Removing rust due to using wrong consumable

By rlitman (***)

Date 07-08-2009 20:33

metallic paint?

By michael kniolek (***)

Date 07-08-2009 21:11

Could an overlay work?

By Nalla

Date 07-09-2009 15:00

ANY SPECIFIC METALLIC PAINT,PLS

By Fredspoppy (**)

Date 07-09-2009 17:41

Wow, how can one respond to a post like this? I like to think of the field of welding as a highly technical field, managed by some of the most competent personnel in Industry. Then along comes something like this. A silly question, but what did the WPS say to use for filler? WPS? What is that?

By CWI555

Date 07-09-2009 17:43

You've got bigger fish to fry than worrying about surface rust if you've used 7016 to weld stainless.

By 3.2 Inspector (***)

Date 07-09-2009 19:42

He welded a cable tray.....Not a USC boiler :)

By Superflux (****)

Date 07-09-2009 20:36 Edited 07-09-2009 20:50

First off,
Is there such a thing as a NON-CRITICAL welded component? "The Butterfly Effect" always comes to my mind.
I know, it is only a cable tray that carries all the Electrical power and Control Circuitry, Safety Systems, Alarms, etc.

I've never seen any welding performed on cable trays (was it really supposed to be welded in the first place?), they've all been mechanical connections and attacments. A S/S cable tray obviously is subjected to some serious corrosives or it would be just a galvanized tray. If this is merely a Farm Code (S/S trays, not likely!!!) job and all you're wanting to do is cover yours and your welder's behind, then, $5.99 at Walmart will get a rattle can of "Chrome" paint and all is good.

Of course, the only proper fix is to coordinate with the Electrical department, remove and replace the defective areas. Do it right...Period.
I have been involved with welding in close proximity to energized cable trays. With thorough protection from fire blankets and sheet metal (pipe insulation tin) it can be done safely.

I'd start off by having the Foreman or whoever is responsible for the welder join you in the Assesment and Corrective Action meeting. It's gonna be an interesting one for sure!

Best of luck to you, I feel your pain.

By 3.2 Inspector (***)

Date 07-10-2009 05:51

I feel no pain, why should I?

By 803056

Date 07-10-2009 18:59

I wouldn't be surprised to see cracks along weld interface and the toe of the weld if they were checked with penetrant test.

I like Superflux's position on this. Few people are going to use stainless steel for anything if it isn't exposed to an aggressive environment or there is a need for "visual appeal". In either event, rusty or worse yet, cracked welds, are not going to be looked upon kindly by the "owner".

Based on limited information provided and I assume someone has deep pockets to pay for this screw up of major proportions; cut the "bad" welds out and reweld them like the should have been to start with.

"Good grief Charlie Brown!" Who discovered the problem and when was it discovered?

Best regards - Al

By Nalla

Date 07-12-2009 13:27 Edited 07-12-2009 13:35

Dear Friends
This mega FPSO Project at final commissioning stage where these cable already being energized.My QC during routine visit onboard noted this really absurd situation.Job done 2 months ago by client contractor to conclude the last minute rush job.Noted about 50 locations.
Optinon 1-Stop comm. activities -raise up the energized cables to remove the weld by grinding and weld usig 309L which is very risky and expansive.
Option 2 - remove these portion cable trays and replace with new ones and joint by splices- also very time consuming and expansive
Option 3 - Remove the rust by power tooling and apply suitable and durable coating.
Seeking your advise

By Lawrence (*****)

Date 07-12-2009 14:49

Nalla

I think that removing rust by power tools and applying a coating would be a poor and "temporary" solution... In a short number of months or a couple years at most the rust will reappear because the cause of the corrosion was never dealt with.

The contractor that applied the wrong filler metal must be heald responsible for the workmanship requirements spelled out in their contract.. Which includes following established procedures like filler metal selection, (and repair of defects)..

Think of it this way.. If two or theree years into the future, the trays corrode again and problems and speculation occur as to who is to blame.. They will come after the prime contractor and you as their quality rep... So it may hurt the subcontractor who made the mistake to fix it now.. but it might hurt more people more severely later.

It's ok to hold contractors to their contract obligations... This may take extra time and may even run a small contractor out of business. Nonetheless.. A contract is a pledge to do the work correctly and you need not accept anything less.

By js55

Date 07-12-2009 15:35

I'm sort of in the middle on this thing. Its easy to sit here and take the high road but in the real world problems like this pop up all the time and the argument generally falls into:
We know we have non compliant product here.
How bad is it?
What can be done to fix it?
And if we do a complete repair will it hold up a multi million dollar project?
Will the cost of the ideal repair bankrupt what may have up until this moment been a valuable supplier?
It is not unusual for an engineering decision (emphasis on engineering decision) to be made that comes up with a less than ideal solution (paint for example) because the cost of holding up a major project cannot be tolerated.
For example (a theoretical that is quite common), if the ideal repair is holding up the setting of a pressure vessel that requires a huge expensive crane, is the GC going to cancel the crane if a more expeditious solution can be arrived at so that he wouldn't have to?

