How many of us have ultrasonic as part of our condition monitoring technologies in addition to lubrication, vibration & thermography?

Are there any standards to refer to for application of ultrasonic to industrial equipment?

No response? Look like ultrasonic testing is NOT a must of being part of a condition monitoring prgram for maintenance purposes. So far I have seen a plant using it for checking steam traps or valve passing.

At a quick glance I did not see any standards on the use of ultrasound for condition monitoring but there are a lot of great sites and papers written on the use of ultrasound in this area. I use Infrared, ultrasound & a corona camera for my customers. I use my ultrasound for detecting corona, compressed air leaks, steam traps, motors, bearings and gear boxes. Works great wouldnt work with out it. You can try this link if you like. I have purchased other standards from them.

http://global.ihs.com

Craig

Does every manuafacturer of ultrasonic equipment have their own standard to do the interpretations?

Until manufacturers all subscribe to a standard for calibrating contact probes for mechanical inspections (bearings, gearboxes, etc..), similar to the standards used by manufacturers of accelerometers, there will be NO standards. Until all ultrasound manufacturers use equipment for calibration that is traceable (NIST, etc..) in the U.S. and its counter part in Europe, there will be NO standards.
Airborne sensors for air leaks, One manufacturer as three piezoelectric crystals mounted in the scanning module, the others have a single piezoelectric crystal for scanning. So the one with three has a patent on mounting three sensors, is three better than one? Who says? What about the "dead spot" between the three mounted sensors? Also, there are issues in regard to distance from the target, the angle at which you are holding the instrument, all have a effect on the measured decibel results. Some use non-standard piezoelectric crystals such as "minature crystals". Are they any better? Or, are they a margeting ploy, they look better.
Also, frequency response and bandwith of filters of these instruments?

In and earlier MAINTENANCE FORUM Question "TRENDING BEARINGS".
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TOPIC: UE trending of bearings STARTED BY: liver DATE: 25 April 2006 09:03 AM REPLY POSTED BY: Allan.
If I may add one thing about frequency selection, or manufacture recommended settings (30khz, 38.4khz etc...) there are a couple things that should also be known.

1. Sensor and frequency setting. If a manufacturer recomends a particular frequency setting, its because the sensor provided with that instrument matches that frequencies optimal response. Since acoustic sensors have very steep frequency responses, or lets say very specific ones, it makes very little sense to use a 40 kHz sensor at a 30 kHz setting. True, there are other side band settings where the 40 kHz sensor may be responsive, but not as responsive as its true center frequency.

2. Bandwidth. Depending on the manufacturer, bandwidth of the filter is also an issue. If bandwidth is for example +/- 6kHz, that means the detector is sampling a frequency that is 12 kHz wide. While a wide bandwidth may be good for detecting some phenomena, it may prove problematic for others. Also, a wide bandwidth may introduce more than one harmonic per sample. Doesn't that make tunable frequency feature redundant?
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The above answer about trending of bearings should give you an incite as to how far this industry is from ever having standards.

When they finally do have, will the standards lean towards one manufacturer over the others? Will you eventually have contact probes and scanning modules available through third parties as you presently have with accelerometers?
Eventually the "INTERFACE OF VIBRATION AND ULTRASOUND" will be more prevalent then ever before for bearing and gearbox analysis as well as electrical analysis of corona, tracking and arcing (use of waveform, spectra, time series, etc..). This is NOT to say ultrasound will take the place of vibration. But, if they do not interface more, ultrasound will again be considered, "just a leak detector".

I think this knowledge should be institutionalised in standardization. It would be more beneficial for all stakeholders when the minimum requirements are clearly stated in a standard. The users then just comply without or with less justifications needed and the service providers could get more business.

As to whether it would be biased to one way or another, I think ASME code has surpassed this hurdle. There are many stakeholders for boilers & pressure vessels but there is only one ASME code (starting from 15 pages to thousands now) with some divisions to cater for varying levels of requirements eg

Sect 8 Part 1 for normal fabrication with more testing & inspection
Sect 8 Part 2 for same fabrication with less inspection & testing after more rigorous calculations. This could be good for competetiveness.

