Hippo CMMS

A Simple Guide to Condition-based Maintenance

By Jonathan Davis | January 15, 2020

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. To learn more about predictive maintenance, check out Make the Right Decision: Is Predictive Maintenance Right for Your Business?

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.

Benefits

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.

Revised graphic-02-01failure 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

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

Before deciding on a strategy, you need to look at your needs and weigh your options. To learn more about finding the right strategy, check out Find the Best Maintenance Management Strategy.

Deep Dive Into PM Success

 

Topics: maintenance management

Jonathan Davis

Jonathan Davis

Jonathan Davis started out writing for textbooks before branching out to video games and marketing collateral. He has a master’s degree in journalism and a certificate in technical writing.

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