John and FOT, Years ago when I worked for the Navy Nuclear Program I was
trained in various Non-Destructive Testing methods and Penetrant Testing was
one of them. It is true that improper cleaning will mask a small crack and
therefore invalidate the test. He was not pulling your leg.
It should also be noted that Mag Particle testing can only be done on
materials that can be magnetized. Since aluminum can not be magnetized it
won't work and Penetrant Testing is your only economical choice.
Jerry Van Vlack
----- Original Message -----
From: "John Herrera" <jrherrera90@hotmail.com>
To: <fot@autox.team.net>
Sent: Tuesday, June 03, 2003 10:19 PM
Subject: RE: hub removal TR3A-6
> My $.02:
>
> Bill Babcock wrote:
>
> >I clean the parts well after (bead blaster with plastic media) and dye
> >penetrant test. Sometimes I magnaflux as well, though I can do the
> >penetrant testing here. I should set up a magnaflux system--it's not that
> >tough.
>
> Years ago, when I worked at Fairchild, I found a small ding in an A-10
> aluminum alloy skin. It had to be dye-penetrant inspected for cracks.
> Instead of waiting for someone from the paint shop to remove the primer in
> the area of the dent with paint stripper, I used a Scotchbrite pad soaked
in
> MEK. The penetrant inspector then said, "Now it's got to be acid etched."
I
> learned from that.
>
> Scotchbrite or other abrasive cleaning methods, such as abrasive blast,
can
> either fill the crack with material or burnish material over the crack,
> possibly preventing the penetrant from seeping into it. Since
dye-penetrant
> inspection can only find irregularities that reach the surface (unlike
> Magnetic-particle inspection, which can detect flaws under the surface),
> such a crack would not show up. Unless the part was acid-etched after
> cleaning.
>
> Maybe plastic media won't do this, I don't know. Maybe steel is different
> from aluminum in this regard, I don't know. But then you could use
> magnaflux.
>
> Nowadays, we always teach our students to use a non-abrasive cleaning
method
> if the part is to be dye-penetrant inspected. The inspection kit comes
with
> a good cleaner, Trichlorethylene, I think.
>
> I think there is a question on the FAA mechanic written test about this
> subject.
>
> Anyone else out there ever hear of this? Or was the penetrant inspector
just
> pulling my leg?
>
> John Herrera
>
> _________________________________________________________________
> Help STOP SPAM with the new MSN 8 and get 2 months FREE*
|