Anyone have the same problem (or reasoning) of welding a tank (catch can/reservoir/etc.) shut?

All goes smooth until I am on the last weld and try to close things up. Is the hot air inside expanding and pushing out, keeping me from getting good gas coverage? Its almost like I cannot establish an arc either.

Any ideas?



***and just as I thought, a small relief hole (where a hose will be) solves the problem. I guess I will have to keep that in mind before I weld these types of things completely shut.

 

drill a small hole somewhere else in the tank before you weld it up, then let it cool down before you fill the hole in

 

If its a catch can / fuel cell then weld on your AN's before you do the last pass. That way it has a relief hole.