What Is Condition Based Maintenance (CBM) & Monitoring?
Condition-based maintenance (CBM) is a proactive approach to maintenance that actively monitors the health of moving and running equipment in real time through the use of device monitoring sensors.
CBM enables maintenance teams to set a condition monitoring culture where staff can determine when maintenance is required to optimise asset performance and determine the maintenance needed for each moving part.
It effectively provides an answer to the question; “how long will this asset remain in good working condition?”.
The components of condition-based maintenance include embedded sensors (vibration, oil and lubricant analysis, temperature, current, etc.), a software program (like CMMS Software), and set trigger events.
Each component contributes to the 3-step process of CBM:
- Asset data acquisition
- Maintenance analysis
The primary focus of a condition-based maintenance system is to improve the reliability and availability of assets that are essential to production by performing maintenance only when necessary, like alerting operators to a drop in asset performance or when set events are triggered.
This is as opposed to a singular preventive maintenance plan, which results in unnecessary maintenance checks and replacing parts that still have an optimal remaining life.
A data-driven, round-the-clock monitoring approach like CBM helps to reduce both unplanned and planned downtime of equipment and moving assets, as well as reduce expensive repair and breakdown costs by 15 to 30 percent.
It is also designed to increase safety when working with equipment in intensive operations such as oil and gas, manufacturing, and infrastructure asset management.
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The Process of a Condition-Based Maintenance Workflow
A review on machinery diagnostics and prognostics implementing condition-based maintenance (Jardine, Lin, and Banjevic, 2006) highlighted a three-step process:
- Asset data acquisition
- Maintenance analysis
1. Asset Data Acquisition
An effective CBM plan requires extensive data surrounding each asset. Data acquisition will take into account historical asset data and the current usage of running parts through the use of sensors.
To achieve the right condition readings, monitoring sensors should be mounted correctly to transfer data (such as vibrations, temperature, pressure, etc.).
Asset data includes:
- Asset History: Past failures, costs of past maintenance, purchase date and price
- Asset Usage: How long has it been running, how many operators has it had, how many cycles has it performed, what date did it start running
- Stressor & Environmental Data: Internal and external factors such as temperature, location, vibration, and strain
- Condition & Health data: The structural and physical condition of an asset
2. Maintenance Analysis
Step two consists of thorough data analysis and processing by aggregating asset data into a software program like a CMMS. That incorporates the analysis of:
- Asset performance
- Employee knowledge
- Reliability data
- Degradation data
3. Maintenance Decision-Making
The final step in a condition-based maintenance strategy is to take all of the collected data and carry out the best course of action for each asset. That includes setting trigger events and identifying optimal performance values.
This can be set out in three phases; detect, diagnose, and prognosis.
Condition-Based Maintenance Examples & Types
There are various types of condition-monitoring techniques used in different scenarios, like condition-based maintenance and non-destructive testing (NDT). These include:
- Lubricant/Oil analysis: Used mostly in heavy-duty machinery and industrial equipment to monitor machine wear, lubricant condition, and contamination.
- Vibration analysis: Used to measure machine health through abnormal waveforms caused by part misalignment, motor failure, belt slips, or bearing failures.
- Infrared thermology (IR): IR is used to detect thermal abnormalities through infrared cameras and identify what parts are rising in temperature and when.
- Ultrasonic: Typically used in the NDT of aircraft parts, ultrasonic sensors detect high-frequency sounds.
- Current/Voltage analysis: Electrical output and meter readings are collected in real time through the use of power measurement modules.
- Acoustic/Pressure analysis: Used to detect sudden drops in pressure for equipment reliant on gas, liquid, and air.
Example 1: Lubrication Factor at Maintain Reliability Ltd
With poor lubrication resulting in the failure of a third of all bearings, Maintain Reliability Ltd replaced scheduled-based lubrication methods with an ultrasound condition-based strategy. This measured the decibel output value of a bearing, which indicated if the value was above or below the set value. Engineers then knew when to add more grease to lubricate the bearing at the right point before the performance was affected.
Example 2: NDT Ultrasonic Axle Testing
Through ultrasonic axle testing (UAT), a non-destructive testing method, the Australian Transport Safety Bureau identified a fatigue crack on the axle of two freight tanker wagons that had both derailed. The crack initially went undetected and grew, resulting in an overstress factor of the axle.
