Condition monitoring consists of measuring equipment parameters that indicate failure. Hopefully, you can spot changes in the usual patterns in time to prevent a breakdown, save on reactive maintenance, and extend your asset’s lifespan. But you can only enjoy these benefits if you choose the right condition monitoring techniques for your equipment and operation.
Condition monitoring, of course, overlaps with predictive maintenance. Tracking asset behaviour is a big part of predictive maintenance – the collected data provides the basis to discover trends and perfect algorithms. It makes sense, however, to talk about real-time condition monitoring even without a predictive maintenance programme.
Condition monitoring, IIOT, and reliability
When it comes to predictive maintenance, two of the biggest “barriers to entry” are the investment it requires and the difficulty in developing algorithms. But the Internet of Things (IoT) and the Industrial Internet of Things (IIoT) brought about a big change in the industry. Condition monitoring sensors and devices are now connected to maintenance platforms, providing real-time data.
This new connectivity is both more affordable and easier to implement than predictive maintenance. Real-time data allows managers to adjust their preventive maintenance plans, while also providing increased reliability. At the same time, AI can process this data to recognise patterns, which is one of the most promising advances for digitally-enabled reliability.
So, regardless of your ability to implement a predictive maintenance plan right away, condition monitoring is a valuable on its own.
Advantages of condition monitoring:
✓ Avoids major breakdowns and reduces downtime.
✓ Enables better asset management across its lifespan.
✓ Decreases costs, particularly with emergency maintenance.
✓ Provides the basis to develop predictive algorithms in the future.
9 types of condition-based monitoring that you must know
Condition monitoring starts with basic inspections. Small changes, like abnormal heat or pressure, strange sounds, excessive vibration or a different smell, are often signs that something is going haywire. However, condition monitoring techniques vary from the simplest inspections to cutting-edge technology. These are 9 types of condition monitoring that you must know:
Oil analysis applies to machine oils, lubricants and fluids. It can detect wear, overheating, and contamination. High levels of iron, for example, often indicate dirt and grit. Spotted on time, this reduces gearboxes failures by 50%. Avoiding contamination decreases bearing failure by 75%. Another Canadian study suggested the return on investment for oil analysis is 20:1.
If you want to prevent these failures, there are several oil analysis methods available: ferrography, water presence tests, viscosity tests, ICP/ spectroscopy, dielectric strength test, microbial analysis, iron content (particle quantification index), infrared spectroscopy, ultraviolet spectroscopy, potentiometric titration (total acid number/ total base number), and sediment tests. Did we miss anything?
Vibration analysis is one of the most well-known predictive maintenance methods. It can detect misalignments, imbalances, and wear about 3 months before they cause a breakdown. It’s also an opportunity to improve energy consumption, since misaligned water pumps, for example, spend up to 15% more energy. Vibration measurement is also heavily featured in ISO 22096.
Vibration analysis condition monitoring techniques include shock pulse analysis (e.g. for rotating equipment), fast fourier analysis, broadband vibration analysis (e.g. to detect bearing wear), ultrasonic analysis (e.g. to detect leaks), power spectral density, time waveform analysis (e.g. for machines with X-Y probes), and spectrograms.
Motor Circuit Analysis
Motor circuit analysis, also known as MCA testing, assesses the condition of electric motors. It can be used to analyse the motor’s condition (including rotors, coupling/ belt problems, power quality), electric imbalances, and insulation. More than preventing failures, MCA can be used to cut energy costs and improve equipment efficiency by 10-15%.
Thermography studies the heat and radiation patterns in machines. Data analysis does the rest, spotting patterns that indicate failure or degradation. It has a wide array of applications, including detecting misalignment, imbalances, improper lubrication, wear, and stress in mechanical parts. In electrical equipment, it identifies overheating, pipe leaks, and pressure vessel weaknesses.
Infrared thermography, in particular, has become a popular method for predictive maintenance and non-destructive testing. A 2013 study found that infrared thermography was extremely effective in improving safety, reducing “dangerous points” – and potential failure causes – by 90%. Overall, thermography reduces risk, prevents failures, decreases costs and losses.
We’ve already mentioned ultrasonic analysis a while back (missed it? Read “vibration analysis” again), but it deserves a place of its own on this list. Ultrasonic monitoring uses high-frequency sound waves to catch leaks, parts seating, and cavitations, which can reduce inspections by 30%.
Ultrasonic monitoring is especially cost-effective when it’s applied together with vibration analysis (some sensors capture both things) and infrared thermography. Airborne and structure-borne ultrasound are gaining traction as a good option to detect ‘stress waves’ on rotating machinery. Other methods include the backscatter technique and backwall echo attenuation.
Like thermography, radiography (including radiation analysis and neutron radiography) is a very thorough method of non-destructive testing. Imaging allows technicians to inspect internal defects, such as corrosion in sintered parts and flaws in welding. However, the main advantage is that it can be used in all types of materials, provided technicians protect themselves.
Laser interferometers measure changes to calculate displacement based on laser-generated wavelengths. They are used in condition monitoring to identify surface and subsurface defects like corrosion and cavities. Interferometry includes laser shearography, laser ultrasonics, strain mapping, electronic speckle pattern interferometry, and digital holography.
A little over 53% of all accidental domestic fires in the UK are electrical fires. Likewise, electricity is one of the biggest reasons behind injuries and fatalities at work. Preventing electrical failures with close monitoring not only avoids breakdowns but also improves safety. This includes tests to assess resistance, induction, capacitance, pulse response, frequency response, and degradation.
Electrical condition monitoring techniques include megohmmeter testing, high potential or dielectric withstand test (e.g. to determine if the insulation is in good condition), power signature analysis (to test current and voltage), battery impedance testing, surge and hipot testing (also to detect insulation flaws) and, to some extent, motor circuit analysis too.
Electromagnetic measurement shouldn’t be confused with electrical monitoring. Electromagnetic monitoring measures magnetic field distortions to spot cracks, dents, corrosion, weaknesses, and other defects (e.g. thinning). Perhaps, the most prominent method of electromagnetic condition monitoring is eddy-current testing (ECT), which is used in the petrochemical industry to detect tight cracks.
Apart from ECT, there are other techniques such as pulsed eddy currents, remote and near field eddy currents, and saturated low-frequency eddy currents testing, eddy current array, magnetic particle inspection, magnetic flux leakage, and metal magnetic memory. These techniques seem especially fit for nonferrous, conductive materials like tubes, condensers, boilers, and aircraft surfaces.
There are dozens of condition monitoring techniques and counting. Some are more costly than others, but we haven’t found one that does not provide good value for money. If you choose the methods that suit your equipment, integrate them into your maintenance platform, and analyse the data, you’ll favour efficiency over reactive maintenance.