Advice for D1.5 UT CPJ 24" pipe welds

Date 10-21-2009 16:39

What type of joint do you have at the Base PL - Pipe joint? Single bevel with backing bar?(TC-U4a)
What type of joint do you have at the Pipe - Pipe joint? Single V groove with backing bar?(B-U2a)

Groove angles adequate to get good access to the root? Root dimn large enough for good access? Fitup tacks getting melted in OK?
Qualified procedure due to process being FCAW, so did they have any trouble with the PQR like you are seeing?

By ssbn727 (*****)

Date 10-21-2009 17:09

Those are all good points John and I would only like to add a few more questions like what brand FCAW filler is being used??? Is there any type of moisture control regarding the FCAW wire??? Then there are some more technique/process control questions such as: What's the ESO, arc length, and gas shielding flow rate, and are the welders using a push as opposed to a dragging/pulling technique??? In other words, what is the method of depositing the filler metal... Is it forehand or a back hand??? 30% has me thinking along these avenues of concern.

Respectfully,
Henry

By flb031

Date 10-21-2009 17:18

Hi Henry and thanks for your post. They're using Hobart .045" E71T-1 wire, moisture control consisting of plastic cover while on the roll. Arc stick out at 5/8 to 3/4", 100% CO2 at 40 cfh, and they're slightly pushing or at 90 degrees from joint.

By flb031

Date 10-21-2009 17:14

The joints are as you list. I wasn't here for the PQR but I reviewed the information on the WPQR report and they welded it using the same wire amps/volts. There is plenty of access to the root, and they're running a 2 stringer root. They're removing or nearly removing all tacks incorporated into the weld. I have put a hood on and viewed the root passes going in and saw nothing that might lead me to think there was slag, or some other type of defect going into their roots. I did see a guy dragging instead of vertical or slightly pushing this FCAW wire. I'm wondering if moving slightly downhill of 90 degrees as a incident angle with an orientation that pushes the wire would help. I don't know, table 6.3 is very difficult to pass using hand held FCAW on a 20 something pass 4.5' long weld no matter how right the essential variables are.

By jwright650 (*****)

Date 10-21-2009 17:22

A slight Drag angle will produce much better/consistant results with FCAW, IMHO. I realize that is a long pass, but even with starts and stops you should be better than 30%

By flb031

Date 10-21-2009 17:27

Thanks for your HO jwright. We tried dragging this wire and ended up trapping slag at the backing bar to bevel tip all around the 24" pipe. The CalTrans inspector has a phaser phased array unit and we've been trying to determine the exact location and orientation of the defects. Haven't been able to ascertain a positive explanation.

By jwright650 (*****)

Date 10-21-2009 17:55

>trapping slag at the backing bar to bevel tip

Sounds like they are gouging the tip and trapping slag under on the first pass of their two pass root(maybe too large of a first pass). I would place the root on the backing bar to base plate with that first pass, just shy of washing up on that tip, and then tie in the groove face with the second pass. That should help from gouging away the tip and rolling slag back under there.

By flb031

Date 10-21-2009 19:29

I appreciate your time John. Your description is exactly what we're doing. The first pass is on the bar tieing the baseplate to the bar, with the second overlapping the edge of the first and tieing that second pass to the face of the bevel. Despite taking every precaution cleaning wise, and even MT'ing these roots I've still got an issue thats here or there but not all around. I've been monitoring the electrical parameters, and have noticed some 50-60 amp and 2-3 volt fluxuations from the shop supplied power. I'm wondering if this can be a viable solution to my issue?

By ssbn727 (*****)

Date 10-21-2009 17:45

I agree with John on using a slightly drag angle because a slight push angle only works well when one is welding vertical in an uphill progression... If you have welders that were depositing nothing but vertical welds for quite some time and haven't done any flat or horizontal FCAW for some time then, they should have at least been requalified provided there was such an extensive lapse in depositing such welds and that might have been something that was overlooked.

Now if I remember correctly there was an FCAW wire that was specifically developed for use on open roots whereby the end user would be able to run the root pass with a slightly push angle for the roots only but, once the roots were deposited the wire could not be used for hot or fill passes and another wire had to be used for those passes.

