Digital Ultrasonic Thickness Meter

[Blazer406]

Doing some API 653 tank inspections and our company needs to purchase 1 or 2 new meters. The ones we have are old and in need or converting to bacup duty.

We need one that is small.

We need one that can have different transducers put on it. We currently use a long transducer when we do sidewall thickness measurements thru a small hole in the insulation and sheeting.

I would like to get one that is pretty common and user friendly.

We check wall thickness' for tank sideshells, bottoms, roofs, nozzle necks (pipe), etc.

The unit need not have flaw detection capabilities.

Any suggestions?

 

[gr2vessels]

You must be kidding, the range of UT testers on the google is immense, just use the first 1000 pages to select one you like or suits your budget.

 

[Blazer406]

No I'm not kidding.

With so many choices out there, I'm sure there are decent portion of the models no one has even heard of..... let alone used.

I am wanting one that has become fairly common..... is easy to use.....and has the capability to switch transducers.

 

[Blazer406]

Another thing I see is some advertise a "thru coating" feature..... where you can tell the thickness of the steel throught the paint.

In our case, this would be a big plus and a cost saver.

 

[Blazer406]

The banner ad here "Dakota Ultrasonics" has some really nice looking meters.... and software..... and a decent selection of transducers.

Anybody here use a Dakota Ultrasonics meter?

 

[Duwe6]

Not famliar with Dakota. The 'Gold Standards" are GE-Krautkramer and Olympus-Panametric.

To get accurate, reliable thru-paint measurements, you will need a screen that displays the return peaks from the transducer. You use a single-element 'ducer and measure from peak-to-peak. This means that you are measuring the sound path as it bounces bakc and forth between the metal surfaces, thus ignoring any coatings or corrosion.

On this single-element 'ducer, it is best to get a solid standoff -- known as a 'delay tip' -- to keep the 'ducer's initial pulse off your screen. This allows you to measure the first echo. Without a delay tip, you loose about 0.1" - 0.2" of echos before something readable emerges from the 'noise' from the initial pulse of the transducer leaving the 'ducer & entering the metal.

Dual-element 'ducers are what usually comes with a thickness gauge. "They lie, they lie, they lie": Anything can give a return echo on a dual-element 'ducer; a flake of carbon, an alloy density change, etc. You never know what the 'ducer is 'looking at', so you can get erroneously low readings and never know it. Also, duals will 'cross-talk' at high amplitude; the 'send' element sends a signal across the isolation pad to the 'receive' element. Thus you get a nice, steady set of readings at about 0.8" on 1.0 to 1.5" material. The 'ducer is talking to itself.

 

[Blazer406]

Got a sales rep coming (be here in 30 min) from Olympus NDT. I am looking into a Olympus 38DL Plus.

They are recommending a dual element transducer for thru-paint thickness readings.

Looks like a nice unit.

Our older units are a Panametrics 36DL PLUS and a Krautkramer DM4.

I'll see what he says about the 38DL PLUS.

 

[Duwe6]

Buy the 38DL -- VERY good unit. Fire the sales rep. Thru-paint measuremants are a specialty, and I was trained by some of the best. Dual-Element X-ducers lie, they lie, they lie . . . .

Single-element 'ducer with a 'delay line' is the current 'Gold Standard'. Don't buy anything else until you have personally used it on 4-mil new paint and 30-mil old & nasty paint, and through heavy mill scale, and moderate rust, taking side-by-side measurements against a Single-element w/Delay Line. Then you can make a reasonable evaluation of a newfangled 'ducer.