Example 3: Alek Zelnins, Maintenance Manager at Contract Pharmaceuticals
Alek spent 12 years at Unilever as Maintenance Supervisor and spoke on the Comparesoft podcast about the overall basis of condition-based maintenance:
“Using [condition-based maintenance] technology, you can put a vibration and temperature sensor and monitor the condition of that, as you run the equipment, which is basically the best way of monitoring the condition. Because when the mechanic goes and the work order says inspect that bearing, you have to lock out the machine. You have to kill the source of power. You don’t want to get [the] mechanic injured.
[The] mechanic will inspect that particular bearing while it’s not running, but it’s not a true representation of the state of the bearing. The bearing needs to run in order to be in a current state, whether it’s starting to deteriorate or not. The technology helps us here by monitoring the performance of this bearing 24/7.”
The Benefits of Condition Based Maintenance
Conditon-based maintenance has long been associated with effective maintenance outcomes. Back in 1998, the American trade magazine, Plant Services, found that 86% of plant production owners used one or more methods of Condition Monitoring (CM).
Today, advancements in data-collecting sensors and IoT technology have enabled condition-monitoring techniques to further excel. Now, a CBM program has several benefits:
- Maintenance is only performed when there are signs of a drop in asset performance
- Fewer disruptions to production
- Less unplanned downtime
- More efficient planned downtime
- Reduced maintenance spending – a 1998 study found businesses that implemented a CM program spent 25% less on maintenance
- Faster diagnosis of problems
- A more knowledgeable workforce
- Reduced mean time between maintenance (MTBM)
It’s also worth noting that, without condition-based maintenance methods, there would be no asset portfolio management, performance-based contracts or big data analysis.
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Are There Disadvantages to Condition-Based Maintenance?
Like any maintenance strategy you choose to implement, there are advantages and disadvantages. The main disadvantage of CBM is the upfront costs associated with it.
Although in the long-term a CBM program will be more financially beneficial than both reactive and fully preventive maintenance strategies, the initial costs are high. This is due to the implementation of high-tech monitoring sensors and the training of staff.
Ideally, implementing a condition-based maintenance model is more suited to a larger operation that can afford the initial set-up costs.
Other disadvantages include:
- Can take a long time to determine set events for part failures
- Requires professionals to retrofit data-collecting sensor devices
- The resources (time and cost) needed to train staff in data analysis and asset performance knowledge
- Expensive data analysis equipment is subject to damage in harsh environments
CBM Vs. Other Maintenance Alternatives
Reactive/Corrective Maintenance Vs. Condition-Based Maintenance
Reactive maintenance sits alongside maintenance types such as emergency maintenance, corrective, breakdown, and run-to-failure. It is a strategy that is deployed to only repair parts when they have failed.
Although this approach can be cost-saving in the short term, it can lead to excessive long-term repair costs and unplanned downtime.
|Advantages of Reactive Maintenance||Disadvantages of Reactive Maintenance|
|No startup fees and low upfront costs when compared to proactive maintenance||Emergency repair and replacement costs create an unpredictable budget|
|No planning of maintenance schedules and services are needed||The pressure to quickly repair equipment makes the process unsafe for workers|
|Less maintenance staff are required||Assets have a shorter life expectancy and a higher turnover rate|
|Increased unplanned downtime of equipment|
Predictive Maintenance Vs. Condition-Based Maintenance
The one glaring similarity between CBM and predictive maintenance is the use of data-collecting tools to identify when it’s time to perform maintenance.
The difference is, condition-based maintenance programs use set thresholds and events to determine when maintenance is due. Whereas predictive maintenance uses advanced statistical methods such as machine learning to predict when service will be required.
|Advantages of Predictive Maintenance||Disadvantages of Predictive Maintenance|
|Minimises unplanned downtime||Detailed and time-consuming planning|
|Reduces time spent on maintenance||High purchasing costs of advanced condition-monitoring equipment|
|Increase the life expectancy of machines and equipment||Expensive hiring of skilled staff or training maintenance teams|
|Minimises costs spent on labour, spare parts, and equipment|
Preventive Maintenance Vs. Condition-Based Maintenance
Condition monitoring sits under the umbrella of preventive maintenance (PM) alongside failure finding and risk-based maintenance types. But, while CBM is proactive, it is more attentive to real-time data readouts.
