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Welding on an hydraulic fluid tank (full or empty?)

Welding on an hydraulic fluid tank (full or empty?)

Welding on an hydraulic fluid tank (full or empty?)

We are required to weld on an hydraulic tank. What would be the safe way to do this (tank full, or tank empty?, etc)

If we drain the tank before welding, there would still be a film of oil on the wall, and the flash point of the fluid (~390°F) will likely be easier to reach than if the tank is full and the heat is dissipated through the oil.

Furthermore, there shouldn't be oxygen near this (in the tank), since it is well below the level of the fluid.

The hydraulic tank wall is 3/8" thick and we are welding a plate 2" x 6" x 3.8"thick. See attached drawing.

I've looked on the web and spoke with welders. But so far, none of them could reassure me (based on some "welding best practice" and science).

This is a 100 gallons hydraulic tank with a breathing cap.

Also, what if there is a hairline crack on the tank, causing a minimal seepage of oil? At this moment, the oxygen will be in contact with the seeping and heated fluid even though we clean up the surface the best we can.

Thanks for your help!

RE: Welding on an hydraulic fluid tank (full or empty?)

Order the new tank with the pads and ports you need.

Cut the existing tank into unusable pieces with a beam saw or similar, not a torch.

A new tank will cost a lot less than the bill from the burn ward, etc.

Mike Halloran
Pembroke Pines, FL, USA

RE: Welding on an hydraulic fluid tank (full or empty?)

Drain the tank of oil and HP steam clean it to remove the residual oil. This would be the safest approach other than replacement.

RE: Welding on an hydraulic fluid tank (full or empty?)

After you have steam cleaned it, put an inert gas blanket " Back up Gas" into the tank before you start welding.

You are judged not by what you know, but by what you can do.

RE: Welding on an hydraulic fluid tank (full or empty?)

and purge it prior to the inert gas treatment... Now we have a complete procedure...


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