Hi! Even though there is a restriction on cooling rate below 56 C Some time it is been accepted , provided you have to convince client . e.g. In case of Heat exchnagers , when it is being heatreated in one piece along with tubes, It is very essential to heat treat with verylow heating rate Some time you require to keep 10C/hr This is to avoid distortion of tubes and damage to T/tsht weld . This is being accepted by Client.Howver you should have qualified PQR for such low heating rate( If the weld requires Impact testing) Therefore it depends upon the configuartion ,thickness variation of job ,require to be PWHT where we have to take the precaution to avoid any damage to the job Regards Hegde p.B.
--- On Thu, 12/7/12, kundan.ahirao@gmail.com <kundan.ahirao@gmail.com> wrote:
From: kundan.ahirao@gmail.com <kundan.ahirao@gmail.com> Subject: RE: [MW:14848] Heating/cooling rate requirement for PWHT To: materials-welding@googlegroups.com Date: Thursday, 12 July, 2012, 11:57 AM
Yes it is not mandatory,it is very clearly stated that need not to less than 56 c/hr without any structural damages -original message- Subject: [MW:14846] Heating/cooling rate requirement for PWHT From: Devin < yanfeixiu@gmail.com> Date: 12-07-2012 8:39 am Dear All, As per ASME section Ⅲ NX-4623,Above 800°F(425℃) the rate of heating and cooling in any hourly interval shall not exceed 400°F(222℃)divided by the maximum thickness in inches of the material being heat treated,but shall not exceed 400°F(222℃)and *need not to be less than 100**°F(56**℃)in an hourly interval.* Now the actual heating and cooling rate in our production we made is 50℃/hour which is less than 56℃/hour required above. Our custom insist that this is unacceptable and should be reheated. But my understanding is that the *56**℃is not a mandatory requirement *and only the upper limitation is required. Do I understand this correctly? PLZ guide me! Appreciate it! -- To post to this group, send email to materials-welding@googlegroups.comTo unsubscribe from this group, send email to materials-welding+ unsubscribe@googlegroups.comFor more options, visit this group's bolg at http://materials-welding.blogspot.com/The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents. -- To post to this group, send email to materials-welding@googlegroups.comTo unsubscribe from this group, send email to materials-welding+ unsubscribe@googlegroups.comFor more options, visit this group's bolg at http://materials-welding.blogspot.com/The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
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