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vibration analysis

12 things to consider when selecting an industrial accelerometer

12 things to consider when selecting an industrial accelerometer

12 things to consider when selecting an industrial accelerometer by Renard Klubnik, Applications Engineer, and James Lundy, Wilcoxon Research

Learn the basics of 12 important considerations for selecting the right industrial accelerometer. This presentation will go over sensor characteristics such as acceleration range and sensitivity tolerance, as well as environmental factors like temperature and hazardous area requirements. In just a few minutes, you'll learn how to pick the right vibration sensor for your application.

 

Vibration Analysis Reporting - Bearing Failure Stages & Responses

This technical note has been written to act as a guide to vibration analysts and maintenance personnel. It outlines the expectations that maintenance personnel should have w.r.t. reporting of bearing defects identified in vibration spectrums.

Structural Failures in Vibrating Screeners at a Petrochemical Plant

Finding A Cure for Troubling Failures

by Maki Onari and Eric Olson

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The Road to PdM Excellence - Achieving Vibration Analysis Best Practices at Orange County Sanitation

The Orange County Sanitation District (OCSD) is a public agency that serves 2.5 million people in central and northern Orange County. OCSD treats more than 230 million gallons of wastewater every day (enough water to fill Anaheim stadium nearly three times each day), making it the third largest wastewater treatment agency west of the Mississippi River.

Look Between The Peaks

In many cases people only focus on the peaks in the vibration spectrum; especially the tops of the peaks. But what happens at the bottom of the spectrum is also very important. The "noise floor", and the shape of the base of the peak, provides useful information.

The Noise Floor

The bottom of the spectrum is the noise floor - but we will focus on the area of the spectrum between the peaks. If the machine is running smoothly, the area between the peaks will be flat and have a low amplitude. But if there is a source of "broadband" energy, it can generate vibration across the entire spectrum or just in specific areas. Rubs, impacts, looseness, cavitation, turbulence, and flow noise can all generate this "energy".

The "energy" can excite natural frequencies, so in specific areas we might see the noise floor rise up. Depending upon the amount of damping, and the amplitude of the energy, the spectrum might rise up quite significantly.

The noise itself can be quite focused (i.e. we will see it in a small band of frequency), so we might see the area around the pump vane rate rise up if there is cavitation. And we might see a large, broad peak below 1X if there is flow turbulence.

Broad Based Peaks

If there is a "pure" source of vibration, such as unbalance or the pump vane rate, then we expect to see a narrow peak. However if we look at the base of the peak and see that it is quite broad, we need to ask; "why is it so?"

There are actually a few reasons:


1. If that source of vibration is exciting a resonance, then the base will be broad - and the amplitude of the peak will be much higher than it would be if there were no resonance.


2. If there were sidebands, however your resolution was insufficient to be able to see the sidebands, then the peak may look broad. It is therefore important to use 3200+ lines to make sure you know what you are dealing with.


3. As mentioned above, if there is cavitation, the area around the pump vane rate peak may also be elevated.

There are two more very important points:

1. If you see an elevated noise floor, check the amplitude scale. If the highest peak in the spectrum has a very low amplitude, the noise floor will "appear" to be higher than what you are used to. Likewise, if the scale is set to a high amplitude, you may never notice a raised noise floor. That is just another reason why a logarithmic scale is very useful.


2. If there is a raised noise floor - look in the time waveform. The waveform will show you the impacts, rubs, bursts of energy from cavitation, and so on. Of course, you need to collect the time waveform correctly, but that is covered in another tip.


Here are a few examples:


Here is an interesting example. The first spectrum is 800 lines. Notices the broad bases of the peaks. Could it be resonance. The next spectrum is 3200 lines - you can see there is more to it. And the third spectrum is zoomed in to the base of the peaks.

 

This looks very noisy, however the amplitude is very low:

 

 

 

 

 

 

 

This case looks like there is no noise - but the peaks are very high in amplitude:

 

Here is the

 

 

 

 

 

 

 

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1-Channel vs. 2-Channel Data Collectors

Two channel vibration data collectors offer additional measurements that are not available in a single channel data collector. Measurements such as orbits, coherence, cross channel phase and ...

Commtest Continues to Build Bench Strength

Knoxville, TN - Commtest, Inc. appoints Tim Whitacre as a Corporate Solutions Specialist, Chris Keniston and Shane Smith as Customer Success Engineers.

 

 

Intrinsically Safe accelerometers receive IECEx certification

Germantown, MD—Wilcoxon Research, a Meggitt group company and a leading supplier of quality vibration sensors and sensor networks, announces an additional Intrinsically Safe certification in accordance with IECEx requirements for six general purpose accelerometers. The six accelerometers were approved for use in Class I Zone 0 hazardous areas.

Having Trouble With Alarm Limits?  Statistical Alarm Generation is the Answer

If you are like most people, you probably do not have alarm limits set up on your machines. You may have tried but you found that the volume of false alarms became so frustrating that you But ...

There is a Cost to Everything!

I grew up in a household as the youngest of five kids so my parents knew a little bit about managing relationships, money, conflict resolution, problem solving and all sorts of things that they

New 672u 20-channel vibration analyzer for high-channel count applications

CLEVELAND, OH, - IOtech has released the USB-based 672u, the newest addition to the 600 Series of Dynamic Signal Analyzers. The 20-channel 672u is ideal for high channel count applications including machine condition monitoring, rotating machine analysis,
predictive maintenance, modal analysis, and more.

Transitions - When to Move from Walk-Around to Online Systems for PdM

by Dennis Shreve

Rotating equipment in production facilities offers optimal performance and reliability when properly installed, maintained, and operated.  Condition monitoring devices and systems are utilized to keep tabs on the operational performance of key production equipment.  All types of tools and technologies exist today in the predictive maintenance field to allow monitoring and assessment of such equipment.

What is Resonance

Resonance is an operating condition where an excitation frequency is near a natural frequency of the machine structure. A natural frequency is a frequency at which a structure will vibrate if

Flake Breaker Vibration Analysis Case Study

by Ronald Blay, Lead Analyst, Allied Reliability - Cargill Oil Seed, Fayetteville, NC

This is a Flake Breaker Vibration Analysis Case Study at the Cargill Salt Division Watkins Glen plant 

Do You Use Time Waveform Analysis?

Time waveform analysis is the ideal tool when diagnosing a range of fault conditions, including rolling element bearing faults, faults associated with gears, cavitation, rubs, looseness and more

...Learn more at iLearn : iUnderstand

Azima DLI to Lead Two Presentations at the Fleet Maintenance & Modernization Symposium 2009

Industry Experts Present on Vibration Analysis and the Results of the US Navy’s Advanced Condition Monitoring Pilot Program

The Challenges of Automated Spectral Analysis

Reflections on eighteen years of development by Jason Tranter, Managing Director, Mobius Institute

Natural Frequency Resonant Amplification Problem

There are several important clues to diagnosing a natural frequency resonant amplification problem.

  1. Natural Frequencies are Non-Synchronous
  2. Natural Frequencies do NOT have Harmonics (unless we are

Wilcoxon Research adds M12-style accelerometers and cables

Germantown, MD—Wilcoxon Research, a Meggitt Group company and a leading supplier of quality vibration sensors and sensor networks, has added to it’s product line three new accelerometers with M12 connectors, an established sensor connector that is used throughout the world and is common in the process industries. Several compatible M12 connector-cable assemblies are also now available.

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