I also noticed that the type of filler is an E-71T1 correct? And you are using 100% CO2 shielding gas @ 40cfh correct? Well, have you tried a 75/25 mix instead or does the manufacturer not recommend it and only recommends 100% CO2 instead? Also, I don't think that you need to have such a high flow rate when manually welding unless that is what the manufacturer is recommending...

I remember busting a test some years back on the horizontal joint because I was also welding the vertical part of the test side by side, and my mistake was that when I went to weld the horizontal joint, I forgot to switch to a slight drag angle, and that's why the shot failed on the horizontal, yet not on the vertical joint so, it just goes to show how important proper technique is in relation to the position one is welding when using FCAW.

Respectfully,
Henry

By 3.2 Inspector (***)

Date 10-21-2009 17:06

Or perhaps just plain bad welders.....

3.2

By flb031

Date 10-21-2009 17:23

That may be, but I've watched them closely and have had a history with these guys and trust me they would be out on their asses if they were bad welders. The UT hits I'm rejecting are +8 and up for the most part, and nothing full length but rather spotty in nature. I've been an inspector/UT level II for 18 yrs and am not able to definitively say what the problem is, if there is a problem. D1.5 table 6.3 is a very strict UT acceptance criteria and putting these welds in the way we are I expect some UT rejects, just not this may.

By Superflux (****)

Date 10-21-2009 18:58

Are you maintainig a tight fit of the pipe to the backing bar? Doesn't take much gap to allow erosion of the tip to get internal undercut and slag entrapment. By pushing on roll-out (roll direction towards the operator?), they are "in effect" welding in a vertical up progression and this gets in to a lot of heat input and loss of slag control. I'm guessing the welders are sitting down?

By flb031

Date 10-21-2009 19:22

The fit is an issue. We're using 3/8" backing bars with a cpj splice thats also UT inspected prior to fit. The bar is fit into the pipe, marked then has to be removed from the pipe and placed on the baseplate with a 1/4" fillet on the interior of the ring to the baseplate, then re fit to the pipe (AASHTO req). As you can imagine even the minimal heat reqiured to place the 1/4" fillet is enough to warp and alter the bars original orientation. This is required and not negotiable. So fit is near the 1/16" tolerance in spots as neither the pipe nor the bar are round. These areas are tightly dimensioned and mapped to help me when I'm UT inspecting the connection. As to the gap and it's effect on how and where the slag is trapped, this is somewhat of a moot point as this condition occurs outside of the relevant weld area as its past the thickness of the material, and the defects have almost all been a pass or so up from this condition. The welders are standing while welding.

By Superflux (****)

Date 10-21-2009 20:07

Cleaning (grinding) the backer bars and Pipe I.D. to bright metal?
Also, oftentimes, even the best of structural welders need a little tweak in their technique when put on the round stuff. Hopefully somewhere in all these suggestions will help and get you past your difficulties and or learning curve.
Maybe the phased array tech is just misinterpreting the data.

By jwright650 (*****)

Date 10-21-2009 20:49

>Maybe the phased array tech is just misinterpreting the data

I thought about that too, UT on Pipe with a backing bar is not for the faint of heart.

By Superflux (****)

Date 10-21-2009 21:31

Couple of projects ago, a friend of mine made a "Mock" C.A.R. that said to the effect ... Linear Phase Array the hell out of it until it disappears!! This was after we found two uncapped welds that were signed off on both the tubes themselves and the L.P.A. Report!

By flb031

Date 10-21-2009 23:11

Not to boast but I've been scrubbing welds for 17 yrs, and passed the F.E.M.A. UT test the 1st time scoring over 86%, and the CalTrans inspector is a seasoned Level III. Between the two of us we're confident the signals we're getting are without a doubt in the fusion zone. Then as these areas are excavated the defects are appearing right where we're plotting them, so it's a matter of why, and how in the F did it get there!

By flb031

Date 10-21-2009 23:04

Thanks for your input. The backing bars are skinned to shiny metal prior to fit-up.

