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Technical Discussions
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
22:10 Jun-25-2014
Conventional UT for HDPE pipe

Hello colleagues, I am looking for a procedure to inspect pipe HDPE using conventional UT, I would like to know what is the recommended procedure in their experience, or the typical drawbacks presented. I hope someone can reach me any information. The pipes are 10mm thick.

 
 Reply 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
08:46 Jun-26-2014
Re: Conventional UT for HDPE pipe
In Reply to Pedro Serruto at 22:10 Jun-25-2014 (Opening).

EN-13100-3 covers the ultrasonic examination of welds in thermoplastic joints from 10mm to 100mm.
There are several ways to weld HDPE, using a "mirror" (heated plate that heats the ends of the pipe after which they are pressed together to form a homogeneous joint); using a sleeve that is welded to the pipe; melting plastic wire with a heat source similar to oxy-acetylene welding with steel.
HDPE scatters ultrasound, you may need to use longitudinal angle probes. All examination will be at half-skip and some surface preparation may be necessary for a good examination. You will need test blocks with side drilled holes to produce a dac (made with a production weld and drilled with holes such that sound travels through the weld) and notches to determine your through thickness. Angles are different to steel due to the material velocity, less than half that of steel, so you will need to do some experimentation on the test block.

 
 Reply 
 
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
18:10 Jun-26-2014
Re: Conventional UT for HDPE pipe
In Reply to Jon Wallis at 08:46 Jun-26-2014 .

Hello Jon, please, explain me how can i get a longitudinal angle probe? I know that with angle probes, what one is looking for is the use only of the shear wave. Please explain me that.

Next, if i use a tandem technique, then i have to make a DAC curve too?? or DAC is only when i use only one probe?

And finally, what sound velocity i have to input in my ut equipment for HDPE? or how can I determine it?

 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
20:38 Jun-26-2014
Re: Conventional UT for HDPE pipe
In Reply to Pedro Serruto at 18:10 Jun-26-2014 .

Standard commercial wedges that are designed to generate a refracted shear wave in steel will generate a lower angle longitudinal wave in high density polyethylene, per Snell's Law. Shear wave velocity in steel is approximately 3250 m/s, which is faster than the longitudinal wave velocity in polyethylene, typically about 2450 m/s. The L-wave velocity in HDPE is also slower than the L-wave velocity in common acrylic or Perspex wedges. Thus, when the wedge is coupled to HDPE, the incident L-wave in the wedge wave bends downward as an L-wave, rather than upward as a shear wave as it would in steel. For example, a wedge that is designed to generate a 70 degree refracted shear wave in steel will generate a refracted L-wave at approximately 45 degrees in HDPE, per the basic Snell relationship

sin θ1 / sin θ2 = velocity 1 / velocity 2

sin θ / sin 70 = 2450 / 3250 = .754

sin θ = (.939) (.754) = .708 θ = 45 degrees

As Mr. Wallis notes, polyethylene is more attenuating than steel, so echo amplitude will be lower that what you might expect.

1
 
 Reply 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
08:05 Jun-27-2014
Re: Conventional UT for HDPE pipe
In Reply to Pedro Serruto at 18:10 Jun-26-2014 .

Forget shear waves, HDPE will only support longitudinal waves, as Tom says a 70° steel probe will produce a 45° (approx.) HDPE longitudinal wave.
This however won't be enough for testing 10mm thick material so you will need to go to a probe supplier and purchase an appropriate probe with a wedge to give you a different angle - see the norm you are working to.
EN-13100-3 also makes reference to the tandem technique and refers you to EN583-4.

 
 Reply 
 
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
06:06 Jun-30-2014
Re: Conventional UT for HDPE pipe
In Reply to Jon Wallis at 08:05 Jun-27-2014 .

So, Jon and Tom, HDPE doesnt make transverse wave? and If i use a wedge of 70° I will have to put 45° in my equipment to inspect HDPE for a correct measurement? and how can I determine the sound velocity?

 
 Reply 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
08:21 Jun-30-2014
Re: Conventional UT for HDPE pipe
In Reply to Pedro Serruto at 06:06 Jun-30-2014 .

HDPE doesn't have a set velocity, it varies from batch to batch. Use notches in the test piece to find your half skip and, if possible, full skip positions on your screen. Start with the 2450 m/s second suggested by Tom.

