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Baoji Petroleum Steel Pipe Orders InspecTech Test Systems:

In the closing months of 2009, InspecTech has been awarded a contract for

on-line ultrasonic test equipment for a new API mill to be installed at Baoji

Petroleum Pipe Co in Shaanxi Province P.R. China.

We are pleased with this outcome, partly because Baoji is a very prestigious customer who vetted and pre-qualified just 3 bidders, but mostly because we were selected on the basis of technical excellence as well as price against very strong competition.

The InspecTech Inquirer
Vol.4 No.1 Winter 2009

Martin Plut, sales manager for InspecTech and Mr Yang Zhongwen of Baoji Steel Signing the contract in November.

Ultrasonic Coupling:  Some Do's and Don'ts

A reader has requested an article on coupling quality with our ultrasonic systems, and we are happy to oblige.

All InspeTech Tube and Pipe testing systems use immersion transducers operating in a holder that retains coupling liquid (we prefer mill coolant for this). In effect then, and unlike most manufacturers, we are doing an immersion test, generating shear waves at the interface between liquid and tube surface. This is very efficient as we eliminate transfers to and from any further media (e.g. plastic).

However, the quality of the coupling liquid is very important for any ultrasonic  test system, and InspecTech supplies a special settling tank with each of our systems to pre-condition the coupling liquid.

Liz Mitchell

Inspectech has a quaint and old-fashioned policy of actually answering our phones and directing your calls in person.

If you call us, (and we hope you do), chances are that Liz Mitchell will be answering your call. In January 2010, Liz will be reaching her 15th anniversary with us. In addition to switchboard work, Liz is involved in logistics and sales support, and maintains some of our customer databases.

We congratulate her on her long service record.

Meet The People

The A-scan trace for a typical InspecTech U/T system is shown alongside. In it one can identify the “main bang” on the left, the water path, the interface signal where the sound enters the product, a typical signal from a test notch and finally, the internal coupling echo.

Usually, most operators simply delay out the left hand part of the screen because the only events of any real interest occur after the interface signal. However, in this case, let's take a look at the full picture.

Because the sound beam is making a return trip through the coupling liquid as a compression wave, we expect to see no reflections in the 'main bang to interface' region. In fact, if we DO see any echoes at all in this region, they can come only from impurities (air or debris) in the coupling liquid. Such impurities will scatter the sound and seriously impair the signal to noise ratio in the test zone.

Recently, an InspecTech engineer was visiting a customer and was surprised to see a very noisy test going on. Investigation revealed that the customer had installed compressed air lines into all 4 compartments of the settling tank, and the tank contents looked to be “boiling” as a result. The customer explained that this was done to reduce crud building up in the tank so it rarely needed cleaning. The air lines were removed and the system started to perform normally.

Although this episode is now part of InspecTech folklore, it is not just at the tank that one must be careful. Even at the low pressures and flow rates used in ultrasonic testing, air can be sucked into the liquid flows at hose unions and barbs. It is for good reason that we always use submersible pumps!

Below is a screen dump from the same set up as before, but we have allowed air to enter the system and the results are obvious.

Finally, the immersion test does require a full probe cavity. The small vents at the top of the transducer should always be discharging excess coupling liquid. If they are not, the liquid level in the probe could fall, and the big echo from the liquid surface can even fall into the flaw gate, giving a false alarm.

To ensure efficient coupling, the rules are simple…make sure there is excess liquid coming from the vents during testing, and check the A-scan between main bang and interface. It should be absolutely squeaky clean.