Eddy current project

[Jamie]

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..

 

[Jamie]

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.

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.

 

[Joerg]

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..

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.

 

[Rich Grise]

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..

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

 

[Tim Williams]

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.

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

 

[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.

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

 

[Jamie]

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

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.

 

[RoV]

"Jamie" wrote in message news:[email protected]...

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.

These sensors work with highly conductive seawater. Coils are obviously
potted.
http://www.teledyne-tss.com/commercial/detection.php

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
http://digilander.libero.it/rvise

 

[Jamie]

"Jamie" wrote in message


These sensors work with highly conductive seawater. Coils are obviously
potted.
http://www.teledyne-tss.com/commercial/detection.php

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
http://digilander.libero.it/rvise

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..