 
 Reply 
 
shibu
India, Joined Jun 2014, 45

shibu

India,
Joined Jun 2014
45
09:21 Jul-10-2014
Re: Conventional UT for HDPE pipe
In Reply to Tom Nelligan at 20:38 Jun-26-2014 .

dear tom,
sound will travel from perpex of probe to hdpe.so why did you show sound travel from polythene to steel.i did not get it

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1307

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1307
14:09 Jul-10-2014
Re: Conventional UT for HDPE pipe
In Reply to shibu at 09:21 Jul-10-2014 .

Shibu, I suspect Tom merely used the steel velocity since most off-the-shelf refracting wedges for shear mode are designed with the assumed velocity of steel. Tom's example shows that using such a wedge would result in a negative refracted angle if used on HDPE. Or more precisely, it would result in the refraction of a compression mode at an angle much less than the shear mode indicated on the wedge.

1
 
 Reply 
 
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
01:07 Jul-11-2014
Re: Conventional UT for HDPE pipe
In Reply to shibu at 09:21 Jul-10-2014 .

I used a 70º wedge and I calibrated my probe using VI, then I put 45º in my equipment and I had good measurement, using the velocity 2450 m/s first, but then I adjusted it to obtain the real distance to my Drilled Hole, and finally I worked with 2400 m/s. So thanks to everyone for all.

 
 Reply 
 
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
16:58 Aug-28-2014
Re: Conventional UT for HDPE pipe
In Reply to Ed Ginzel at 14:09 Jul-10-2014 .

Dear Jon, Tom and Ed, you already explained me that with wedges of 70° in conventional UT i will have an angle of 45° aprox. in HDPE. So, my question now is, that happends with phased array too?? we know that the angles vary since 60° to 75° aprox. but I supposed that those angles are for steel material. In HDPE those angles will change as well as occurs with conventional UT?

 
 Reply 
 
Laurie Beasley
Laurie Beasley
13:08 Aug-29-2014
Re: Conventional UT for HDPE pipe
In Reply to Pedro Serruto at 16:58 Aug-28-2014 .

You need to remember that the weld you're inspecting has a square fusion face and the most likely imperfection is lack of fusion.
A 45 degree beam isn't going to be any good.
You need 70 plus degrees the same as with a steel weld.
You should also use a composite crystal probe, which has better impedance matching to HDPE, and a lower frequency, possibly around 2 MHz depending on the thickness you're testing, square wave pulse will help, maximum pulser voltage and impedance, 1/2" or bigger crystal, again depending on thickness.
There are plenty of probes that fit these criteria and you could get a 90 degree steel wedge and then sand the end down to tweak another degree or 2 out of it - you can work out the resulting angle in HDPE.
It's a must to have a reference block, at an absolute minimum you could use a piece of pipe with a side drilled hole and you could use this to calibrate velocity, angle and sensitivity.
Krautkramer make a wedge and probe combination for polyethylene WB70B2GT or WB65BGT.
If you must use a 45 degree angle you'll have to use tandem probes and probably at two or more spacings to catch any reflected signal - very slow if you're going to be testing more than a few welds.
I would think it'd be very expensive to try phased array - you're going to need a custom wedge and low frequency probe and it may not work.

 
 Reply 
 
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
07:28 Sep-02-2014
Re: Conventional UT for HDPE pipe
In Reply to Laurie Beasley at 13:08 Aug-29-2014 .

Dear Laurie, did you say steel wedge? please explain me more about to improve the inspection using conventional UT. You said something about sand the end of the wedge to reach 2 more degrees and about the tandem technique (disadvantages) and how an inspection with phased array, using a custom wedge, may not work.

 
 Reply 
 
Laurie Beasley
Laurie Beasley
07:49 Sep-02-2014
Re: Conventional UT for HDPE pipe
In Reply to Pedro Serruto at 07:28 Sep-02-2014 .

Hi Pedro, most wedges are manufactured for steel and the angle on the side is for steel.
If you use the wedge for aluminium or any other material, including HDPE, the angle in the material under test will be different, this as you would remember from your training is basic ultrasonic theory.
So a wedge marked at 90 (for steel) will be much less in HDPE.
See the calculations by Tom how to work out what angle a 90 degree wedge for steel will be in HDPE.
Using the tandem method should only be attempted after development of a procedure by a level 3.
Olympus actually do have some custom gear for phased array, see http://www.olympus-ims.com/en/ultrasonic-phased-array-examination-butt-fusion-joints/
In doesn't seem like you have a level 3 to guide you through the process so I would recommend you get an off-the-shelf produce, the WB70B2GT probe and wedge from Krautkramer.

