Issue 107
Save Time, Save Money and Promote Safety for
C-130 and Aircraft Fleets

When an aircraft must be grounded due to measured engine vibration or turboprop balancing issues, it is costly and time consuming for everyone involved. Many times, bad velocimeters (also referred to as velometers) are - and should be - the first suspect. Vibration sensors that have sustained physical damage can provide inaccurate measurements. This issue is so common that suspect sensors are often immediately replaced when a vibration issue is detected, and the aircraft is sent out for a test flight.

Of course, the disadvantage to this approach is that it is a time-consuming and expensive method of determining the true source of the problem. Perfectly good (and expensive!) sensors may be tossed out unnecessarily. Bad sensors can be particularly costly in turboprop balancing situations. No matter what mechanical adjustments are made, the turboprop will not balance and may then be replaced. I n these situations, it is possible that the vibration sensors were the culprits, producing erroneous readings at critical frequencies that prevented a successful balancing job. 

With The Modal Shop's Portable Vibration Calibrator, you can validate velocimeters quickly and easily using a pre-programed test. No need for a vibration expert - you can see pass/fail results right on the screen.  Fifteen minutes of testing, right in the hangar, by the maintenance technicians might be the difference between a frustrating balancing job and a successful one. It might be the difference between scheduling crew for yet another test flight or diagnosing, repairing an issue, and putting the aircraft back in service.

Of course, this functionality is not limited to military applications. Industrial I&C technicians can also use the semi-automation and pass/fail notification to determine proper operation of proximity probes, accelerometers and velocity sensors used on compressors, turbines, pumps, and motors. 

Industry News 

  • Chemical Engineering interviewed several industry experts for its article "The Changing Face of Maintenance". One quote in particular from Brian Joe of Emerson Automation Solutions caught our eye: "The extent to which predictive practices are deployed will increase as more diagnostic instruments become available at lower costs combined with simpler and cheaper data collection and analytics platforms. We're seeing that happen right now." Mr. Joe is right. In the world of vibration, it is happening rapidly. The advent of the digital accelerometer is opening up vibration as a predictive maintenance tool to plants that could not afford to do so before. A digital accelerometer, magnet and smart phone application may be all that stands between you and applying this technology.
  • Underground mining (shaft mining) has always been a difficult application in which to apply vibration monitoring. However, Kerry Hope makes a good case for it and other methodologies in "Building a Case for Predictive Maintenance for Mining" from IT News Africa. How do we get the data out of the mine? How do we make sure miners are safe? Maybe a simple yet reliable vibration switch can improve safety without triggering false alarms. The aforementioned digital accelerometer and a smart phone at least provide a way for the Firebosses, technicians who walk the shaft each day, to acquire data and bring it topside for analysis. 
  • Our favorite part about this video by Adash - a vibration analyzer manufacturer headquartered in the Czech Republic - is the explanation of what +/- 3 dB means when applied to an accelerometer's sensitivity tolerance. Finally! The video also is full of good advice regarding selecting the right accelerometer for your application. 
Analyzer Calibration Coming Soon

Want to create NIST-traceable calibration certificates for your vibration analyzers or meters? Our team is developing Version 3.0.8 of the Calibration Workbook supplied with Portable Vibration Calibator Models 9110D and 9210D. This will allow you to create NIST-traceable calibration certificates for all kinds of vibration analyzers and meters. 

Interested? Just let us know you want the new version of the workbook, and we can email or send it on a USB drive to you at no cost. Keep an eye out for our next newsletter, when we will feature a complete overview of this new functionality. 
Question of the Quarter

Have you ever tried to calibrate a proximity probe that is stuck in the probe holder? Should The Modal Shop create a proximity probe mount that allows technicians to mount the entire probe holder sleeve assembly over the shaker?  Let us know!

Michael R. Scott
Category II Vibration Analyst
The Modal Shop, Inc.
An MTS Systems Corporation