Does anyone have any sucessfull mehtods for locating a hairline crack in a stainless weld?
The tank is a typical double wall conditioning tank. There is a very slow leak in, what I feel, is a fatigued weld. A step by step process that we are trying is yielding slow results. The leak only shows itself under pressure. Naturally, this limits the ability to observe the interior of the tank. Attempting to pressurize the insulated space between the walls was not as sucessful as desired. At that point we tried the simple method of soapy solution over interior welds hoping to see some bubbles...no bubbles!
Any thoughts would be appreciated.
Locating hairline cracks in pressure vessels
I have run across this problem in a past life and we found a way to locate the problem spots. The welding community has developed a system called a Dye-penetrant inspection kit or Crack Check. You can get it from a welders supply or Mcmaster Carr.
The Crack Check kit has three parts; cleaner, dye penetrant, and developer. You are going to need some sort of breathing apparatus while you are in the vessel due to the fumes. You will look like a crushed strawberry due to the red dye and you'll smell like a refinery when you are done but it works . First, clean the area where you suspect the crack could be; around welds or other features. Second, spray on the dye to the cleaned area. Next, clean the area again with the cleaner. Now spray on the developer and look for the crack.
The way the system works is as follows: The dye is able to get into the hairline crack, then you clean off the surface dye thus leaving only the dye remaining in the crack which is not cleaned away. Now when the developer is applied it reacts with the remaining dye in the crack producing a much larger "indicator" where the crack is located.
Now you have to find a Stainless welder who is willing to climb into your tank to re-weld and polish the work to sanitary standards
I hope this helps
The Brewing Science Institute
The Fastest Yeast in the Business
Outstanding! I am sure it will help.
Interestingly, no one in the welding community that I spoke with has mentioned this... Oh well.
"Magnaflux" is the most common trade name for crack checking dye. It's a standard step in engine rebuilding, so start with an engine rebuilder if you have any trouble locating it.
In my experience, the crack will be at the spot which a welder would have the most difficulty reaching and doing his/her normal quality job. Not being a cynic, it's just the way welders (etc.) work. Kinda like the least sanitary part of the brewery is what is least easy to clean.