[rlitman]

[quote="seabee"]Hi guys,when I ran my hobart 180 mig I had a 50foot run to my garage.I used 8gauge,3wire underground "romex" I then ran the wire thru electric pvc,cemented joints and put it about 1' deep/quote]

That's actually pretty bad form.
For one thing, if your garage already has a power feed (say for lights), then you are providing a second power feed into that building. Big no-no.
What should be done, is to wire a 50A (or larger) feed to the garage, cut out the old wiring, add a breaker panel at the garage end of the feed, and have the welder and everything else in the garage run off that panel.

PVC is a good choice for underground, as it doesn't corrode like metal conduit, BUT between 18" underground and 8' up, it is supposed to be sch80. Sch40 PVC is supposed to be buried more than 18" under dirt, but you can go shallower under concrete.

Anyway, you're not supposed to put romex in conduit. It -can- be sheathed for up to 2' for protection, but your UF "romex" should be directly buried. If you already ran conduit, then it should be filled with THHW wire (an cheaper alternative to UF).
Also, the UF wire in 8 gauge only has an ampacity of 40A because it needs to be derated for 60C service. THHW/THHN in conduit would provide enough ampacity for your 50A service though.