An oil company that I weld for is considering having new crude oil stock tanks fabbed and welded up for them. The price when I heard it,made me wonder if the tanks were welded inside and out and if maybe had a minimum wage welder building them,because of the low price. One tank was delivered to one of their oil leases and it started leaking as soon as the oil level was above the 2-2inch collars. It leaked around the collars. Welds were terrible. Lots of pinholes,poor penetration[some of the welds looked like toothpaste when a person squirts it out on the table, all hilled up and round with no penetration].The oil company was told the first tank was ok and would not leak.The first tank was returned after my inspection. I never met the welder,but I was told he has 30 years experience,hard to believe. The tank building company said they had problems with wire and gas quality and was having a guy come in to check out the mig welders to make sure they were running ok. I can`t under stand why if they knew they had problems why they continued welding,and even worse why they sold such an inferior product. They made and shipped out 3 with the bad welds. I don`t know what wire they are using now,but I do know they are using a hardcore wire with 90/10 gas [CO2 Argon mix]. They said they were using 75/25 but switched to 90/10. I never ran 75/25 or 90/10 just straight CO2 when I worked in the fab shops years ago. Finally to my question,which gas would be best to use on this new steel and what should the regulator be set at for the shielding gas. They told me they set the regulator at 30 which I thought was kind of high. Thanks for any input.
I dont see why 75/25 wouldnt be good, I use it all the time with good results. And anything over 25 is just a waist. Unless your in a wind tunnel.
If these tanks are being built to a code then there should be procedures in place and in writing. Picking gas mixes, flow rates, voltages and wire feed speeds willy nilly by the operator (even one with 30 years) is a recipie for non-compliance/disaster.
If the material is over 1/8" in thickness than GMAW spray transfer would be the most common Mig selection.. GMAW spray transfer requires a minimum of 80% argon so straight C02 and 75/25 won't work. The 90/10 is a common choice for spray GMAW but proper parameters and surface prep are still required to get quality.
For most operations between 25 and 35 CFH are normal flow rates depending on nozzel size and breezes in the shop.
But none of this advice is worth beans unless it also complys with the WPS.
Get a look at their production WPS and find out if the operators are even working within the ranges given and let us know what you find.
Just because they been doing it for 30 yrs doesnt mean they been doin it right.
Not that it really "Helps" your situation, but the last tank manufacturing facility I worked at used 0.035" solid wire ER70S-6.
Back then it was sold in a BOC package (SolidArc 125 I think) but it was Lincoln Electric wire. We used an Argon C02 mix that was either 90/10 or 92/8. Spray Arc whenever possible - Lots of times running 32.5V and 575IPM welding the floor halves together, putting the re-pads and the tapers on, AND welding the floors into the shells.
Lots O' Heat, and you'd better travel.
Same shop also used Metal Core to weld out the inside of the shells, and to put on the roof while rotating on the fit-up rolls.
Also used Sub Arc to weld outside shell seams and cross seams.
After the tanks arrived and the "Pressure Test" work area, and all the fittings, hatches, and man doors were installed - All seams were checked for leaks using soapy water, and vessel pressurized to 2-3 psi. Any repairs were done with E-6010.
What can I say... Company had been around for years, a new batch of welders arrived there long after I was gone - They did some crappy work, produced some crappy vessels for customers that leaked much like you described, and the company closed it's doors.
Any one of us can make a bad weld on any given day... But those of us that take PRIDE in out work, and actually give a Sh!t DON'T let it leave without being corrected.
Sorry you had a poor experience. Craftsmanship like that gives all of us in the trade a Bad Name.
These fall under API 12F. All penetration welds are to be welded on both sides or full pin with a diesel test.
Manufacturer is responsible to see the test are done. BUT it is the end users responsibility to be sure the manufacturer is doing it.
These did not happen to come out of Andrews did they?
No, I`m from Michigan, the company is located in central Michigan,and just starting to get into the tank building business.It made me just sick to my stomach to see the work they did and to send it out to customers. They knew they had a problem,yet sent the tanks out anyway. This probably would have continued if I hadn`t made it an issue. This welder with 30 years experience apparantly didn`t care about quality.The oilfield pumper who along with me seen the poor quality workmanship said that he`s not a welder but he could have done better.When one of the oil company employees told me they were getting new tanks made for $6700, I immediately asked,are they welding inside and out,and I also figured for that price quality could be an issue. I was told by another pumper,that the company he works for is buying new tanks out of state and they are in the $8000-$10000 range,a better quality tank and they have no problems. I was told tanks were over $8000 years ago,so when I heard this price I started to wonder.Also I don`t know why this company would only weld on the outside only,unless it was just to keep costs down. After being part of this forum for a few years I know everyone on here produces quality work and it would have made anyone of you sick to see the welds that were allowed to go out the door. One other thing this tank building company mentioned that may help their quality of work,they said they will soon be installing robotic welders to weld on the tanks.
"the company is located in central Michigan,and just starting to get into the tank building business" and from the sound of it they are just starting on getting out of the tank business!! Thanks for the post, this is good reading.
Shawn
By welderbrent 
Date 12-17-2010 04:40
Edited 12-17-2010 04:43
Lawrence mentioned that it should be '25-35 cfh' rating on the regulator. You did not mention if your regulator measures in pounds or cfh. So many have cheap gauges that measure in pounds. It makes a difference. If it is measuring lbs then 15 is adequate. But you really need to be using a regulator that measures in cubic feet.
I don't use straight CO2 on anything. GMAW-S runs so much nicer with less spatter on 75/25 Ar/CO2 (you called it a CO2/Ar mix in one place, that is backwards on the ratio). FCAW dual shield depends upon some characteristics you wish to achieve but I generally prefer the 75/25 mix for it as well. If you run enough and have a good supplier the cost difference is not that much. Not considering the end results and the clean up savings.
The main determination on the GMAW process is to determine which transfer mode you wish to use, Short Arc or Spray Arc. Then you need to choose between 75/25 or 90/10.
Have a Great Day, Brent
By Tommyjoking 
Date 12-17-2010 02:29
Edited 12-17-2010 02:53
I can tell you this, they did not p test those tanks or they did not care. ALL the containment vessels I ever had a hand on where pressure tested (soap and water) or leak down tested. That is the ONLY way to be sure....just to let you know a 6 psi test is more then adequate on a 1/4 inch wall vessel. As far as welding 75/25 for straight wire mig, flux core innershield go with the CO2 .....you can use either but the Co2 is cheaper on the innnershield. Some more experienced people may have better advice on the shielding gases. But on straight wire with 75/25 welding simple tank flanges, 30 is more then enough, 20 with no wind.
When I mentioned pinholes I should have mentioned that the welds in some areas looked like swiss cheese,kind of like there was no shielding gas for the moment.Yea most of the porosity I saw looked like this. I also mentioned that their overhead fans could be part of the problem also. They were circulating the air and felt like a steady breeze.I advised the oil company I weld for[ I am an independent contract oilfield welder] to not purchase any tanks from here until and if this company can establish itself putting out a quality product. This oil company has oil wells in 5 fields across the the state and the farthest one from me is 9 hours round trip. Travel time alone to this field is $720 each trip. This could end up as one very expensive poorly built tank.
