The Complete List Of Condition Monitoring Techniques

Introduction

As more and more sensors are getting developed that can get mounted on equipment, condition monitoring holds an excellent future. The equipment built to the Internet of Things (IoT) standards is on the rise. Different condition monitoring techniques have proven how ahead technology moving.

According to Kelvin Bui, Marketing Associate at SMC, industrial devices at present has an unprecedented amount of processing, sensing and communications capabilities that is built into the product. The basis for predictive maintenance for condition monitoring is the data that is analyzed. A machine part might deteriorate or begin to fail as per the patterns that emerge from the data. And based on the analysis, maintenance is scheduled to avoid emergency downtime or to prevent failure.

Complete list of Condition Monitoring Techniques

Let us now see the complete list of condition monitoring techniques grouped into a category and which shows the extent to which technology has helped moved monitoring rising upwards. It is important to remark that the list mentioned below may or may not be related to an IoT network but are suitable for analysis and automatic data collection.

Oil Analysis or Tribology

The technique includes collection and testing machine oils, equipment lubricants or fluid samples to ascertain the condition of both the fluids or machines or one of them. Machines get overheated, wear down, or trend toward failure, and the contaminants get deposited in lubricating oils and other operating fluids. Through oil testing, it has revealed these contaminants. To indicate impending failures, data from these studies then get interpreted.

The techniques are as follows:

• Presence of water
• Ferrograpgy
• Atomic emissions spectroscopy or ICP to identify the presence of contaminants
• Viscosity/ Kinematic Viscosity test
• Dielectric strength test
• Microbial analysis
• Iron content or Particle quantification index
• Fourier transform infrared spectroscopy
• Ultraviolet spectroscopy
• Potentiometric titration/total acid number and the total base number
• Sediment test

Dynamic Monitoring of Vibration Analysis

Dynamic Monitoring of Vibration Analysis is one of the condition monitoring techniques. For identifying defects occurring due to misalignments, imbalances or flaws in the design, vibrations are used from the response of equipment and parts that respond in a variety of ways. Different reasons cause wear on machine parts, rotors, bearings, and shafts with specific patterns which are recorded and then analyzed. As other parts vibrate in different ways and get worn out or out of, balance parts have unique vibration signatures, and they can be tracked and used to predict parts and bearing failures.

The techniques include:

• Shock pause analysis
• Broadband vibration analysis
• Fast Fourier transforms
• Ultrasonic analysis
• Power spectral density or PSD
• Time waveform analysis
• Spectrogram or spectrum
  analysis

Motor circuit analysis (MCA)

A battery of computer-aided tests on an electric motor to discover the motor's whole condition and possible sources of potential failure is known as motor circuit analysis or MCA. The chief causes of motor failure are electric imbalances and degradation of insulation, and these are the focus of MCA testing. Some of the tests are going or not-go tests while the test results for others should get tracked over time for the identification failure development.

These are grouped into current bases tests, or voltage based tests and the inspection points include:

• Power circuit or current signature
• Online and offline testing rather testing regimes
• Rotor
• Stator
• Insulation
• Quality of power
• Air gap

Infrared Thermography or Thermography or Temperature Measurements

The study of heat patterns in objects and machines is infrared thermography. This condition monitoring technique uses images to capture the thermal radiation patterns emitted from the equipment. To identify potential failures or equipment parts, the use of degradation data analysis is a must. As parts failure develops, equipment and parts start heating. For indicating misalignment, imbalances, improper lubrication, worn components, undesirable mechanical stresses and electrical overheating, thermal anomalies and temperature differences are generally used. For identifying safety issues like overheating of electrical connections, pressure vessel weaknesses and pipe leaks, thermographic inspections help. Different infrared techniques that are based on the principles of IR radiation are developed to fit specific industrial applications.

The methods are as follows:

• Comparative thermography
• Testing of pipe works, electrical and machinery
• Comparative quantitative thermography
• Comparative qualitative thermography
• Paint stickers that change colour without specific temperatures
• Fluids that change colour at out-of-spec temperatures
• Lock in thermometry
• Pulse phase thermometry
• Pulse thermometry

Acoustic Analysis or Ultrasonic Monitoring or Airborne Ultrasonics

For detecting part defects such as leaks, parts seating and cavitations, high-frequency sound waves are used in ultrasonic monitoring of equipment, bearings and rotating parts. Ultrasonic monitoring as a condition monitoring technique is also used in detecting tiny changes in friction forces, and these small changes might get missed with vibration analysis of IR. Thus, UM can be considered an excellent companion testing technique along with IR and vibration analysis. Ultrasonic monitoring UM can benefit almost all areas of manufacturing processes. It also provides an early warning for machine parts that get deteriorating which otherwise might get masked by ambient plant noises and temperatures.