As for the tweak in my welders, these guys (4 WELDERS) have been either on the 24" mostly to 2.5 to 3.5" baseplates with a few pipe to pipe splices, or 42" pipe to baseplates and 42" to 42" splices all using table 6.3 UT criteria. When I first came to this shop they were welding these CPJ welds with FABCOR ER70S-6 GMAW wire and process. The reject rate for these UT welds was nearly 95%! I convinced them to switch back to flux core and have been much more successful but still would rather see the reject rate drop down to under 10%.

The phased array tech is a Level III, and his ability interpreting the data is not in question. The reason I say this is we both did an A scan with an EPOCH, and a Kraut USN 60 where we both plot nearly identical indications, then we used the phased array to show us a better defect orientation in respect to the backing bar.

I appreciate everyone's input and hope I am able to reciprocate someday.

By Superflux (****)

Date 10-21-2009 23:23 Edited 10-21-2009 23:40

If all procedure and process variables, QC/Inspection methods are to your satisfaction, then...OPERATOR ERROR!
As I envision the shop environment and the welders' at their stations with the set-up and gun angles you describe in my minds eye...I find it difficult to imagine how the welder can see the puddle. Considering the size pipe you're dealing with and the welders are standing, where is your displacement (locaton of puddle, ie. 12:00, 1:00 etc) of the weld being made.

If all else fails...Fire one of them and rest will shape up!

By ssbn727 (*****)

Date 10-22-2009 00:52 Edited 10-22-2009 02:44

You know this has been an interesting thread but, there are certain variables that should have been addressed by now... I took a nap because of my blood sugar being the way ti can get sometimes so I apologize for dropping off the thread for a few zzzzzzzzzzz... ;)

Seroiusly though, what are the type of discontinuities and/or defects are you encountering that you describe within the fusion zone? in between passes are the welders using a wire wheel to clean otu any residual slag that with some FCAW deposits can be very thin and unnoticable especially in low ligt conditions which brings me to the next question...

What is the type of environment the welder are working in? in other words, is it a controlled environment where moisture is controlled somewhat, or is the welding being done in an environment where the both the pipe and base plates as well as the backing bars are being subject to exposure to potential moisture pick-up due to it's close proximity to the ocean and can you monitor the relative humidity around the welding area's?

Finally, what I jsut re-read was very important with respect to process control... "Despite taking every precaution cleaning wise, and even MT'ing these roots I've still got an issue thats here or there but not all around. I've been monitoring the electrical parameters, and have noticed some 50-60 amp and 2-3 volt fluxuations from the shop supplied power. I'm wondering if this can be a viable solution to my issue?"

Well, a 50 to 60 amp fluctuation certainly can be worrisome as well as 2 to 3 volts as well but that can also be operator inconsistency in regards to technique as well although it might even just be that the equipment having some sensitive meters too... have you checked with an amp probe what you primary input power is coming inot the machines and do theses machines have power factor correction which would then make the issue moot?

Also, are the power sources such that one can lock the set parameters? Can you describe the equipment to me? Have you checked with another person the actual V/A output parameters from the business end of the guns as opposed to just relying on the meters on the machines themselves and have these machines/power sources been calibrated and if so, how were they calibrated? Is there any sort of minimal preheat at all being performed on the joint prior to welding of let's say, 150 degrees F?

I know I'm stretching it a bit but, when you're stymied by you results ,and you say that you have backed up just about everything with respect to possible fault conditions well, sometimes one needs to think outside of the box in order to find the root cause and that's why I'm asking these specific questions although, you have also revealed more since I stopped paying attention to the thread. :) :) :) Finally, if you're going to use 100% CO2, then why aren't they running the Kobelco equivalent from Japan which is designed specifically for CO2 as opposed to the Hobart wire that's better suited for a mixed shielding gas for optimal results...

