Better Transducer Technology Pays Off in
the Tube Mill.
Ultrasonic testing of welded tube must match production rates,
so it is a high-
decides accept or reject status on the fly.
International standards govern the set-
of testing, and they are mostly very similar. They require the
detection of machined notches of known depth on both the
inside and outside surfaces of the tube, with alarm thresholds
based upon the received echoes. Many standards also
include the use of drilled holes.
Unfortunately naturally occurring defects have different textures
and orientations and give widely different echo amplitudes.
For many natural defects echo amplitude is not necessarily
related to defect severity, and in truth it can be a poor guide
to reject status.
Why then, do we continue to set up our flaw detectors using
the same method of OD and ID notches and drilled holes?
It is because we have no better way.
However, there are some things that we can do better. Whilst
defect echo amplitudes vary according to defect type, they
can also depend upon the ultrasonic beam size and shape.
It is important for any test system that, as much as possible,
the received signal should be independent of target size
and orientation. For example, if a defect that is 10% of wall
thickness is 2mm long, it should be located just as readily
as the same 10% defect that is 25mm long. Sadly, this is often
not the case. In fact, many test systems, even modern ones,
are engineered to detect the specified standard notches,
(which are quite long), but they can be marginal on drilled
holes or shorter defects.
It is important therefore that not only should various shapes
and sizes of defect be detectable, but also, because
amplitude of signal is the sole arbiter of accept/reject status,
echo amplitudes should vary as little as possible between
defect types and sizes.
InspecTech has long been aware of this, and over the years
we have studied different beam configurations and devoted
engineering effort to providing our customers with transducers
that are effective on short as well as long defects, and at the
same time have good response to reflectors of different
shapes and positions. This has resulted in our standard
Let's look at the pictures!
Using a standard InspecTech test system on a 9.625” x 0.375”
sample, we compared the responses from standard notches,
special notches and drilled holes. The notches were
standard 10% of wall, however, one was standard, the
second quite short at ¼”. The holes were 1/8”, 1/16”, and 1/32”.
The notches and holes were all machined in the same line,
and after setting up on the standard OD notch, the test piece
was moved linearly past the transducer without any
adjustments being made to probe positions, exactly as in
a regular test.
Ultrasonic response to drilled holes of course, can be limited
to the reflecting surfaces at the top and bottom corners. In fact,
the ultrasonic signal level (in theory at least) should be
unrelated to the hole diameter. This is because the signal
from a drilled hole originates from just a single point, which
is the true radius of the hole.
What we are demonstrating here is not just that all artificial
defects are detected, but more importantly that the signal
levels are very similar for such a wide variety of reflectors;
meaning that the system will be more effective and
dependable when it encounters natural defects on the tube
mill. It is much less likely to give exaggerated response to
some defects and to miss others completely.
The tube sample was picked at random from our in-
stock of samples. Results with other diameters and walls
may be different, but the principle remains, that first-
transducer technology will give better real-
on the tube mill.
New InspecTech Web Site Launched
Spring 2011 saw the launch of InspecTech's new website.
We have made the site more user-
For improved convenience, in the coming months, our site will be released in Spanish and Russian.
If you have not visited us recently try www.inspectech.ca: your feedback on how we could improve the site is also welcome.
Meet The People
Taraneh marked her 12th anniversary with InspecTech this year. Over the years she has created and maintained all of the software used in InspecTech test systems.
Taraneh earned her bachelor’s degree in Electrical Engineering in 1994 at the Iran University of Science and Technology.. She moved to Canada with her husband and two sons in 1997. Taraneh first came to InspecTech in 1998 on contract, and joined our staff in 1999.
Fortunately, Taraneh is a life-
In 2003, she obtained her Ontario Professional Engineers Licence, and in January 2010, she achieved the Professional Development Designation in ".NET Application Developer", from Ryerson University.