There are dedicated sections for power boilers & nuclear power plants. I'm just a simple maintenance guy and I guess those experts in ultrasonic can shuffle the knowledge better.

The very last thing that we need to screw up practical ultrasound technology is an ASME-like specification or standard! I could be wrong, but my impression is that manufacturers are content to fight it out in the market place instead of developing calibration and application standards, and users don't seam to care about this topic either.

Walt

Respect your view. I thought there are many flexibilities in the ASME code. By practical ultrasound technology, are you implying ASME code is not practical for use? Maybe users don't care because they don't have the knowledge about ultrasound and totally dependent on service providers or manufacturers. Any other reasons why some people don't favour standardization to contain the minimum requirements?

This message has been edited. Last edited by: Josh,

I agree with Walt. I've found that no matter what model instrument you use there is no substitute for practical experience and common sense. Trying to codify something that is so application sensitive can create problems. We use ultrasound for bearings, monitoring grease application, valve leakage and air system leaks. The success or failure on the investigation depends on the experience of the user and their familarity of the instrument and the machine being scanned. Like many users we had a tough time getting enough experience and confidence to make the program effective. Training and experience goes a long way.
rgf

Josh,

Here are a few issues with ultrasound (UT) as compared to vibration and sound technologies:
1) No standard physical units of measure for either airborne or structureborne UT
2) No uniform calibration standard for NIST taceable reference
3) No device or method for field calibration (end-to-end) of sensor and meter system {there is an ASTM standard for arborne sound}
4) No electrical instrument performance standards (like ANSI)
5) No measurement procedure standards (like ANSI and ISO)
6) No uniform severity standards (like ISO)
7) No uniform or well accepted fault diagnostic guides
8) Use of decibels (dB) with no physical reference {a reference voltage does not apply}

In spite of these issues I continue to use and recommend UT for many applications

Walt
w_f_strong [at] msn [dot] com

Just reading over the post by Walter Strong and the list of issues (1-8) affecting Ultrasound Testing. Agreeable to most of these, but number 8 is not correct for SDT.

Over the past 15 years both selling and training people on the use of ultrasound I noticed that the use of the word Decibel is a grey area for many... even some other manufacturers.

SDT specifies a dB as the ratio of voltage generated at the sensor pins over 1 µV (micro volts. The exact technical term for the dBSDT is dBµV. The displayed engineering unit on the SDT 170 LCD is dBµV. But even that is not of any value to anyone unless the reference value is known. SDT's reference value is: 0dB = 1µV).

The decibel is a relative unit. When using dB’s to specify an absolute voltage, current or power level, a reference level must qualify the decibel value. For example, in a discussion of sound intensity a reference level of 1 dB corresponds to acoustical field strength of 10-16 W/cm² (the normal human threshold at 600Hz). A lion’s roar at 20 feet might have a sound intensity of 90dB, and the threshold of pain occurs at 130dB. Thus, the human ear/brain has a dynamic range of 130dB, or a ratio of 10 trillion to one.

Other examples of dB scale usage:

*In radio work, power is often rendered in dBW (decibels referenced to 1 watt) or in dBm (decibels referenced to 1 milliwatt).

*In antennas technicians specify dB’s with respect to some standard reference element such as isotropic radiator or a dipole. The measurement units are the dBi (gain over isotropic) and dBd (gain over half-wave dipole).

*In spectrum analysis, noise, spurious signals and distortion products can be referenced to the carrier (if one exits), dBc.

A certain frequency synthesizer might have a phase-noise specification of -40dBc, 100Hz removed from the carrier.

*The acoustics people specify the sound in dBA.

*Voltages (SDT) are sometimes given as decibel values with respect to 1 Volt (dBV) or to 1 µV (dBµV).

Clear as mud now I suppose...