The techniques include:

• Airborne ultrasonics
• Ultrasonic backscatter technique
• Backwall echo attenuation
• Ultrasonic thickness and gauging, e.g., pipe walls, etc
• Phased array testing
• Automatic and continuous ultrasonic inspection
• Internal rotating inspection systems
• Acoustic emissions testing
• Dry-coupled ultrasonic testing
• Long-range ultrasonic testing
• Acoustic ranging
• Time of flight diffraction

Radiography or Radiation Analysis or Neutron Radiology

For identifying internal defects in equipment and parts, this method uses radiation imaging. Applications include inspection of weldments, casting and sintered parts. This approach is one of the most thorough methods used in non-destructive testing available. It is based on measuring the differential absorption of radiation and penetrates the parts or materials. Different amounts of radiation are absorbed by internal corrosion and flaws, which can be measured and analyzed.

The techniques include:

• Neutron backscatter
• Computer radiography
• Computer tomography or CT
• Direct radiology
• Positive material identification (PMI)
• Neutron radiography

Laser Interferometry

The laser interferometry measures changes in wave displacement based on a laser-generated, highly accurate wavelength of light. For identifying surface and subsurface defects in composites and other materials, this technique is used. Based on the interference of light waves generated by a laser, the laser interferometry also uses sound and radio or electromagnetic waves. The interferometer then captures and measures the interference pattern. For showing differences in material characteristics like the presence of corrosion, surface defects or cavities in the material, various interference patterns can be analyzed.

The techniques include:

• Laser shearography
• Laser ultrasonics
• Strain mapping
• Electronic speckle pattern interferometry
• Digital holography is used worldwide to test turbine blades and surgical parts.
• Holographic interferometry is still used in laboratory testing and not used in general widespread condition monitoring currently.

Electrical monitoring

Application of the principles of deviations in electrical parameters to identify defects and faults is made by electrical monitoring. Resistance, capacitance, induction, pulse response, frequency response and other characteristic are used to detect potential maintenance issues. To take preventative action in advance of any system failure, degradation trends in an electrical system is also a methodology.

The techniques include:

• Megohmmeter testing
• Power signature analysis
• High potential testing
• Battery impedance testing
• Surge testing
• Motor circuit analysis
• Alternating current field measurement (ACFM)

Electromagnetic Measurement

For measuring magnetic field distortions and eddy current changes to identify corrosion, cracks, weaknesses and other defects, this category of the test is used. These fields cause patterns when they interfere with one another. The electromagnetic testing induces an electromagnetic field or electric current inside the test object or tubing, and the defects will create disturbances that are measurable and analyzed.

The techniques are as follows to take advantage of these properties:

• Magnetic particle inspection
• Magnetic flux leakage
• Metal magnetic memory method
• Pulsed eddy currents
• Remote and near field eddy current
• Saturated low-frequency eddy currents
• Other eddy testing current

Performance Monitoring or Observation and Surveillance or Process Variable and Performance Trending

A traditional approach for monitoring production equipment that uses visual inspection and physical sense to judge the proper functioning of a machinery piece is Performance Monitoring.

The technique used in monitoring equipment is valuable, and advanced technological testing methods are not available. Results interpreted depends on careful record-keeping and application of hands-on-experience.

The techniques are as follows:

• Visual inspection
• Audio inspection
• Flow rates
• Touch inspection
• Touch inspection
• Temperatures
• Pressures
• Performance trends or output
• Downtime analysis

Conclusion

Not everything but a majority of condition monitoring techniques available in the market were covered. Hope you have gotten a fair idea of list of Condition Monitoring Techniques. The practice is becoming more vital as the industry moves closer to adopting IoT in condition monitoring

Machines can now communicate through sensors to communicate through the Internet to central databases. In real-time, the condition of the equipment can get monitored to prevent costly equipment failures by scheduling planned downtime and proactive maintenance.

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