Crack Detection Methods for ERW Pipe

1. The crack at the depth of 3-4mm and not opened to surface? quite abnormal. Check up whether it is a crack or lack of fusion or even plate lamination.

2. The 2-3mm is just at the edge of the MPI and deadzone of the UT. Try HWDC MPI it should reach that depth and supplement with Shear wave/ angle beam UT. With higher MHz you should be able to reduce your dead zone to near zero.

3. depending upon where you can economically afford- try RT.

4. Now there are a few other techniques available especially suited for the pipes lile AE (acoustic emission test and a few others but that may not be necessary)

I presume you are referring to crack in the weld and not in the parent metal, though it does not matter as regards detection of discontinuities. But still, if the pipe material is defective, you need to choose good plates prior to ERW. Please specify the MPI technique used. In all probability, you will need DC/HWDC with dry powder. First prepare some mock ups to work with. If this technique fails (I doubt though), Eddy Current Testing will definitely help. Here you need an experienced operator with high enough sensitive equipment. Judging from your location, I would say this:Drop a line to : Shirish Vagal<svagal@smartpowerusa.com / eis@bom3.vsnl.net.in, shirishvagal@yahoo.co.in ; he will guide you further. Accoustic Emission is a wrong suggestion.

Only 2 posts...?...in almost 2 weeks?

As #2, I assume the cracks are within the fusion zone...(?) Curiosity begs to know whether the process of machining might possibly be contributing to their development. How many have occurred, and what is their length along the seam (as well as depth ; From that 2-3mm point, have you measured cracks going all the way to the inner diameter? or only a fraction thereof?)

A properly performed ultrasonic examination of the weld zone will be done in shear wave mode, NOT contact-longitudinal mode, and as such will NOT involve a "Dead Zone" coming into play. (The dead zone would be contained *within* the wedge/shoe used to introduce the beam into the cylinder at an angle... unless, of course, you choose to perform focused-beam immersion test using shear waves: then, the 'dead zone' would be eliminated within the water-column used for coupling.)

Contact testing in longitudinal mode would, indeed, introduce the dead zone into the picture...but this would be an incorrect approach. The beam would be looking at the narrowest dimension of the crack-faults, instead of their major areas.

A properly performed ultrasonic interrogation will provide more information for you than magnetic particle examination, radiographic examination, and eddy current (limited in its depth of penetration) examinations combined.

The method is more than mature enough for this application. Employ someone with the proper skills to set up the exam, or, you may expect results exhibiting the same success rate as hunting grizzly bear using a BB gun.

Best Regards ~