What is Condition Monitoring? Techniques, Benefits, and Implementation

Condition Monitoring Defined

At its core, condition monitoring is a reliability strategy that answers one question: what is this asset telling us right now? By continuously or periodically measuring indicators such as vibration amplitude, lubricant contamination levels, surface temperatures, and acoustic emissions, reliability engineers can establish a baseline for normal operation and detect deviations that signal impending failure.

Condition monitoring sits within the broader family of condition-based maintenance (CBM) strategies. Where preventive maintenance acts on elapsed time, CBM acts on evidence. This distinction carries significant commercial weight — unnecessary maintenance interventions consume labour, parts, and production time without adding reliability. A well-designed condition monitoring program eliminates most of that waste.

Why Condition Monitoring Matters

The business case for condition monitoring is well established across heavy industry. Siemens’ True Cost of Downtime 2022 research found that fixing failures before they occur cuts the need for replacement parts by up to 40 per cent, and the US Department of Energy’s O&M Best Practices Guide estimates a functional predictive maintenance program saves a further 8 to 12 per cent over preventive maintenance alone. Early fault detection also reduces the risk of secondary damage — a failed bearing that runs to destruction can damage shafts, housings, and adjacent components, turning a $500 repair into a $50,000 shutdown.

Beyond direct maintenance cost, the availability and production arguments are equally compelling. Unplanned failures carry a substantially higher cost than planned interventions. In mining, a single unplanned haul truck or crusher outage during peak production can cost more in lost output than months of monitoring programme expenditure. Condition monitoring shifts the maintenance profile from reactive to planned, compressing downtime duration and improving the predictability of maintenance windows.

Key benefits in practice:

• Earlier detection of developing faults, often weeks or months before failure
• Reduced mean time to repair (MTTR) through planned parts and labour availability
• Improved mean time between failures (MTBF) by addressing root causes rather than symptoms
• Lower lubrication and consumables costs through oil analysis-driven change intervals
• Stronger safety outcomes by identifying failures before they create hazardous conditions

Condition Monitoring Techniques

There is no single condition monitoring technology that suits every asset or failure mode. Selecting the right technique requires understanding what each method detects and at what stage of the failure development process it becomes effective.

Vibration Analysis

Vibration analysis is the most widely applied condition monitoring technique for rotating equipment. Accelerometers measure displacement, velocity, or acceleration at defined measurement points, and the resulting data is analysed for characteristic fault frequencies associated with bearing defects, unbalance, misalignment, looseness, and gear damage. Vibration analysis is appropriate for pumps, fans, motors, gearboxes, compressors, and any rotating machinery operating above approximately 600 rpm.

Oil Analysis

Oil analysis examines lubricant samples for wear metal concentration, particle count, viscosity, acid number, and contamination levels. It provides a window into the internal condition of gearboxes, hydraulic systems, engines, and other oil-wetted components that cannot be directly observed. Oil analysis is particularly valuable for detecting early-stage wear in high-value assets and for optimising lubrication change intervals based on actual oil condition rather than hours-run assumptions.

Thermography

Infrared thermography detects surface temperature anomalies caused by increased electrical resistance, friction, insulation breakdown, or fluid blockages. It is widely used for electrical switchgear, transformer inspections, refractory and kiln shell assessments, and mechanical components running under abnormal load. Thermography delivers fast, non-contact inspection across large areas and is particularly effective for electrical assets where other techniques cannot access internal condition.

Ultrasonics

Ultrasonic inspection detects high-frequency sound emissions from sources including compressed air and gas leaks, early-stage bearing defects, electrical arcing and corona discharge, and valve seat integrity. Airborne ultrasonic surveys are effective for identifying pressurised system leaks across large areas. Contact ultrasound on slow-speed bearings (below 600 rpm) often provides earlier fault detection than vibration analysis, which may lack sensitivity at low rotational speeds.

Motor Current Signature Analysis (MCSA)

MCSA analyses the current waveform drawn by an electric motor to detect stator winding faults, rotor bar defects, eccentricity, and driven load anomalies. It requires no physical contact with the motor shaft and can be performed on energised equipment from the motor control centre. MCSA is increasingly used where vibration access is restricted or where early detection of electrical motor faults is a priority.

The P-F Interval Explained

The P-F interval is one of the most important concepts in condition monitoring. It describes the time between two points on the failure development curve:

• P (Potential Failure): the earliest point at which a developing fault becomes detectable using a given monitoring technique
• F (Functional Failure): the point at which the asset can no longer perform its required function

The P-F interval defines the window within which condition monitoring can deliver value. Different techniques have different P-F intervals for the same failure mode. Oil analysis typically detects bearing wear earlier than vibration analysis; ultrasonic methods often detect incipient bearing defects before vibration signatures become apparent. Selecting the technique with a P-F interval that comfortably exceeds your monitoring frequency is a fundamental design requirement of any effective program.

