Organizations can take advantage of a wide variety of tools and technology to boost their equipment reliability and monitor conditions. Optimal results require selecting the best tool for the job. Predictive maintenance (PdM) tools offer a wide range of options, but choosing the correct device for measurement provides the best information.
There are six primary PdM tools available:
- Vibration analysis
- Ultrasonic analysis
- Infrared analysis
- Oil analysis
- Laser-shaft alignment
- Motor circuit analysis
Below, we’ll explore these six predictive maintenance tools, as well as a newer PdM tool referred to as video analysis.
Note: Many Predictive Maintenance tools described below offer continuous readings for situations that require rapid reporting. Both wired and wireless connections provide these readings.
Vibration Analysis (VA) uses a sensor to detect vibrations from an asset. An analysis of vibration readings to known problem signals, or changes over time from current to previous data, provides information for action.
VA measures these topics:
- Velocity (speed of the vibration)
- Displacement (how far the measured component moves with each wave)
- Frequency (the vibration’s cycle of occurrence)
These measurements provide information about the type of vibration detected. Choice of the correct scale or measurement ensures analysis accuracy.
PROs of VA tools
- Gathers real-time data on a wide variety of assets
- Detection of potential problems
- Identifies mechanical components that are failing
- Identifies equipment alignment issues
- Verifies correct equipment installation and service
- A 30-day cycle is adequate for generating and acting upon VA data
CONs of VA tools
- Not good at resolving electrical issues
- Optimal results require knowledge to select the proper tools
Ultrasonic analysis (UA) tools take high-frequency sounds picked up by a sensitive microphone and turns them into audio and digital data that are used by humans and computer software. New UA data is compared with known potential issues or compared against previous recordings for performance tracking.
Portable UA sensors collect data for immediate use or for uploading to a database for further analysis. Some UA units have onboard thermometers, cameras, and spectral analyzers for even higher data analysis.
UA can provide data about:
- Leak detection
- Failed steam traps and steam systems
- Electrical inspection
- Valve testing
- Optimal lubrication practices
PROs of UA tools
- Easy to use and understand. (Humans can frequently hear the issue.)
- Tuning the detector overcomes noisy environments
- Offers ability to take measurements at a distance without contact in some cases
- Offers rapid detection and location of potential issues
CONs of UA tools
- Repeatability is hard due to the position of the detector from a test subject
Infrared radiation (IR) is the wavelength of light that is invisible to the human eye. The varying levels of light indicate an object’s temperature.
The infrared analysis uses IR to compare the difference in temperature between components in one view or multiple views over time. The temperature differences can indicate an asset’s condition or performance.
IR is valuable in determining:
- Temperature variations of mechanical components such as bearings or motor cases
- The condition of electrical components (prevalent for ARC flash analysis)
- Process temperatures
- Insulation or building conditions
- Piping and plumbing conditions
- Solar panel conditions (a new use for many building owners)
PROs of IR tools
- Exposes potential problems that are not visible to the naked eye
- Readings can be taken from distances that do not put the tool user at risk
- Locates conditions obscured by other material
CONs of IR tools
- Not effective when measured against reflective surfaces.
A frequent source of mechanical failure is poor installation practices when putting equipment into service. Many technicians do not realize the importance of aligning a shaft on all three axes when connecting asset components.
Misaligned components place extraordinary pressure on all elements within an asset’s drive train. Bearings frequently bear the brunt of misaligned shafts.
PROS of laser-shaft alignment tools
- Verification of proper shaft alignment
- Documentation of shaft alignment
- Dramatic reduction in mechanical failures when equipment is installed correctly
CONS of laser-shaft alignment tools
- Equipment may need to be stopped to conduct analysis
Motor Circuit Analysis
Motor circuit analyzers can find faults and potential faults in electric motors and their components.
Motor circuit analysis can determine issues in:
- Incoming power
- Motor electrical circuitry
- Motor mechanical components
- Motor mechanical couplings (driven load)
Motor circuit analyzers use electric signature analysis (ESA) to identify faults. ESA measures a motor’s supply voltage and operating current to determine issues. ESA works on AC and DC motors.
PROS of motor circuit analyzer tools
- Tests can be conducted while equipment is running
- Tools can be used in a de-energized state. (It’s a powerful tool to test an incoming motor’s condition before placing it in the parts room.)
CONS of motor circuit analyzer tools
- Only electric components are tested. (Connected components are tested, but not the entire equipment chain.)
- Must enter nameplate data and operational settings for a full analysis
Oil analysis tests samples of oil for its condition. Equipment issues are also determined through oil analysis.
The oil condition is tested for viscosity, water, and other wear indicators. Oil samples can indicate metal fatigue when particles of metal are detected in the samples.
Oil analysis is frequently used on high speed or critical equipment. The choice of whether to use predictive oil analysis is often dictated to maintain equipment warranty standards.
Oil analysis began as a process of oil sample collection onsite and forwarding the sample on to a remote laboratory for investigation. Portable options are now available for sites requiring faster analysis.
PROS of oil analysis
- Provides a stable snapshot of the condition of lubricants
- Leads to lower oil consumption by reducing periodic oil changes until a change is required
- Sampling collection can be made by untrained personnel
CONS of oil analysis
- Lead time between sample collection and analysis reporting can put equipment at risk
- Portable or onsite equipment requires dedicated space
- Personnel needs to be trained to operate laboratory equipment for the portable and onsite analysis
Multiple vendors are offering oil analysis services. Oil suppliers and equipment manufacturers can provide recommendations regarding particular vendors.
Portable tool providers
Hydraulic oil analysis kit
Video analysis is a new twist on an older idea. Graphic images were produced to show the movement of equipment and components when measured over a period of time and at multiples points of measurement. Vibration equipment gathered the data to show equipment deflection during operations.
The shape of the movements of the equipment is called Operating Deflection Shape (ODS). Video analysis uses video information to capture vibrations of equipment in minute detail that is difficult to replicate with the previous process. The image is no longer a drawing but a video of the image as it was being measured.
Pros of video analysis
- Does not require multiple points of measurements
- Can be done without contact with the equipment
- A realistic (actual) image of the equipment is provided rather than a drawing
Cons of video analysis
- Requires extensive equipment and training.
Note: Video analysis is a relatively new PdM tool and providers are just becoming available for consideration.
Which types of Predictive Maintenance tools do you use, and for which types of assets? Let other maintenance professionals know in the Maintenance Talk forum.