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  #21  
Old 07-19-2005, 06:15 AM
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Here is a picture of a UT machine, wish I had a better shot of the screen.
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  #22  
Old 07-19-2005, 06:18 AM
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Ultra-sound is a different animal. They ultra-sound transmission lines for us when we are going to put a pressure control or a tap on an existing line. Gives us the wall thickness.

The x-ray pictures are very accurate on their depiction of all the different passes of the weld. I'll try to get a picture of some film next time.
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  #23  
Old 07-19-2005, 06:21 AM
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Quote:
Originally Posted by Pile Buck
Here is a picture of a UT machine, wish I had a better shot of the screen.
Your picture looks just like the machines that they use here.
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  #24  
Old 07-19-2005, 06:25 AM
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So are you saying on 1-inch thick material (or greater) an X-ray can tell you exactly how deep the problem is? That’s not my experience at all. I agree an X-ray is more accurate, but for a better explanation is only 2-D, X and Y, but sucks for the Z. I’m not arguing here at all I’m trying to learn
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  #25  
Old 07-19-2005, 06:33 AM
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Quote:
Originally Posted by Pile Buck
So are you saying on 1-inch thick material (or greater) an X-ray can tell you exactly how deep the problem is? That’s not my experience at all. I agree an X-ray is more accurate, but for a better explanation is only 2-D, X and Y, but sucks for the Z. I’m not arguing here at all I’m trying to learn
When you get into the greater wall thicknesses, the welder makes as many passes as the x-ray technician tells him that he can shoot accurately.

It might mean making a pass, and then let the technician shoot it, and then weld again, shoot a picture, weld again.........................
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  #26  
Old 07-19-2005, 06:36 AM
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Looks like I'm late for work, gotta go
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  #27  
Old 07-19-2005, 06:48 AM
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wow eh!!!, learning lots here on this. thansk for sharing.

thansk
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  #28  
Old 07-19-2005, 08:03 AM
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Ok Chris, I know you had to run off to work just as we were starting to have fun! Why does work always get in the way of fun? Now I think you and I are looking at this from two different ways. In your world pipe / pipelines, you are very limited on how you are going to repair a weld. On the whole you are going after a problem spot from the outside in, correct? You don’t have the option of climbing inside the pipe to go after a bad spot; it’s just not feasible, and on the whole you probably don’t deal with any pipe much thicker than ½-inch. Ok now for my world. We deal in material a lot thicker. The majority of the weldors I would call by name out of the hall, have the same mind set as myself, 3/8-inch material is considered body and fender / sheet metal work. Again the majority of our work is structural shapes, H-pile, H-beams, and I-beams, whenever the job required outside inspection, on the whole it was UT only, but what few times it was x-ray, we had the option of going after the repair from either side. Well we both know it’s all about the money, so when you have the option of going after a bad spot form either direction you would want to know the shortest path, correct? So when I was paying the bills I would request to have a UT qualified member in the x-ray crew. They could take the picture, then UT the spot, tell me how deep the problem was, then we could determine if it was better to go after it from the outside or inside. When splicing structural shapes, it could very well be more cost effective to go in from the backside of a flange than the outside. If the problem is only 3/16-inch deep, and you have a 1-inch thick flange, do you want to scarf / bevel only 3/16-inch of material or 13/16-of an inch? Now on the whole when doing structural shapes we were required to bird mouth the web, and slide a backing bar through the web, and tack to the backside of the flange, also on the whole the joint design called for the bottom half to be cut 90° to itself, and the top half have a 45° bevel. The reason for this design, is all impact, the engineers want full bearing on the bottom section.
Here is a picture of a welding job I did down town Seattle, this picture only shows about half of the project. Every one of these pipes were 100% UT. We did not have one official reject. Now that’s not saying I didn’t have things repaired. One of the first joints, I had completely cut apart 3-times, and I fired 3-weldors over this joint. I fired a totally of 12-weldors on this project. I had weldors who would walk away from a joint with pinholes in the welds the size of pencil erasers. The union rep still hates me to this day.
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  #29  
Old 07-19-2005, 03:53 PM
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Good afternoon Pile Buck,

Since Chris had to go to work, I'll see if I can help answer your questions, since we are both retired and can play on the computer a little longer.

