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Here's a quick guide to everything you need to know about condition-based maintenance. What it is and how it works. What makes it similar to and different from other maintenance strategies. And, most importantly, what it can and can't deliver.

Let's start with the basics and build from there.

What condition-based maintenance is

It's the maintenance strategy of the here and now. Not in the sense that it's new or currently in fashion. Literally, it's focused on the here and now. By looking at the current condition of your assets, you decide what maintenance, if any, is needed.

The most basic example is the age-old visual inspection. Technicians walk through the facility looking for small signs of lurking problems. Puddles of water or oil. Strange clunking sounds. Steam where there shouldn't be any. The more high-tech examples are also the more recent ones. Technicians use portable equipment for periodic tests or install sensors for continuous monitoring. Common types include vibration, infrared, oil analysis, pressure, temperature, and flow.

What condition-based maintenance is not

One of the challenges of understanding Condition Based Maintenance is that it sounds similar to both preventive and predictive maintenance. And it's true that it boasts many of the same benefits, including reduced downtime, increased productivity, and improved resource and inventory management. But there are important differences between the strategies.

Condition-based vs. preventive maintenance

With preventive maintenance, you avoid problems in the future by carefully looking at the past. If your pump failed every three months over the previous twelve, this year you set up PMs to inspect and lube the pump every two and a half months. To learn more about preventive maintenance, check out 4 Steps to Start Your Preventive Maintenance Program off on the Right Foot.

But with condition-based maintenance, you focus only on the pump's current condition. Past problems aren't a part of your calculations.

Condition-based vs. predictive maintenance

Here there's more overlap, so it's even harder to see the differences. Both maintenance strategies rely on a steady stream of current asset data, either from scheduled testing with portable equipment or constant monitoring with dedicated sensors. The difference is in how you use the data. With predictive maintenance, it's pushed through complex algorithms to create predictions on future performance. The math is so complex it's easier to just think of the algorithm as a crystal ball that actually works. 

But with condition-based maintenance, there's a lot less math. In fact, you can reduce everything to one set of three numbers. The first is the current condition. The second is the upper limit, and the third is the lower limit. Take a fan's vibration, for example. As long as the current number, which is how much the fan is vibrating, is somewhere between the upper and lower limits, you don't do any maintenance. A PM is triggered only when the current number lands outside the predetermined comfort zone.

More examples of condition-based maintenance techniques 

A couple more examples should make it easier to see the differences between condition-based maintenance and other maintenance strategies. 

Remember, common types of condition-based maintenance can include: 

  • Ferrography 
  • Infrared
  • Electrical
  • Performance
  • Ultrasonic
  • Acoustic
  • Vibration
  • Flow

Performance

The all-time classic of condition-based maintenance, here you're using visual inspections and checking for weird smells and funny noises. On top of looking at the assets or equipment, you can also look for unexpected results. If the machine is supposed to produce five tin cans a minute but you're only getting four, something is the matter. Unexpected results could also include getting five tin cans but three of them are the wrong size. Also: six cans. 

The problem with performance is that it often takes a while before the problems are so bad you can notice them with the five senses. Generally, an asset is far down the P-F curve before you can see the symptoms unaided.  

With other techniques, though, you use highly sensitive sensors, so you're suddenly Superman with X-ray vision and super hearing.  

Ferrography

Just a fancy word for oil analysis, ferrography is a technique for finding particles in lubricating oil that indicates the asset is moving toward a failure. You can also look at the other lubricants and fluids inside the asset, testing for things like the presence of water and various microbials. 

Vibration

If it rotates, you can likely use vibration to check for problems. So, you can check compressors, pumps, or motors by using vibration sensors. Generally, you would need to have enough to check for vertical, horizontal, and axial movement. 

A possible drawback with vibration, though, is that you can accidentally pick up background movement. An extreme example would be trying to use vibration sensors on the engine of a large ship. The engine is moving, but so is everything around it. 

Infrared

Heat is often a clear sign of oncoming failure, and IR cameras help you detect it much earlier in the P-F curve. When you see new heat or a temperature difference between similar parts, it could be an indication of misalignments, imbalances, bad lubrication, general wear, mechanical stress, or even electrical overheating. 