By 803056

Date 07-12-2009 17:08 Edited 07-12-2009 17:16

I'll return to my previous position; I wouldn't be surprised to find cracks along the weld interface or in the weld. The combination of austenitic stainless steel welded with a carbon steel electrode is going to result in some undesirable microstructures that are prone to cracking. Before wishing the problem away or sweeping it under the rug, the owner or contractor responsible better have the welds checked with dye penetrant (as a minimum) to determine if cracks are present.

High viscosity paint is a contractor's best friend for concealing many weld related problems. The PT has to be performed before someone does try to paint over their mistakes. MT isn't an option here because indications are going to form along the weld toes because of the differences in permeability of the stainless steel and carbon steel.

If the welds are sound, as verified by PT, the Engineer may determine the best course of action is to paint the welded connections. However, since the welds are already rusting, it is apparent the environment is conducive corrosion. Proper surface preparation and selection of the proper paint system is paramount to obtaining long term corrosion protection. Slapping a quick coat of spray paint is going to provide little in the way of long term protection.

There is much more to be considered than can be reasonably discussed here given the limited information we have.

You have to ask the question, "Where was QC while the welding was being performed and why wasn't a visual inspection performed?" I guess we know the answer; "too expensive", "there are time constraints," "the contractor knows what he's doing", "the inspector's always finds something to complain about", and many more that will come to mind later. These are the type of jobs that I depend on. They keep me busy as a beaver. The owner usually finds the time and money for inspection after the poop hits the fan. It's kind of like closing the door of the barn after the animals have escaped. I wish I could say that I haven't fallen victim to the same human frailties before, but we all have at one time or another. It's just that is is so embarrassing after the fact! ;)

Best regards -Al

By js55

Date 07-13-2009 12:47

Al,
I didn't state my opinion very well. Cracks, if assessed are of course always a serious thing. I wanted to emphasize that the most ideal solution isn't always expeditiously or financially possible, but it must always be the judgment of engineering to make the call.

By 803056

Date 07-13-2009 14:34

I just hope that this is placed in the hands of Engineering so a proper assessment of the painting system appropriate for the application can be made. What I envision happening is someone with a "rattle-can" will spray the welds and expect it to do miracles.

"Heck, this is good as if they had done it right to begin with!" NOT

Best regards - Al

By Nalla

Date 07-16-2009 23:48

Dear Friends
My Engineering Dept & Coating Experts have come together to have some form of reliable and practical solution.
Thanks for all the input.

By Lawrence (*****)

Date 07-17-2009 02:17

Please share the solution with us.

By Nalla

Date 07-17-2009 23:11

Dear Friends
Well, It was decided Const group has to come with soloution, not Engr Dept.
So,
Options 1- Propose to client cut the rusted tray partially and reinforce with clamps and release the welded joint.Next week I'll get my guys to do demo, and see what happens.
Still the problem is how to treat the rusted area along the weld joints.
Thanks

By tazmannusa (**)

Date 07-18-2009 13:18 Edited 07-18-2009 13:30

I will take stab at it, sence it is a tray I assume you can get to the welds easy? If thats the case take a grinder with thin wheel and grind the welds down enough to run a cap pass of 309 , dont get to carried away with grinding heat and run the cap pass rather cold, At that point clean in up good with stainless cup brush. make sure any splatter from the steel welds are ground off. clean clean then passsivate it. Oh yea before grinding on the steel welds spray all the stainless with WD 40 that way the crap comming off the grinder does not embed itself on the surface of the stainless.
You could go with more cover passes on top of the 309 with 316 if need?
If the job was orderd stainless I dont think you could expect them to accept painted steel welds?
Tom
PS If the surface next to the welds allready has heavy rust you could clean it up before grinding with muratic acid, would be a better option than grinding or sanding and getting it embeded in the surface.

By CWI555

Date 07-19-2009 20:14

Nalla,

Unfortunetly, there is no good solution. I suspect all parties concerned are going to find this coming back to haunt them.
If the project lost control of it's filler material/weld program, QC and all it entails to the extent that '50' of these welds were made with CS filler, the odds are those cable tray welds are going to be the least of your problems.

I suspect the Engineering group either wanted a new weld, or wanted no part of it. I can't say I blame them in either case. The construction group is in trouble whomever they may be.

I don't think it wise to make suggestions on "how to fix it" in light of this.

Regards,
Gerald

By Nalla

Date 08-04-2009 12:24

Dear Friends
Finally, Exisiting cable tray removed and replaced with new ones using correct consumable
Thanks for all the help

By CWI555

Date 08-04-2009 14:53

That, in the long run, will turn out to be the best course of action.