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skmagnum (Structural)
10 Mar 10 21:16
Hello, I am fairly new to the engineering world. I work for a small steel fabricator. I am having an issue with about a mile of fence we built for a customer.

We recieved the drawings already detailed from a detailing firm which we normally dont do but we were sub contractors.

The panels of the fence are made up of HSS 2x2x3/16 capped both ends with a PL 1-3/4x1-3/4x1/8.

The weld they specified was a fillet weld all around the cap with the notation "seal typ." in the tail of the weld symbols.

The shop used .030 hard wire and welded the caps all around with a standard "fillet" weld. Its hard to really call it a fillet weld because the conditions of the weld don't really allow for a fillet.

Now they are saying they wanted water proof welds because they claim they are having trouble with rust dripping out of the tube through the weld.

So my question is, by them marking their welds with "seal" does that mean we were supposed to provide a water tight weld as in a pressure tested weld?
weab (Structural)
10 Mar 10 22:00
Seal means to seal it closed- air and water tight.  That is the only purpose of a seal weld.  If you used a bead all the way around, they should have been inspected to assure that they are "sealed".

The only out that I see for your firm is that if normal usage caused cracks in the seal welds.  Seal welds are not guaranteed any strength.  So if normal usage stresses somehow over-stressed the weld, then you may have a case.  In that case, the engineer should have specified weld size.
racookpe1978 (Nuclear)
11 Mar 10 16:53
Nope.  

Ain't likely to happen as you describe:  As pointed out, a seal weld is a non-strength constant weld all the way around a joint between two surfaces to prevent (incidental water or liquid or whatever) xxx from leaking in or out - not a "pressure barrier" against fluid fluid driving through.  So a seal weld might leak if a standing fluid held (a corrosive) were trapped inside for a long period of time... But this doesn't sounds like that case.

but you're describing rust (caused by water inside the pipe) "leaking out" (up somehow?) through the weld.  

You (the fabricator) probably can't prevent all and every water particle  from getting the (unpainted) inside of the tube steel.   But you're case resides in figuring how so much could getin side so that it "leaks up" from inside in that short a period of time.   

Rust coming through the walls of a weld in that short a time at the top of a post?

Can you post pictures?  This doesn't sound right.

---...--

OK.  Now, your mission is: find out what they used for the weld, what the tube steel material was, and how they did the welding.

Hint: A 0.030 "hard wire" is meaningless, because they didn't tell you what material the "hard wire" was made of, nor how hey welded what base metal in the tube steel.  (At least there, it's reasonable to assume plain (cheap) carbon steel.)    
skmagnum (Structural)
11 Mar 10 18:35
I see very interesting. I do not have any pictures as no one from our company has actually seen this rust yet. They have just told us about it on the phone.

The caps were not welded on the top of a post. The posts for the fence are 3/4" plate steel.  The 2x2 tube which is capped is like a panel. The tube sits horizontally and bolts to the 3/4" plate posts via connection plates welded to the face of the tube.

I would have to look back through the records but i know the tube steel was just standard carbon steel typical of almost all our tube steel and i would have to dig out the spec for the wire but it the same stuff we use on all our handrail interior or exterior and we have never had a problem with:

"since the welds were not sealed and air was allowed to get into the tube steel and condense forming water inside the tube, it is our opinion that corrosion on the inside of the tube steel is forming a large deposit of rust powder.  Each time the temperature changes enough to cause condensation on the inside of the tube steel the rust is 'reconstituted' and drips out through the pourus areas of the weld"

that is a direct quote from some paint and finishing "expert" the had examine one of the panels.

I've been in the steel business for almost twelve years and i've never heard of anything like this before, neither has anyone else at our company, that's why we are so baffeled.
MintJulep (Mechanical)
11 Mar 10 20:14
Interesting, I'd like to see pictures.

I hope you didn't pay your "expert" more than you are paying us here on Eng-Tips!

Some info on seal welds:

http://www.jflf.org/pdfs/papers/design_file6.pdf
dik (Structural)
11 Mar 10 20:20
Close up pictures as well as a *.pdf of the detail would be appreciated...

Dik

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