Ultrasonic

Even before you would likely find issues using vibration and infrared, ultrasonic testing can reveal problems with a wide variety of assets, including high- and low-speed equipment and parts using high-pressure fluids. You can also catch issues related to excessive friction and cavitation, which is exactly what it sounds like: holes where there shouldn't be any. 

Just like vibration and IR, ultrasonic is great for looking inside assets without having to first pull them apart. Just like when you go to the doctor, and they can X-ray you looking for problems instead of having to get you up on the operating room table. 

Benefits of condition-based maintenance

A good condition-based facility management software reduces the number of reactive, on-demand work orders because little issues get found and fixed before growing into giant problems. Downtime decreases. Productivity increases. Fewer costs, less stress.

But a good program also reduces the number of scheduled work orders because PMs are only ever triggered by current conditions. That means condition-based maintenance solves the problem of over-maintenance, where you're using time, energy, parts and materials when you don't need to be.

Getting ahead of the P-F curve and stretching the P-F interval

Another benefit of condition-based maintenance is how far it puts you ahead of the P-F curve, which is the curve your asset follows as it moves toward failure. The key here is to think of failure as an ongoing process, not a single event. It's the same when you get sick. You don't suddenly wake up one morning with the flu. First, you get up feeling a bit more tired than usual. Maybe you notice a slight headache. By lunch, there's a frog in your throat. Mid-afternoon, a slight case of the chills and the start of a fever. Next morning, it's finally developed into full-blown flu. If only you'd had some chicken soup early on, you could have saved yourself the misery.

It's the same with failure. There are symptoms along the way, each more easily detectable than the one before. For an extreme example, first your asset gets hot. Then it catches fire. Condition-based maintenance should make the early symptoms easier to detect, giving you more time to plan and organize a maintenance plan.

Blog Graphics Hippo-P-F-intervalfailure is a process with various symptoms along the way

By carefully matching each asset with the right type of monitoring, you increase the amount of time between P, when the asset begins to move down the curve, and F, when it completely fails. The better the match, the more time you have to react.

Drawbacks of condition-based maintenance

There are a few minor ones related to scheduling and inventory management. Basically, it's a bit harder to schedule your resources because you don't know when PMs are going to pop up. Unlike a schedule based on the preventive maintenance model, condition-based maintenance gets harder to predict the further out you try to plan. And because it's so closely connected to when you schedule your PMs, inventory management ends up being trickier with condition-based maintenance. Because you need to compensate for your schedule being a bit less predictable, you need to carry more materials and parts.

There are also a few more serious drawbacks. Setting up and running a condition-based maintenance program takes expensive expertise and equipment. It costs money to train technicians to work with new equipment, and the equipment itself is pricey and finicky. Sensors are expensive, and it can cost a lot to retrofit them into older assets. Good sensors should be able to survive the extremes of a manufacturing setting, so you won't have to replace them often, but there are ongoing costs for periodic re-calibration. And then on top of the money you spend to collect data, there's the cost of the CMMS software you need to make sense of it.

Condition-based maintenance is one of many options

The more you learn about different maintenance strategies, the more it makes sense to get a CMMS.

Hippo's here to help you get the solution that works best for you, including answering your questions about maintenance management software, helping you book a live software demo, or even setting you up with a free trial.  

Summary

Condition-based maintenance is one of several maintenance strategies that can help you keep your critical assets and equipment up and running, saving you money and frustration. At the most basic level, condition-based maintenance is simply looking for signs of small issues before they have a chance to develop into large problems. But it can get a bit more complicated when you move away from looking for leaks and touching pipes feeling for excess heat. With high-tech sensors, you can analyze oil and other lubricants for particles and look inside asset for early signs of wear and leaks. The advantage of the strategy is that, ideally, you never over maintain your assets. The drawback, though, is that it costs more money to get set up and run. Also, it’s harder to line up parts and people because you never know when you’re going to need to assign the work. With something like preventive maintenance, you know exactly when you’ve scheduled work and who you’ve assigned to complete it. 

About The Author

Jonathan Davis

Jonathan has been covering asset management, maintenance software, and SaaS solutions since joining Hippo CMMS. Prior to that, he wrote for textbooks and video games.
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