The 1375 temp is correct. We recently welded 9Cr pipe (8" sch 40) using a E505-16 electrode. Post weld heat treatment was the same as you had described and we did not have any trouble with the hardness. Was your cool down rate properly controled. When was the electric heating pads...
There are requirements as per code but generally there are two rules of thumb, which one you use is up to you. They are either use 2 times the diameter or 8 times the wall thickness of the pipe.
There are ASME standards which require annual inspection of cranes in accordance with their standards. Which standard depends on what type of crane it is you have.
