Any success stories you'd like to share? Advice on how done? Is ultrasound augmented by slow-motion strobe study?

Thanks for any advice/information anyone may provide.

Gary Forsythe

Gary,

I could have sworn that we discussed this subject in detail before, but the only thing I could find was this.
http://maintenanceforums.com/eve/forums/a/tpc/f/3751089...091044071#3091044071

Maybe I'm remembering a discussion from the Reliability-Magazine.com site.

Danny,

Thanks for the link. Based upon what was stated, the conversation primarily dealt with gear type rigid couplings. Is ultrasound effective on flex couplings too?

BTW, when will David spring for a dinner for you and your loved ones? He can certainly afford it!

Gary Forsythe

Gary,

I seem to remember a general discussion about ultrasonic on couplings too.

Walt Strong has done lots of work on the topic ans will probably spot this soon.

I thought Dave was on his last can of beans.

Gary,

The basic principle is that coupling (flexible type) faults will cause excessive friction or impacting (or both) that can be detected by airborne ultrsound. Typical coupling faults include:
1) Shaft misalignment (offset and angular)
2) Shaft ends or element clearance insufficient
3) Internal worn or damaged components
4) Loose parts
5) Poor lubrication

Ultrasound is measured near coupling's assemby joint as close as reasonably and safely possible. The overall level (dB) is measured and audio characteristcs are noted. Friction has no real character and may sound like White Noise or Static or whoosh or (__??). Impacting has a distinctive sound like Clicking or Popping. Be aware that there are background ultrasounds that can mask the coupling sound, such as:
a) Machine bearing fault
b) Machine shaft seal rub or leak
c) Pump Cavitation
d) Compressor leak
e) Direct or reflected sound from another machine or source
f) Coupling's windage from spinning bolts or protruding surfaces or holes

A good consistent measurement is not necessarily a fixed measurement point, but one or more locations that may be needed to optimize receiving the sound from the coupling.

I have used ultrsound on several types of couplings including: elastomer element, metal grid, gear, and metal disk-pack.

Try it , you'll like it!

Walt

Walt:

Thank you so much for your detailed reply, just what I was seeking!

I have also used ultrasound on slow speed conveyor bearings but after awhile, all sound the same. When I pick-up an unusual sound, I get a grease sample, as instructed by our lubrication specialist, and have analyzed. I have had some decent luck doing that.

Thanks again for taking your time to reply. I appreciate it.

Gary Forsythe

Gary,

Whether you are doing bearings, couplings, or V-belts, you need to measure an amplitude value and listen for the audio characteristics. You can't rely just on numerical values nor use the meter like a stethoscope for listening. You must combine the two. I also used a third descriptor that I call dynamic level. This can be the movement of an analog meter needle or a digital bargraph display. It tells you if the level is steady, unsteady, periodic, or impulsive (quick transients). Some folks talk about trending and alarming on ultrasound levels, but that can be very misleading. A little science and a little art (technique) are needed for good results.

Walt

Walt,

Have you tried recording the TWF from an ultrasound instrument? This may take out the "art" element and subjectivity allowing for better analysis of what you call dynamic characteristics.

David

David,

I have recorded audio from headphones and used waveform and spectrum analysis. I have also plotted dB level Vs time (strip chart). These techniques can be helpful occasionally, but are not needed for routine surveys.

Walt

Walt,

We have lost probably 4 couplings lately. My managers are looking for answers to how we can detect problems before they become failures.

Can you email me a aubrey.green(at)ipaper.com so I can pick your brain?

Thanks,

Aubrey

Aubrey,

Ultrasound is a great technology for coupling fault detection.

Walt

Thanks for your help Walt,

I think due to our converstation that my plant will have a two prong attack plan in place in the next couple of weeks.

Thanks to the group

Aubrey,

What have you done with ultrasound on shaft couplings and bearings in the past 3 months?

Walt