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Better Transducer Technology Pays Off in

the Tube Mill.

Ultrasonic testing of welded tube must match production rates,

so it is a high-speed process, and the test equipment itself

decides accept or reject status on the fly.

International standards govern the set-up criteria for this type

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

high-aspect transducer technology.

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-house

stock of samples. Results with other diameters and walls

may be different, but the principle remains, that first-class

transducer technology will give better real-world test results

on the tube mill.

Vol.6 No.1 Summer 2011
The InspecTech Inquirer

New InspecTech Web Site Launched

Spring 2011 saw the launch of InspecTech's new website.

We have made the site more user-friendly with drop down menus for navigation. It also allows for the downloading of our product data sheets in pdf format.

For improved convenience, in the coming months, our site will be released in Spanish and Russian.

If you have not visited us recently try 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-long learner because new developments in hardware and programming technology keep driving the need for ever more advanced software.

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.

1/8” HOLE
1/16” HOLE
1/32” HOLE