Your local NDT lab should be able to provide either UT or RT services to detect these types of cracks. If the root is accessible you can us PT or MT. This is where an NDT Level III comes in handy!
Call us if we can help. William E. Blum
Managing Director
Bright Technical Services Inc.
You can not UT a fillet weld. RT could serve you but, you would need an experienced film reader who could recognize the difference between a crack and the root it self. You could use the DC mode with MT unit that is effective to about 1/4 inch in depth. Forget PT that is only applicable for surface defects. My question would be is there a reason why you think there might be cracking. Did you have failure of the welds? If you established you weld procedure in accordance with AWS D1.1 there in not a need to investigate the root of a fillet weld unless, there are indication of cracking in the weld. If that is the case you have to establish why is it cracking. To investigate roots of fillets on fear is not pratical nor reasonable or required unless established by supplication specification.
During a MT inspection I found a centerlien crack, about 1/6" (1.6mm) in length. Carefully grinding the crack out it was almost 4" inches in length when we got near the root.
Found this crack on 16% of welds on this project. Currently, doing a weld metal analysis, checking WPS against what was used, and checking mill certs, on material. We have been using this WPS and filler material for 5 years without problem. crackis in welds by multiple welders, using multiple machines. A little baffling.
These welds are in tension and are cyclic, fatigue could be a problem. The Technical Engineering Manager for the wire vendor will be here tomorrow and I am currently working with Edison Welding Institute to determine cause.
Rich, you said you are using multiple arcs? I assume you are using SAW and you are producing cracks with this process. If so check: 1 fit up, 2 flux contamination, surface prep, and 3 bad weld wire. If you are using SAW first start with your flux look for dirt of dampness. Be careful with the recycling. The Fed. Highway calls this stuff "crack in the bag" for obvious reason. From my experience although longitudinal cracking comes mostly from shrinkige due to poor joint configuration. I hope I helped.
Sometimes with Dry MT, you will actually pick up the void in a tee joint if you have enough amps. You have to be real careful in the application of the particles and observe the indication while VERY LIGHTLY dusting the part. Look at the characteristics of the indication. If it is broad and fuzzy normally, you will be looking at the void created by the joint. If the indication is sharp and distinct, a little light grinding is useful. If the indication appears to be straight-edged,its the fit-up again. One other helpful technique is to "walk" particles across the indication and observe where and how they appear to "hesitate" at the area of the suspected indication. Richard Schram
Mechanical Integrity Specialist
Pharmacia Global Supply Arecibo-P. Rico
rschram@pharmacia.com
Sounds like without grinding them, you may have to RT them. How many are you talking about? This is going to be expensive. We saw some cracking in the base metal for 5/16" welds. It was a combination of too much heat with no post-weld heat treatment and high vibration causing base metal fatigue. Am I wrong in believing there is no requirement in AWS D1.1 for examining the root of a structural 5/16" fillet weld?