Allan,

I have been a long time user of SDT products, and I stand by my #8 statement. A voltage used as a dB reference simply makes the meter a "micro-volt meter reading in decibels". An ultrasound microphone converts sound pressure into voltage, so the sensor's reference value must be pressure unit, such as Pascals. Furthermore any devation in ultrasound sensitivity during sensor manufacture or drift over time and use cannot be compensated for by the meter, since the meter does not have a sensitivity adjustment nor a field calibration physical standard. The same arguement applies to structureborne ultrasound with a contact sensor where the physical unit is related to force on the crystal or surface acceleration. I consider this basic sensor and instrument system fundamentals, and two trips to SDT in Belgium have not convinced me otherwise.

Walt

Hm, mathematics comes into play, question:
1 dB + 2 dB = 3 db?

We can talk about "change the bearing, when you have an increase of 60%" (Good for the bearing manufacturers)

The ASME pressure vessel code exists, because they have blown a lot of boilers, on ships, on trains, in industries, in the basement of simple people and lots of refineries.

Nowadays it is unacceptable to buy something that eventually can kill you (despite weapons and other means of mass destruction). The ultrasound gun is not a boiler, before the gun we used water with detergent to detect leaks, and there was not any written standard needed to define the concentration.

You have the right to know you are in danger

Are the ultrasound results always reliable to depend on? Are we sure we use the proper ultrasound technology available in the market?

A little story in the ship industry, long time ago, a live dove was thrown into the ship tanks to check for poisonous gas before vessel entry for repairs etc. If the dove remains alive, will you straight away start working inside?

Got this from another website, yesterday

The discussion started about the rate for doing a job

quote:

Sometimes the plumbers charge extra hours because they sent some Bozo that doesn't know what he's doing!

I once had a water leak in my house. My house has a concrete slab foundation and the leaking pipe was in the slab. I called a plumber out of the phone book who's ad mentioned specifically being a leak expert.

The guy that showed up was a "kid" in his low 20's probably. Talking to him I got the feeling that he wasn't the "expert" mentioned in the ad. I figured I didn't have a lot to lose so I let him go at it.

Well, he had this listening device to locate the leak. It was a large box with some headphones and a probe and all kinds of scientific looking knobs and dials. He went on the hunt for the leak. For a very long time. A VERY long time. He couldn't locate it, so he decided to use the "explore with a jack hammer" technique. He started digging and digging, chewing up my foundation. After eating up half of a bedroom and about 8 square feet of hallway, he found the leak.

About that time, the "real expert" showed up. A guy probably in his late 50's. He looked at the crater and the rubble and asked why he dug so much up. The "expert" told the "real expert" that the listener thingie wasn't working. The "real expert" went and looked at the listening thingie. He took one look at it and said, "Oh, you've got the microphone plugged into the headphone jack, and the headphone plugged into the microphone jack."

As you can imagine, I was not pleased!

Sorry for being such a long post, but someone mentioned plumbers!

The guys from this forum probably don't know what equipment it is, but that doesn't prove that ultrasound is not reliable

quote:

Originally posted by Josh:
If the dove remains alive, will you straight away start working inside?

Which are the threshold limits for a dove, too different than humans? If first test (dove) is not conclusive, send in the chimp. If the chimp survives them the crew can go ahead.

quote:

Originally posted by svanels:
The guys from this forum probably don't know what equipment it is, but that doesn't prove that ultrasound is not reliable

Similar to Computers Systems Reliability, it is as good as the quality of the piece in front of the monitor.

Walter, who will yes all the NO statements by you above? Any institutions working on them at the moment? At what stage is ultrasonic technology now, maturity, adolesent or infancy stage?

Josh,
I don't know who will step forward and either refute my statements or offer an optimistic view that these issues are being addressed. None of the issues are "show-stoppers" that keep people from using the technology. Where is the technology? In your words, it is an infant, adolesent, and mature all at the same time. I see a lot of "bells and whistles" being added to products that have not been fundamentally improved over previous models. There is no point in continuing a negative discussion.

Walt

Walt

I'm not trying to be negative but I try to understand the weaknesses and strengths of this ultrasonic technology. Anyway, you seems to be knowledgable in this matter.