Billy,
WELCOME TO THE AWS WELDING FORUM!!
I would hazard a GUESS that the lines were not welded under strict oversight to a piping code. Then, add the corrosive nature of the product with the abrasive action of the flow with heavy product in it and you will get fast deterioration at the 'Y'.
In your situation thickness is your friend. The more material, even utilizing a doubler of some sort, you get on there the longer it will last. Add a couple of extra passes/layers over top.
If you are making the repairs without totally purging and cleaning the lines then running the 6010/6011 as your first pass, and probably without pre-heat to burn things out and bring the temp up, will contribute to underbead/hydrogen cracking. A lot of factors are fighting you on this one.
It would probably work better to run the 7018 all the way out and I would still recommend using some pre-heat first. I hope you are at least draining down the line. Not that it can't be done with 'product' in it, but it will definitely be easier with no inside heat sink, hydrogen contributor reducing your chances of success.
Have a Great Day, Brent
The fact that you use E6011 and E7018 seems to indicate that the piping material is carbon steel. The fact that you apply weld to the pipe seems to indicate that it's plain carbon steel, i.e., not rubber lined.
Conclusion: the material is wrong. Waste water plants effluents are corrosive, more or less corrosive according to the kind of waste it's treated, but always corrosive.
Strong recommendation: change the pipe material. Not knowing what kind of waste is treated in your plant, I can't make any suggestion.
Giovanni S. Crisi
Sao Paulo - Brazil
thank you bothfor the info...it is a large sewage plant and to replace the pipe would be very costly...we are now welding 3/8" steel plates to "box" in the 45's and contain where our problems are.
Usual piping material in sewage plants is ductile iron.
Superflux has given a comprehensive recommendation. It's worthwhile to follow it.
Giovanni S. Crisi
williewelds,
Ahhhh the wonderful world of turd herding.
Welcome to the forum.
My best trick on this is to use a #2 or larger Oxy/Acetylene blowpipe (cutting tips will work, but a blowpipe is more focused) and aim it at the start of the crack. Begin your welding 1/2" or more ahead and keep the flame (slightly oxydizing and MAX out on your flow. ie run way more pressure and volume through the torch to the extent that it wants to blow itsself out) and pointed at a 45° or lesser angle into your direction of travel. Keep the torch flame as close as you can to the arc without disrupting the shielding gases or arc. It seems to be a multifold effect of the flame heat expanding the metal to help close the crack, the flame "cleanses" the escaping contaminates, and the flow of gasses seem to force the fluids back into the groove, crack, what ever. You of course have to be multi tasking with both hands unless you have a skilled partner. From the looks of the foto though, it is tight quarters and barely enough (or not enough) room for one.
Hope this makes sense and works for you.
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