Hi all,
in technical drawings it is shown welding present all around the bolts and nuts. my concern is already the bolts are tightened, and they are very dirty (much grease), is there a trick way to clean the grease in practical way. ( i dont want to remove all bolts and clean and re-tighten, because there are more than tousands of bolts are presents)
Regards
T,
Was this information known before the start of the job if it is "new" construction, or is this some kind of after the fact thing someone came up with after it's been there for a certain amount of time?
If it is new, why weren't the bolts clean and welded in the 1st place? If it's the latter, was this considerated for estimating? In any case, I would say the nuts and bolts need to be cleaned....completely. If you only clean the exposed surfaces, I would think there would be a possibility of contamination from the grease, dirt, and oil that could be drawn out from the threads.
Be careful too, your customer may require a specific WPS for this work.
actually there must me specific WPS, i requested from company to supply vendor WPS. but they were not able to do it.and let me to perform with my own regular WPSs
it is a very specific and sensitive equipment, General electric gas turbine's exhaust.And i have got 4 turbines !
Without getting into any concerns brought up in the other comments; I think pressure washing with water and detergent is the safest and cheapest method. Hot water would be great if you are able to do it. There are detergents available the are supposedly environmentally safe, that will do a good job.
Keep in mind that water will get into small nooks and crannies (as will any other solvents) that can seep out into the weld zone if you don't take care of it first.
Chet, I agree. Trisodium-phosphate (TSP) works great, hose it down, give it a good soak and maybe blow them down with some compressed air.
unfortunately vendor inspector advised us to clean the bolts and nuts after untighten them,
the reason why the bolts and nuts tightened before cleaning. sometimes construction guys dont like to listen QC guys.
thank you all for help,
T,
Fortunately though, in some unsusual circumstances like these, SOMETIMES people start actually listening to the QC guy. Look at it this way, now you have a costly event as leverage next time the construction guys don't want to listen. It's hard to try to get it through their heads.....but we're not all idiots. :)
Why are they being welded?
It sounds like you are talking about the required lubricant on Structural Fasteners, that is essential for proper tightening.
If you are talking about Structural Bolts and Nuts, IE. ASTM A325 and ASTM A194 nuts, those bolts and nuts should not be welded. Very few fasteners can maintain their design mechanical properties after welding!
If you are going to weld them anyway, they must be lubricated when they are installed. If you loosen them and then clean the lubricant off, you will most likely not re-install them properly.
I recommend that you have a conference call to the fastener manufacturer and the Engineer of Record on the project.
I totally agree with Joe - high strength nuts and bolts are frequently heat-treated and should not even be tacked. Agree with the conference call suggestion, too.
Bob Garner
Thank you for your interest, the problem solved now. we removed all bolt and nuts and cleaned (all lubrication liquid removed) them then they were tighten and welded.
why they welded? : because these bolts and nuts are a part of exhaust system and there must be gas proofing connection between the parts of the exhaust system. I already got confirmation from the inspector of the system(GE)
Not that there's much point in continuing to discuss it now, but what the heck.
I think the person who recommended talking to the fastener manufacturer and the EOR was correct. An "inspector" may not really know what's okay and what isn't. Removing lubrication prior to installation sets off all kinds of alarm bells for me (that lubricant isn't just on there for convenience but so that the appropriate tension (not torque) is achieved), and you really should have talked to the fastener manufacturer to find out what effect welding was going to have.
Hg
By dee 
Date 11-24-2006 12:36
Edited 11-24-2006 12:41
HG
In general I agree with you as well right down the line.
This is apparently not a structural connection though. I guess the biggest hazard is merely asphyxiation from leaking exhaust gasses?
My trouble with the project began when the inspector ordered the fasteners to be loosend to begin with. Beyond the tension applied to the fastener there are also issues with the gasket material which we are unprepared to address, and a host of other unknowns with this job still remain. We're at a great disadvantage I think when we dont know enough about the application so that after each opinion or attempt at a solution to the problem a little more detail gets metered out and brings us back to square one.
I could hope that the original engineers who initially designed the nuts to be welded gave that detail due consideration. Presuming the system was designed to handle hot exhaust gas and get hot itself, I say try to cook off the hydrocarbon contamination with the least amount of sufficient heat, without any disassembly at all.
Arguably not the cheapest way to clean, but it is effective and might avoid many problems- at least both mine and yours.
Anyway, my point is that my alarms went off early, back when the inspector ordered that his nuts be loosened. Who can really tell about the actual job?
Regards
d
