PWHT cooling tolerances.

[radd02]

What are the cooling tolerances for the rate-of-cooling for SA-516-70 plate 1.5 inch plate welded to 5/8 inch plate. this is a box header. If spec calls for cooling no more that 500deg / hour, what if the rate is 600deg / hour? Thanks, RA

 

[metengr]

The cooling rate and tolerances for cooling rate for PWHT for Section I are not defined but there are suggested cooling rates in Nonmandatory Appendix A of Section I - see below.

Granted, these are for materials 2" or greater in thickness. For those materials less than 2", you can use the same suggested ramp or cool down rates. What if they exceed this? There is a slight risk of cracking or more likely, thermal distortion.

A-101 HEATING AND COOLING RATES FOR
POSTWELD HEAT TREATMENT

A-101.1 Heating and cooling rates for weldments and
materials should be established by the Manufacturer.
These rates should be sufficient to avoid inducing distortion,
residual stresses, cracking, and other detrimental effects
into the weldment during postweld heat treatment.
Heating and cooling rates should be established based,
in part, upon successful past practice for specific materials
and thicknesses, by using other Codes and Standards as a
guide, or by engineering analysis.

 

[Bmechz]

Kindly mention the applicable code of construction..

Bmechz

 

[JIPMKWA]

I recently had the same question. The two main codes I am involved with are The BPVC and B31.1.

Where B31.1 2012 edition clearly states in 132.5 - The rate of heating and cooling shall not exceed 600/Hr divided by one half the maximum thickness of material in inches at the weld.

ASME Sec.1 says shall be heated and cooled "Slowly".

Like metengr mentioned above , the BPVC Sec. 1 does have a should/recommended rate ,which is similar to B31.1 - found in the Appendix ( Sec. A-101 ).