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491 views
01:27 Oct-01-1998

Rolf Diederichs

Director, Editor, Publisher, Internet, PHP MySQL
NDT.net,
Germany,
Joined Nov 1998
602
NDTnet October '98: Forum Introduction

Most of this month's issue focuses on the full-text papers of the ECNDT '98

Sessions:
Chemical and Petrochemical Industries - NDT of Welds - Nuclear Industry.

In conjunction with this month's topics, we are pleased to introduce
Ed Ginzel, Rainer Maier and Hermann Wüstenberg as Virtual Session
Chairmen of our Discussion Forum.

Ed Ginzel
Materials Research Institute.
His area of expertise is the NDT of welds.

Rainer Meier
works for the Siemens KWU Power Generation Group

Hermann Wuestenberg of BAM Berlin.
He is Member of Germany's Reactor Safety Board.

For a Start:
- Discussion of TOFD continues with new arguments.
Instead of replacing other techniques, should TOFD be used as an add-on,
increasing the Probability Of Detection (POD) from 90 to 95% TOFD ?!

- Is the worldwide nuclear industry safe enough?
Or do we need more NDT service intervals?

- NDT helps make environments safe from accidents in the Chemical and
Petrochemical Industries

We welcome any questions or comments that you may have.

Rolf Diederichs


 
02:27 Oct-02-1998

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1197
Re: NDTnet October '98: Forum Introduction In the intro to this month's discussion Rolf Diederich suggested considering
that TOFD only adds 5% POD to traditional Pulse-Echo (PE) UT.

Has there been a similar evaluation of adding Pulse-Echo to a TOFD test?
Does traditional PE add only a small incremental value in POD? Is the cost benefit
of missing the 5% either way (adding TOFD to PE or PE to TOFD) so small it can be ignored?

The application of TOFD is not so difficult now as it had been in the past and if an encoded
system is used the addition of a TOFD pair of probes should not represent a
significant cost consideration. Besides, the concept of TOFD is nothing more than forward scatter UT.
Sizing and linearising features are just "Bells and Whistles" that make it more quantitative.

If we simply look at POD then TOFD is probably better than PE as it is not amplitude based.
However, from an evaluation point of view most acceptance criteria are based on amplitude response,
and echo dynamics using PE allows a much better characterisation method.

It seems now that both TOFD and PE hold a niche in UT.
However, considering the relative ease with which mechanised systems can now incorporate both
PE and TOFD it seems a waste of technology not to use both at the same time if they are available.
It is only a matter of time before customers figure out that the standard software in a mechanised
system has both PE and TOFD data displays available and they are being ripped off if they are
charged a great deal more for an extra 2 probes and a toggle on the software display to activate TOFD.

Ed

: - Discussion of TOFD continues with new arguments.
: Instead of replacing other techniques, should TOFD be used as an add-on,
: increasing the Probability Of Detection (POD) from 90 to 95% TOFD ?!




 


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