Online vs. Offline Condition Monitoring: Choosing the Right Approach for Your Maintenance Strategy

One of the most common questions we get asked at Factory AI is how to compare the advantages and disadvantages of the two primary methods of condition monitoring: online and offline.

This is a frequent query because many manufacturing sites approach us when they’re considering making the shift. They’ve been doing offline, quarterly vibration inspections for years, and now they see their peers adopting online, continuous condition monitoring. Should they make the switch just because everyone else is doing it?

The answer is: not necessarily. First, you need a clear understanding of the distinctions between these approaches. This understanding is essential for developing an effective condition monitoring strategy as part of your wider reliability goals. Once you grasp the differences and the objectives of each approach, you can evaluate which one best suits your needs. Let’s dive in and explore.

Defining the Terms: What Do Online and Offline Monitoring Mean?

Offline Condition Monitoring

Offline condition monitoring refers to all monitoring activities conducted manually at scheduled intervals. This is often equated to “manual vibration inspections,” particularly in industries like food and beverage. However, offline monitoring encompasses more than vibration analysis; it may also include thermal imaging, oil analysis, ultrasound, and more. That said, vibration analysis is often the most common.

Typically, vibration analysis is performed by highly qualified technicians, such as VCAT-certified vibration analysts. These professionals usually complete rigorous training, like the Mobius course, to master the basics of vibration analysis and condition monitoring. Beyond certifications, they bring years of experience in maintaining similar assets, enabling them to identify failure patterns effectively.

Because these inspections happen on-site, technicians can quickly investigate further if something seems off, offering a detailed understanding of potential issues.

Offline condition monitoring is like checking your fridge at random intervals to see if it’s still cold. While it works, often there’s no substitute for having a thermostat providing continuous feedback.

Advantages:

• Targeted Recommendations: On-site technicians can provide granular insights and actionable recommendations when anomalies are detected.
• Simplicity: Minimal technological infrastructure and effort are required.

Disadvantages:

• Intermittent Data Collection: Issues developing between inspections may go unnoticed, leading to unexpected failures.
• Labour-Intensive: Technicians must physically access equipment, which is time-consuming and potentially hazardous.
• Delayed Response: The lag between data collection and analysis can delay corrective actions.
• Cost-Prohibitive: Vibration analyst services can be expensive compared to modern alternatives.
• Underutilisation of Reports: Many PDF reports end up ignored, with reliability engineers only glancing at critical (red) alerts while ignoring broader insights.

Online and Continuous Condition Monitoring

Online condition monitoring offers continuous, 24/7 tracking of your equipment. Sensors installed on critical components like motors, pumps, and conveyors measure parameters such as vibration, temperature, and noise in real time. When something deviates from normal, the system alerts you immediately, allowing proactive action.

Unlike manual checks, which occur periodically, online monitoring captures anomalies as they happen. It’s like having a fitbit or Whoop with real-time intelligent insights delivered at your fingerprints.

How It Works:

1. Data Collection with Sensors: Sensors measure critical parameters, such as vibration, temperature, and pressure, directly on equipment components.
2. Data Transmission: The data is sent wirelessly to a central system or cloud platform for storage and organisation.
3. Analysis: AI-powered algorithms analyse the data, comparing it to historical trends to detect anomalies.
4. Alerts and Recommendations: The system sends alerts and actionable recommendations when issues arise.
5. Preventive Action: Insights enable engineers to take proactive measures, preventing costly failures and downtime.

Advantages:

• Continuous Monitoring: Immediate detection of anomalies, especially for random failures.
• Enhanced Accuracy: Real-time data provides a comprehensive picture of equipment health.
• Reduced Labour Requirements: Automation frees up personnel for other tasks.
• Optimisation of Maintenance Tasks: Time-based PMs can be reduced or eliminated, often offsetting the cost of the system.

Disadvantages:

• Higher Initial Investment: Costs include sensors, communication networks, and software.
• Complexity: Requires specialised knowledge for integration and operation.

Hot Take: If your site isn’t leveraging online condition monitoring, you’re likely leaving money on the table and exposing yourself to unnecessary risks. The unit economics of the price of the solution versus the immense upside for sites is almost always so positive that not implementing it simply can’t be justified.

Key Differences Between Online and Offline Monitoring

1. Data Collection Frequency:
   • Offline: Periodic, based on scheduled intervals.
   • Online: Continuous, with real-time insights.
2. Resource Allocation:
   • Offline: Labour-intensive, requiring manual inspections.
   • Online: Automated, reducing manual effort.
3. Response Time:
   • Offline: Delays due to intermittent data collection.
   • Online: Immediate detection and response.
4. Implementation Cost:
   • Offline: Lower upfront costs but potentially higher long-term expenses.
   • Online: Higher initial costs with significant long-term savings.

Hot Take: In five years, sites still relying on purely offline monitoring will struggle to compete in an increasingly automated industry. A common objection we hear is: if the rate of improvement in technology is so rapid and costs are decreasing, why not just wait? Well, firstly, as mentioned above, the unit economics are already so far in favour of adopting online monitoring that waiting simply isn’t necessary anymore (compared to how it might have been 10 years ago). Secondly, in the world of condition monitoring, every single day you’re collecting critical asset data. Starting in five years means you’re five years behind—creating an immense data gap compared to your competitors.

Choosing the Right Approach

The choice between online and offline condition monitoring depends on several factors:

• Start with What You Have: If you already use offline monitoring, maximise its value by ensuring reports are actionable. There’s often a lot that can be done with what you have already in place.
• Work Backwards from Failure Modes: Random failures often require continuous monitoring for effective mitigation. The reason why online and continuous monitoring is so helpful is that most failures are random. If you can’t accept this fact, look at this short from Dave Reiber, CRL, CMRP, is Senior Reliability Leader from Reliabilityweb.com who talks about this very simply. Because failures are random, a set, time-based interval for routine inspections will very often miss big failures. A bearing could literally go off the day after an inspection was carried out, and that wouldn’t be fault of the technician.
• Criticality of Equipment: For critical assets, online monitoring will help a lot. We’ve found for sites that have a medium to high hourly cost of downtime, it’s a no-brainer to install continuous monitoring on key pieces of equipment, even if they are part of an offline program already.
• Budget Constraints: In today’s world, it’s hard to get approval for anything. We get it. So do some simple math on what benefits you can expect from any approach. This is something we’ve talked about before in previous articles here : https://www.f7i.ai/blog/the-failure-history-method-for-predictive-maintenance-roi-calculation
• Operational Environment: Online monitoring reduces the need for personnel in hazardous areas, and is often very well suited for assets that are difficult to access.
• Data Needs: If predictive maintenance and detailed trend analysis are priorities, online systems are more beneficial.

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Conclusion

Both online and offline condition monitoring have their merits. However, with technological advancements and reduced costs, continuous online monitoring has become increasingly accessible and valuable. If you’ve dismissed it in the past, it’s worth revisiting now. There’s a good chance it’s the right time to make the shift.

Hot Take: The real question isn’t whether online condition monitoring is worth it—it’s whether you can afford not to implement it. Doing the exercise of evaluating the cost versus benefit can be done in just an hour with some very basic data. You don’t need to get overly sophisticated here. If you’re still hesitant, at least start there so you can be confident you’re not dismissing a good idea without even some high-level data to back up your claims.

For more insights on maintenance strategies and condition monitoring, explore our other articles and resources.