I know he has more experience at pipelining, since he works at it everyday, and I only worked for 2 years on the 42-inch gas line in centeral Oregon (1992-1993) and in 1976-1977 on the Trans-Alaska pipeline. Most of the work I've done was on nuclear power plants, such as Hanford, Trojan and plants in California and Arizona.

For the most part, an x-ray of a weld in about the same as an x-ray of a bone. On medical x-rays, bone is denser than skin and organs and bone will show up clearer than organs, exposing cracks, breaks, thin bone mass and whatever else the doctor might be looking for. Welds are more denser than the material around it, so it will show as being a brighter white than the surounding area, which will show up as a lighter shade of white or gray. A perfect example of this is: you are tig welding and you just happen to dip the tungston in the weld and the tip breaks off and is left in the weld. When it is x-rayed and the film is looked at, a person would have to be completely blind if they couldn't see the tungston in the weld, since tungston is quite a bit more dense than the weld, it will show up bright white and well defined, the weld will be a lighter shade of white and the surrounding area will look somewhat white of gray. Depending on the angle the x-ray was made, you can almost tell exactly where the tungston is, in the weld i.e. root area, filler area or cap area, since shooting at an angle will produce somewhat of a 3D effect, of the weld.

While working on some of the nucs, I would happen to get the wonderful job of working on a weld repair crew and this was A REAL JOY. It could be fun but most of the time it was a pain. The x-ray tech would show you a strip and tell you what he thought was wrong with the weld then you would sit down and look it over and see if you could find anything else that might be bad, then go out and make the repair. Now, the reason I said that he would tell you what he thought was wrong was because during the construction of Trojan, in the 70's, not all the x-ray people had the education and certs that are now required, so quite a few mistakes were being made and if you got too many hits, you would be the one the that got fired. In order to protect yourself, you'd try to find someone that knew their job pretty well and could teach you what to look for in an x-ray so that you could at least level up the playing field somewhat. The contractor one summer, (1975), brought in a bunch of people (cheap labor) and gave them a crash course in reading x-rays and things went downhill fast. What brought things to a screaming halt was when another guy, on the crew I was on, cut into a weld and found out that what was listed as excessive root penatration, on the bottom of the weld, was really a few sunflower seed hulls that somebody had spit in the pipe earlier. Don't laugh, things like this happened, more than once. I've seen rod stubs laying beside a rootbead listed as being excessive misalignment and after spending the time to cut into the weld, this is what was found. Then you would have to reweld the area and call for another x-ray. Expensive and time consuming, at the least, and also the NRC would be on your butt.

If the pipe was large enough and the repair was in the root area you could crawl in the pipe and make the repair, but mostly all the reapirs were made from the outside in, due to safety reasons such as, trapped argon inside of stainless pipe, location of repair, etc..

If you are interested, look in the Lincoln book titled "The Procedure Handbook Of Arc Welding" and in section 11 part 11.2-8 and 2-9 there is a discription of how angle x-rays of pipe are made and some photos showing different types of bad welds. It states that fillet welds are the most difficult to x-ray and to interpert.

I know this was lenghty, but I hope that this has answered some of your questions.

Bill
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  #30  
Old 07-19-2005, 05:35 PM
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Pile Buck Pile Buck is offline
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OK Bill, I went back and read chapter 11, from 11.2-6 to 11.2-10, it’s been 7 or 8 years since I’ve read that chapter. Unless I missed something, I’m still not convinced that I threw my companies money away by having the welds UT also. On page 11.2-8 I only see a 2-D photo, long with a drawing describing what you are looking at in the x-ray. I still do not see a scale of any kind, as far as I know when it comes to an accurate measurement for the “Z” it has to be UT ed. Then the depth is all mathematical. With an x-ray the “Z” is just a guess-ta-ment! Now on pages 11.2-9, and 11.2-10 They all but say the “Z” is a guess-ta-ment. The UT is not a guess-ta-ment, it’s all math.

Here I scanned the pages we are talking about for the ones who do not have the “Procedure HandBook of Arc Welding”. It’s hard to get a good scan in the binding of the book, I hope you can still read it if you are interested.
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