PWHT heating and cooling rate

[Titirli]

Hello, all.

I would like to know if there is any standard that specify for heating or cooling rate for the PWHT (stress relief, more exactly). I have checked the EN ISO 13480-4 but I found out only the temperature range and the soak time.
I saw in some articles on internet that the heating and cooling rate should be between 50-100degree C, but I want an exactly number.

Thank you.
Best regards.

 

[metengr]

Probably your best bet would e to follow one of the ASME B&PV Code standards;

Typically, the heating rate is less than 600 deg F (315 deg C)/hr and 400 deg F (204 deg C)/hr for cooling for PWHT. Components thicker than 50mm should be the above rates divided by largest section thickness.

 

[davefitz]

There are some interesting online presentations by the PWHT company "superheat " on this issue. If you place the heating coils far from the weld zone or you heat up quickly, then you are likely to over-temper the material under the heating coils. To avoid the over -temper issue, the latest AWS guidelines recommend that you also place a monitoring thermocouple directly under the heating blanket to ensure that material is not overheated due to a too rapid heat up rate. Although I have not personally modeled the combined conduction heat transfer and internal heat generation problem , I would guess that the permitted ramp rate is inversely proportional to the distance from the center of heating coils to the weld zone.

"Nobody expects the Spanish Inquisition!"