 
 Reply 
 
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
08:10 Sep-02-2014
Re: Conventional UT for HDPE pipe
In Reply to Laurie Beasley at 07:49 Sep-02-2014 .

Dear Laurie, You wrote steel wedge, not "wedge for steel". And the rest of my comment was only for compare with our own procedure.

 
 Reply 
 
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
06:19 Sep-10-2015
Re: Conventional UT for HDPE pipe
In Reply to Pedro Serruto at 08:10 Sep-02-2014 .

Dear Collegues

I would like to share this demostration of Inspection in HDPE using Conventional UT. Any comment will be appreciated.

https://youtu.be/CYZVkzVKB98 (in Spanish)

 
 Reply 
 
jon wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

jon wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
07:54 Sep-10-2015
Re: Conventional UT for HDPE pipe
In Reply to Pedro Serruto at 06:19 Sep-10-2015 .

Thanks for showing us the video Pedro, I have a few observations although they are based on my not understanding a word of the commentary unfortunately.
The technique you demonstrated was through transmission, not tandem.
Where are you bouncing your signal from, is it reflecting off the protrusion on the inner surface?
What angle (in HDPE) are your probes?
How do you think you will find fusion defects with this method?
If through transmission is to have any effect then one beam should travel through the body of the weld and the bounce should occur off-centre of the weld, it seems that your probe set-up is equidistant over the weld.

 
 Reply 
 
Manuel Haces
Director, - Wire rope inspection
Haces Inspección del Noreste and Wire Rope Inspection, Mexico, Joined Jun 2002, 125

Manuel Haces

Director, - Wire rope inspection
Haces Inspección del Noreste and Wire Rope Inspection,
Mexico,
Joined Jun 2002
125
13:15 Sep-10-2015
Re: Conventional UT for HDPE pipe
In Reply to Pedro Serruto at 22:10 Jun-25-2014 (Opening).

Any coment regarding cold fusión or kissbonding or another term for lack of fusión not found from UT, it seems there is more to discuss from this issue.

 
 Reply 
 
David Djaja
David Djaja
12:20 Nov-02-2015
Re: Conventional UT for HDPE pipe
In Reply to jon wallis at 07:54 Sep-10-2015 .

Hello all,

Thanks Pedro for your demonstration as I do have similar idea using through transmission method. I've been thinking, in addition to the through transmission method that I should use a single pulse echo method using longitudinal probe (70 to achieve approx. 45 as mentioned earlier in this thread) to ensure the near top surface is also covered (should there be any defect on the near surface it will be picked up by UT conventional machine because it is going to be a corner like in a square fusion joint ). And to answer Jon Wallis on how to find the fusion defect: there will be NO pulse when fusion defect (depends on the height and location of the defect vertically) is evident. Pedro's demo shows two pulses with reduced Pulse Height because of the side drilled hole he created in the block. So if the defect is to say half of the the thickness or lesser, thus it may show reduced pulse on the screen.

Question: is it going to be acceptable in the HDPE pipe industry that "the nonexistence of pulse represents a flaw (the void or lack of fusion in this case)?

I believe when we do find lack of fusion the acceptance criteria shall be: Rejected (Not Comply - I have to yet purchase and learn the EN code). But the other common defect would be bubbles I assume. Please share if bubble found, could we use Side drilled hole (HDPE) of diameter 1.5mm or 3mm (which one better to be used) with above 50% DAC should be Rejected? I'm planning to make the sensitivity block for testing. Your suggestion is highly appreciated. Thanks.

 
 Reply 
 
Bahadir Tekin
Turkey, Joined Oct 2019, 3

Bahadir Tekin

Turkey,
Joined Oct 2019
3
17:47 Oct-09-2019
Re: Conventional UT for HDPE pipe
In Reply to Laurie Beasley at 07:49 Sep-02-2014 .

Dear Laurie

I searched Krautkramer WB70B2GT probe and wedge for HDPE inspection but I could not find. I think it is not produced.

 
 Reply 
 
laurie
Australia, Joined Feb 2019, 41

laurie

Australia,
Joined Feb 2019
41
02:45 Oct-10-2019
Re: Conventional UT for HDPE pipe
In Reply to Bahadir Tekin at 17:47 Oct-09-2019 .

See link below but you'll have to contact a representative to see if it's still in production since the brochure was produced in 2005.
https://www.tcontrol.ro/Content/prospecte/UTSpecialProbes.pdfhttps://www.tcontrol.ro/Content/prospecte/UTSpecialProbes.pdf

 
 Reply 
 

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