Hi Lawrence, thanks for the info on the 455STT, so i'll see if i can return the favour.
I teach a lot on walking the cup at our facility. First start with using the sch. 80 pipe until you get better control on walking the cup. Practice walking the cup first in the 5g position before u move to other positions. We will be using ER70S-2 or 3 (1/8 C.S.). For the first pass use a number 7-9 cup (if the cup is too small u will get porosity). We also use air cooled torches because we can buy them in flex, which is a lot better for walking the cup. A foot pedal is preferred, but not essential. High frequency is a plus, especially on exotic metals.
We also use gas lenses for all our welding (the smaller gas lense for root passes and maybe pass 2 & 3; then we switch to the larger gas lense>>>3/4 " (19mm).
Set up your coupon, just so that the 1/8 rod doesn't fall inside the pipe (4 tacks). Now in the 5g, position the rod in the root of the joint (a little pressure on the rod [no dipping]; move the torch from side to side using the wrist and don't go too far up the sidewall. Use about 130-150 amps. Make sure your bevel and the top of your bevel has no burrs because u need a smooth sidewall to move your torch side to side and forward.
Try this first and let me know how u r making out before going on to the cap.
DH