Ultrasonic & IR questions

[sawdust_128]

I have seen a number of references to ultrasonic air leak detectors. Do they work and would anyone happen to have an idea as to what range of frequencies they are scanning?

Also, I have seen a number of dicussions of members using IR thermometers for checking the temp of their tires. So, if you have a hot tire, what are the things that cause it to heat up above normal? I understand friction from running low. Does a bad bearing, or other such problem in the wheel cause an increase in the temperature of the tire?

[Jon Wehrenberg]

Ed,

Ultrasonic leak detectors have a role in leak detection, but are not capable of identifying all leaks. There is nothing I know of suitable to locate every air system leak. Among the tools which include the ultrasonic detector will be your ears. soapy water, and a stethoscope. Recently the use of freon and a detector was suggested.

Where the ultrasonic leak detector has its greatest strength is in minute leaks, internal leaks (such as a valve leaking, it can hear air flow), and leaks located where you cannot see soapy bubbles such as behind a fitting or device.

It will not find a leak in a rubber hose or air bag. I don't know why or what frequency makes it work, but it does. It can also be used to listen to electric arcing inside a relay for example.

An infrared heat detector is a great tool to measure tire temps. If a tire differs greatly from others (higher) it is likely it has low pressure. But it can also detect at the center of the tire high temps such as from a dry bearing.
It is no substitute for checking tire pressures before driving, but after pulling into a rest area it is a great way to monitor tire pressures if you do not have a monitor.

As Jim Elmore will attest it is also a very high tech way to determine when fish has been properly grilled, but that's another story.

[Orren Zook]

Ed,

Another benefit of the ultrasonic detectors is that some are available with an optional tone generator that can help you to locate window,door or other seal/gasket leaks.

[sawdust_128]

The low end model of the commercial leak detectors operates in the frequencies ranging from 36 to 44 khz.

The high end units operate in the range between 20 to 100 khz.

The warblers generate the frequencies between 20 to 47 khz.

Has anyone purchased one of these, what was the rough cost? I've heard that it is in the range of $1500 to $2500 for the low end models.

[sawdust_128]

[quote=Jon Wehrenberg;43481]Ed,



But it can also detect at the center of the tire high temps such as from a dry bearing.


quote]


Jon: will the heat generated by the dry bearing be expressed as a rise in temperature of the tire at the tread?

[JIM CHALOUPKA]

Ed, there are actually a few of the units in POG.

You can find a good selection at Grainger's, or google around for the best price.

"wrongagain" Ed in Boston bough a high end model and now wants to sell it. He is in the HVAC business and said he needed that kind.

The other devise is an electronic stethoscope which is what I have.

Generally the guys bring these to rallies where you are welcome to use them there.

As Jon said all the methods for finding leaks might have to be used, some are more costly than others


I am selling my SDT FLEX US leak detector.
Paid over $1600.00
Will let go for $1000.00
If interested email me at ehchvac@verizon.net
Or if you dont want to deal with a personal sale, it is currently on ebay.
Here is a link if you are unsure what it is.
http://www.reliabilitydirect.com/ultrasoundproducts/SDT-FLEXUS.htm
Thanks

http://forum.prevostownersgroup.com/showthread.php?t=1979&highlight=ultrasonic+detector

Dusty, There has been much said about the various detection methods. Do a simple search for ultrasonic detector for all posts and read ALL, if you still want to talk about them by all means type away, we're all still out here.

As an aside, anyone that has the time and the interest would do well to start a methodical reading of each and every post. There are some of us that have read all at least once. You will get a better perspective of everything that has transpired with P O G and how it has developed and changed from the beginning.
I think , .........., well enough for now.

You new guys that lurk, GET TO A RALLY AND MEET EVERYONE EYE TO EYE, That's the real P O G.


JIM

[Jon Wehrenberg]

Mine has the sound generator and I use it in the cabin of my plane to check for leaks in the cabin seals. My detector with the sound generator was around $325. It is an Amprobe I think.

[sawdust_128]

Jim: Much of what has been said on the topic may well need some reconsideration. I am asking because I am trying to understand some of the comments that have been made. Let me summarize some of my thoughts.

I have heard repeatedly on these forums that there is not a single method for detecting leaks that is comprehensively effective.

I can get my head around that, but why?

Reading back over the posts as I have done, I seem to see a situation of inconsistent results with the same method. O.K. again the head is around that, but why?


Here's my problem:
Any leak is going to make a sound. Correct?
The material that is flawed should have little/nothing to do with whether a sound is created or not. Correct?
Whether air leaks from a plastic pipe, valve body, seal, case. etc. the movement of the air creates the sound. Correct?

The "color" (read frequency[ies]) of the created sound is effected by things like pressure, volume, flow rate of escaping air, and size of the orifice of escape, and others. Correct?

So, my question became, If all leaking air makes a sound, why haven't folks using these tools been able to find some leaks. This has lead us to conclude that you can't find some leaks even with an ultrasonic detector. That I just cannot get the head around. As they say here, "It just ain't right!"

As everything else here is governed by laws of nature, we need to change the nature of the conversation to, what's wrong with the detectors?

Here is what I found:

Human hearing : 20 - 20KHz

Jon's Detector (~$300) : sensitive betwen 35K - 45 KHz, thus blind to ultrasonics between 20K - 35 KHz and blind above 45 KHz.