Most if not all Domestic manufacturers of FCAW wire formulate their flux contents to favor mixed gas shielding rather than CO2 and the reason why the Kobelco wire is preferred is the fact that Japan is a nation where argon isn't as abundant as here in the states and they are then practically forced to develop their wires accordingly to run optimally with CO2... I'm confident that your results will improve if you find out that every nook and cranny revealed nothing yet you're still only getting a 30% reject rate... If you use an FCAW wire that's specifically designed for 100% CO2 ,you'll notice the difference almost immediately... It certainly something worth investigating! ;) ;) ;)

Respectfully,
Henry

By hogan

Date 10-22-2009 02:15

you should have stuck with fabcor. The shop power has gremlins. That is why it was switched from FCAW to begin with.The voltage swings are what is killing you. How did the fabcor PQR and previous reject rate look?

By hogan

Date 10-22-2009 02:27

One more thing, shouldn't this be a SAW weld?

By flb031

Date 10-22-2009 16:04

Quite right, it was supposed to be a SAW weld. There is a problem or two with our SAW process.

1st the SAW operator is not a welder (painter) therefore he is so inexperienced that he isn't able to ascertain what is or is not a problem with the fit, weld defects like cold roll, lack of fusion, slag, and porosity so he isn't able without direct supervision to do anything but align the SAW head and hit the button.

2nd the SAW unit we have is on a track system and is for beam production, or 40' long cpj welds. Trying to manipulate the head to a position where good orientation is achieved is nearly impossible. The system has been altered to allow for a weld to be deposited but the quality is not up to table 6.3 UT acceptance.

It's unfortunate that the painter somehow passed his 1st welder operator test. Now he has a false sense of ability, and lacks the experience to do much more than push the button.

By flb031

Date 10-22-2009 14:00

I wasn't here when they did the Fabcor PQR, but I did spend 3 months rejecting 42" pipe to baseplate connections at the rate of 92.6% for the 16 welds we had to do. The Fabcor in my opinion is not a table 6.3 UT quality producing wire. I've never seen so much flying carbon arc debris and grinder dust! The Fabcor just doesn't have the fluid puddle of flux core, it's non forgiving puddle didn't allow for good fusion at the edges of the puddle at the weld to bevel area which produced root indications or just up from the root. Had they not changed to flux core I think we would still be welding those 16 welds!

By ssbn727 (*****)

Date 10-22-2009 17:00 Edited 10-22-2009 23:54

Apparently Hogan has already worked there and is more familiar with your shop conditions, so I'm going to say that your problem is two fold...
#1.) you need to fix whatever it is thats causing such fluctuations in your primary input power because apparently if your power sources do have some sort of power factor correction, then it's not enough for you to still experience such V/A deviations which are more than likely the main cause of such inconsistencies in you deposits... And if you're using CO2 with a FCAW filler that's really more than likely formulated for optimal result with the use of a mixed gas then your output V/A deviations will be affected even more so

#2.) You mentioned as well as Hogan mentioning it, or rather questioning the fact that this job was to be run originally with the SAW process correct? and then you mentioned that the operator was no longer up to snuff so to speak, so you decided to switch to FCAW instead... Did the EOR approve the switch, and did you qualify the joints to FCAW before running the welds on the pipe joints???

If I were you, I would first get the electrical issue corrected before you start anymore welding... Next, I would switch to a wire from Kobelco which is designed specifically for use with CO2 and I know they have FCAW wire that's approved for your use and application... Finally, I would take Al's advice with respect to the quality of your work connection to the pipe itself as it rotates, and run the wire at the same positions he mentioned earlier if you're not going to change to an E-70T1 wire designed for use in the flat position, and use the same technique that Al mentioned also, because once you follow through on all of these suggestions, you'll see your reject rate improve significantly.

What I don't understand is why you switched from SAW to FCAW in the first place because that reason you gave us could have been resolved in a different way without having to go through all of the steps necessary in requalifying to another process unless you or the EOR opted not to which doesn't make sense to me at all!!!

You still haven't answered the question of calibration of the power sources and to me, that tells me that it's either nonexistent or you're ignoring the electrical issues that are causing the majority of your rejections. Oh well, suit yourself!!! We are only trying to be helpful!!!

Respectfully,
Henry

By hogan

Date 10-22-2009 17:18

This problem can be fixed quickly and with little difficulty.

