Weld Cracking In A Stainless Water Tank
Weld Cracking In A Stainless Water Tank
(OP)
I have a problem with a weld cracking on a 303 stainless tank. At the base of the tank is 42 1/2" by 13 1/8". Along the longer edges of the tank there are 3/4" flanges that protrude from the base of the tank to the inside wall. Along the shorther edges, there are no flanges and it is welded from the outside and ground down.
We have had many reports of these tanks cracking in the field and leaking water, but as of now have only recieved one tank, and there is a clear crack, centered in the middle, along one of the 13 1/8" edges. The crack runs right along the weld material.
Statically the tank holds about 600 pounds of water, and the material thickness (14 Gauge) is sufficient to hold this weight without any sign of failure.
So the current conclusions are:
1. That it is a design issue. Being that the crack occured on the edge without a flange, there is poor weld pennetration in this thin material. (but we only have data frome one tank...)
2. It is a welding issue. Maybe there are some things that we could change in the process that would eliminate this problem (like welding the seam from inside the tank or not grinding the weld).
So what is everyone's take on this issue? Your input is greatly appricated.
We have had many reports of these tanks cracking in the field and leaking water, but as of now have only recieved one tank, and there is a clear crack, centered in the middle, along one of the 13 1/8" edges. The crack runs right along the weld material.
Statically the tank holds about 600 pounds of water, and the material thickness (14 Gauge) is sufficient to hold this weight without any sign of failure.
So the current conclusions are:
1. That it is a design issue. Being that the crack occured on the edge without a flange, there is poor weld pennetration in this thin material. (but we only have data frome one tank...)
2. It is a welding issue. Maybe there are some things that we could change in the process that would eliminate this problem (like welding the seam from inside the tank or not grinding the weld).
So what is everyone's take on this issue? Your input is greatly appricated.





RE: Weld Cracking In A Stainless Water Tank
RE: Weld Cracking In A Stainless Water Tank
RE: Weld Cracking In A Stainless Water Tank
If metallographic examination could be performed one would know.
http://www.welding-advisers.com/
RE: Weld Cracking In A Stainless Water Tank
I agree that 304L and 321 are better choices for material in this application because of how they respond to the heat of welding.
RE: Weld Cracking In A Stainless Water Tank
Filler or autogenous? Is it the correct filler?
Check some micros, is there sensitization? If so you could get CSCC just sitting there.
Is the crack actuall in the weld? or off to the edge? If it is smack in the middle, and there is good penetration, then I would suspect centerline shrinkage or porosity.
= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
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RE: Weld Cracking In A Stainless Water Tank
I don't know precisely what our fabricator is using for a filler material, no material is specified in our drawings.
As for weld quality, there is no evidence of porosity within the weld that cracked. It looks like weld pennetration is real good as evidence of the 1/4" wide blue marks along each side of every weld seam.
RE: Weld Cracking In A Stainless Water Tank
I would try to ascertain the exact weld procedure.
A lot of times if lack of weld metal is the problem and you can see evidence of the problem in uncracked areas of the weld. Also look at the cracked area to see if it tends to be sunk in.
The blue line really doesn’t indicate very much other than it's a tell on the welder's uniformity or precision in welding. It tells about his speed and technique.
There should be no problem welding 304 SS with 308, in fact I've never seen a problem with the alloy combination only the welder.
There is another possibility:
Where are the tanks used?
Are they subject to vibration?
Is it possible for the side plate to act like a drum head?
RE: Weld Cracking In A Stainless Water Tank
Easy check for chloride SCC is through metallography. Stress corrosion cracks will run transgranularly and are branching in nature.
One centerline crack in a weld though does not sound like SCC, but you never know.
RE: Weld Cracking In A Stainless Water Tank
Superduper-: I agree with Unclesyd that centerline cracking in the weld points focus to a welding problem. Metallography to look for oxides in the crack (lack of fusion for an autogenous weld), hot tears, etc.
RE: Weld Cracking In A Stainless Water Tank