Ultra Probe 100 (~$1500) : sensitive between 36K - 44 KHz, thus blind to ultrasonics between 20K - 36KHz and blind above 44 KHz.

Ultra top-of-the-line (expect $4-5K) : sensitive from 20K - 100KHz and is focused in 1 KHz wide bands through that range. Blind only above 100 KHz.

Electronic stephoscopes ($100 - 300) : sensitive in less than the full normal sonic range, thus blind at the lower and upper ends of normal hearing and blind to all ultrasonics. They provide amplification, and ambient noise cancelling. You hear more sound color without them at lower volume and if your leak happens to have a signal that it mistakes for noise, it is cancelled out and you miss it.

So, here comes the group participation aspect. If one had a full range ultrasonic detector (e.g., 20k - 100K HZ) would one be able to detect 100% of the leaks?

Sorry to be long-winded.

[Jon Wehrenberg]

Ed, I am not an expert on why detectors cannot "hear" leaks in different materials, but surmise since sound is a vibration, a leak in the side of an air bag is dampened by the rubber material, this making the vibrations or sound not detectible by the ultrasonic detector. Trust me. It can't be heard.

About why no single way of detecting leaks is suitable....you have to go through the process. First you assume leaks are audible. Not always. Not with your ears, not with the stethoscope, and not with the ultrasonic detector. But that silent leak may blow bubbles in a soapy solution, such as on the side of an air bag.

Not all leaks are big enough to hear. Some are audible by a stethoscope, an especially good tool to get you closer to the source when the sound is echoing off various surfaces. Your ears and the stethoscope and soapy water may never detect a bad Norgren five port back by the drive axle that is exhausting the leak in the steer compartment. (That is the flow path in my Liberty and possibly in your Vantare.) But the ultrasonic may hear that internal leak. Each device has its advantages. Soapy water is simple. A stethoscope less simple, but still has its place. The ultrasonic detector has widespread use, but just isn't going to find that leak in the air bag crimp or sidewall. Bubbles work there.

I have not tried freon as a leak detector. I have freon, and a freon leak detector. When the time comes I will pressurize my system with freon and see how the detector works compared to all other methods. I think it will prove to be another tool and not the universal answer.

Hector uses a bubbler and he posted info on that. I have not used one yet. To do so properly means it is necessary to not only rig one up, but to get all the adapters so it can be attached to all the fittings that are going to be encountered. That method is a bullet proof way to find leaks, but it involves a lot of patience and the ability to start at the system source and follow it thoughout its path. It requires an understanding of the systems. I intend to try that method also.

Leak detection is a black art, and to locate all the bus system leaks involves a lot of time, the right tools and patience. It will drive you nuts as everyone of us who has worked to tighten the system so the air compressor will cycle only once a day or less.

[rfoster]

Once upon a time I purchased a amplified microphone with a light on it from one Brian E. at a POG auction. I probably paid too much, but it was for a very worthwhile charity, and we were having a great time.

Well at the the mini POG/TGO rally, my close neighbor Pete Petree discovered he was losing air at his fan belt, but could not find the leaks' location.

With the handy dandy device in the hands of Captain Leak Detector (alias Toolman Jim Keller) and assisted by Truck and Pete, they quickly located the leak and With the turn of the wrench to tighten up an air line going to the regulator the leak was stopped - it was good to go.

Thanks to Brian E for donating it to the auction in Spearfish and we all enjoyed a few good laughs with the earphones on and fortunately did not damage anyones hearing, I think.

Attend a rally - who knows what you can find up for sale.
http://i52.photobucket.com/albums/g31/parkwayautoofbristol/CIMG4367.jpg

[JIM CHALOUPKA]

Ed, sorry I made some incorrect assumptions in answering your questions.

I thought you were inquiring with an inclination to buy one.

Some things that I believe also come into play are selectivity, sensitivity, operator skill, patience, and luck. Remember every inch of surface under pressure must be subjected to a search. You must find all surfaces and inspect them. Some leaks are internal so soapy solution won't work there, nor will the stethoscope, unless the operator has special skills in interpreting what he hears in the earphone.
The tool might hear sounds of leaks within specific frequencies, but at what amplitude.
Can your specific tool hear a sound of very low amplitude? The bubbles might show that leak.

There are some leaks that might vibrate at frequencies that are out of range of the particular detector being used. Not all detectors are the same quality.
Some leaks might be on the backside away from the tool probe. They would be missed.
Not everyone knows what and where to check, nor do all have hearing sensitive enough to hear all frequencies the various tools can hear.

JIM

[sawdust_128]

Nothing to be sorry about. Reading the posts has just peaked my curiosity.

I am more than willing to buy something that will work. Or buy something that I can accept the limits of where it will and won't work.

I would be very happy to buy something that worked to ease the pain of this process and didn't create a pain in my wallet.

[JIM CHALOUPKA]

Anyone using either the stethoscope, or sonic detector must be mindful of damaging their hearing.

Start out with the volume adjusted all the way down and work it up gradually.

JIM

[truk4u]

Jimmy C - WHAT?

[JIM CHALOUPKA]

I see what you are saying Tom:) now talk louder I can't hear you.

Tinnitus anyone?

JIM