PWHT furnace conditions
PWHT furnace conditions
(OP)
Dear All
Is there any Standard procedure that covers the furnace conditions for PWHT in a way that satisfies the ASME BPVC requirements of UCS-56 and UW-40? Or do the professional companies that perform PWHT have their own procedures? My concern is about the proper location of thermocouples and the right spacing of them. Also the appropriate number and location of the burners. The code refers to WRC-452. Is it enough?
Thank you all in advance.
Is there any Standard procedure that covers the furnace conditions for PWHT in a way that satisfies the ASME BPVC requirements of UCS-56 and UW-40? Or do the professional companies that perform PWHT have their own procedures? My concern is about the proper location of thermocouples and the right spacing of them. Also the appropriate number and location of the burners. The code refers to WRC-452. Is it enough?
Thank you all in advance.





RE: PWHT furnace conditions
RE: PWHT furnace conditions
RE: PWHT furnace conditions
RE: PWHT furnace conditions
You need to place the thermocouples on and inside and underneath YOUR actual parts (do several parts in each of the HT company's ovens!) and and monitor the results over time: DO the parts heat up at the right rate? Does ALL of a complex part get to the soak temperature for the right amount of time. Are any small sections too hot?
RE: PWHT furnace conditions
RE: PWHT furnace conditions
RE: PWHT furnace conditions
RE: PWHT furnace conditions
The head in one end of the vessel is not welded when the PWHT is being performed. Since we are worried that without this head there may be excessive deflection, we want to use some spider beams to protect the shell from getting oval. Is it not a problem as per the code to weld these beams and after PWHT cut the spider beams?
Furthermore, I want you to know that I am not worried about carbon diffusion in the carbon steel but about carbon diffusion in 304L stainless steel. Since the content of carbon is less than 0.03 per cent, I thought that this may increase the possibility of carbon diffusion.
RE: PWHT furnace conditions
Regards
r6155
RE: PWHT furnace conditions
We are now in an era where PWHT requires engineered procedures, which is reflected in documents like AWS D10.10 and WRC-452 you mentioned, and practices and procedures such as attested to by racookpe1978. While the BPV Code offers little guidance, it behooves you to apply 'engineering judgment' and address all concerns around heat treatment - distortion, structural integrity, effective relief of stresses, avoidance of undesirable metallurgical alteration, protection of exposed surfaces where necessary, and of course conforming to Code.
"Everyone is entitled to their own opinions, but they are not entitled to their own facts."
RE: PWHT furnace conditions
Or is this a lower temp process? (unless this is very low C <0.015% sensitization is still a risk)
You really only have two options, either HT in air and then blast and pickle to clean, or HT in dry hydrogen to keep the surface oxide free. I have seen furnaces that heat with products of combustion (no radiant tubes) and they introduce significant excess air to assure oxidizing conditions.
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P.E. Metallurgy, Plymouth Tube
RE: PWHT furnace conditions
PWHT Furnace calibration is done together with calibration of thermocouples and temperature recorders. Accuracy of these components typically decides the accuracy of any PWHT operation.
Look under paragraph 8.0 of AWS D-10.10 and other clauses. It talks about the various ways to calibrate above underlined components. While dealing with PWHT procedures I've come across the several ASNI standards applicable for calibrating thermocouples.
A good way to cross refer would be read through the manual of the PWHT contractor and verify the accuracy. Definitely certified PWHT vendors know , what they're up tp and what standards to be followed.
Thanks.
Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
ca.linkedin.com/pub/pradip-goswami/5/985/299