Condition Monitoring: A Comprehensive Guide to Inspections and Predictive Maintenance

Condition monitoring encompasses every activity that detects problems early, from the simple visual checks you perform by seeing, listening, smelling, and touching, to advanced techniques such as vibration analysis, infrared thermography, wear‑particle analysis, ultrasonic testing, and acoustic emission.

While many organizations focus solely on predictive maintenance, the real cost‑savings often come from basic inspections that uncover issues before they evolve into costly failures.

Why Basic Inspections Matter

Training operators and maintenance staff in straightforward inspection methods—and assigning them to a route‑based inspection schedule—is a highly effective first step to reduce reactive maintenance. Multiple studies show that the majority of problems are discovered during these early inspections.

Essential Inspection Tools

• Portable high‑intensity flashlights improve visual inspections.
• Inspection mirrors and fiber optics reach hard‑to‑access areas.
• Ultrasonic leak detectors are ideal for vacuum and other leaks.
• Ultrasonic material testing reveals cracks or thinning in high‑wear components.
• Stroboscopes enable inspections while equipment runs.
• Dye penetrant discovers micro‑cracks.
• Tensiometer checks and sets V‑belt tension accurately.
• Infrared thermometers detect misaligned couplings, leaking valves, and other hydraulic or media system issues.

Real‑World Success Stories

During a tour of New Zealand sawmills, I introduced a simple chain‑wear measurement method—recording the distance between five to ten links and replacing chains when wear exceeds a set threshold. Initially, chains were changed annually “because that’s what we’ve always done.” After adopting the measurement approach, a maintenance manager replaced chains every eighteen months, doubling their lifespan at half the cost.

In the 1970s, we worked in a steel plant in northern Norway and suggested marking couplings with a line across the halves. Using a stroboscope, technicians could track the distance between marks to detect bolt or bushing wear caused by misalignment. Two decades later, a manufacturer used this documented method to defend against a patent claim, underscoring the value of well‑recorded inspection techniques.

Condition Monitoring Techniques

Beyond basic inspections, modern maintenance employs:

• Vibration analysis for bearings and rotating equipment.
• Wear‑particle analysis, including ferrography and spectrometric oil testing.
• Acoustic emission to find early material cracks.
• Infrared cameras to visualize temperature patterns.

Technology is rapidly evolving, with many machines now equipped with online systems for continuous monitoring and data collection.

Designing an Effective PM System

Fixed‑time preventive maintenance (PM) can use work orders, but tasks performed while equipment runs are best managed with a route‑based system. When setting up a new PM system, follow these steps:

1. Identify the required tasks.
2. Assign tasks to the most appropriate personnel.
3. Prioritize roles: operators → maintenance craftspeople → in‑house experts → external experts.

Operators should handle tasks close to their work area that can be safely performed with minimal training (under 30 minutes). If training is not feasible, assign the task to maintenance craftspeople. Tasks requiring specialized tools—vibration analysis, ultrasound, etc.—should be performed by in‑house experts, while external experts are reserved for rare, high‑cost interventions.

Many legacy PM systems were established years ago and often contain redundant or overly complex tasks. By modernizing these systems and incorporating affordable predictive tools, it’s possible to cut total PM effort by 30‑50 %, while improving overall reliability.

Choosing the Right Maintenance Approach

Reliability‑Centered Maintenance (RCM) principles help determine whether to run to breakdown (OTB), use fixed‑time replacement (FTM), or apply condition‑based maintenance (CBM). Random failures—like valves that fail between 1 and 12 years—may require redundancy or proactive spare‑part planning. For components with a predictable failure window, condition monitoring can extend life regardless of whether the failure pattern is random or regular.

While full RCM or FMEA analyses are valuable during design phases, experienced teams often rely on observable failure symptoms and suitable detection methods for everyday maintenance decisions.

Conclusion

Basic inspections, when combined with advanced monitoring tools and a thoughtfully designed PM system, form the backbone of efficient, reliable operations. Avoiding over‑reliance on fixed‑time schedules and embracing data‑driven, condition‑based strategies leads to significant cost savings and longer equipment lifespans.

Christer Idhammar is the founder of IDCON, Inc., a management consulting firm (idcon.com). This article was excerpted from his recent book Knocking Bolts. More information can be found on this book at https://www.idcon.com/reliability-and-maintenance-books/