ultrasonic inspection of welds but there's a backing bar let's take a look first off the shirt that I've got on is the NDT hero shirt this is from Eddie Pompa Eddie is really passionate about the NDT industry there's some cool stuff on the back all this great comic stuff theme for NDT I mean what a time to be alive so I'll put the web link right here and you can get a shirt of yourself I'll use this well right here this is a weld test coupon it's half an inch thick with a single bevel backing bar on the bottom and we're going to talk about three things about backing our well inspections that can make them challenging and maybe even easier and we won't do it with phase direct I know every video seems to have faced array in it we're going to actually do it with conventional UT today I'll use the sun test wave on Olympus 5 megahertz 70 degree transducer and we'll use this ruler from Australian which has both millimeter standings on it but today we'll use millimeters because Canada and Australia they're like this okay first up number one it's the backing bar signal it's that annoying thing that shows up on your screen and it's this sound that goes through the joint at the bottom where the actual welt metal is fused the backing bar the sound gets in there bounces to the end of the backing bar comes in and you see a great big huge clot on Race game we know that's the backing bar signal and I'll tell you how we do we move the probe sort of down to a position where I've got a nice signal there's nothing really in the way out before these two flaws on the plate I'll hit freeze and you can see at the top of the screen it says gate one Peak surface distance minus X okay so I've done the X offset or measured the beam index point on the wedge so now everything is measured to the front of the wedge and not to the beam index point so we put that probe back where it was and I measure about 40 millimeters over that takes me way over here kind of next to this little rust block right there okay so I take this you can see that position lines up with the end of the backing bar another thing is that when they put the backing bars on they usually put these tack Wells to hold them on when you are doing the inspection you'll often times see those signals I'll see the active bar signal dip right there in the middle of the plate so you're going to see that effect as you're scanning the length of the backing Mark the second thing about backing bar welds and I actually think this makes them easier to do or at least easier to position your transducer and know where you are is the fact that when the weld fuses to that backing bar on the far side of the route you do get a nice reflector so you can tell immediately where you are you may not get this on a piping weld because the amount of penetration that you get on the bottom and the amount of root cap is not really going to be that consistent on the piping weld but when you have the bathroom bar you do have that at one location where you should get a little bit of sound off of it you can demonstrate that here just moving that back and forth that's pretty easy does that one that's lining up right there at that first line so that's the ID or the back wall and you can see that as I go down the length of the well it's always kind of there this helps us position the probe no knowing where we are so you know that if you push the probe forward enough and you get that signal to kind of line up at that first line on your screen your leg line then you know that you've gone down to the roof of the weld on the first leg and then simply just oscillate the probe and pull that back in order to get your full two leg inspection number three is the fact that on backing bar welds we're often times looking at a single bubble wet in my experience we usually have one plate which is prepped completely flat and the other side is perhaps say in a 30 or 45 degree angle and sometimes it can be a really big root Gap because of this it becomes difficult to define the center of the web if you're doing piping or pressure vessels where a lot of the time it's just a v then you look at the cap and you sort of draw a line down the middle of the cap and you say that's the middle of the left that's not the case on a single dotted weld so I find it easier on welds like this to measure everything from the unbeveled edge you can see here on my scan plan that that indication lines up right there at around sort of the eight millimeter mark from the edge of that unbeveled side so if I put the ruler down right here you can see it's pretty much right on that's three really quick things about backward bar welds again when I started I found them really complicated and then as I got further and further on into UT I actually got released and I actually really like the fact that there's some repeating recognizable geometry signals in there that make it really easy to know where your your probe without actually been looking at your fingers I hope you enjoyed the video if you did please hit the like And subscribe button thanks for watching good night sweet prince [Music] thank you