welding old pipe to new pipe of P91
welding old pipe to new pipe of P91
(OP)
Dear expert engineers,
would anybody help to suggest any special precautions to be taken while welding 10 years old P91 pipe of Main steam to new pipe?
thanks in advance.
Akbar1968
would anybody help to suggest any special precautions to be taken while welding 10 years old P91 pipe of Main steam to new pipe?
thanks in advance.
Akbar1968





RE: welding old pipe to new pipe of P91
a) confirm the lineage of the new P91 pipe; if it was from China and the material certs were themselves forged, you may wish to reconsider the use of that pipe
b) grind away the 2005 HAZ and weld to parent metal
c)preheat and PWHT as defined in the latest version of B31.1 . Monitoring thermocouples to be applied to both the weld zone and also directly underneath the pipe sections that are blanketed by the heating coils as per latest AWS guidelines, to ensure the sections under the blanket are not overtempered during heat-up.
d) double check that the welder's procedures follow "low hydrogen procedures", and triple check that the weld wire used for both the root pass and filler are not "rogue materials". Trust me, there is a lot of rogue material out there.
e) formally document ( and archive) the thermocouple readings of preheat and PWHT and the batch number of the weld wire.
"Nobody expects the Spanish Inquisition!"
RE: welding old pipe to new pipe of P91
(c) after welding cool the weld region to below 200 deg F before PWHT, this is important to avoid retained austenite and prevention of fresh martensite during PWHT. Perform PWHT as soon as the temperature has reached no less than 200 deg F.
(e) perform a volumetric examination of the completed weld and surface NDT.
RE: welding old pipe to new pipe of P91
how many set do we need for that test?
RE: welding old pipe to new pipe of P91
1. don't hijack threads, start a new one
2. The number that the user has specified. If left to my own decisions I would use 4. Discard the outlier (after the statistical test) and average the others.
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P.E. Metallurgy, Plymouth Tube
RE: welding old pipe to new pipe of P91
You follow the requirements of the original code of construction for the vessel.
RE: welding old pipe to new pipe of P91
<http://www.iimtiruchy.org/pdf/FAB%2091%20Final.pdf...;
"Nobody expects the Spanish Inquisition!"
RE: welding old pipe to new pipe of P91
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