By ssbn727 (*****)

Date 10-22-2009 18:12 Edited 11-03-2009 20:24

One last question... Do you guys store your FCAW wire when you're not using it at all? Because you need to do this especially if you're near the water!!! And why aren't you preheating at all with the thicknesses you mentioned???

Okay these are the last questions... What type(s) of carbon steel are you welding together???
Also, why are you not using an E-70T1 spool of filler wire if you're depositing the welds in the flat position???
Why even use an E-71T1 if you're not welding out of position???
What is the included angle of the groove as well as the root opening???

I ask this because if you are using the same geometry as when using the SAW process then you're definitely shooting yourself in the foot so, if you want to be enlightened by one of the most knowledgeable experts in FCAW as well as GMAW and other processes keep reading below...

You need to check out what Ed Craig has to say here:

http://www.weldreality.com/flux_cored_pipe_welding.htm

http://www.weldreality.com/flux%20cored%202.htm

It's either ESAB or Kobelco!!! All the rest are suspect at best!!! Yet, I would hire someone who is an experienced SAW operator instead to get your project/procedure back on track!!!

Enough SAID!!! Good luck in sorting the mess out!!! :) :) :)

Respectfully,
Henry

By hogan

Date 11-03-2009 18:14

I'm wondering what happened to our friend flb031? Did you get anything resolved? Still need some consulting?

By waccobird (****)

Date 10-21-2009 19:06

Not to take from your thread and I only have the AWS D 1.5 2002.
1.1 Application
1.1.1 This code covers welding fabrication requirements
applicable to welded highway bridges. It is to be used in
conjunction with the AASHTO Standard Specification for
Highway Bridges or the AASHTO LRFD Bridge Design
Specifications.
The code is not intended to be used for the following:
(1) Steels with a minimum specified yield strength
greater than 690 MPa [100 ksi]
(2) Pressure vessels or pressure piping
(3) Base metals other than carbon or low alloy steels
(4) Structures composed of structural tubing
Fabrication of structures or components not specifically
addressed by this code shall be performed in conformance
with the special provisions of the contract or in
conformance with the written directives of the Engineer
who may choose to reference an alternate applicable
welding standard.
Why the Bridge Code? The pipe you mention is not in this Code.

By 803056

Date 10-22-2009 13:19

I would also check the work piece connection and work lead. I've been in shops where the work piece connection was a length of the copper cable stripped of the insulation and laid over the pipe. A more positive connection is required to minimize voltage and amperage variation as the pipe rotates.

"But we've been doing it for years this way and never had a problem!"

They always had the problem; the welds had never been inspected using a volumetric NDT method before.

Speaking as a welder, I always preferred to weld the root between the 2:00 and 3:00 position so that I was welding vertical uphill. This allowed the flux to clear more easily and reduced the tendency to produce slag inclusions along the edge of the root. This position also afforded the best view of the weld puddle without the obstruction of the slag and the increased heat input helped assure complete fusion. The amperage might have to be reduced slightly, but the reduction in travel speed is offset by the reduced rejection rate.

Welding in the flat is not the easiest welding position as one would expect. It is not that unusual to see slag get ahead of the weld puddle if the welder isn't using the backhand technique (drag angle of 15 degrees or so). Trying to place two passes in the root can also be a challenge. My instincts would push me in the direction of using a slight weave to deposit the root in a single pass. That again can result in slag along the edge if sufficient amperage isn't used and a hot fluid puddle maintained.

The introduction of argon in the shielding gas will reduce the spatter, but it will also increase the alloying of the weld with the deoxidizers not utilized for that purpose. You haven't mentioned spatter, so the need for argon in the shielding gas isn't evident.

Since you are using E71T-1, you have the ability to weld in all positions. Try welding in the 2:00 or 3:00 position with a slight weave to complete the root in a single pass. Make sure the welders hesitate at the corners and make sure the gun is rotated toward each side of the root as the pipe is rotated. You want them to direct the arc into the corners each time they move from one root edge to the other.

Best regards - Al