But for purposes of this episode, we’re going to use the term CBM or Condition Based Maintenance. In this episode, we’re going to talk about three important things.
1. What is CBM?
2. What is one of the biggest traps you can fall into when implementing CBM?
3. What governs how often you do a Condition Based Maintenance task?
Now we know as asset managers that most Failure Modes occur randomly, and that can seem a little intimidating or maybe even a little scary, but it doesn’t have to be because that’s where Condition Based Maintenance comes in.
Because most Failure Modes give us some sort of a warning that failure is about to occur. So, the whole point of Condition Based Maintenance is to detect that Potential Failure Condition and take action before failure occurs. That’s the strength of Condition Based Maintenance. It allows us to detect failure before it happens.
Let’s start out by talking about a really big trap you can fall into when doing Condition Based Maintenance and it is called Shiny Object Syndrome. Now on this podcast, we talk about the basics, and I often relate Reliability issues to my real life. And this topic is no different.
I fell into the same trap that you can fall into when doing Condition Based Maintenance if you’re not careful and if you don’t understand the basics. Let me show you the Smoove. What is it? It’s a fancy gimbal system that you, you know, you put your cell phone in here and you hold it and you can make your videos. You can make your vlogs.
And when you look on their website, they’ve got people using this thing and they’re skateboarding and doing all these funky things, climbing mountains. And so of course the idea is that it takes out, to a large degree, takes out the motion. So, when people are watching your vlogs, they’re not getting dizzy because things are all moving around.
When I decided that I wanted to start vlogging, the first thing I did, or one of the first things that I did is I went out and I spent $150 on this Smoove because I had it in my head that if I had the latest technology, this funky thing was going to make my vlogs super successful and people were going to want to watch me. Well, I learned very quickly that, although the Smoove could enhance my vlogs, it was not going to make me successful.
Let me tell you what happened. I got the Smoove and I could not figure out how to make it work. I downloaded three different apps to use this thing. I just could not figure out how to work and I have an engineering degree. My husband is a surgeon and he couldn’t figure it out either. That made me feel a little bit better.
The moral of the story is this. The Smoove does not make my vlog successful because if I don’t know my stuff, if I don’t know my material, if I can not present it in a way where people can understand it, and if I don’t know how to make a video in general, well, my vlog is going to be a disaster. So, all this can do is enhance it. So, this is not the first step. Shiny Objects are not the first step. And this goes for Condition Based Maintenance as well.
I have talked to a lot of people in our industry, and I’ve been told that what happens is when they decide they want to do Condition Based Maintenance, because they think that it can help them with time management and can help them with Reliability costs, which it absolutely can when it’s implemented properly. But what happens is these organizations went to the sophisticated monitoring device first, instead of starting with the basics. So let us begin with the basics.
The first basic thing that we need to know is what is CBM? What is Condition Based Maintenance? Basically, what Condition Based Maintenance means is we’re going to monitor for a Potential Failure Condition. We’re going to monitor for some sort of phenomenon that’s going to tip us off that failure is in the process of occurring. In that way, we can intervene before failure occurs.
Potential Failure Conditions could be any number of things. It could be heat or vibration or measuring cracks or measuring temperature. And we can do CBM by using our human senses, or we can use more sophisticated devices. That is what Condition Based Maintenance is. But we have to make sure that we’re looking for that Potential Failure Condition often enough – so we don’t miss it.
That’s where the P to F curve comes in. Now, if you are listening and not watching, I am holding up a piece of paper and I’ve drawn an X axis and a Y axis. And at the top of the Y axis, I’ve drawn an arc that goes all the way to the bottom, to the end of the X axis.
The X axis is age, and that can be considered in any number of units. It could be operating time or miles or cycles. And the Y axis is the Resistance to Failure. So let’s say that we put a new item into service and we’re at the very top on the Y axis, which means our Resistance to Failure is at its greatest. Well, we know from thermodynamics that anything exposed to the real world will eventually degrade.
And that goes for items that are in our equipment right now. We also said that most things fail randomly. But most things give us a warning that failure is in the process of occurring. So, if we’re at the top of a Y axis and we’re following our arc down, you know, maybe about a third of the way down, I’ve just drawn a black dot.
That evidence, that failure is in the process of occurring. That Potential Failure Condition starts to show itself, right? Let’s just take, for example, a filter. What happens when the filter starts to clog? The differential pressure starts to increase, right? This is as an example where the increase in the differential pressure can be a Potential Failure Condition.
So, let’s just say, for example, that our differential pressure is 6 psi. That that could be a warning to us that when the differential pressure, the pressure across the filter approaches 5 psi, that now we’re clued in. We now know that the filter is in the process of occurring. Now, if we do nothing, eventually we’re going to keep sliding down this arc.
And we’re going to get to the point on the X axis at the very end where now failure occurs. In this example, our failure is that the filter clogs. Now here’s the key to Condition Based Maintenance. The interval from the time that I can detect via my differential pressure gauge that the differential pressure is five PSI to the point that the filter fails, that is called the P to F interval.
