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- since 1996 -

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Technical Discussions
Kris Smestad
Kris Smestad
01:07 Apr-20-2001
void detection

Hello NDT colleagues...

Here is scenario:

I need to detect for and size air pockets that have been located under a press-fitted brass band. Our product is a steel 6 inch round cylinder with a knurled band groove cut in. After the groove is cut, a brass band is inserted and then pressed in. The brass is supposed to make 100% contact with the steel, no voids. Recently, voids of approximately .070" were found with a tangental x-ray shot.

Here is my question:

Without going out and setting up an expensive x-ray system, what is the best method to detect and size these voids? I was thinking eddy current. Any suggestions on how to go about this? Equipment? Procedure? Limitations?

Thank you for your input in advance.

-Kris Smestad


    
 
 Reply 
 
Tom Murphy
NDT Inspector
USA, Joined Jul 2000, 16

Tom Murphy

NDT Inspector
USA,
Joined Jul 2000
16
01:30 Apr-20-2001
Re: void detection
Hello all,

If the brass is very securely mechanically coupled to the steel shaft then ultrasonic back reflection from the ID of the brass band would be dampened by intimate contact with the steel shaft. Where the back reflection amplitude increases the brass band would be less well coupled to the shaft. You can look for this effect either by amplitude comparisons or phase inversions of the back reflection.

Just a shot in the dark, but good luck.

Tom

If: Hello NDT colleagues...
.
: Here is scenario:
.
: I need to detect for and size air pockets that have been located under a press-fitted brass band. Our product is a steel 6 inch round cylinder with a knurled band groove cut in. After the groove is cut, a brass band is inserted and then pressed in. The brass is supposed to make 100% contact with the steel, no voids. Recently, voids of approximately .070" were found with a tangental x-ray shot.
.
: Here is my question:
.
: Without going out and setting up an expensive x-ray system, what is the best method to detect and size these voids? I was thinking eddy current. Any suggestions on how to go about this? Equipment? Procedure? Limitations?
.
: Thank you for your input in advance.
.
: -Kris Smestad
.



    
 
 Reply 
 
JIGNASA
JIGNASA
03:17 Aug-28-2002
Re: void detection
: Hello NDT colleagues...
.
: Here is scenario:
.
: sir, I want to know the techinque for void detection
in Live Tank SF6 Circuit Breaker Rod , which is
made up of Glassfiber reinforced Epoxy tube.


    
 
 Reply 
 
Philippe Rubbers
Engineering
SCM, South Africa, Joined Nov 1998, 21

Philippe Rubbers

Engineering
SCM,
South Africa,
Joined Nov 1998
21
01:37 Sep-02-2002
Re: void detection
: : Hello NDT colleagues...
: .
: : Here is scenario:
: .
: : sir, I want to know the techinque for void detection
: in Live Tank SF6 Circuit Breaker Rod , which is
: made up of Glassfiber reinforced Epoxy tube.

Dear Sir
I assume that the equipment is at high voltages, and that voids are undesirable as they will cause partial discharge?
If so a possible solution which is not main stream NDT may be your solution here:
How about perfoming partial discharge detection.
This will not size your voids directly, but the severity of the partial discharge, and the pattern of the discharges on the excitation waveform (50 or 60Hz) will give an indication of the void severity, and directly quantify the imact of the voids on the fitness for purpose of your equipment.
There are a number of high voltage laboratories who perform this service, but if you do not come right, send me an e-mail.

Best regards



    
 
 Reply 
 

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