[denrep]

Yes, there are risks and a hydraulic reservoir could explode during hot repairs.
However, with precautions it's an extremely unlikely scenario.
Welding of hydraulic oil reservoirs is a fairly common maintenance task.
I say forget the Boogie Man and deal with facts.

Regardless, so far we lack the details sufficient for anyone to make a decent reply.
Gauge of tank?
Does it have a large removable clean-out, or filler neck?
Application and fluid type?

. . .I Googled "welding causes tank to explode" =254,000 results IS that enough proof for you?????

Not enough proof for me. When making repair decisions I wouldn't put much much weight in even a million Gooogle hits

For what it's worth, I Googled "welding causes fudge to explode."
Click it to see for yourself:
http://lmgtfy.com/?q=Welding+causes+fudge+to+explode
Came up with over a half million hits. Meaningless.


Good Luck