One thing I want you to note here. I’m not talking about how long it took from the point that I installed the new filter to the point that it clogged. I’m talking about once I can detect that the differential pressure is 5 psi to the point that the filter clogs, that interval is called the P to F interval. And that is up to you and within your organization to identify, because these numbers vary. They can vary wildly depending upon the kind of filter you have, how often you’re running a machine, your operating environment, et cetera. That varies from organization to organization and from specific case to specific case.
Here’s the thing about Condition Based Maintenance. It doesn’t matter how often something fails. What matters is how quickly failure occurs once a Potential Failure Condition is detectable.
And we are not talking about an MTBF or on average how often the filter will clog. We are not talking about a useful life. We’re not talking about how long it takes the filter to clog. We are talking about how long it takes the filter to clog once we have detected what we have defined as that Potential Failure Condition.
Like I said, this is one of the most wildly misunderstood or unknown topics in our industry. And it is a vital Reliability basic. See, the thing about Condition Based Maintenance is, you may go and inspect for six months or even years and not find the Potential Failure Condition. But that doesn’t matter, right? Because when we’re talking about that, we’re at the point on our curve, from where something is new before that Potential Failure Condition is detectable. That’s not what we’re concerned with when it comes to Condition Based Maintenance.
So, we may inspect for six months for one year, for five years, for eight years before we find that Potential Failure Condition. But once we do, we have to identify how quickly failure will occur. And then we can set our Condition Based Maintenance task intervals at intervals less than the P to F interval.
So, one of the keys to Condition Based Maintenance is you have to make sure you have enough time to take action to manage the consequences of failure. In other words, can you do the maintenance that you need to do with the time you have left?
Let’s just say you go through this analysis for a Failure Mode and, you know, worst case you’ll only have a week left to take action. Well, if you’ve got a one-month lead time on your part that you will need, one week won’t be enough. So, you’ll either have to manage it a different way, or you can decide to keep one of those parts on the shelf.
To recap, here’s the thing about Condition Based Maintenance.
1. When we do CBM, we are looking to detect a Potential Failure Condition, like an increase in differential pressure, like vibration signatures, like a specific heat. We’re looking for the Potential Failure Condition.
2. And once we do that, we have to figure out how quickly failure will occur. That is what is called the P to F interval.
Now you may be thinking, oh my gosh, where do we get these P to F intervals? And that is an excellent question. I’ve never worked with any organization that had a database full of that data, but this is where your equipment experts come in.
For a large number of your Failure Modes that you’re going to manage with Condition Based Maintenance, the people who understand the operating environment and know the equipment best when you ask them the right questions can provide P-F intervals.
When the experts understand this concept, and you ask them the right questions, to a very large degree they can provide you with these P to F intervals. Now, when it comes to the most sophisticated Condition Based Maintenance techniques, to a large degree, you can work with your vendor and he can help you to figure out what these levels are.
But if there’s one thing I can hammer home today, it’s this. You and anyone responsible for equipment has to understand this concept. You can’t just leave it up to your vendor because you will not be able to properly judge if what he is telling you makes common sense for your equipment.
So, you don’t have to be an expert in vibration analysis or thermography to get the P to F interval, right? But you have to understand the concept behind Condition Based Maintenance so that you can adequately judge for yourself. When you work with CBM vendors, I can’t stress enough about Shiny Object Syndrome.
I talked about the Smoove and how I thought it could really make my vlogging successful. And I quickly learned, and it came at an expense to me, for me, luckily it was only $150. But in our industry, it could cost tens of thousands, if not hundreds of thousands of dollars in mistakes when you implement CBM the wrong way.
I’ll give you one more example. I mentioned that my husband is a surgeon and he is very big into robotic surgery. He uses the DaVinci robot where he actually sits at a console about six feet away from the patient. He sits at the robotic console and operates the controls. But here’s the thing about the DaVinci robot and robotic surgery. A surgical robot does not make a mediocre surgeon better. Because in order to capitalize on the robotic technology, a surgeon first has to understand the anatomy and has to be able to do that surgery either open or laparoscopically.
So, there are the basics. There’s that foundation that a surgeon has to have before transitioning to robotic surgery. So, the robot can be a shiny object. It doesn’t make a mediocre surgeon good. But the surgical robot can make a great surgeon even better.
So you see, even in other disciplines, in our personal lives and in our professional lives, we can all fall prey to Shiny Object Syndrome. So don’t let that happen with you and Condition Based Maintenance.
So, there you have it. That is Condition Based Maintenance in a nutshell. To quickly recap, Condition Based Maintenance means that on a specified interval, we go and we look for Potential Failure Conditions. And we only do maintenance if we find that Potential Failure Condition. And how often we go looking for that Potential Failure Condition is based entirely on the P to F interval. In other words, how quickly failure occurs once a Potential Failure Condition is detectable.
It has nothing to do with MTBF, mean time between failure. MTBF is an average. When we do Condition Based Maintenance, we’re not talking about, we’re not concerned with how often something fails, but rather we need to know how quickly something fails once a Potential Failure Condition is detectable.
So, there you have it, the basics of Condition Based Maintenance. Thank you so much for joining me for this fourth episode of The Heart of Reliability.
I invite you to join me for episode five. We’re going to be talking about something really important. We’re going to be talking about the Human Element when it comes to Reliability. So I hope to see you back for episode five.
I’m Nancy Regan. Thank you for joining me today.