A purely preventive maintenance approach, however, relies on scheduled checks and replacing of parts – even if those parts being replaced still have good optimal life remaining.
|Advantages of Preventive Maintenance||Disadvantages of Preventive Maintenance|
|Fewer breakdowns of equipment and machinery that are essential for production||Possibility of excessive preventive maintenance|
|Improved reliability of mission-critical assets||High start-up and implementation costs|
|Fewer expensive corrective and emergency repairs||Need for more resources (spare parts, staff, etc.)|
|A prolonged life expectancy of assets results in a lower turnover rate||Can be time-consuming|
|Improved RCA data collection|
5 Steps to Start Implementing a CBM Plan
1. Keep Staff Informed & Knowledgeable
A knowledgeable maintenance team is the foundation of a good condition monitoring program. Implementing a condition-based maintenance strategy will ultimately require a culture change in how a maintenance team performs and trains.
Each engineer, technician, and machine operator must have a general understanding of how an asset operates and how to identify an issue or understand a diagnosis. That means staff must be trained or experienced staff must be hired, something that Alek Zelnins highlighted:
“The most important part is the skill of your team. You need to have the team cross-trained. So, you don’t have just one mechanic looking after one line, and this mechanic goes on holiday tomorrow and you will have fewer experienced people to be able to deal with that particular line.”
2. Perform Critical Analysis
A deep assessment of working assets and environmental conditions is key to having a working condition-based maintenance plan. It’s important to map out what equipment, machines, and other assets will be part of your program. Also, consider:
- What CM devices are needed
- What assets will be critical for your CM plan
- The historical data of each asset (first run date, the average number of cycles, etc.)
- Any external environmental factors that might affect data readouts
3. Identify Failure Modes & Set Trigger Events
Historical asset data analysis is important as it helps to understand failure modes that have occurred previously. That could be part misalignments, lubricant issues, or bearing failures. By combining historical data and aggregating new data, you know what trigger events need to be set to reduce these failure modes.
4. Purchase Condition-Monitoring Equipment & a CMMS
To collect essential data and record accurate real-time readouts, you need the right equipment. Whether that is thermocouples, vibration sensors, power measurement modules, or pressure sensors. Each CM device then needs to be properly installed and calibrated. To aggregate, analyse, diagnose, and assign maintenance staff you also need an efficient data-collection tool such as CMMS Software.
5. Start Running Data Analysis
Now comes the fun part; executing your CBM program. In the initial stages, you’ll be continuously calibrating the way you collect data and the trigger events you set. But, as time goes on, the data you collect becomes more valuable. From this point, you can begin to increase the speed and accuracy of your maintenance and improve your decision-making.
What Is Condition Monitoring?
Condition monitoring is the process of analysing the real-time readouts of equipment and noting any changes in performance through devices that measure vibrations, pressure, sound, and lubricant levels. It is the basis of a condition-based maintenance program and the subsequent decision-making process when it comes to replacing and repairing assets.
Is CBM a Preventive Maintenance Strategy?
Yes and no. Although condition-based maintenance is a form of proactive/preventive maintenance, it more resides with a predictive maintenance program.
CBM is a more focused approach that recommends maintenance only when necessary so that asset performance is kept in an optimal timeframe. Whereas a purely PM approach is set around scheduled and regular maintenance, meaning equipment and spare parts could be replaced even though they have optimal life remaining.
What Businesses Benefit From Implementing Condition-Based Maintenance?
Asset-intensive businesses that rely on their physical and heavy assets for productive output are the ones that will benefit most from implementing CBM. These include:
- Oil and gas industry (oil rigs, production plants, downhole monitors)
- Medical operations
- Industrial plants (manufacturing, logistics)
- Automotive companies
- Commercial (HVAC operators, white goods)
What’s the Difference Between CBM and TBM?
Whereas CBM is performed around real-time data analysis from condition monitoring devices, time-based maintenance (TBM) is triggered by a maintenance calendar schedule. TBM is a planned approach to maintenance that is put in place by analysing historical asset data to schedule specific set dates for planned equipment maintenance.
What Is Non-Destructive Testing – Is It a Part of Condition-Based Maintenance?
Non-destructive testing (NDT) is a condition monitoring method used for non-moving parts and equipment such as pipes, metals, and structures. NDT is performed through techniques such as ultrasonic testing and eddy current testing to identify defects, damage, welds, and thickness measurements without causing damage to parts.