based on some heat treating we have been doing recently, I would not be surpised in a steady state soak, that a non-working heat treat pad (element) would drop that much. It isn't too hard for the pipe to suck the heat out the end. It would depend on the width of the heated band and insulated band though. I've typically found that when a TC fails, it give erratic readings, but haven't found "wrong" readings that I know of when the temperature wasn't fluctuating all over the place. In either case, a re-heat treat is necessary, and some hardness checking would probalby be in order after the 2nd heat treat as well.
The WPS qual was conducted to a PWHT temperature of 1390 deg. Charpy V were conducted at HAZ and Weld with results of all 3 tests in the HAZ 148 J and between 39~62 of the 3 tests in the weld. Aussie requirement is 18 J @ 0 deg min. Aussie standard allows the temperature to to be with in a given range with out requalification. the 1330 is still within that range however yes our target is still 1390 deg.
This was the target temperature the PWHT was heading for before the element failure. Yes it was an element failure, tail connection burn out. The chart record has a mid slope decrease to to the 1210 deg on the failed element, then it flat lined, with no erratic movements that would be expected with a TC problem.
I am concerned that another PWHT, even at the correct temperature, will reduce yield strenght, tensile strength and notch toughness, as I have seen is some documents particularily if soaktime (accummulated) exceeds 6 hrs
Thanks Ken