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Like any job there is a right way and a wrong way to do things. Simply listening to a bearing with an ultrasound device that gives no quantitative feedback is a recipe for disaster. The audible feedback is too subjective to draw any comparative conclusions. No two people hear the same and there is no way to remember what the bearing sounded like a month ago.
The third mistake is depending solely on subjective ultrasound data when precise quantifiable data is available. Always use an ultrasound instrument with digital decibel metering. Better still, use a device that provides multiple condition indicators. Max and Peak RMS decibel measurements indicate alarm levels and greasing intervals while Ultrasonic Crest Factor provides insight about the bearing condition in relation to its lubricant. Crest factors help us differentiate between bearings that need grease and bearings that need to be replaced.
Download the Ultrasound Lubrication Technician Handbook

by Allan Rienstra - SDT Ultrasound Solutions

Bearings are widely used in industrial applications and considered as crucial component. Bearing failures, when not detected in time, are responsible for unscheduled shutdown and expensive downtime. They may even lead to catastrophic breakdowns.
Slow speed bearing monitoring is a different story. When speaking about rotation speeds of less than 250 rpm the “normal” technologies, such as vibration or thermography, are usually blind to problems until it is too late. In slow speed bearing application early failure detection remains a notorious problem … for those who do not use ultrasound.
slow-speed-bearings
Monitoring the condition of slow speed bearings with ultrasound can reveal pitting, impacting, rubbing, and other mechanical defects well in advance of failure stage. Dynamic data is best analyzed in the time domain but it is important that a long enough time sample be captured. The golden rule is to capture 3 to 4 revolutions of the bearing.
So deciding how long is long enough is a matter of multiplying the number of shaft rotations (4) by the period (p). Period is the reciprocal of frequency or:
p = 1?f
If you want to capture 4 rotations on a 15RPM bearing, therefore:
p = 1?0.25 * 4 = 16 seconds of data
To make data collection easy, the acquisition time parameter can be set up as part of your survey. So when you are creating your database in Ultranalysis Suite Software (UAS) simply enter 16 seconds.

by Allan Rienstra - SDT Ultrasound Solutions

June 2011 • PUMPS & SYSTEMS
Ensure proper bearing assessment and maintenance with this proven method
Of the methods used to assess the operating condition of rolling element bearings, one of the most successful and popular techniques is that of Shock Pulse evaluation. Shock Pulses are a special type of vibration that can be clearly distinguished from ordinary machine vibrations:
• The actual Shock Pulse is the pressure wave generated at the moment when one metallic object strikes another.
• The bulk of the impact momentum, however, acts to deform the target object, which then oscillates at its natural frequency. This vibration ultimately dissipates primarily as heat due to internal friction material damping.
Shock Pulses in Bearings
Shock Pulses occur during bearing operation when a rolling element passes over an irregularity in the surface of the bearing race. Of course, there is no such thing as a perfectly smooth surface in real life. Therefore, even new bearings emit a signal of weak Shock Pulses in rapid succession. This Carpet Value rises when the lubrication film between rolling elements and their races becomes depleted.
A defect on the surface of a rolling element or bearing race produces a strong Shock Pulse reaction with up to 1,000 times the intensity of the Carpet Value. These clusters of high amplitude peaks or Maximum Value stand out clearly from the background noise and are ideal indicators of bearing damage.
Measurement
Shock Pulses propagate within a much higher frequency range than that of ordinary machine vibration, and their energy content is relatively low.
Therefore, the accelerometer used for Shock Pulse measurement is tuned with a 36 kHz resonance frequency that lies precisely within the Shock Pulse frequency range. In addition, a 36 kHz band pass filter is applied to the accelerometer signal to help filter out lower frequency mechanical vibration. When Shock Pulse is present the tuned accelerometer resonance is excited and amplifies the Shock Pulse signal resulting in an excellent indication of bearing lubrication and damage.
Shock Pulse is responsive even when far more energetic machine vibration is present. Therefore, lower frequency mechanical conditions such as unbalance, shaft misalignment or vibration from adjacent machines have little effect on Shock Pulse. In addition, high-frequency signals tend to dissipate rapidly so very little interference is encountered from adjacent bearings.
Read article Reliable Shock Pulse Evaluation of Anti-Friction Bearing Condition

Learn about our VIBXPERT II Portable Vibration Analyzer —with Full Color Display, Fast Data Acquisition and Powerful Vibration Diagnostic Tools. VIBXPERT uses the Shock Pulse method to detect lubrication condition and bearing damage.

by Ana Maria Delgado, CRL

Measure vibration overall levelsThe ROTALIGN ULTRA VIBRATION ACCEPTANCE CHECK works in combination with the VIBTOOL vibration meter to measure vibration level according to ISO 10816-3 international standard. The RMS velocity value is wirelessly transferred and stored back onto ROTALIGN ULTRA computer where the result is instantly evaluated against the machine classification threshold. This fulfills the recommendation of the acceptance check after installation of rotating machinery or any alignment job, ensuring that machines run without restrictions.The VIBTOOL vibration meter can measure the following parameters: Vibration Severity, Bearing Condition, Temperature, RPM and Pump Cavitation.More information about the new ROTALIGN ULTRA VIBRATION ACCEPTANCE CHECK

by Ana Maria Delgado, CRL