In practice, a structured reliability engineering assessment of each critical failure mode should inform both technique selection and inspection frequency. This analysis is often completed as part of an RCM or FMECA study.

Condition Monitoring vs Preventive Maintenance

Condition-based maintenance is not a universal replacement for time-based preventive maintenance. The right strategy depends on the failure mode, the consequence of failure, and the availability of a reliable monitoring technique with an appropriate P-F interval.

Condition monitoring is preferable when:

• The failure mode has a detectable degradation period (a P-F interval exists)
• The consequence of failure — production loss, safety risk, secondary damage — is high
• The cost of monitoring is lower than the cost of unnecessary scheduled replacement
• The failure development time is variable, making fixed-interval replacement inefficient

Time-based maintenance remains appropriate when:

• Components are low-cost and easy to replace (filters, belts, seals)
• The failure mode does not produce a detectable P-F signature
• Regulations or OEM warranty conditions mandate scheduled replacement
• The consequence of reaching failure is safety-critical and cannot be tolerated

Most mature maintenance strategies combine both approaches, assigning each failure mode to the most appropriate task type through a structured maintenance strategy review. Applying condition monitoring broadly without this analysis often results in monitoring assets where it adds little value while missing high-consequence failure modes that would benefit most.

How to Build a Condition Monitoring Program

A condition monitoring program built on guesswork rarely delivers sustained results. The following seven steps reflect the structured approach used by HolisticAM across mining, manufacturing, and industrial clients:

1. Identify critical assets — conduct a formal asset criticality assessment to rank equipment by consequence of failure. Focus monitoring resources on assets where failure has the greatest impact on safety, production, and cost.
2. Define failure modes — for each critical asset, identify the specific failure modes that condition monitoring can address. This is typically done through an FMECA or RCM analysis.
3. Select appropriate techniques — match monitoring techniques to failure modes based on P-F interval, equipment type, access constraints, and cost.
4. Establish baseline data — collect initial readings under known good operating conditions to define normal behaviour for each asset.
5. Set alert and alarm thresholds — define statistical or OEM-referenced limits that trigger investigation and intervention actions.
6. Integrate with CMMS and maintenance workflow — condition monitoring findings must connect to the work order system and maintenance scheduling process to drive action.
7. Review and refine — track program effectiveness through MTBF trends, failure avoidance events, and cost data. Adjust techniques, frequencies, and thresholds as the asset history builds.

Full detail on each step is covered in our guide: How to Build a Successful Condition Monitoring Program.

Condition Monitoring in Mining

Mining presents some of the most demanding condition monitoring challenges in industry. Assets operate continuously in high-dust, high-vibration, and high-temperature environments, and the consequence of unplanned failure is measured in production tonnes per hour lost. The following applications illustrate where condition monitoring delivers the highest value in a typical open-cut or underground mining operation.

Haul Truck Engines and Drivetrain

Haul trucks are among the highest-value assets on any mine site. Oil analysis on engine lubricant and hydraulic fluid, combined with thermal imaging of brake and wheel motor components, provides early warning of developing mechanical faults. Vibration monitoring of driveline components identifies misalignment and bearing degradation before catastrophic drivetrain failure occurs.

Conveyor Bearings and Idlers

Conveyor systems present the challenge of monitoring hundreds or thousands of idlers distributed across kilometres of structure. Ultrasonic surveys of rotating idlers detect early bearing noise well before thermal signatures or vibration amplitudes exceed alarm levels. Automated acoustic monitoring systems have reduced conveyor-related unplanned downtime on major operations by identifying failing idlers during normal production rather than during inspection shutdowns.

Crusher Liners and Wear Components

Crusher performance degrades progressively as liner wear increases, reducing throughput and increasing power draw. Motor current signature analysis tracks changes in load profile that indicate liner wear beyond optimal replacement point. Vibration analysis on crusher drive components detects bearing deterioration and structural looseness that commonly follows liner wear events.

Pump Seals and Slurry Systems

Slurry pump failures carry significant consequence in mineral processing — seal failures introduce water or process fluid into bearings, accelerating degradation and contaminating the process stream. Vibration monitoring of pump bearing housings, combined with periodic oil analysis on bearing lubricant, provides early indication of seal deterioration and internal wear before pump failure and process interruption occur.

Condition Monitoring Consulting in Australia

HolisticAM provides condition monitoring strategy development and implementation support for mining, manufacturing, and industrial clients across Australia. Our reliability engineers have an average of 20 years of on-site industry experience, and our work is grounded in structured analysis rather than prescriptive technology recommendations.

Typical engagements include asset criticality assessments, maintenance strategy reviews, condition monitoring program design, and ongoing technical support for in-house monitoring teams. We also deliver reliability engineering services that integrate condition monitoring into a broader asset management framework aligned to ISO 55001.