Re: [MW:14856] Heating/cooling rate requirement for PWHT

Dear Hegde,

PWHT is performed to the butt weld with production steel thickness of 89mm requiring impact requirement, And the applicable PQR is made with the PWHT in the minimum cooling rate above 56℃/hour..So,Does that means that I need to requalify a new PQR with a more slow cooling rate as you mentioned?, I feel a little bit confused because the heating and cooling rate is not essential variable.

Regards,

Devin

在 2012年7月12日星期四UTC+8下午6时11分45秒，Prakash Hegde写道：

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.com To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com For 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.com To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com For 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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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.