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Eddy current project

We have a project at work that has been doing well for some time now, and that is an Eddy/(foucault)current method of detecting surface defects and cracks in copper conductor.. This includes stranded and solid.. I guess it works for Tungsten, AL, and nickel, too!

There is going to be some changes made in the processing of the material and I was asked, if it would be possible to submerge the coils in the coolant water. I didn't give them an answer, still thinking about this..

We can protect the coils from water how ever, we use recycled water for cooling and its not drinkable but on the other hand, does come out clean looking, due to our filtration system.. Was wondering if any one could shed some light on the effects I should be seeing when I place the detector coils in the water? We do add a chemical to the water because it's too hard from what I understand..

I guess the problem is, they need more coolant time and need the space the detector is using, inline.. So the solution would be to have this device in the water where the wire will be passing through.. This test can also detect the sudden lose of insulation due do the Eddy currents generating a phase shift. So, the thought of water around the area tells me that this part of the test maybe ignored?

We do have a unit that measures wall thickness that uses eddy currents how ever, that is not designed to be submerged in water..

Any comments on this would be appreciated..

Jamie..

Reply to
Jamie
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How about turning the problem inside-out: use copper tubing for the sensor coil; the water can be clean enough so that salts, acids, etc do not corrode the tubing. This way, all samples going thru the coil for strip-search xxxxxxxxxx(oops) will be in the same original environment.

Reply to
Robert Baer

I'll need to do some R&D on that idea. The coil I have now is potted, I was wondering what the effects would be when water is filling the void between the coils and SUT.

I suppose I could calibrate the system with water required if there is an adverse change..

Thanks.

Jamie.

Reply to
Jamie

This section of NDT isn't too familiar to me but I have heard of "underwater" use in the nuclear energy field. AFAIK to measure the crud layer on fuel rods. There is also a pulse eddy current technique used on oil rigs and the like, underwater, but IIRC that is limited to steel.

You might want to take a peek into those fields.

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Reply to
Joerg

Pure, clean (i.e., distilled) water is a pretty good insulator - people use it all the time for cooling stuff, but if it's got ions in it (which your supply sounds like - even "deionized" or "soft" water still has ions, just not the kind that precipitate out on your faucets and stuff) it will be conductive.

Before I use your reclaimed water, I'd check its conductivity - you probably don't want your coolant shorting out your experiment. =:-O

Good Luck! Rich

Reply to
Rich Grise

DI is DI, period. "Soft" means replacing hard ions with soft ions (replacing calcium and magnesium with sodium or potassium). In general, water softeners add TDS.

C'mon Rich, this stuff is on *Wikipedia* for petes sake.

Tim

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Reply to
Tim Williams

Well, OP didn't say what kinds of voltages are involved, but personally, I wouldn't use "reclaimed" water to cool something electric.

Thanks, Rich

Reply to
Rich Grise

The coils are potted, so their won't be an issue with conductivity, Its the behavior of the eddy currents through this water that is in question.

Tomorrow if I get a chance, i'll find a production line I can experiment on..

Jamie.

Reply to
Jamie

These sensors work with highly conductive seawater. Coils are obviously potted.

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Water will certainly attenuate your returned signal and give extra returns. For example this is an issue for the above cited instrument in very shallow water, when you can have returns from the top when you are actually looking towards the bottom.

Ciao,

-- RoV - IW3IPD

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Reply to
RoV

Interesting..

I will be back to work tomorrow and will subject the coils to some harsh testing.

It's hard to do R&D out side of work with out dumping too much information that may end up in the competitors lap..

The idea of this isn't new and the implementation of it has its various methods. We have come up with working units that didn't cost hardly much at all to design and construct.

The lowest cost unit we could find that would do what we wanted out of water was starting at $12k per unit. We just thought that was a little much and stuck with the more archaic devices we were using at the time.

This will probably end up like one of my other little designs that some how ended up in the lap of a fab house where they had their own engineers. It was funny because we have other plants and share our information of course. We received a unit that was being used at one of our competitors, to evaluate the performance and if it looked ok, they were going to buy some. It was a big surprise when we looked in the back of the small paper back manual, A photo copy of my schematic with my initials down at the lower right. Not very sharp looking due to the poor copy but they were mine, nonetheless.

You see, the CAD program we were using and still do for some things is a custom written program and the file format is not compatible with anything out there, so I guess a photo copy was the simplest thing to do.. Which means, some one in one of our plants must of distributed the manual or a complete device.

I think what really happen was they had this fab shop assemble them and they took up the pose of distributing them. The unit on the outside didn't look like ours and had their name on it how ever, the board inside was exactly as ours.

So, since this has happen, I was told not to get to friendly with the information of future projects.. Since most of us signed a confidentiality agreement..

I am sure many others here have run into similar situations.

Oh well, such as life..

Jamie..

Reply to
Jamie

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